+publisher:"University of Texas – Austin" +contributor:("Yu, Edward")

University of Texas – Austin

1. Li, Ping-Chun, active 21st century. Large-area resonant and non-resonant optical nanostructures.

Degree: PhD, Electrical and Computer Engineering, 2014, University of Texas – Austin

► Manipulation of light via subwavelength nanostructures is currently a subject of intense research interest, and is enabling the development of nanostructured photonic crystal, metamaterials and… (more)

▼ Manipulation of light via subwavelength nanostructures is currently a subject of intense research interest, and is enabling the development of nanostructured photonic crystal, metamaterials and metasurfaces that provide a variety of new optical and electromagnetic functionalities, or that enable existing functionalities to be realized in new and often extremely compact form factors. This dissertation will include wide-angle wavelength-selective metasurface, omnidirectional enhancement in photovoltaic performance via subwavelength gradient anti-reflection coating, and applications of birefringent nanocylinders for single-molecule spectroscopy. In wide-angle wavelength-selective metasurface, high and broad reflectance (~95%) with low absorption (<5%) are shown to be achieved with multilayer metasurface structures. These characteristics are shown to be independent of interlayer misalignment and defects within individual layers. Interactions between different metasurface layers due to Fabry-Perot resonance are also examined with analytical models and numerical simulations. Wavelength-selective focusing at optical wavelengths which is enabled by large-area nanosphere lithography on a flexible substrate is demonstrated. In omnidirectional enhancement in photovoltaic performance via subwavelength gradient anti-reflection coating, large-area "moth-eye" structure fabricated on a flexible substrate is shown to have high transmittance (>85%) at large angle of incidences (>70°) and insensitivity to polarizations. Integration of the "moth-eye" anti-reflection coating together with nanostructured gradient A1₂O₃/TiO₂ on a GaAs solar cell shows significant improvements on external quantum efficiency (EQE) and short circuit current over all angle of incidences compared with conventional thin film anti-reflection coating. Detailed design, simulation, and fabrication of these nanostructured anti-reflection coating for reducing the discontinuity in refractive index profile will also be discussed. In application of birefringent nanocylinders for single-molecule spectroscopy, the design and fabrication method for large quantity of subwavelength birefringent nanoparticle are also discussed. These birefringent nanoparticles are shown to be stably trapped in an optical torque wrench setup, and enable observation of the dynamical response of a double-stranded DNA under torsional and extensional forces. Advisors/Committee Members: Yu, Edward T. (advisor).

Subjects/Keywords: Plasmonic; Subwavelength

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APA (6^th Edition):

Li, Ping-Chun, a. 2. c. (2014). Large-area resonant and non-resonant optical nanostructures. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/25937

Chicago Manual of Style (16^th Edition):

Li, Ping-Chun, active 21st century. “Large-area resonant and non-resonant optical nanostructures.” 2014. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/25937.

MLA Handbook (7^th Edition):

Li, Ping-Chun, active 21st century. “Large-area resonant and non-resonant optical nanostructures.” 2014. Web. 25 Jan 2021.

Vancouver:

Li, Ping-Chun a2c. Large-area resonant and non-resonant optical nanostructures. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2014. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/25937.

Council of Science Editors:

Li, Ping-Chun a2c. Large-area resonant and non-resonant optical nanostructures. [Doctoral Dissertation]. University of Texas – Austin; 2014. Available from: http://hdl.handle.net/2152/25937

University of Texas – Austin

2. -2291-9232. Nanoelectronics based on epitaxial oxides.

Degree: PhD, Electrical and Computer engineering, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/32364

► Crystalline oxide materials and heterostructures have been under extensive investigation owing to the richness of the physical, chemical, and electrical properties they exhibit, including ferromagnetism,… (more)

▼ Crystalline oxide materials and heterostructures have been under extensive investigation owing to the richness of the physical, chemical, and electrical properties they exhibit, including ferromagnetism, ferroelectricity, ferrotoroidicity, superconductivity, metal-insulator transition, multiferroics, and 2-dimensional electron liquids. In recent years, the advancement of thin film growth techniques such as molecular beam epitaxy and atomic layer deposition has made possible monolithic integration of these crystalline oxide materials with mainstream semiconductor substrate materials such as Si and Ge, which opens new avenues for improving existing device performance and provides many opportunities for adding various solid-state device functionalities to electronic devices that are unachievable with conventional semiconductor materials. Epitaxial oxide heterostructures with a perovskite crystal structure are emerging as outstanding candidates for realization of devices in which diverse material properties - ferromagnetism, piezoelectricity, ferroelectricity, and others - are flexibly coupled to achieve new functionality. In the first part of this dissertation, the strain-dependent ferromagnetism in LaCoO3, piezoelectric response in SrTiO3, and their strain coupling in a single-crystal oxide heterostructure grown on Si (001) are employed to enable a novel approach to modulating ferromagnetism and magnetoresistance by application of a gate voltage in a suitably fabricated device. The second part of the dissertation addresses the resistive switching behavior and physics of epitaxial single-crystal anatase TiO2 on silicon and demonstrates several unique advantages of using single-crystal metal oxide films as an active switching layer, including a high ON/OFF ratio, a great potential for device scaling, highly linear current-voltage characteristics, and room-temperature, reproducible quantization of conductance, etc. Finally, epitaxial SrHfO3-based gate stacks for Ge metal-oxide-semiconductor devices are investigated as an approach to alleviate the gate dielectric interface quality problem that has tremendously hampered the adoption of next-generation Ge-based transistors. Different methods are shown to effectively decrease the interface trap density, and the gate stacks developed in this dissertation represent the state of the art in terms of the combination of equivalent oxide thickness and gate leakage. In summary, this dissertation presents several results in the design and modeling, process integration, characterization, and analysis of device prototypes for functional and nano- electronics applications using epitaxial oxide films. These results provide a foundation for further exploration of solid-state device applications using epitaxial crystalline oxide materials. Advisors/Committee Members: Yu, Edward T. (advisor), Lee, Jack C (committee member), Register, Leonard F (committee member), Ekerdt, John G (committee member), Sun, Nan (committee member).

Subjects/Keywords: Nanoelectronics; Epitaxial oxides; Thin films; Functional materials; Magnetoresistance; Resistive switching; Device physics; Semiconductors; Dielectrics

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APA (6^th Edition):

-2291-9232. (2015). Nanoelectronics based on epitaxial oxides. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/32364

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Chicago Manual of Style (16^th Edition):

-2291-9232. “Nanoelectronics based on epitaxial oxides.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/32364.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-2291-9232. “Nanoelectronics based on epitaxial oxides.” 2015. Web. 25 Jan 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-2291-9232. Nanoelectronics based on epitaxial oxides. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/32364.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-2291-9232. Nanoelectronics based on epitaxial oxides. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/32364

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Texas – Austin

3. Nguyen, Thien-An Ngoc. Enhanced transceiver performance through self-interference cancellation in multiple modalities.

Degree: PhD, Electrical and Computer Engineering, 2019, University of Texas – Austin

URL: http://hdl.handle.net/2152/72554

► Interference in front end transceivers directly impact system performance by saturating receiver circuitry and generating non-linearities. While proper shielding can effectively eliminate external interference, self-interference… (more)

▼ Interference in front end transceivers directly impact system performance by saturating receiver circuitry and generating non-linearities. While proper shielding can effectively eliminate external interference, self-interference continues to limit the performance of sensing and communication systems today. Self-interference exists when the transmitted signal interferes with the received signal through parasitic signal paths and from spurious reflections. This dissertation explores the use of novel transducers, front-end designs, and active cancellers to eliminate self-interference in multiple sensing and communication modalities: acoustic, optical, and electronics. First, we demonstrate integration of electroadhesion with a piezoelectric multimaterial fiber transducer to reduce acoustic signal reflection at the interface with the target substrate. The large acoustic impedance of air introduces a 10⁵ mismatch with the acoustic transducer and the substrate. By monolithically integrating electroadhesive and acoustic functions into a single fiber device, the fiber transducer can controllably adhere to the target and subsequently eliminate the interfacial air microvoids during operation. Second, the limited directivity of optical circulators give rise to parasitic signal paths in optical Mach-Zehdner based laser Doppler vibrometers. Parasitic signal paths are signal paths in an interferometer which are unexpected and unbalanced with respect to the signal and reference arms. The path length imbalance demodulates laser phase noise as amplitude noise at the receiver which degrades sensitivity due to the decrease in signal to noise ratio. We derive an expression for this this parasitic phase induced intensity noise (P-PIIN) and develop a new interferometer design which enables mutually balanced signal, reference, and dominant parasitic paths to achieve 90 dB of signal to noise ratio and femtometer vibration sensitivity. Third, self-interference in modern electronic communication systems limit the maximum achievable throughput in a given bandwidth. Self-interference from both parasitic signal paths and spurious reflections overwhelms the significantly weaker receive signal when both are operating simultaneously. As such, communication systems such as cable only operate either in time domain duplexing (alternate between transmitting and receiving) or frequency domain duplexing (transmit and receive on different frequencies) modes. By actively eliminating self-interference, communication systems are able to send and receive information at the same time on the same frequency: full duplex operation. Advisors/Committee Members: Wang, Zheng, Ph. D. (advisor), Yu, Edward T (committee member), Bank, Seth (committee member), Yeh, Tim (committee member), Vishwanath, Sriram (committee member).

Subjects/Keywords: Full duplex; Self-interference; Multimaterial fiber; Interferometer; Photonic; Optical

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APA (6^th Edition):

Nguyen, T. N. (2019). Enhanced transceiver performance through self-interference cancellation in multiple modalities. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/72554

Chicago Manual of Style (16^th Edition):

Nguyen, Thien-An Ngoc. “Enhanced transceiver performance through self-interference cancellation in multiple modalities.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/72554.

MLA Handbook (7^th Edition):

Nguyen, Thien-An Ngoc. “Enhanced transceiver performance through self-interference cancellation in multiple modalities.” 2019. Web. 25 Jan 2021.

Vancouver:

Nguyen TN. Enhanced transceiver performance through self-interference cancellation in multiple modalities. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/72554.

Council of Science Editors:

Nguyen TN. Enhanced transceiver performance through self-interference cancellation in multiple modalities. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://hdl.handle.net/2152/72554

University of Texas – Austin

4. Dillen, David Carl. Strain and modulation doping in epitaxial Si/Ge core-shell nanowire heterostructures.

Degree: PhD, Electrical and Computer Engineering, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/32857

► For over five decades, silicon based electronics relied on scaling of individual field-effect transistors (FETs) for improvements in integrated circuit performance. Recently, however, further enhancement… (more)

▼ For over five decades, silicon based electronics relied on scaling of individual field-effect transistors (FETs) for improvements in integrated circuit performance. Recently, however, further enhancement of packing density and switching speed was limited by the increase in power consumption of short channel devices. New materials and device geometries were introduced to help expand CPU performance while also decreasing power dissipation. Semiconducting nanowires have also been recognized for potential applications as channel material in highly scaled FETs. These structures present opportunities for strain and energy band engineering through the use of radial, or core-shell, heterostructures. To fully exploit the benefits of radial heterostructures, however, requires knowledge of elastic strain distributions and energy band alignments, necessitating the development of new characterization methods. This is especially true in Si/Ge material systems, where a large lattice mismatch over 4% is possible. In this thesis, we grow Si/Ge core-shell nanowires and demonstrate multiple techniques to characterize the nanoscale heterostructure, including strain measurements and extraction of valence band offsets. We grow Ge-SixGe1-x core-shell nanowires and measure the elastic strain using Raman spectroscopy. The Ge core’s Raman spectrum is consistent with a compressive strain in this region due to lattice mismatch with the SixGe1-x shell. The strain distribution and expected Raman peak positions are calculated using continuum elasticity models and lattice dynamic theory, finding excellent agreement to experimental data. We also demonstrate radial modulation doping in Ge-SixGe1-x core-shell nanowire heterostructures by doping a portion of the SixGe1-x shell with boron during growth. The modulation doped nanowire FETs show an enhanced low temperature hole mobility and also a decoupling of transport between core and shell. Through comparison to finite-element calculations, we extract the valence band offset at the core-shell interface. Lastly, we grow coherently strained Si-SixGe1-x core-shell nanowires and characterize the structure using Raman spectroscopy. We first optimize the Si nanowire growth process to favor the diamond crystal structure and to minimize sidewall coverage by Au catalyst, followed by epitaxial growth of the SixGe1-x shell using the Si nanowire as substrate. Raman measurements on core-shell samples indicate a tensile strain in the Si core and a compressive strain in the SixGe1-x shell, both consistent with calculations of the strain and the strain-induced shift of the Raman peaks in this structure. Advisors/Committee Members: Tutuc, Emanuel, 1974- (advisor), Banerjee, Sanjay K (committee member), Dodabalapur, Ananth (committee member), Yu, Edward T (committee member), Korgel, Brian A (committee member).

