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1.
Jiang, Yuxuan.
Magneto-infrared spectroscopy of emerging topological materials.
Degree: PhD, Physics, 2017, Georgia Tech
URL: http://hdl.handle.net/1853/58694 
► Topological insulators (TIs) have recently attracted much attentions due to their robust edge/surface states against disorders and external disturbance under the protection of symmetries. Such…
(more)
▼ Topological insulators (TIs) have recently attracted much attentions due to their robust edge/surface states against disorders and external disturbance under the protection of symmetries. Such robust states hold great promise for application in spintronics and quantum computing. Therefore, intense explorations and characterizations of possible TIs have been carried out in the scientific community. In this thesis, we use magneto-infrared spectroscopy to study the electronic band structures of two TI candidates. The first candidate is InAs/GaSb double quantum wells. We showed that when its band structure crosses the boundary from the normal state to the inverted state, multiple absorption modes emerge. This normal-inverted state transition can be described semi-quantitatively with an eight-band k. p model. We further demonstrate that the transition is widely adjustable with the effects of strain, magnetic field and quantum well widths, which paves the way for band engineering of optimal InAs/GaSb structures for realizing novel topological states as well as for device applications.
Another candidate studied in this thesis is zirconium pentatelluride (ZrTe5). The transmission spectra measured at zero magnetic field is suggestive of a quasi-2D nature in bulk ZrTe5 similar to that in graphene. The Landau level transitions clearly follow a square-root magnetic field dependence, which is a signature of Dirac bands, only with a small energy gap of about 9.4 meV. A four-fold splitting in low lying interband transitions are resolved under high magnetic fields, while circular polarization resolved measurements help identify a significant contribution from electron-hole asymmetry. We employ a model based on the Bernevig-Hughes-Zhang effective Hamiltonian to determine the values of the Fermi velocity, Dirac mass (or gap), electron-hole asymmetry, and electron and hole g-factors in ZrTe5. Our results support the topological Dirac semimetal picture with a small energy gap.
Advisors/Committee Members: Jiang, Zhigang (advisor).
Subjects/Keywords: Infrared spectroscopy; Landau levels; Topological materials
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APA (6th Edition):
Jiang, Y. (2017). Magneto-infrared spectroscopy of emerging topological materials. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/58694
Chicago Manual of Style (16th Edition):
Jiang, Yuxuan. “Magneto-infrared spectroscopy of emerging topological materials.” 2017. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/58694.
MLA Handbook (7th Edition):
Jiang, Yuxuan. “Magneto-infrared spectroscopy of emerging topological materials.” 2017. Web. 10 Jul 2020.
Vancouver:
Jiang Y. Magneto-infrared spectroscopy of emerging topological materials. [Internet] [Doctoral dissertation]. Georgia Tech; 2017. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/58694.
Council of Science Editors:
Jiang Y. Magneto-infrared spectroscopy of emerging topological materials. [Doctoral Dissertation]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/58694
Georgia Tech
2.
Miettinen, Anna L.
Edge State Characterization of Epitaxial Graphene Nanoribbons and Modifications of the Electrical Structure of Buffer Graphene after Aluminum Oxide Deposition.
Degree: PhD, Physics, 2020, Georgia Tech
URL: http://hdl.handle.net/1853/62749
► Graphene attracted a great deal of public interest because of its novel electrical characteristics, structural integrity, high electron mobility, and most important for my work,…
(more)
▼ Graphene attracted a great deal of public interest because of its novel electrical characteristics, structural integrity, high electron mobility, and most important for my work, it was shown to be a room temperature ballistic transport material when it is epitaxially grown on SiC steps. However, there have been inconsistencies between graphene research groups studying the electronic properties of zig-zag (ZZ) edge graphene nanoribbons (GNR). While 2-probe variable geometry measurements demonstrate room temperature ballistic transport along ZZ-edge GNR (Baringhaus, 2014), direct band structure measurements using angle resolved photoemission spectroscopy (ARPES) find that conducting graphene does not grow on the 4H-SiC ZZ-edge sidewalls (Nevius, 2016). I have shown that these different results are due to the starting SiC polytype used as the graphene growth substrate. It has been typically assumed that the SiC polytype is not relevant to graphene growth on SiC, but the stability of SiC steps from which ZZ-edge ribbons grow is very different between polytypes (Nordell, 1999).