Subjects/Keywords: Semiconductors; Nanowire; Core-shell; Germanium; Silicon; Strain; Raman spectroscopy; Modulation doping

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APA (6^th Edition):

Dillen, D. C. (2015). Strain and modulation doping in epitaxial Si/Ge core-shell nanowire heterostructures. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/32857

Chicago Manual of Style (16^th Edition):

Dillen, David Carl. “Strain and modulation doping in epitaxial Si/Ge core-shell nanowire heterostructures.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/32857.

MLA Handbook (7^th Edition):

Dillen, David Carl. “Strain and modulation doping in epitaxial Si/Ge core-shell nanowire heterostructures.” 2015. Web. 25 Jan 2021.

Vancouver:

Dillen DC. Strain and modulation doping in epitaxial Si/Ge core-shell nanowire heterostructures. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/32857.

Council of Science Editors:

Dillen DC. Strain and modulation doping in epitaxial Si/Ge core-shell nanowire heterostructures. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/32857

University of Texas – Austin

5. Dey, Rik. Theoretical and experimental studies on topological insulators and topological insulator based spintronic devices.

Degree: PhD, Electrical and Computer Engineering, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/5792

► Three dimensional (3D) topological insulators (TIs) are unique materials with insulating bulk and two dimensional (2D) metallic surface states having spin-momentum locked Dirac-band dispersion. The… (more)

▼ Three dimensional (3D) topological insulators (TIs) are unique materials with insulating bulk and two dimensional (2D) metallic surface states having spin-momentum locked Dirac-band dispersion. The remarkable property of spin-momentum locking of the 2D surface states provides an opportunity for manipulating the coupled spin and charge degrees of freedom of electrons on the surface of a 3D TI by controlling one or the other. The charge current-induced spin polarization of the 2D surface states of a 3D TI and subsequent diffusion or tunneling of spin current in an adjacent material, or conversion of spin current to charge current on the surface of a 3D TI, are a few among many effects of this spin-momentum locking, which renders TIs as promising candidates for spintronic applications. In this dissertation, we provide a theoretical description of the electronic transport of the TI surface states in proximity to a non-magnetic (NM) or a ferromagnetic (FM) material, and derive the transport equations based on quantum kinetic equation of non-equilibrium Green’s function. The transport equations are solved for appropriate boundary conditions to obtain the efficiency of the spin current-to-charge current conversion in TI/NM/FM or TI/FM heterostructure, or to calculate the efficiency of the detection of charge current induced spin polarization on the surface of a TI with FM tunnel contacts. We find that these efficiencies strongly depend on the tunnel conductance of the interface and decreases with increasing tunnel conductance, implying the necessity of design optimization of the tunnel interface in actual devices. Here, we also describe low-temperature magnetotransport measurements on an epitaxial Bi2Se3 thin film, and identify the contribution of the surface states and the quasi-2D bulk states to the transport from localization and interaction effects. We present two-terminal resistance measurement with FM and NM contacts on the surface of epitaxial and exfoliated Bi2Te3 films, and find change of resistance with reversal of the FM magnetization direction. We also measure magnetic hysteresis properties of sputtered Bi2Te3-Fe heterostructure and obtain enhancement of coercive field of Fe in the heterostructure, which could be due to strong spin-orbit coupling proximity effect arising from the Bi2Te3 film. Advisors/Committee Members: Banerjee, Sanjay (advisor), Register, Leonard F. (advisor), Tsoi, Maxim (committee member), Incorvia, Jean (committee member), Yu, Edward T (committee member).

Subjects/Keywords: Topological insulator; Spintronic

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APA (6^th Edition):

Dey, R. (2019). Theoretical and experimental studies on topological insulators and topological insulator based spintronic devices. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/5792

Chicago Manual of Style (16^th Edition):

Dey, Rik. “Theoretical and experimental studies on topological insulators and topological insulator based spintronic devices.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://dx.doi.org/10.26153/tsw/5792.

MLA Handbook (7^th Edition):

Dey, Rik. “Theoretical and experimental studies on topological insulators and topological insulator based spintronic devices.” 2019. Web. 25 Jan 2021.

Vancouver:

Dey R. Theoretical and experimental studies on topological insulators and topological insulator based spintronic devices. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Jan 25]. Available from: http://dx.doi.org/10.26153/tsw/5792.

Council of Science Editors:

Dey R. Theoretical and experimental studies on topological insulators and topological insulator based spintronic devices. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/5792

University of Texas – Austin

6. Dong, Hui, Ph. D. Ultra-stable nano-manipulation of mechanically-variable system : optical forces and beyond.

Degree: PhD, Electrical and Computer Engineering, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/1367

► Optical force and acoustic force have been intensively investigated over the past several decades in the applications ranging from the optical/acoustic trapping, high-resolution biomedical imaging,… (more)

▼ Optical force and acoustic force have been intensively investigated over the past several decades in the applications ranging from the optical/acoustic trapping, high-resolution biomedical imaging, sensing technology, signal processing to acoustic levitation, ultrasonic calibration, etc. I started from the calculation of the optical force including both radiation pressure and electrostriction force in stimulated Brillouin scattering using finite-element method. Then I investigated the sufficient condition of creating conservative optical force field, which is hard to realize as the optical force generally contains inevitable rotational component in a multi-port system. To verify the conclusion, this condition has been subsequently applied to three scenarios, realizing auto-alignment of millimeter-scale photonic crystal slabs, simultaneously trapping and orientating nano-particles, and self-aligned topological photonic crystal. To overcome the material loss which breaks the conservativeness of the optical force, a compensating method using the gain media to recover the conservative optical force field is presented and verified by the vorticity ratio derived from Helmholtz-Hodge decomposition (HHD). As an analog to the optical radiation pressure but generally millions larger in magnitude, the acoustic radiation pressure calculation using the response theory is also proposed, which perfectly agrees with the traditional Reynold stress tensor integration and, more importantly, reveals the sufficient condition of conservative acoustic force. The contributions of this work are significant in four aspects in the area of numerical device simulation and parallel scientific computing: first of all, it paves the fundamental way to ultra-stable trapping by providing correct ways of numerically calculating optical/acoustic forces, which are corroborated by response theory developed in this work; secondly, the complete temporal coupled-mode theory unveils all spectral response of waveguide-resonator systems; thirdly, the parallel algorithm of HHD applied to periodic structure provides reliable metric to evaluate stability of trapping; finally, the newly developed weak-form formulation of topological photonic crystal with loss/gain helps design of novel photonic devices. Advisors/Committee Members: Wang, Zheng, Ph. D. (advisor), Hall, Neal (committee member), Lai, Keji (committee member), Lu, Nanshu (committee member), Yu, Edward (committee member).

Subjects/Keywords: Optical force; Acoustic force; Coupled-mode theory; Parallel Helmholtz-Hodge decomposition; Finite-element; Device optimization

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APA (6^th Edition):

Dong, Hui, P. D. (2019). Ultra-stable nano-manipulation of mechanically-variable system : optical forces and beyond. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/1367

Chicago Manual of Style (16^th Edition):

Dong, Hui, Ph D. “Ultra-stable nano-manipulation of mechanically-variable system : optical forces and beyond.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://dx.doi.org/10.26153/tsw/1367.

MLA Handbook (7^th Edition):

Dong, Hui, Ph D. “Ultra-stable nano-manipulation of mechanically-variable system : optical forces and beyond.” 2019. Web. 25 Jan 2021.

Vancouver:

Dong, Hui PD. Ultra-stable nano-manipulation of mechanically-variable system : optical forces and beyond. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Jan 25]. Available from: http://dx.doi.org/10.26153/tsw/1367.

Council of Science Editors:

Dong, Hui PD. Ultra-stable nano-manipulation of mechanically-variable system : optical forces and beyond. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/1367

University of Texas – Austin

7. Valsaraj, Amithraj. Atomistic simulations of 2D materials and van der Waal’s heterostructures for beyond-Si-CMOS devices.

Degree: PhD, Electrical and Computer Engineering, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/3132

► The unique electrical and optical properties of two-dimensional (2D) materials has spurred intense research interest towards development of nanoelectronic devices utilizing these novel materials. The… (more)

▼ The unique electrical and optical properties of two-dimensional (2D) materials has spurred intense research interest towards development of nanoelectronic devices utilizing these novel materials. The atomically thin form of 2D materials translates to excellent electrostatic gate control even at nanoscale channel length dimensions, near-ideal two-dimensional carrier behavior, and perhaps conventional and novel devices applications. Monolayer transition metal dichalcogenides (TMDs) are novel, gapped 2D materials. Toward device applications, I consider MoS₂ layers on dielectrics, in particular in this work, the effect of vacancies on the electronic structure. In density-functional-theory (DFT) simulations, the effects of near-interface oxygen vacancies in the oxide slab, and Mo or S vacancies in the MoS₂ layer are considered. Band structures and atom-projected densities of states for each system and with differing oxide terminations were calculated, as well as those for the defect-free MoS₂-dielectrics system and for isolated dielectric layers for reference. Among the results, I find that with O-vacancies, both the HfO₂-MoS₂ and the Al₂O₃-MoS₂ systems appear metallic due to doping of the oxide slab followed by electron transfer into the MoS₂, in manner analogous to modulation doping. The n-type doping of monolayer MoS₂ by high-k oxides with O-vacancies is confirmed through collaborative experimental work in which back-gated monolayer MoS₂ FETs encapsulated by oxygen deficient high-k oxides have been characterized. Van der Waal’s heterostructures allow for novel devices such as two-dimensional-to-two-dimensional tunnel devices, exemplified by interlayer tunnel FETs. These devices employ channel/tunnel-barrier/channel geometries. However, during layer-by-layer exfoliation of these multi-layer materials, rotational misalignment is the norm and may substantially affect device characteristics. In this work, by using density functional theory methods, I consider a reduction in tunneling due to weakened coupling across the rotationally misaligned interface between the channel layers and the tunnel barrier. As a prototypical system, I simulate the effects of rotational misalignment of the tunnel barrier layer between aligned channel layers in a graphene/hBN/graphene system. Rotational misalignment between the channel layers and the tunnel barrier in this van der Waal’s heterostructure can significantly reduce coupling between the channels by reducing, specifically, coupling across the interface between the channels and the tunnel barrier. This weakened coupling in graphene/hBN/graphene with hBN misalignment may be relevant to all such van der Waal’s heterostructures. TMDs are viable alternatives to graphene and hBN as channel and tunnel barrier layers, respectively, for improved performance in interlayer tunnel FET device structures. In particular, I used DFT simulations to study the bilayer-graphene/WSe₂/bilayer-graphene heterostructure as well as single and multilayer ReS₂-layer systems. Significant roadblocks to the… Advisors/Committee Members: Register, Leonard F. (advisor), Banerjee , Sanjay K. (committee member), Tutuc, Emanuel (committee member), Yu, Edward T. (committee member), MacDonald, Allan H. (committee member).

Subjects/Keywords: 2D materials; Van der Waal's heterostructures; DFT; ITFET; High-k doping

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APA (6^th Edition):

Valsaraj, A. (2019). Atomistic simulations of 2D materials and van der Waal’s heterostructures for beyond-Si-CMOS devices. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/3132

Chicago Manual of Style (16^th Edition):

Valsaraj, Amithraj. “Atomistic simulations of 2D materials and van der Waal’s heterostructures for beyond-Si-CMOS devices.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://dx.doi.org/10.26153/tsw/3132.

MLA Handbook (7^th Edition):

Valsaraj, Amithraj. “Atomistic simulations of 2D materials and van der Waal’s heterostructures for beyond-Si-CMOS devices.” 2019. Web. 25 Jan 2021.

Vancouver:

Valsaraj A. Atomistic simulations of 2D materials and van der Waal’s heterostructures for beyond-Si-CMOS devices. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Jan 25]. Available from: http://dx.doi.org/10.26153/tsw/3132.

Council of Science Editors:

Valsaraj A. Atomistic simulations of 2D materials and van der Waal’s heterostructures for beyond-Si-CMOS devices. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/3132

8. -6699-1973. Subwavelength and nonreciprocal optical and electromagnetic systems for sensing and communications.

Degree: PhD, Electrical and Computer Engineering, 2017, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/3111

► This dissertation is organized into three parts. First, the design for a radio frequency fiber transmission line built out of a grid of micrometer-scale conductors… (more)

▼ This dissertation is organized into three parts. First, the design for a radio frequency fiber transmission line built out of a grid of micrometer-scale conductors embedded in an insulating polymer cladding is presented to mitigate the skin and proximity effects. By adopting a checkerboard out-of-phase current phasing scheme, the internal inductance of the line is significantly lower than in two-conductor lines and results in an LC bandwidth of approximately 2 GHz, with flat attenuation and linear phase dispersion. The device performance is characterized in terms of its geometric degrees of freedom and a fabricated prototype is presented. Second, the kinetic inductive and plasmonic response of monolayer graphene in the terahertz spectrum is examined in the context of several important applications. The dispersive responses of two-dimensional graphene and three-dimensional copper transmission lines are compared to map the dispersive signaling performance in terms of transmission line cross-sectional size. This demonstrates a surprisingly broadband LC response with flat attenuation in nano-scale lines. This kinetic inductive response of graphene is demonstrated to miniaturize the photonic band structure of a photonic crystal slab where an in-plane periodicity of 300 nm has its photonic band gap in the terahertz spectrum. The sub-diffraction photonic band structure resembles that of the two-dimensional photonic crystal, supporting a wide photonic band gap in extremely thin slabs. The viability of graphene for cavity optomechanics is analyzed from near infrared to terahertz wavelengths, demonstrating a large optomechanical coupling, on the order of 3D optomechanical materials. Third, a class of nonreciprocal devices is proposed based on coupling to the sideband states, called Floquet resonances, that arise in temporally modulated optical resonators. The degrees of freedom in the modulating waveform tailor the energy exchange and phase of the Floquet resonances to realize unique nonreciprocal spectral responses in compact devices. We examine optical scattering from Floquet resonators coupled to narrowband waveguides using temporal coupled-mode theory. A three-port circulator is built out of a cascade of Floquet resonators to demonstrate broadband forward transmission and ideal isolation for dual-carrier waves. Full-wave numerical simulations in the coupled frequency domain demonstrate the circulator in an on-chip photonic crystal platform Advisors/Committee Members: Wang, Zheng, Ph. D. (advisor), Alù, Andrea (committee member), Bank, Seth R (committee member), Wang, Yaguo (committee member), Yu, Edward T (committee member).

Subjects/Keywords: Radio frequency; Microwave; Terahertz; Thz; Infrared; Optical; Optics; Communications; Sensing; Polycarbonate; Graphene transmission lines; Photonic crystals; Kinetic inductance; Plasmonics; Optomechanics; Nonreciprocal; Floquet; Modulation; Time-modulation

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APA (6^th Edition):

-6699-1973. (2017). Subwavelength and nonreciprocal optical and electromagnetic systems for sensing and communications. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/3111

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Chicago Manual of Style (16^th Edition):

-6699-1973. “Subwavelength and nonreciprocal optical and electromagnetic systems for sensing and communications.” 2017. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://dx.doi.org/10.26153/tsw/3111.

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Author name may be incomplete

MLA Handbook (7^th Edition):

-6699-1973. “Subwavelength and nonreciprocal optical and electromagnetic systems for sensing and communications.” 2017. Web. 25 Jan 2021.

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Author name may be incomplete

Vancouver:

-6699-1973. Subwavelength and nonreciprocal optical and electromagnetic systems for sensing and communications. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2017. [cited 2021 Jan 25]. Available from: http://dx.doi.org/10.26153/tsw/3111.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-6699-1973. Subwavelength and nonreciprocal optical and electromagnetic systems for sensing and communications. [Doctoral Dissertation]. University of Texas – Austin; 2017. Available from: http://dx.doi.org/10.26153/tsw/3111

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Texas – Austin

9. -0698-5627. Tip-enhanced Raman spectroscopy of strained semiconductor nanostructures.

Degree: PhD, Electrical and Computer Engineering, 2018, University of Texas – Austin

URL: http://hdl.handle.net/2152/65733

► Raman spectroscopy can serve as a powerful tool to probe the vibrational modes of solid state materials. By taking advantage of the enhanced electric fields… (more)

▼ Raman spectroscopy can serve as a powerful tool to probe the vibrational modes of solid state materials. By taking advantage of the enhanced electric fields caused by the surface-enhanced plasmon resonance of a noble metal coated atomic force microscopy tip, tip-enhanced Raman spectroscopy can dramatically increase local signal intensity and measurement spatial resolution. In this dissertation, work is presented on conventional and tip-enhanced Raman measurements of various semiconductor nanostructures with a specific focus on analyzing strain and strain related properties in these material systems. We use tip-enhanced Raman to study Ge-Si₀.₅Ge₀.₅ core-shell nanowires where we observe two distinct Ge-Ge mode Raman peaks that are affected by strain in the core-shell structure. Tip-enhanced measurements show dramatically increased sensitivity to the modes at the interface between the core and shell and a shift in position of this mode due to plasmonic field localization at the tip apex and the resulting change in phonon self-energy caused by increased coupling between phonons and intervalence-band carrier transitions. We also use tip-enhanced Raman spectroscopy to characterize unstrained and strained MoS₂ and show spatial resolution of approximately 100 nm in the measurements. The strain dependence of the second order Raman modes in MoS₂ reveals changes in the electronic band structure in strained MoS₂ that are manifested through changes in the Raman peak positions and peak area ratios, which are corroborated through density functional theory calculations. Finally, we use conventional Raman spectroscopy to probe uniaxially strained monolayer and three-layer WSe₂. Using mechanical modeling of strain in atomically thin WSe₂ on a stretched elastic substrate, we confirm complete transfer of strain from the substrate to the WSe₂ flakes and analyze the evolution of the Raman spectra with applied uniaxial strain above 1 percent. These studies enable us to experimentally determine the strain induced Raman shift for various Raman modes and to calculate the Grüneisen parameter and strain deformation potential for the first order in-plane Raman mode, with experimental values confirmed with theoretical values calculated using density functional theory. Advisors/Committee Members: Yu, Edward T. (advisor), Tutuc, Emanuel (committee member), Banerjee, Sanjay (committee member), Akinwande, Deji (committee member), Lai, Keji (committee member).

Subjects/Keywords: Raman spectroscopy; Scanning probe microscopy; TERS; Nanowire; 2D materials; Transition metal dichalcogenide; Strain

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APA (6^th Edition):

-0698-5627. (2018). Tip-enhanced Raman spectroscopy of strained semiconductor nanostructures. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/65733

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Chicago Manual of Style (16^th Edition):

-0698-5627. “Tip-enhanced Raman spectroscopy of strained semiconductor nanostructures.” 2018. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/65733.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-0698-5627. “Tip-enhanced Raman spectroscopy of strained semiconductor nanostructures.” 2018. Web. 25 Jan 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-0698-5627. Tip-enhanced Raman spectroscopy of strained semiconductor nanostructures. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2018. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/65733.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-0698-5627. Tip-enhanced Raman spectroscopy of strained semiconductor nanostructures. [Doctoral Dissertation]. University of Texas – Austin; 2018. Available from: http://hdl.handle.net/2152/65733

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Texas – Austin

10. Jin, Mingzhou. High sensitivity infrared nano-spectroscopy in ambient and water environment.

Degree: PhD, Electrical and Computer Engineering, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/2126

► Mid-infrared (mid-IR) vibrational spectroscopy is a universal label–free tool for identifying molecular compounds via their ‘fingerprint’ vibrational absorption lines. Infrared nano-spectroscopies with nanoscale spatial resolution… (more)

Subjects/Keywords: Near-field imaging; Infrared spectroscopy; Nano-spectroscopy; Atomic force microscopy

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APA (6^th Edition):

Jin, M. (2019). High sensitivity infrared nano-spectroscopy in ambient and water environment. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/2126

Chicago Manual of Style (16^th Edition):

Jin, Mingzhou. “High sensitivity infrared nano-spectroscopy in ambient and water environment.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://dx.doi.org/10.26153/tsw/2126.

MLA Handbook (7^th Edition):

Jin, Mingzhou. “High sensitivity infrared nano-spectroscopy in ambient and water environment.” 2019. Web. 25 Jan 2021.

Vancouver:

Jin M. High sensitivity infrared nano-spectroscopy in ambient and water environment. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Jan 25]. Available from: http://dx.doi.org/10.26153/tsw/2126.

Council of Science Editors:

Jin M. High sensitivity infrared nano-spectroscopy in ambient and water environment. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/2126

University of Texas – Austin

11. Ahn, Jaehyun. Optoelectronic devices for power conservation and generation.

Degree: PhD, Electrical and Computer Engineering, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/1280

► Energy conservation and generation have become increasingly important in society. Here, we pursue novel transistor technologies based on three-dimensional (3D) FinFETs and two-dimensional (2D) materials… (more)

▼ Energy conservation and generation have become increasingly important in society. Here, we pursue novel transistor technologies based on three-dimensional (3D) FinFETs and two-dimensional (2D) materials to make low power, high speed transistors. We also develop quasi-2D silicon thin film solar cells for power generation. First, a novel approach of doping III-V semiconductors is presented. Oxygen rich silicon oxide (SiO [subscript x], where x > 2) is found to behave as a solid dopant source when deposited on InGaAs, followed by thermal annealing. Oxygen, when diffused into InGaAs, act as n-type dopants where the active carrier concentration reaches up to 1.4 x 10¹⁸ cm³. Besides the simple, CMOS compatible doping technique of solid source doping, another interesting factor is the dopant concentration can be altered by the deposited dopant thickness, which adds an additional control knob therefore allowing enhanced control over the doping process. Thermally induced compressive stress within InGaAs due to the difference in coefficient of thermal expansion (CTE) between InGaAs and SiO [subscript x] is known to increase the number of vacancies within InGaAs therefore giving rise to active dopant concentration. This approach can be used to make high speed, low power transistors. Second, study of thin indium metal contacts on InGaAs is presented. Unlike silicon, III-V compound semiconductors such as InGaAs decomposes around 450 ˚C which result in out-diffusion of indium and gallium and decrease in metal-InGaAs contact resistance. By adding a thin layer of indium between the metal-InGaAs interface, the out-diffusion of gallium was minimized. Third, solar cells based on graphene-silicon (GS) heterojunction architecture are demonstrated on bendable crystalline silicon substrates. Flexible, thin silicon films are fabricated by using the thermal expansion difference between electroplated nickel and bulk silicon, which generates residual strain upon thermal cycling. By controlling the amount of thermal stress, silicon thicknesses between 8 and 35 µm are exfoliated through a kerf-less mechanical method. Together with multi-layer graphene (MLG) grown by chemical vapor deposition (CVD) and atomic layer deposition (ALD) of Al₂O₃ as a silicon passivation layer, power conversion efficiencies (PCE) of 7.4 % were achieved on bendable silicon substrates. Finally, Chapter 7 summarizes the all the chapters from this dissertation and some thoughts for future work. Advisors/Committee Members: Banerjee, Sanjay (advisor), Yu, Edward (committee member), Register, Leonard F (committee member), Sreenivasan, S V (committee member), Korgel, Brian (committee member).

Subjects/Keywords: Post-silicon; Energy generation

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APA (6^th Edition):

Ahn, J. (2019). Optoelectronic devices for power conservation and generation. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/1280

Chicago Manual of Style (16^th Edition):

Ahn, Jaehyun. “Optoelectronic devices for power conservation and generation.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://dx.doi.org/10.26153/tsw/1280.

MLA Handbook (7^th Edition):

Ahn, Jaehyun. “Optoelectronic devices for power conservation and generation.” 2019. Web. 25 Jan 2021.

Vancouver:

Ahn J. Optoelectronic devices for power conservation and generation. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Jan 25]. Available from: http://dx.doi.org/10.26153/tsw/1280.