The choice of SiC polytype determines whether or not ZZ-edge graphene ribbons are strongly or weakly bonded to the SiC trench sidewall. ZZ-edge ribbons grown on 4H-SiC are so strongly bonded to the substrate that there is no evidence of a linear Dirac cone in ARPES unless the graphene-substrate bonds are broken using a hydrogen intercalant. The resulting passivated ribbon is wide, spanning nearly the entire sidewall. In contrast, ZZ-edge ribbons grown on 6H-SiC readily show a modified Dirac cone with a pair of edge states close to the Fermi level. Analysis of the facet Dirac cone shape and valence bands imply that the sidewall graphene on 6H-SiC forms many narrow ribbons, unlike those grown on the 4H polytype. This is confirmed using STS measurements on the 6H-ZZ ribbons. Furthermore, 2-point transport measurements show that only the 6H-ZZ sidewall ribbons are ballistic conductors. If there is to be a carbon-based electronic revolution, understanding the characteristics of GNR grown on different polytypes and with different orientations will provide the foundation for that platform.
In addition to my ribbon studies, I have also looked at the effects of a gate oxide grown with atomic layer deposition (ALD) on the semiconducting graphene buffer layer (BL) on SiC(0001). It is known that gate oxides do not strongly interact with the metallic graphene layer that grows above the BL, but the BL itself is highly reactive. The complex carbon-substrate bonding structure of this layer opens a band gap. Core-level XPS and valence-level ARPES show that the BL partially delaminates from the SiC after a thin aluminum oxide film is deposited, making it metallic rather than semiconducting. While voltage gating the BL is essential to produce flat graphene devices, I show that ALD oxides are not an ideal method because they destroy the unique semiconductive character of the BL.
Advisors/Committee Members: Conrad, Edward (advisor), First, Phillip N. (advisor), Jiang, Zhigang (advisor), Kindermann, Markus (advisor), Tejeda, Antonio (advisor).
Subjects/Keywords: Graphene; Epitaxial; Silicon carbide; Graphene nanoribbons; Aluminum oxide; Edge states; Band structure; Facet Dirac cones; Hydrogen intercalation; Atomic layer deposition; voltage gating
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APA (6th Edition):
Miettinen, A. L. (2020). Edge State Characterization of Epitaxial Graphene Nanoribbons and Modifications of the Electrical Structure of Buffer Graphene after Aluminum Oxide Deposition. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/62749
Chicago Manual of Style (16th Edition):
Miettinen, Anna L. “Edge State Characterization of Epitaxial Graphene Nanoribbons and Modifications of the Electrical Structure of Buffer Graphene after Aluminum Oxide Deposition.” 2020. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/62749.
MLA Handbook (7th Edition):
Miettinen, Anna L. “Edge State Characterization of Epitaxial Graphene Nanoribbons and Modifications of the Electrical Structure of Buffer Graphene after Aluminum Oxide Deposition.” 2020. Web. 10 Jul 2020.
Vancouver:
Miettinen AL. Edge State Characterization of Epitaxial Graphene Nanoribbons and Modifications of the Electrical Structure of Buffer Graphene after Aluminum Oxide Deposition. [Internet] [Doctoral dissertation]. Georgia Tech; 2020. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/62749.
Council of Science Editors:
Miettinen AL. Edge State Characterization of Epitaxial Graphene Nanoribbons and Modifications of the Electrical Structure of Buffer Graphene after Aluminum Oxide Deposition. [Doctoral Dissertation]. Georgia Tech; 2020. Available from: http://hdl.handle.net/1853/62749
Georgia Tech
3.