Council of Science Editors:

Ahn J. Optoelectronic devices for power conservation and generation. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/1280

University of Texas – Austin

12. Kim, Ki Hyun. Development of high-speed imaging techniques for C. elegans nervous system studies.

Degree: PhD, Electrical and Computer Engineering, 2016, University of Texas – Austin

URL: http://hdl.handle.net/2152/68306

► We report high-speed imaging techniques for C. elegans nervous systems studies. We introduce C. elegans, the main model organism in this dissertation, and neuroscientific and… (more)

▼ We report high-speed imaging techniques for C. elegans nervous systems studies. We introduce C. elegans, the main model organism in this dissertation, and neuroscientific and biomedical studies using C. elegans involving calcium imaging, nerve regeneration, and drug screening. We review technologies including confocal microscopy and microfluidic devices used in the neuroscientific and biomedical studies We discuss development of a high-speed laser scanning confocal microscope capable of flexible control of imaging conditions, fast imaging speed, and large field-of-view. We provides the design principles used in the development of the confocal microscope including the optical, electrical, and software implementation, and the details of the confocal microscope we built based on the design principles. We present the performance characterization of the confocal microscope, then a few sample images obtained with the confocal microscope. We present development of time-lapse volumetric confocal imaging of whole animal C. elegans Ca²⁺ dynamics. We provide the design of the time-lapse volumetric confocal imaging system including a microfluidic device to accommodate the whole animal within the field-of-view of the imaging system. We examine the feasibility of the volumetric confocal imaging of a whole animal, and demonstrate imaging of the whole animal C. elegans neurons’ response to NaCl within a 630 × 150 × 25 μm³ volume at 2 Hz rate. We report a high-throughput automated imaging platform for C. elegans nerve regeneration study. We describe the design of the automated imaging platform and the automation flow, and characterizes the performance of the platform. The imaging platform can obtain high-resolution 3D confocal images of 20 animals in 10 minutes. We show sample images of C. elegans anterior lateral microtubule nerve regeneration examples acquired via the automated imaging platform. We demonstrate a planar laser activated neuronal scanning platform (PLANS), a high-throughput animal examination system for drug screening. We explain the construction of PLANS involving the optics, the microfluidic device, and the electronics. The PLANS system can scan an animal in less than 5 ms with a spatial sampling resolution of 3 μm FWHM. We show sample scanning results of a Huntington’s disease model of C. elegans. We summarize the studies discussed in this dissertation, and suggest relevant future research to follow up on the studies. Advisors/Committee Members: Ben-Yakar, Adela (advisor), Yu, Edward (committee member), Tunnell, James (committee member), Pierce-Shimomura, Jonathan (committee member), Bank, Seth (committee member).

Subjects/Keywords: Confocal microscopy; Instrumentation; Biomedical

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APA (6^th Edition):

Kim, K. H. (2016). Development of high-speed imaging techniques for C. elegans nervous system studies. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/68306

Chicago Manual of Style (16^th Edition):

Kim, Ki Hyun. “Development of high-speed imaging techniques for C. elegans nervous system studies.” 2016. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/68306.

MLA Handbook (7^th Edition):

Kim, Ki Hyun. “Development of high-speed imaging techniques for C. elegans nervous system studies.” 2016. Web. 25 Jan 2021.

Vancouver:

Kim KH. Development of high-speed imaging techniques for C. elegans nervous system studies. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2016. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/68306.

Council of Science Editors:

Kim KH. Development of high-speed imaging techniques for C. elegans nervous system studies. [Doctoral Dissertation]. University of Texas – Austin; 2016. Available from: http://hdl.handle.net/2152/68306

University of Texas – Austin

13. Hsieh, Cheng Chih. Cerium oxide based resistive random access memory devices.

Degree: PhD, Electrical and Computer Engineering, 2017, University of Texas – Austin

URL: http://hdl.handle.net/2152/63012

► Resistive Random Access Memory (RRAM) is an emerging technology of non-volatile memory (NVM). Although the observation of metal oxide that can undergo an abrupt insulator-metal… (more)

Subjects/Keywords: Non-volatile memory; Neuromorphic computing; Deep learning; Machine learning; Memory

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APA (6^th Edition):

Hsieh, C. C. (2017). Cerium oxide based resistive random access memory devices. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/63012

Chicago Manual of Style (16^th Edition):

Hsieh, Cheng Chih. “Cerium oxide based resistive random access memory devices.” 2017. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/63012.

MLA Handbook (7^th Edition):

Hsieh, Cheng Chih. “Cerium oxide based resistive random access memory devices.” 2017. Web. 25 Jan 2021.

Vancouver:

Hsieh CC. Cerium oxide based resistive random access memory devices. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2017. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/63012.

Council of Science Editors:

Hsieh CC. Cerium oxide based resistive random access memory devices. [Doctoral Dissertation]. University of Texas – Austin; 2017. Available from: http://hdl.handle.net/2152/63012

University of Texas – Austin

14. Zhang, Zizhuo. Area-selective deposition of ferromagnetic cobalt films.

Degree: PhD, Chemical Engineering, 2018, University of Texas – Austin

URL: http://hdl.handle.net/2152/68479

► Cobalt is a classic ferromagnetic material and finds applications in magnetic random access memory devices. As an emerging patterning technique, area-selective atomic layer deposition (AS-ALD)… (more)

▼ Cobalt is a classic ferromagnetic material and finds applications in magnetic random access memory devices. As an emerging patterning technique, area-selective atomic layer deposition (AS-ALD) of cobalt films has the advantages of low cost and low film damage compared with the current patterning approach of photolithography followed by etching of cobalt films. This research explores the routes to realize the AS-ALD of ferromagnetic cobalt films. Carbon-free Co films have been deposited on MgO(001) and SiO₂/Si substrates by low temperature thermal ALD of CoO and subsequent low temperature atomic deuterium reduction of CoO. While high temperature D₂ reduction of CoO results in rough and disconnected Co islands, low temperature D reduction of CoO produces smooth and continuous Co films. The Co films produced by low temperature D reduction exhibit a smaller coercivity than the Co films produced by high temperature D₂ reduction. Reduction conditions affect the microstructure and the magnetic properties of the reduced Co films. The process-structure-property relationship has been elucidated. The increase of reduction temperature, partial pressure of deuterium, and reaction time increases the average grain size and coercivity of the reduced Co films. Co films that are grown on substrates with lower dewetting tendency, such as MgO and Al₂O₃, show smaller average grain size and smaller coercivity. Polystyrene (PS) has been proposed to work as a passivation material to realize the AS-ALD of cobalt films. PS is effective in inhibiting the nucleation and film growth of CoO on oxide substrates. Micro-patterns and nano-patterns of CoO have been grown by AS-ALD through PS templates produced by photolithography and PS templates created by directed self-assembly of diblock copolymer, respectively. CoO patterns can be further reduced to form Co patterns without deformation. Advisors/Committee Members: Ekerdt, John G. (advisor), Hwang, Gyeong S. (committee member), Lynd, Nathaniel (committee member), Yu, Edward T. (committee member).

Subjects/Keywords: Area-selective deposition; Ferromagnetic material; Cobalt

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APA (6^th Edition):

Zhang, Z. (2018). Area-selective deposition of ferromagnetic cobalt films. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/68479

Chicago Manual of Style (16^th Edition):

Zhang, Zizhuo. “Area-selective deposition of ferromagnetic cobalt films.” 2018. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/68479.

MLA Handbook (7^th Edition):

Zhang, Zizhuo. “Area-selective deposition of ferromagnetic cobalt films.” 2018. Web. 25 Jan 2021.

Vancouver:

Zhang Z. Area-selective deposition of ferromagnetic cobalt films. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2018. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/68479.

Council of Science Editors:

Zhang Z. Area-selective deposition of ferromagnetic cobalt films. [Doctoral Dissertation]. University of Texas – Austin; 2018. Available from: http://hdl.handle.net/2152/68479

University of Texas – Austin

15. Chen, Boxue. Electrically active microfluidic fibers.

Degree: PhD, Electrical and Computer Engineering, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/2217

► In recent years, novel materials processing techniques involving PDMS and paper materials have enabled revolutionary progress in performance and capability of chip-scale microfluidics. However, microfluidic… (more)

▼ In recent years, novel materials processing techniques involving PDMS and paper materials have enabled revolutionary progress in performance and capability of chip-scale microfluidics. However, microfluidic systems remain largely single-chip constructs, and are far from the level of sophistication that is typically seen in multi-chip multi-board electronic systems. A major limitation lies in the fluidic chip-to-chip interconnects, where the simple tubing materials and structures lack the pumping and monitoring functionalities that are needed in reliable microfluidic systems. In this dissertation, we address these challenges with the new structures and materials made available by multimaterial fiber processes, which have recently emerged as a materials platform for a variety of sensing modalities. Various functionalities, such as flow actuators or sensors, are integrated into multimaterial fibers for functional chip feedlines. Integrated fiber pumps are enabled by electrowetting-on-dielectric (EWOD) actuation to precisely manipulate liquid flow. Fiber drawing process allows creating an ultra-thin and uniform dielectric layer, and hence achieving rapid flow response and predictable flow behaviors. Fiber thermal flow sensors, on the other hand, take the advantage of ultra-fast heat transfer at microscale to break the fundamental trade-off between sensitivity, pressure drop, measurement range, and temperature rise in conventional thermal flow sensors. Record-setting flowrate sensitivity was demonstrated over a wide measurement range and unprecedentedly low pressure drop. As a natural extension to the project of fiber flow sensors, we also present the theoretic optimization of geometric and segmentation design of fiber flow sensors to further boost sensitivity and extend measurement range. A new two-segment structure was demonstrated in simulation with greatly extended measurement range and much simpler post-drawing process. At last, we proposed a general strategy for distributed sensing, which was later applied to present distributed flow sensors. Sub-cm spatial resolution was demonstrated in simulations. Taken as a whole, electrically active microfluidic fibers take advantage of novel materials and new device structures that deliver new functionality and significant improvements in performance. This unconventional form of devices paves the way towards a complete functional overhaul of microfluidics feed lines needed in large-scale multi-chip integration in microfluidics and opens new possibilities in lab-on-fiber technologies. Advisors/Committee Members: Wang, Zheng, Ph. D. (advisor), Ho, Paul S (committee member), Lu, Nanshu (committee member), Zheng, Yuebing (committee member), Yu, Edward T (committee member).

Subjects/Keywords: Multimaterial fibers; Microfluidics; Fiber pumps; Fiber flow sensors; Fiber distributed sensors; Flexible electronics

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APA (6^th Edition):

Chen, B. (2019). Electrically active microfluidic fibers. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/2217

Chicago Manual of Style (16^th Edition):

Chen, Boxue. “Electrically active microfluidic fibers.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://dx.doi.org/10.26153/tsw/2217.

MLA Handbook (7^th Edition):

Chen, Boxue. “Electrically active microfluidic fibers.” 2019. Web. 25 Jan 2021.

Vancouver:

Chen B. Electrically active microfluidic fibers. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Jan 25]. Available from: http://dx.doi.org/10.26153/tsw/2217.

Council of Science Editors:

Chen B. Electrically active microfluidic fibers. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/2217

University of Texas – Austin

16. -2257-1969. Exploring novel properties of atomically smooth metal films as an ideal platform for nano photonics.

Degree: PhD, Physics, 2016, University of Texas – Austin

URL: http://hdl.handle.net/2152/47133

► Plasmonics is the science of manipulating light at the metal and dielectric interface. Therefore, a high-quality metal film plays a critical role in this exciting… (more)

▼ Plasmonics is the science of manipulating light at the metal and dielectric interface. Therefore, a high-quality metal film plays a critical role in this exciting frontier of research. Among available plasmonic metals, silver (Ag) and aluminum (Al) is of particular interest. Ag is a widely used plasmonic material because of its intrinsic low loss. However, conventional thermal Ag films usually show rough surfaces (root-mean-square roughness is as large as several nanometers) and polycrystalline structures with grain boundaries. These features lead to significant plasmonic loss. Preparing an atomically smooth epitaxial Ag film is thus a very critical step in the developement of plasmonics. However, due to the pinning of grain boundaries by contaminants and the propensity to dewetting from commonly used semiconductor substrates (such as Si and GaAs), Ag is a very unforgiving material in the perspective of film growth. In this dissertation we are going to report novel methods to overcome these difficulties and realize the epitaxial growth of atomically smooth Ag films on Si(111). We will show that our films possess excellent optical properties with extraordinarily low loss. The significantly narrow distribution of the lifetime of giant quantum dots placed on our Ag film is another demonstration that our films perfectly apply to, and thus facilitate, the research in plasmonics and quantum photonics. In recent years Al is demonstrated to be an excellent platform for ultraviolet (UV) plasmonics. However, Al is highly reactive with oxygen and can be rapidly oxidized once exposed to even a low partial pressure of oxygen (10⁻⁸ Torr). Therefore it will be very challenging to prepare high-purity Al films. In this dissertation we are going to demonstrate the epitaxial growth of high-purity, atomically smooth Al films on Si(111) with different growth methods accompanied by an optimally controlled, ultraclean method of oxidation. Our epitaxial Al films demonstrate considerable loss reduction in the UV spectral range, in comparison to the polycrystalline Al films. These high-quality epitaxial Al films provide an ideal platform for UV plasmonics. Moreover, the availability of newly-obtained intrinsic optical constants on our single-crystalline Al films from the spectroscopic ellipsometry measurement enables a more accurate theoretical prediction in the design of nano-plasmonic devices. Advisors/Committee Members: Shih, Chih-Kang (advisor), de Lozanne, Alejandro (committee member), Demkov, Alexander (committee member), Li, Xiaoqin (committee member), Yu, Edward T. (committee member).

Subjects/Keywords: Epitaxial growth; Single-crystalline silver and aluminum; Intrinsic optical constants; Ellipsometry; Plasmonics; Nano photonics

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APA (6^th Edition):

-2257-1969. (2016). Exploring novel properties of atomically smooth metal films as an ideal platform for nano photonics. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/47133

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Chicago Manual of Style (16^th Edition):

-2257-1969. “Exploring novel properties of atomically smooth metal films as an ideal platform for nano photonics.” 2016. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/47133.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-2257-1969. “Exploring novel properties of atomically smooth metal films as an ideal platform for nano photonics.” 2016. Web. 25 Jan 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-2257-1969. Exploring novel properties of atomically smooth metal films as an ideal platform for nano photonics. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2016. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/47133.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-2257-1969. Exploring novel properties of atomically smooth metal films as an ideal platform for nano photonics. [Doctoral Dissertation]. University of Texas – Austin; 2016. Available from: http://hdl.handle.net/2152/47133

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University of Texas – Austin

17. Lu, Ph. D., Feng. Infrared nano-spectroscopy via molecular expansion force detection.

Degree: PhD, Electrical and Computer engineering, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/33402

► Mid-infrared absorption spectroscopy in the “molecular fingerprint” region (λ = 2.5–15 μm) is widely used for in situ analysis of chemical and biological samples. Due… (more)

▼ Mid-infrared absorption spectroscopy in the “molecular fingerprint” region (λ = 2.5–15 μm) is widely used for in situ analysis of chemical and biological samples. Due to the diffraction limit, traditional far-field techniques such as Fourier-transform infrared spectroscopy cannot take sample spectra with nanometer spatial resolution. To conduct nanoscale infrared measurement, in photoexpansion nano-spectroscopy, an atomic force microscope cantilever is used as a light absorption detector, in the way that the cantilever is deflected proportionally by the localized sample heating and expansion induced by infrared pulses. Previous studies of this new opto-mechanical technique demonstrated its powerfulness and simplicity, but relied on using high-power laser pulses to produce detectable cantilever deflection signal and it was difficult to measure ultra-thin samples below ~100 nm. In addition, the spatial resolution, though improved, is limited by the thermal diffusion length inside samples. This dissertation presents a set of experiments which have substantially improved photoexpansion nano-spectroscopy in terms of sensitivity and spatial resolution, and have explored other aspects of this technique. For the first time, high-quality photoexpansion spectra have been obtained from molecular monolayers using low-power infrared pulses from a tunable quantum cascade laser. The orders of magnitude improvement in sensitivity is due to the two methods we implemented: mechanical enhancement by the cantilever resonance, and optical enhancement by the metalized cantilever tip. The spatial resolution is also improved and only determined by the locally enhanced field below the tip. After that, the dissertation shows the spectral background signal, which comes from infrared absorption by the substrate and tip, can be suppressed using a second laser. We have also investigated the nonlinearity of tip-sample interaction, and are able to detect sample photoexpansion force at heterodyne frequency. In the last part of this dissertation, we use our technique to image local optical energy distribution and ohmic heat dissipation of the metal nanoantennas. Advisors/Committee Members: Belkin, Mikhail A. (advisor), Yu, Edward (committee member), Dodabalapur, Ananth (committee member), Shvets, Gennady (committee member), Ellison, Christopher (committee member).

Subjects/Keywords: Infrared spectroscopy; Nanoscale characterization

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APA (6^th Edition):

Lu, Ph. D., F. (2015). Infrared nano-spectroscopy via molecular expansion force detection. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/33402

Chicago Manual of Style (16^th Edition):

Lu, Ph. D., Feng. “Infrared nano-spectroscopy via molecular expansion force detection.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/33402.

MLA Handbook (7^th Edition):

Lu, Ph. D., Feng. “Infrared nano-spectroscopy via molecular expansion force detection.” 2015. Web. 25 Jan 2021.

Vancouver:

Lu, Ph. D. F. Infrared nano-spectroscopy via molecular expansion force detection. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/33402.

Council of Science Editors:

Lu, Ph. D. F. Infrared nano-spectroscopy via molecular expansion force detection. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/33402

University of Texas – Austin

18. Lee, Kayoung. Quantum transport in bilayer graphene and its heterostructures.

Degree: PhD, Electrical and Computer Engineering, 2016, University of Texas – Austin

URL: http://hdl.handle.net/2152/68250

► Bilayer graphene represents an attractive two-dimensional electron system for electron physics and potential device applications. In this dissertation, we present a comprehensive experimental study of… (more)

Subjects/Keywords: Bilayer graphene; Quantum transport

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APA (6^th Edition):

Lee, K. (2016). Quantum transport in bilayer graphene and its heterostructures. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/68250

Chicago Manual of Style (16^th Edition):

Lee, Kayoung. “Quantum transport in bilayer graphene and its heterostructures.” 2016. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/68250.

MLA Handbook (7^th Edition):

Lee, Kayoung. “Quantum transport in bilayer graphene and its heterostructures.” 2016. Web. 25 Jan 2021.

Vancouver:

Lee K. Quantum transport in bilayer graphene and its heterostructures. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2016. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/68250.

Council of Science Editors:

Lee K. Quantum transport in bilayer graphene and its heterostructures. [Doctoral Dissertation]. University of Texas – Austin; 2016. Available from: http://hdl.handle.net/2152/68250

University of Texas – Austin

19. Dev, Sukrith Umesh. Infrared detection and materials characterization using microwave resonators.

Degree: PhD, Electrical and Computer Engineering, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/8144

► The radio frequency (RF) and microwave regions of the electromagnetic (EM) spectrum have seen incredible advances over the last few decades. RF components have become… (more)

▼ The radio frequency (RF) and microwave regions of the electromagnetic (EM) spectrum have seen incredible advances over the last few decades. RF components have become more compact, inexpensive, and accessible while still maintaining high performance. Applications such as communications or sensing that were originally intended for the military have now become commercial and used regularly by the majority of citizens. On the other hand, the mid-infrared (MIR) region of the EM spectrum, although gaining significant attention in recent years, does not have the same widespread material and device infrastructure associated with the RF. This dissertation seeks to exploit the maturity of the RF spectral range for infrared applications. Specifically, we utilize resonant microwave circuits, microwave split ring resonators (SRRs), as an effective means of mid-infrared detection and materials characterization. The presented work is primarily divided into three research thrusts. Ultimately, because the goal of this dissertation is to employ microwave resonators to interact with semiconductor materials, to determine the position of greatest field strength in our microwave circuits, the first technique introduced is the microwave mapping by optically induced conductance (MMOIC). In the MMOIC, a resonant microwave circuit is driven by a continuous wave (CW) RF source, while a laser simultaneously optically excites the semiconductor on which the circuit is fabricated. It is shown that the optically modulated signal is proportional to the square root of the RF power, suggesting that the response provides a measurement of relative electric field strength. It is demonstrated that when the circuit is driven on resonance, the spatial position of greatest field is located within the capacitive split-gap of the SRR. In the second presented technique, the micro-scale time-resolved microwave resonator response (µ-TRMRR), the SRR circuit is used to characterize the time-response of a micro-scale infrared pixel capacitively loaded in the split-gap. While driving the circuit on resonance, a pulsed laser excites electron-hole pairs (EHPs) in the pixel, modulating the amplitude of the transmitted carrier wave. By reading out the modulated carrier amplitude as a function of time via a Schottky diode RF detector, the minority carrier lifetime of the micro-scale material is effectively characterized. Results are compared with time-resolved photoluminescence (TRPL), and it is demonstrated that for this material system, the µ-TRMRR has a > 10⁵ improvement in sensitivity relative to TRPL. Next, the coupled pixel-SRR architecture, dubbed as the resonant microwave photoconductor (RMPC), is evaluated as a candidate for room temperature MIR detection. A noise analysis is performed on the RMPC, and it is found that the resonator can shape and suppress Johnson noise generated from the reactively coupled pixel. When compared to a standard DC photoconductor (DCPC) utilizing similar infrared absorber material, the RMPC architecture demonstrates a factor of three… Advisors/Committee Members: Wasserman, Daniel, 1976- (advisor), Bank, Seth R (committee member), Tutuc, Emanuel (committee member), Yu, Edward T (committee member), Allen, Jeffery W (committee member).

Subjects/Keywords: Infrared detection; RF-photonics

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APA (6^th Edition):

Dev, S. U. (2019). Infrared detection and materials characterization using microwave resonators. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/8144

Chicago Manual of Style (16^th Edition):

Dev, Sukrith Umesh. “Infrared detection and materials characterization using microwave resonators.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://dx.doi.org/10.26153/tsw/8144.

MLA Handbook (7^th Edition):

Dev, Sukrith Umesh. “Infrared detection and materials characterization using microwave resonators.” 2019. Web. 25 Jan 2021.

Vancouver:

Dev SU. Infrared detection and materials characterization using microwave resonators. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Jan 25]. Available from: http://dx.doi.org/10.26153/tsw/8144.

Council of Science Editors:

Dev SU. Infrared detection and materials characterization using microwave resonators. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/8144

University of Texas – Austin

20. Ji, Li. Metal-oxide-semiconductor photoelectrodes for solar water splitting.

Degree: PhD, Electrical and Computer engineering, 2016, University of Texas – Austin

URL: http://hdl.handle.net/2152/40317

► The rapidly increasing global demand for energy, combined with the environmental impact of fossil fuels, has spurred the search for alternative sources of clean energy.… (more)

▼ The rapidly increasing global demand for energy, combined with the environmental impact of fossil fuels, has spurred the search for alternative sources of clean energy. One promising approach is to convert solar energy into hydrogen fuel using photoelectrochemical cells. However, the semiconducting photoelectrodes used in these cells typically have low efficiencies and/or stabilities. This dissertation will describe engineering of metal-oxide-semiconductor (MIS) photoelectrodes for application in solar water splitting. First, we show that a silicon-based photocathode with an epitaxial oxide capping layer can provide efficient and stable hydrogen production from water. In particular, we grow a thin epitaxial layer of strontium titanate (SrTiO3) directly on Si (001) by molecular beam epitaxy. Photogenerated electrons can be easily transported through this layer because of the conduction band alignment and lattice match between single crystalline SrTiO3 and silicon. The approach is used to create a metal-insulator-semiconductor photocathode that under broad-spectrum illumination at 100 mW/cm2 exhibits a maximum photocurrent density of 35 mA cm2 and an open circuit potential of 450 mV; there was no observable decrease in performance after 10 hours of operation in 0.5 M H2SO4. Then, we propose and demonstrate a general method to decouple the two roles of the insulator by employing localized dielectric breakdown. This approach allows the insulator to be thick, which enhances stability, while enabling low-resistance carrier transport as required for efficiency. This method can be applied to various-oxides, such as SiO2 and Al2O3. In addition, it is suitable for silicon, III-V, and other optical absorbers for both photocathodes and photoanodes. Finally, the thick metal-oxide layer can serve as a thin-film antireflection coating, which increases light absorption efficiency. Advisors/Committee Members: Yu, Edward T. (advisor), Bard, Allen J. (advisor), Lee, Jack C (committee member), Ekerdt, John (committee member), Akinwande, Deji (committee member).