Guang, Zhe.
Single-frame complete spatiotemporal measurement of complex ultrashort laser pulses.
Degree: PhD, Physics, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/58133
► Today one of the frontiers in light measurement is to measure ultrashort pulses from ultrafast laser systems, which demonstrate extremely fast temporal variations, and are…
(more)
▼ Today one of the frontiers in light measurement is to measure ultrashort pulses from ultrafast laser systems, which demonstrate extremely fast temporal variations, and are necessarily associated with large spectral bandwidths by Fourier transform. In addition to the temporal and spectral structures, ultrashort pulses can also be complex in space. Especially, the field can have spatiotemporal couplings which relate pulse temporal profile to spatial coordinates. Therefore, a complete spatiotemporal measurement technique is needed. In this work, we demonstrate our study on measuring complex ultrashort pulses by development of a method, called Spatially and Temporally Resolved Intensity and Phase Evaluation Device: Full Information from a Single Hologram (STRIPED FISH). Based on digital holography, this simple single-frame method can measure the complete spatiotemporal intensity I(x,y,t) and phase ϕ(x,y,t) of pulses at a particular z-plane. By experiments, we investigated sub-picosecond chirped pulse beating, pulses from multimode optical fibers, ultrafast lighthouse effect and so on, using STRIPED FISH. We also performed numerical simulations to understand the effects of different spatiotemporal distortions on STRIPED FISH trace. With its improved apparatus, processing algorithm, and display method, STRIPED FISH offers a simple and compact solution to monitor, measure, and display spatiotemporal structures in ultrashort pulses.
Advisors/Committee Members: Trebino, Rick (advisor), Adibi, Ali (advisor), Curtis, Jennifer (advisor), Chapman, Michael (advisor), Jiang, Zhigang (advisor).
Subjects/Keywords: Ultrafast optics; Ultrafast measurement
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APA (6th Edition):
Guang, Z. (2016). Single-frame complete spatiotemporal measurement of complex ultrashort laser pulses. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/58133
Chicago Manual of Style (16th Edition):
Guang, Zhe. “Single-frame complete spatiotemporal measurement of complex ultrashort laser pulses.” 2016. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/58133.
MLA Handbook (7th Edition):
Guang, Zhe. “Single-frame complete spatiotemporal measurement of complex ultrashort laser pulses.” 2016. Web. 10 Jul 2020.
Vancouver:
Guang Z. Single-frame complete spatiotemporal measurement of complex ultrashort laser pulses. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/58133.
Council of Science Editors:
Guang Z. Single-frame complete spatiotemporal measurement of complex ultrashort laser pulses. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/58133
Georgia Tech
4.
Chauhan, Vikrant Chauhan Kumar.
Pulse compression and dispersion control in ultrafast optics.
Degree: PhD, Physics, 2011, Georgia Tech
URL: http://hdl.handle.net/1853/37153
► Pulse Compression and Dispersion Control in Ultrafast Optics Vikrant K. Chauhan 116 Pages Directed by Dr. Rick P. Trebino In this thesis, we introduced novel…
(more)
▼ Pulse Compression and Dispersion Control in Ultrafast Optics
Vikrant K. Chauhan
116 Pages
Directed by Dr. Rick P. Trebino
In this thesis, we introduced novel pulse compressors that are easy to align and which also compensate for higher order dispersion terms. They use a single dispersive element or a combination of dispersive elements in single-element-geometry. They solve the problem of extra-cavity pulse compression by providing control of the pulse width in almost all of the experiments performed using ultrashort pulses, and they even compensate for higher order dispersion. We performed full spatiotemporal characterization of these compressors and demonstrated their performance. We also developed a theoretical simulation of pulse compressors which is based on a matrix based formalism. It models the full spatiotemporal characteristics of any dispersion control system. We also introduced a simple equation, in its most general form, to relate the total dispersion and magnification introduced by an arbitrary sequence of dispersive devices. Pulse compressor characterization was done using interferometric measurements in the experiments presented in this work, but we also developed a method to measure pulses that uses polarization gating FROG for measuring two unknown pulses. In the last part, we briefly discuss the designing of a high energy chirped pulse amplification system.