Subjects/Keywords: Metal-oxide-semiconductor; Water splitting

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APA (6^th Edition):

Ji, L. (2016). Metal-oxide-semiconductor photoelectrodes for solar water splitting. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/40317

Chicago Manual of Style (16^th Edition):

Ji, Li. “Metal-oxide-semiconductor photoelectrodes for solar water splitting.” 2016. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/40317.

MLA Handbook (7^th Edition):

Ji, Li. “Metal-oxide-semiconductor photoelectrodes for solar water splitting.” 2016. Web. 25 Jan 2021.

Vancouver:

Ji L. Metal-oxide-semiconductor photoelectrodes for solar water splitting. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2016. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/40317.

Council of Science Editors:

Ji L. Metal-oxide-semiconductor photoelectrodes for solar water splitting. [Doctoral Dissertation]. University of Texas – Austin; 2016. Available from: http://hdl.handle.net/2152/40317

University of Texas – Austin

21. Ironside, Daniel Joseph. Embedded dielectric microstructures in molecular beam epitaxy : high-quality planar coalescence toward enhanced optoelectronic materials.

Degree: PhD, Electrical and Computer Engineering, 2018, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/2861

► Seamless integration of embedded dielectric microstructures in III-V crystal growth is a continued area of research due to its numerous high-impact applications. Historically, investigations into… (more)

▼ Seamless integration of embedded dielectric microstructures in III-V crystal growth is a continued area of research due to its numerous high-impact applications. Historically, investigations into embedded dielectric microstructures within existing crystal growth techniques were focused on blocking dislocations at the III-V/dielectric interface in the production of low defect relaxed high mismatched heteroepitaxy. However, recent efforts have broadened the use of embedded dielectric microstructures for enhancement of optoelectronic device functionality and development of monolithic growth schemes toward integrated photonic circuits. The central challenge of embedding dielectric microstructures in III-V materials is achieving single-crystal high-quality planar coalescence within existing conventional III-V crystal growth techniques without defect. While prevalent in the field of III-V crystal growth, solid-source Molecular Beam Epitaxy (MBE) has a well-known "coalescence problem," historically lacking approaches that achieve planar coalescence over dielectric microstructures. Limited coalescence is in large part due to low diffusion of III-adatoms on dielectric surfaces, typically below 300nm, readily forming polycrystalline deposition on dielectric surfaces exceeding this diffusion length. Several solid-source MBE highly-selective growth and lateral epitaxial overgrowth (LEO) growth approaches have been reported; however, none demonstrating complete planar coalescence over dielectric microstructures. In this dissertation, to overcome the "coalescence problem," we demonstrate for the first time a general methodology for an all-MBE growth of high-quality planar coalescence over a variety of embedded dielectric microstructures. Underpinning the approach, we developed a two-stage all-MBE growth approach for GaAs and InAs on (001) substrates, producing highly selective LEO and planarization, returning the growth front to the (001) surface. Characterization of the growth approach demonstrates for the first time an all-MBE approach to planar coalescence. In application of the two-stage all-MBE growth approach towards photonics, we demonstrate enhancement of quantum emitters using buried silica gratings arrays and develop several methodologies for embedded high-contrast photonic materials through self-formed air voids and molded air channel processes. Lastly, in application to high-quality relaxed high mismatch heteroepitaxy, we demonstrate for the first time an all-MBE approach to III-V metamorphic heteroepitaxy, demonstrating threading dislocation reduction in InAs/GaAs metamorphics with high fill factor embedded silica gratings. Thus, from the material presented here, we provide several significant advances to the long-standing challenge of marrying high-quality semiconductor crystal growth with dielectric microstructures, unlocking several high-impact applications, including high-quality material pathways for enhanced quantum emitters and embedded metasurfaces as well as an all-MBE approach toward… Advisors/Committee Members: Bank, Seth Robert (advisor), Wasserman, Daniel (committee member), Li, Xiaoqin (Elaine) (committee member), Yu, Edward T (committee member), Wang, Zheng (committee member).

Subjects/Keywords: Crystal growth; MBE; III-V; Semiconductor; LEO; Lateral growth; Photonics; Metamaterials; Metamorphics; High contrast; Emitter

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APA (6^th Edition):

Ironside, D. J. (2018). Embedded dielectric microstructures in molecular beam epitaxy : high-quality planar coalescence toward enhanced optoelectronic materials. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/2861

Chicago Manual of Style (16^th Edition):

Ironside, Daniel Joseph. “Embedded dielectric microstructures in molecular beam epitaxy : high-quality planar coalescence toward enhanced optoelectronic materials.” 2018. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://dx.doi.org/10.26153/tsw/2861.

MLA Handbook (7^th Edition):

Ironside, Daniel Joseph. “Embedded dielectric microstructures in molecular beam epitaxy : high-quality planar coalescence toward enhanced optoelectronic materials.” 2018. Web. 25 Jan 2021.

Vancouver:

Ironside DJ. Embedded dielectric microstructures in molecular beam epitaxy : high-quality planar coalescence toward enhanced optoelectronic materials. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2018. [cited 2021 Jan 25]. Available from: http://dx.doi.org/10.26153/tsw/2861.

Council of Science Editors:

Ironside DJ. Embedded dielectric microstructures in molecular beam epitaxy : high-quality planar coalescence toward enhanced optoelectronic materials. [Doctoral Dissertation]. University of Texas – Austin; 2018. Available from: http://dx.doi.org/10.26153/tsw/2861

University of Texas – Austin

22. Jiang, Aiting. Widely tunable terahertz semiconductor laser sources.

Degree: PhD, Electrical and Computer engineering, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/33388

► Terahertz Quantum Cascade Lasers (THz QCLs) and Terahertz Difference Frequency Generation Quantum Cascade Laser sources (DFG-QCLs) are two types of semiconductor THz radiation sources that… (more)

▼ Terahertz Quantum Cascade Lasers (THz QCLs) and Terahertz Difference Frequency Generation Quantum Cascade Laser sources (DFG-QCLs) are two types of semiconductor THz radiation sources that are compact and amenable to production in mass quantities. THz QCL can generate over 1W of power under cryogenic temperatures, while THz DFG-QCL can be operated under room temperature over 1mW level output. For either case, widely tunable solution is highly desired for spectroscopy applications. For THz QCLs, operation is still limited to cryogenic temperature and broad tuning is not available. Our experimental study shows that using variable barriers is a viable approach to enhance the design space for THz QCLs. We also propose to tune the spectral output of these devices using an optically projected variable distributed feedback grating. Tuning will be achieved by changing the projected grating period. Preliminary experimental results support the idea but higher pumping light intensity is required for this method to work. For THz DFG-QCLs, very broad tuning in 1-6 THz range has been demonstrated using rotating diffraction grating in an external cavity setup. Similar tuning range can also be achieved in a monolithic configuration. Based on the previous work which demonstrated an electrical monolithic tuner with 580 GHz tuning range, we design and test in this dissertation a linear array of 10 DFG-QCL devices to cover a 2 THz tuning range. An independent gain control scheme is developed to achieve high yield (~100%) of individual device. It is implemented via independent current pumping of two electrically isolated sections. Surface DFB grating and independent current pumping scheme used in our DFG QCLs is found to be useful for mid-IR QCL array sources. We propose a longitudinal integration scheme of multiple grating sections. It enables a single ridge to emit single mode radiation at different wavelengths upon selection. This helps to reduce mid-IR QCL array far field span. We demonstrated single ridge devices that can emit 2 or 3 different wavelengths upon selection. Advisors/Committee Members: Belkin, Mikhail A. (advisor), Akinwande, Deji (committee member), Bank, Seth R (committee member), Yu, Edward T (committee member), Belyanin, Alexey (committee member).

Subjects/Keywords: THz; Semiconductor laser; Tunable

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APA (6^th Edition):

Jiang, A. (2015). Widely tunable terahertz semiconductor laser sources. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/33388

Chicago Manual of Style (16^th Edition):

Jiang, Aiting. “Widely tunable terahertz semiconductor laser sources.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/33388.

MLA Handbook (7^th Edition):

Jiang, Aiting. “Widely tunable terahertz semiconductor laser sources.” 2015. Web. 25 Jan 2021.

Vancouver:

Jiang A. Widely tunable terahertz semiconductor laser sources. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/33388.

Council of Science Editors:

Jiang A. Widely tunable terahertz semiconductor laser sources. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/33388

University of Texas – Austin

23. -1924-7831. Electrochemical materials for the production and storage of renewable energy.

Degree: PhD, Chemistry, 2020, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/9153

► The production of electricity from renewable sources, including solar power, is increasingly important as our society seeks to move to cleaner energy sources. Organolead halide… (more)

▼ The production of electricity from renewable sources, including solar power, is increasingly important as our society seeks to move to cleaner energy sources. Organolead halide perovskites, a class of thin film photovoltaic (PV) materials, are an exciting competitor to traditional Si devices, but suffer from poor material stability. Further, PV power is intermittent, creating a need for efficient energy storage during times when solar power is unavailable. H₂ gas, produced via electrochemical water electrolysis, is a promising way to store this energy in chemical bonds but efficient electrocatalysts are required to drive the reaction. This need for electrocatalysts is particularly acute for the complementary oxygen evolution reaction (OER), the rate-limiting half reaction of electrolysis. Here, we address both halves of the renewable energy problem above, production and storage, and study how the chemistry of PV and OER electrocatalyst materials impacts electrochemical performance and material stability. In regard to production, we studied the performance and stability of quasi-2D Ruddlesden-Popper phase (RPP) perovskites under humid conditions. We found that RPP perovskites are more stable than typical 3D perovskites due to a unique moisture-driven disproportionation mechanism that passivates and protects the surface of the RPP perovskite. This process can also result in the formation of discrete RPP crystallites within the bulk of a perovskite film or device. We also found that changing the composition of the RPP perovskite enables control of the halide diffusion barrier, further impacting material stability. We next investigated energy storage, and studied how elemental composition affected the performance of two transition metal-based OER electrocatalyts. We found that for a Co-containing oxide perovskite, changes in the crystal structure of the catalyst from hexagonal to orthorhombic had little effect on OER performance, while adding small amounts of Fe improved catalytic behavior. Likewise, we found that the addition of Se to a nickel sulfoselenide material improved OER performance, even though the sulfoselenide material itself oxidizes during electrocatalysis to produce a catalytically-active nickel (oxy)hydroxide surface. Altogether, our work highlights the importance chemical composition when studying the material stability and electrochemical performance of both PV and electrocatalytic materials for renewable energy applications. Advisors/Committee Members: Mullins, C. B. (advisor), Crooks, Richard M (committee member), Roberts, Sean T (committee member), Eberlin, Livia S (committee member), Yu, Edward T (committee member).

Subjects/Keywords: Chemistry; Electrochemistry; Materials chemistry; Electrocatalysis; Oxygen evolution reaction; OER; Perovskite; Photovoltaic

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APA (6^th Edition):

-1924-7831. (2020). Electrochemical materials for the production and storage of renewable energy. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/9153

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Chicago Manual of Style (16^th Edition):

-1924-7831. “Electrochemical materials for the production and storage of renewable energy.” 2020. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://dx.doi.org/10.26153/tsw/9153.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-1924-7831. “Electrochemical materials for the production and storage of renewable energy.” 2020. Web. 25 Jan 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-1924-7831. Electrochemical materials for the production and storage of renewable energy. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2020. [cited 2021 Jan 25]. Available from: http://dx.doi.org/10.26153/tsw/9153.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-1924-7831. Electrochemical materials for the production and storage of renewable energy. [Doctoral Dissertation]. University of Texas – Austin; 2020. Available from: http://dx.doi.org/10.26153/tsw/9153

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Texas – Austin

24. Yum, Jung Hwan, 1978-. Atomic layer deposited beryllium oxide as a gate dielectric or interfacial Layer for Si and III-V MOS devices.

Degree: PhD, Electrical and Computer Engineering, 2012, University of Texas – Austin

URL: http://hdl.handle.net/2152/ETD-UT-2012-05-4987

► The continuous improvement in the semiconductor industry has been successfully achieved by the reducing dimensions of CMOS (complementary metal oxide semiconductor) technology. For the last… (more)

▼ The continuous improvement in the semiconductor industry has been successfully achieved by the reducing dimensions of CMOS (complementary metal oxide semiconductor) technology. For the last four decades, the scaling down of physical thickness of SiO₂ gate dielectrics has improved the speed of output drive current by shrinking of transistor area in front-end-process of integrated circuits. A higher number of transistors on chip resulting in faster speed and lower cost can be allowable by the scaling down and these fruitful achievements have been mainly made by the thinning thickness of one key component - Gate Dielectric - at Si based MOSFET (metal-oxide-semiconductor field effect transistor) devices. So far, SiO2 (silicon dioxide) gate dielectric having the excellent material and electrical properties such as good interface (i.e., Dit ~ 2x10¹⁰ eV⁻¹cm⁻²), low gate leakage current, higher dielectric breakdown immunity (≥10MV/cm) and excellent thermal stability at typical Si processing temperature has been popularly used as the leading gate oxide material. The next generation Si based MOSFETs will require more aggressive gate oxide scaling to meet the required specifications. Since high-k dielectrics provide the same capacitance with a thicker film, the leakage current reduction, therefore, less the standby power consumption is one of the huge advantages. Also, it is easier to fabricate during the process because the control of film thickness is still not in the critical range compared to the same leakage current characteristic of SiO₂ film. HfO₂ based gate dielectric is considered as the most promising candidate among materials being studied since it shows good characteristics with conventional Si technology and good device performance has been reported. However, it has still many problems like insufficient thermals stability on silicon such as low crystallization temperature, low k interfacial regrowth, charge trapping and so on. The integration of hafnium based high-k dielectric into CMOS technology is also limited by major issues such as degraded channel mobility and charge trapping. One approach to overcome these obstacles is using alternative substrate materials such as SiGe, GaAs, InGaAs, and InP to improve channel mobility. High electron mobility in the III-V materials has attracted significant attention for a possible application as a channel material in metal/oxide/semiconductor (MOS) transistors. One of the main challenges is that III-V MOSFETs generally lack thermodynamically stable insulators of high electrical quality, which would passivate the interface states at the dielectric/substrate interface and unpin the Fermi level. To address this issue, various dielectric, such as Si/SiO₂, Ge, SiGe, SiN and Al₂O₃, were considered as an interface passivation layer (IPL). Atomic Layer Deposited (ALD) Al₂O₃ has demonstrated superior IPL characteristics compared to the other candidates due to its high dielectric constant and interface quality. However, defect density in Al₂O₃ is still too high even as several… Advisors/Committee Members: Banerjee, Sanjay (advisor), Bank, Seth (committee member), Bersuker, Gennadi (committee member), Yu, Edward T. (committee member), Downer, Mike (committee member), Ho, Paul S. (committee member).

Subjects/Keywords: ALD beryllium oxide; ALD BeO; Dimethylberyllium; Diethylberyllium

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APA (6^th Edition):

Yum, Jung Hwan, 1. (2012). Atomic layer deposited beryllium oxide as a gate dielectric or interfacial Layer for Si and III-V MOS devices. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2012-05-4987

Chicago Manual of Style (16^th Edition):

Yum, Jung Hwan, 1978-. “Atomic layer deposited beryllium oxide as a gate dielectric or interfacial Layer for Si and III-V MOS devices.” 2012. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/ETD-UT-2012-05-4987.

MLA Handbook (7^th Edition):

Yum, Jung Hwan, 1978-. “Atomic layer deposited beryllium oxide as a gate dielectric or interfacial Layer for Si and III-V MOS devices.” 2012. Web. 25 Jan 2021.

Vancouver:

Yum, Jung Hwan 1. Atomic layer deposited beryllium oxide as a gate dielectric or interfacial Layer for Si and III-V MOS devices. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2012. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/ETD-UT-2012-05-4987.

Council of Science Editors:

Yum, Jung Hwan 1. Atomic layer deposited beryllium oxide as a gate dielectric or interfacial Layer for Si and III-V MOS devices. [Doctoral Dissertation]. University of Texas – Austin; 2012. Available from: http://hdl.handle.net/2152/ETD-UT-2012-05-4987

University of Texas – Austin

25. -8943-9305. Intrinsic unipolar SiOx-based resistive switching memory: characterization, mechanism and applications.

Degree: PhD, Electrical and Computer engineering, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/32441

► Floating gate (FG) nonvolatile memory has been the main structure of nonvolatile memory devices, since its invention in 1967 by D. Kahng and S. M.… (more)

▼ Floating gate (FG) nonvolatile memory has been the main structure of nonvolatile memory devices, since its invention in 1967 by D. Kahng and S. M. Sze. They have been widely employed in the portable electronic products such as mobile phones, digital cameras, notebook computers, mp3 players and USB flash drives. However, as device size continues to shrink, the typical flash memory device will continue to suffer from issues of retention and endurance. In order to solve the problems, researchers have considered new storage layers and novel structures in nonvolatile memory devices to replace the conventional floating gate device. Therefore, a great deal of potential memory structures have been proposed, with some transferring into a production line, such as phase change memory (PCM), magnetic random access memory (MRAM) and ferroelectric random access memory (FeRAM). In the innovation of memory devices, resistance random access memories (ReRAMs) have gained significant research interest as an alternative for next-generation nonvolatile memory due to its high density, low cost, low power consumption, fast switching speed and simple cell structure. In this dissertation, the intrinsic unipolar silicon oxide (SiOx-based) Resistive-RAM (ReRAM) characterization, mechanism and applications have been presented. I investigate device structures, material compositions and electrical characteristics to realize ReRAM cells with high ON/OFF ratio, low static power consumption, low switching power, and high readout-margin using complementary metal-oxide-semiconductor (CMOS) compatible SiOx-based materials. These ideas are combined with the use of horizontal and vertical device structure designs, composition optimization, electrical controlling and external factors for understanding resistive switching mechanism. Modeling of resistive switching mechanism, including temperature effect, pulse response and carrier transport behaviors are performed, to develop a compact model in energy diagram, trap-level information in SiOx resistive switching layer, even for computer-aided design (CAD) in very-large-scale integration (VLSI) design. Finally, synapse-based neuromorphic system is demonstrated in SiOx-based ReRAM, combining with bio-inspiration and biomimetics process illustrations. This work presents the comprehensively investigation of SiOx-based resistive switching characteristics, mechanisms, applications for future post-CMOS devices era. Advisors/Committee Members: Lee, Jack Chung-Yeung (advisor), Akinwande , Deji (committee member), Fowler , Burt W (committee member), Yu, Edward T. (committee member), Ho, Paul S (committee member).

Subjects/Keywords: ReRAM; Silicon oxide

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APA (6^th Edition):

-8943-9305. (2015). Intrinsic unipolar SiOx-based resistive switching memory: characterization, mechanism and applications. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/32441

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Chicago Manual of Style (16^th Edition):

-8943-9305. “Intrinsic unipolar SiOx-based resistive switching memory: characterization, mechanism and applications.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/32441.

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MLA Handbook (7^th Edition):

-8943-9305. “Intrinsic unipolar SiOx-based resistive switching memory: characterization, mechanism and applications.” 2015. Web. 25 Jan 2021.

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Author name may be incomplete

Vancouver:

-8943-9305. Intrinsic unipolar SiOx-based resistive switching memory: characterization, mechanism and applications. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/32441.

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Author name may be incomplete

Council of Science Editors:

-8943-9305. Intrinsic unipolar SiOx-based resistive switching memory: characterization, mechanism and applications. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/32441

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Texas – Austin

26. Lin, Edward Lawrence. Atomic layer deposition of epitaxial perovskites for electronic and photonic applications.

Degree: PhD, Chemical Engineering, 2018, University of Texas – Austin

URL: http://hdl.handle.net/2152/69181

► This research focuses on growth of ferroelectric and conductive perovskite oxides for both electronic and photonic applications. The advancement of computing technologies requires new device… (more)

▼ This research focuses on growth of ferroelectric and conductive perovskite oxides for both electronic and photonic applications. The advancement of computing technologies requires new device architectures, new materials, and new processing techniques. Perovskite class oxides, which have the general formula of ABO₃, possess various types of properties. The ability to grow perovskite oxides epitaxially on Si and Ge(001) single crystals provides an opportunity for incorporating various properties of perovskite onto semiconductor devices. In particular, barium titanate (BaTiO₃, BTO) is ferroelectric enabling opportunities in reducing transistor power consumption and fabricating photonic devices. The advancement in growing epitaxial perovskite oxides on Si(001) with a strontium titanate (SrTiO₃, STO) buffer layer via atomic layer deposition (ALD) shows the promise of using ALD to integrate perovskite properties into semiconductor materials. In order to realize the benefit brought by BTO, BTO films deposited by ALD need to exhibit ferroelectric polarization. This work initially focuses on ALD growth of BTO on Ge(001) and STO-buffered Si(001) single crystal substrates. Ferroelectric polarization was observed on the BTO films deposited on STO-buffered Si(001) substrates. The c-axis direction, which is the direction of BTO ferroelectric polarization, of BTO films with thickness up to 66 nm can be controlled by adjusting post-deposition annealing parameters. Ferroelectric switching of BTO on STO-buffered Si(001) in out- of-plane and in-plane directions were demonstrated by piezoresponse force microscopy and electro-optic measurement, respectively. Another part of this work concerns the mismatch between the range of BTO polarization and the polarization range needed to switch Si transistor channels. One proposal to address the mismatch is to introduce a thin conductive layer to attenuate BTO polarization. An MBE-ALD approach was developed to grow the conductive La:STO layer between a ferroelectric BTO film and the Si(001) substrate. Capacitance-voltage measurements of the BTO/La:STO film grown on STO-buffered Si(001) demonstrate attenuation of an externally applied electric field by La:STO, which is a result of the La:STO film conductivity. Lastly, this work explores the possibility of selective growth of BTO. Pattern transfer of the ALD grown film was observed by atomic force microscopy. The patterned film crystallizes after annealing the film in vacuum to the temperature of 800 °C. Advisors/Committee Members: Ekerdt, John G. (advisor), Demkov, Alexander A (committee member), Hwang, Gyeong S (committee member), Korgel, Brian A (committee member), Yu, Edward T (committee member).

Subjects/Keywords: Perovskites; Atomic layer deposition; Thin films; Epitaxial growth

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APA (6^th Edition):

Lin, E. L. (2018). Atomic layer deposition of epitaxial perovskites for electronic and photonic applications. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/69181

Chicago Manual of Style (16^th Edition):

Lin, Edward Lawrence. “Atomic layer deposition of epitaxial perovskites for electronic and photonic applications.” 2018. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/69181.

MLA Handbook (7^th Edition):

Lin, Edward Lawrence. “Atomic layer deposition of epitaxial perovskites for electronic and photonic applications.” 2018. Web. 25 Jan 2021.

Vancouver:

Lin EL. Atomic layer deposition of epitaxial perovskites for electronic and photonic applications. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2018. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/69181.

Council of Science Editors:

Lin EL. Atomic layer deposition of epitaxial perovskites for electronic and photonic applications. [Doctoral Dissertation]. University of Texas – Austin; 2018. Available from: http://hdl.handle.net/2152/69181

27. -0109-2595. Design of an optical microelectromechanical-system microphone with sub 15-dBA noise floor.