Advisors/Committee Members: Trebino, Rick (Committee Chair), Buck, John (Committee Member), Curtis, Jennifer (Committee Member), Jiang, Zhigang (Committee Member), Raman, Chandra (Committee Member).
Subjects/Keywords: Ultrafast optics; Pulse compression; Picosecond pulses
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APA (6th Edition):
Chauhan, V. C. K. (2011). Pulse compression and dispersion control in ultrafast optics. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/37153
Chicago Manual of Style (16th Edition):
Chauhan, Vikrant Chauhan Kumar. “Pulse compression and dispersion control in ultrafast optics.” 2011. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/37153.
MLA Handbook (7th Edition):
Chauhan, Vikrant Chauhan Kumar. “Pulse compression and dispersion control in ultrafast optics.” 2011. Web. 10 Jul 2020.
Vancouver:
Chauhan VCK. Pulse compression and dispersion control in ultrafast optics. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/37153.
Council of Science Editors:
Chauhan VCK. Pulse compression and dispersion control in ultrafast optics. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/37153
Georgia Tech
5.
Vaughan, Peter Matthias.
Optical-parametric-amplification applications to complex images.
Degree: PhD, Physics, 2011, Georgia Tech
URL: http://hdl.handle.net/1853/41134
► We have used ultrafast optics, primarily focused on the nonlinear processes of Polarization Gating and of Optical Parametric Amplification, one for measurement and the other…
(more)
▼ We have used ultrafast optics, primarily focused on the nonlinear processes of Polarization Gating and of Optical Parametric Amplification, one for measurement and the other for imaging purposes. For measurement, we have demonstrated a robust method of measurement to simultaneously measure both optical pulses used in a pump-probe type configuration. We refer to this method of pulse measurement as Double Blind Polarization Gating FROG. We have demonstrated this single-shot method for measuring two unknown pulses using one device. In addition to pulse measurement, we have demonstrated the processes of Optical Parametric Amplification (OPA) applicability to imaging of complex objects. We have done this where the Fourier transform plane is used during the interaction. We have amplified and wavelength converted a complex image. We observe a gain of ~100, and, although our images were averaged over many shots, we used a single-shot geometry, capable of true single-shot OPA imaging. To our knowledge, this is the first Fourier-plane OPA imaging of more than a single spatial-frequency component of an image. We observe more than 30 distinct spatial frequency components in both our amplified image and our wavelength shifted image. We have demonstrated all-optical spatial filtering for these complex images. We have demonstrated that direct Fourier filtering of spatial features is possible by using a shaped pump beam. We can isolate certain portions of the image simply by rotating the crystal.
Advisors/Committee Members: Trebino, Rick (Committee Chair), Adibi, Ali (Committee Member), Brown, Kenneth (Committee Member), Jiang, Zhigang (Committee Member), Perry, Joseph (Committee Member).
Subjects/Keywords: Ultrafast optics; Nonlinear optics; OPA; Picosecond pulses Measurement; Imaging systems; Laser pulses, Ultrashort
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APA (6th Edition):
Vaughan, P. M. (2011). Optical-parametric-amplification applications to complex images. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/41134
Chicago Manual of Style (16th Edition):
Vaughan, Peter Matthias. “Optical-parametric-amplification applications to complex images.” 2011. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/41134.
MLA Handbook (7th Edition):
Vaughan, Peter Matthias. “Optical-parametric-amplification applications to complex images.” 2011. Web. 10 Jul 2020.
Vancouver:
Vaughan PM. Optical-parametric-amplification applications to complex images. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/41134.
Council of Science Editors:
Vaughan PM. Optical-parametric-amplification applications to complex images. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/41134
Georgia Tech
6.
Sojoudi, Hossein.