Degree: PhD, Mechanical Engineering, 2018, University of Texas – Austin

URL: http://hdl.handle.net/2152/68085

► This research work presents the modeling, fabrication, and characterization of the optical microphone. The optical microphone detects diaphragm displacement due to input sound pressure, using… (more)

▼ This research work presents the modeling, fabrication, and characterization of the optical microphone. The optical microphone detects diaphragm displacement due to input sound pressure, using an interferometric-based displacement detection scheme instead of using capacitive readout technique, which is extensively used in commercial microelectromechanical-system microphones. The optical-based transduction mechanism enables a backplate design with an extremely high perforation density, which in-turn drastically reduces the backplate flow resistance, which is a dominant noise source in miniaturized microphones. Therefore, an accurate estimation of the backplate-induced flow resistance is a critical step to predict signal-to-noise ratio precisely. A flow resistance modeling technique via computational fluid dynamics is presented in this work. A prototype backplate is fabricated for a verification of the flow-resistance modeling technique. A 22.0-dBA noise floor is demonstrated using the prototype backplate, which is 6-dB better than state-of-the-art commercial capacitive MEMS microphones. Design of experiments were performed with the verified microphone model to illustrate design implications toward sub 15-dBA optical microphone. The design-of-experiments study focused on various microphone components including diaphragm compliance, acoustical low cut-off frequency, back-cavity volume, inlet port and vent to show how each parameter affect to the microphone signal-to-noise ratio and acoustic overload point. Finally, a force-feedback optical microphone concept is presented to achieve a higher acoustic overload pressure, which is defined by 10% total harmonic distortion, using a Si membrane with piezoelectric thin-film actuators. A feasibility study was performed to explore the concept of a force-feedback optical microphone, including a fabrication of the minimalistic backplate with high aspect-ratio spokes and Si membrane with piezoelectric-film actuators at Microelectronics Research Center at The University of Texas at Austin. Advisors/Committee Members: Hall, Neal A. (advisor), Hamilton, Mark F. (committee member), Ho, Paul S. (committee member), Wilson, Preston S. (committee member), Yu, Edward T. (committee member).

Subjects/Keywords: MEMS; Interferometry; Microphone; Optical; Diffraction; Noise; SNR

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APA (6^th Edition):

-0109-2595. (2018). Design of an optical microelectromechanical-system microphone with sub 15-dBA noise floor. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/68085

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Chicago Manual of Style (16^th Edition):

-0109-2595. “Design of an optical microelectromechanical-system microphone with sub 15-dBA noise floor.” 2018. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/68085.

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MLA Handbook (7^th Edition):

-0109-2595. “Design of an optical microelectromechanical-system microphone with sub 15-dBA noise floor.” 2018. Web. 25 Jan 2021.

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Vancouver:

-0109-2595. Design of an optical microelectromechanical-system microphone with sub 15-dBA noise floor. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2018. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/68085.

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Author name may be incomplete

Council of Science Editors:

-0109-2595. Design of an optical microelectromechanical-system microphone with sub 15-dBA noise floor. [Doctoral Dissertation]. University of Texas – Austin; 2018. Available from: http://hdl.handle.net/2152/68085

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Author name may be incomplete

University of Texas – Austin

28. -8200-8716. Template directed self-assembly of particle monolayers.

Degree: PhD, Chemical Engineering, 2020, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/9961

► The template directed self-assembly (TDSA) is a promising method for cost-efficient and robust fabrication of nanoscale features. In this dissertation, we study the TDSA of… (more)

▼ The template directed self-assembly (TDSA) is a promising method for cost-efficient and robust fabrication of nanoscale features. In this dissertation, we study the TDSA of particle monolayers to assess the possibility of its application in manufacturing. The 2D directed self-assembly of micron-sized hard spherical particles within square confinements is studied theoretically and experimentally. Grand Canonical Monte Carlo simulations are used to predict the equilibrium packing structures of particles in square wells of specific dimensions. Spin coating and mechanical rubbing processes are used to direct the self-assembly of a monolayer of particles into the square wells. The precision of the graphoepitaxy decreases as template size increases. Both simulations and experiments show that ordered graphoepitaxy of square lattices vanishes with square templates of side length greater than five times the particle diameter. Missing particles and polydispersity of particles are two main causes disrupting the square packing structure in cells of three to five particle diameter side length. The phase diagram of a monolayer of soft particles described by the Daoud–Cotton model for star polymers is presented. Ground state calculations and grand canonical Monte Carlo simulations are used to determine the phase behavior as a function of the number of arms on the star and the areal coverage of the soft particles. The phase diagram exhibits rich behavior including reentrant melting and freezing and solid–solid transitions with triangular, stripe, honeycomb and kagome phases. These structures in 2D are analogous to the structures observed in 3D. The evolution of the structure factor with density is qualitatively similar to that measured in experiments for polymer grafted nanocrystals [Chen et al., Macromolecules, 2017, 50, 9636]. The formation of particle chains with long range order and orientational control is studied computationally. Monolayers of spherical particle usually self-assemble into isotropic structures. It has been found that some core-shell particles undergo anisotropic compression at elevated density when the particle interaction is piecewise. We expected these particles to self-assemble into aligned particle chains with controlled orientation under the guidance of some parallel confinements. Grand Canonical Monte Carlo simulations are used to predict the equilibrium packing structures of particle monolayers with parallel guidelines. Two different core-shell particles are studied. A graphoepitaxy behavior is observed and the formation of ordered particle chains is found for both particles at certain packing density with widely spaced templates. The orientation of formed particle chains can be controlled with the rigid template and the particle spacing is predicted. The self-assembled particle monolayer is an important alternative for photolithography in nanofabrication. The intolerable high defect rate has been the main challenge before the process can be used in the fabrication of high precision structures. The… Advisors/Committee Members: Bonnecaze, R. T. (Roger T.) (advisor), Truskett, Thomas Michael, 1973- (advisor), Yu, Edward T (committee member), Willson, Carlton G (committee member), Lynd, Nathaniel A (committee member).

Subjects/Keywords: Self-assembly; Colloids; Template; Monolayer

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APA (6^th Edition):

-8200-8716. (2020). Template directed self-assembly of particle monolayers. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/9961

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Chicago Manual of Style (16^th Edition):

-8200-8716. “Template directed self-assembly of particle monolayers.” 2020. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://dx.doi.org/10.26153/tsw/9961.

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Author name may be incomplete

MLA Handbook (7^th Edition):

-8200-8716. “Template directed self-assembly of particle monolayers.” 2020. Web. 25 Jan 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-8200-8716. Template directed self-assembly of particle monolayers. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2020. [cited 2021 Jan 25]. Available from: http://dx.doi.org/10.26153/tsw/9961.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-8200-8716. Template directed self-assembly of particle monolayers. [Doctoral Dissertation]. University of Texas – Austin; 2020. Available from: http://dx.doi.org/10.26153/tsw/9961

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Texas – Austin

29. -3001-3171. Magnetotransport studies of tungsten diselenide holes.

Degree: PhD, Electrical and Computer Engineering, 2018, University of Texas – Austin

URL: http://hdl.handle.net/2152/68920

► This dissertation describes the electronic transport properties of holes in tungsten diselenide (WSe₂), a prototypical transition metal dichalcogenide (TMD) material, probed using low-temperature magnetotransport measurements,… (more)

▼ This dissertation describes the electronic transport properties of holes in tungsten diselenide (WSe₂), a prototypical transition metal dichalcogenide (TMD) material, probed using low-temperature magnetotransport measurements, and facilitated by a device structure with platinum (Pt) bottom-contacts and hexagonal boron nitride (h-BN) encapsulation. The discovery of graphene has stimulated an intense interest in exploration of materials with stable two-dimensional allotropes, TMDs being one of them. Of the myriad variety of TMDs, sulfides and selenides of molybdenum and tungsten have garnered great attention on account of their semiconducting nature. A major roadblock to investigation of TMDs' electronic transport properties has been the poor quality of electrical contacts. The top-gated device structure with Pt bottom-electrodes presented in this dissertation ensures Ohmic hole contacts to WSe₂ down to a temperature of 0.3 K and permits low-temperature magnetotransport measurements. Encapsulating WSe₂ in h-BN preserves its intrinsic quality, resulting in high hole mobilities at low-temperatures, and thereby enabling observation of Shubnikov-de Haas (SdH) oscillations and quantum Hall states (QHS) in perpendicular magnetic fields. Analysis of the SdH oscillations in monolayer and bilayer WSe₂ reveals two-fold degenerate Landau levels and a hole effective mass of 0.45m [subscript e]; m [subscript e] is the free electron mass. Bilayer data also show carrier localization in the two layers signifying weak interlayer coupling, and negative compressibility of holes in the bottom layer. The QHS data reveal interesting transitions between even and odd filling factors as the hole density is tuned, which can be explained by a Zeeman-to-cyclotron energy ratio that changes as a function of density due to strong electron-electron interactions. Tilted magnetic field measurements reveal that the holes reside in the K valleys, as evinced by their spins which are locked perpendicular to the WSe₂ plane. In trilayer WSe₂, holes are found to populate two subbands with different effective masses, 0.5m [subscript e] and 1.2m [subscript e], associated with the K and Γ valleys, respectively. At a fixed total hole density, the K and Γ occupations are tunable via an applied transverse electric field, an observation which can be explained in terms of an electric field dependent bandstructure. Advisors/Committee Members: Tutuc, Emanuel, 1974- (advisor), Banerjee, Sanjay (advisor), Register, Leonard F (committee member), Yu, Edward T (committee member), Akinwande, Deji (committee member), Demkov, Alexander A (committee member).

Subjects/Keywords: Tungsten diselenide; Quantum Hall effect; Magnetotransport; High-mobility; SdH oscillations

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APA (6^th Edition):

-3001-3171. (2018). Magnetotransport studies of tungsten diselenide holes. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/68920

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Chicago Manual of Style (16^th Edition):

-3001-3171. “Magnetotransport studies of tungsten diselenide holes.” 2018. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/68920.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-3001-3171. “Magnetotransport studies of tungsten diselenide holes.” 2018. Web. 25 Jan 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-3001-3171. Magnetotransport studies of tungsten diselenide holes. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2018. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/68920.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-3001-3171. Magnetotransport studies of tungsten diselenide holes. [Doctoral Dissertation]. University of Texas – Austin; 2018. Available from: http://hdl.handle.net/2152/68920

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Texas – Austin

30. -3011-5998. Process integration and logic applications of SiOx based resistive memory.

Degree: PhD, Electrical and Computer Engineering, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/33351

► Flash memory has been the fastest growing non-volatile memory technology, and it has been widely used in many portable electronic products. Due to its charge… (more)

▼ Flash memory has been the fastest growing non-volatile memory technology, and it has been widely used in many portable electronic products. Due to its charge based memory mechanism, there are more and more challenges scaling down the flash memory device. Researchers have been looking for new memory materials and novel structures for non-volatile memory devices to replace the conventional floating gate flash. Resistive switching memory stands out from other leading contenders such as phase change memory, magnetic random access memory, and spintronic random access memory. Resistive switching memory has the advantages of non-charge based memory mechanism, simple two-terminal device structure, and fast switching speed. Therefore, it demonstrates great potential for replacing NAND flash and even DRAM to become the next-generation non-volatile memory. A comprehensive investigation on amorphous silicon oxide (SiOx) based resistive memory, starting from fabrication and material analysis, to performance optimization, then to advanced characterization, and finally ending with novel logic circuit applications, have been presented in this dissertation. New device structure and encapsulation process are developed to enable SiOx based resistive memory to operate in air ambient. External resistance effect and substrate optimization have been made to achieve good switching window, low endurance variation. Current sweep technique was used to study the Set process, which simplified multiple resistance level operation of SiOx based resistive memory. Characterization of resistive switching behavior at elevated temperature showed that SiOx resistive material has great potential for high temperature memory applications. Random Telegraph Noise and Energetic Dispersive Spectroscopy provided insights into the physical model of the resistive switching phenomenon. Finally, bidirectional implication scheme using SiOx based resistive memory was proposed and tested, which forms the corner stone of memristor based logic operations. Taking one step further, one bit full adder logic function was theoretically realized on a logic circuit consisting of 4 × 4 crossbar structure resistive memory 1D-1R array and select transistors, the findings show pros and cons of memory enabled logic circuit. In summary, this work presents the optimization and application researches on SiOx based resistive switching memory. Advisors/Committee Members: Lee, Jack Chung-Yeung (advisor), Banerjee , Sanjay K (committee member), Register, Leonard F (committee member), Yu, Edward T (committee member), Fowler , Burt W (committee member).

Subjects/Keywords: RRAM; SiOx

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APA (6^th Edition):

-3011-5998. (2015). Process integration and logic applications of SiOx based resistive memory. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/33351

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Chicago Manual of Style (16^th Edition):

-3011-5998. “Process integration and logic applications of SiOx based resistive memory.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed January 25, 2021. http://hdl.handle.net/2152/33351.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-3011-5998. “Process integration and logic applications of SiOx based resistive memory.” 2015. Web. 25 Jan 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-3011-5998. Process integration and logic applications of SiOx based resistive memory. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2152/33351.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-3011-5998. Process integration and logic applications of SiOx based resistive memory. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/33351

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

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