The synthesis, doping, and characterization of graphene films.
Degree: PhD, Mechanical Engineering, 2012, Georgia Tech
URL: http://hdl.handle.net/1853/50125
► Graphene, a two-dimensional counterpart of three-dimensional graphite, has attracted significant interest, due to its distinctive electrical and mechanical properties, for developing electronic, optoelectronic, and sensor…
(more)
▼ Graphene, a two-dimensional counterpart of three-dimensional graphite, has attracted significant interest, due to its distinctive electrical and mechanical properties, for developing electronic, optoelectronic, and sensor technologies. In general, doping of graphene is important, as it gives rise to p-type and n-type materials, and it adjusts the work function of the graphene. This adjustment is necessary in order to control charge injection and collection in devices such as solar cells and light emitting devices. Current methods for graphene doping involve high temperature process or interactions with chemicals that are not stable. Moreover, the process of transferring graphene from its growth substrate and its exposure to the environment results in a host of chemical groups that can become attached to the film and alter its electronic properties by accepting or donating electrons/holes. Intentional and controllable doping of the graphene, however, requires a deeper understanding of the impact of these groups. The proposed research will attempt to clarify the unintentional doping mechanism in graphene through adsorption or desorption of gas/vapor molecules found in standard environments. A low temperature, controllable and defect-free method for doping graphene layers will also be studied through modifying the interface of graphene and its support substrate with self-assembled monolayers (SAMs) which changes the work function and charge carriers in the graphene layer. Furthermore, current methods of chemical vapor deposition synthesis of graphene requires the film to be transferred onto a second substrate when the metal layer used for growth is not compatible with device fabrication or operation. To address this issue, the proposed work will investigate a new method for wafer scale, transfer-free synthesis of graphene on dielectric substrates using new carbon sources. This technique allows patterned synthesis on the target substrate and is compatible with standard device fabrication technologies; hence, it opens a new pathway for low cost, large area synthesis of graphene films.
Advisors/Committee Members: Graham, Samuel (advisor), Cola, Baratunde (committee member), Hess, Dennis (committee member), Garmestani, Hamid (committee member), Kalaitzidou, Kyriaki (committee member), Jiang, Zhigang (committee member).
Subjects/Keywords: Graphene; Doping; Characterization; Vacuum annealing; Self assembled monolayers (SAMs); Transfer-free synthesis; Trace carbon source; Solid carbon source; Graphene; Thin films
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APA (6th Edition):
Sojoudi, H. (2012). The synthesis, doping, and characterization of graphene films. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/50125
Chicago Manual of Style (16th Edition):
Sojoudi, Hossein. “The synthesis, doping, and characterization of graphene films.” 2012. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/50125.
MLA Handbook (7th Edition):
Sojoudi, Hossein. “The synthesis, doping, and characterization of graphene films.” 2012. Web. 10 Jul 2020.
Vancouver:
Sojoudi H. The synthesis, doping, and characterization of graphene films. [Internet] [Doctoral dissertation]. Georgia Tech; 2012. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/50125.
Council of Science Editors:
Sojoudi H. The synthesis, doping, and characterization of graphene films. [Doctoral Dissertation]. Georgia Tech; 2012. Available from: http://hdl.handle.net/1853/50125
Georgia Tech
7.
Jiang, Wenchao.
Spin dependent transport in ferromagnetic particles.
Degree: PhD, Physics, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/52204
► Spintronics is an emerging technology that arises from the interplay between spin of the charge carrier and the magnetic property of the materials. The miniaturization…
(more)
▼ Spintronics is an emerging technology that arises from the interplay between spin of the charge carrier and the magnetic property of the materials. The miniaturization of spintronic devices requires a deep understanding of ferromagnetic materials at the nanometer scale. This thesis studies the properties of ferromagnetic particles (2-5nm in diameter) using electron transport measurements. A technique to fabricate nanoparticle devices and incorporate microwave in the electron tunneling measurement of the particles is presented. Repeated microwave pulses can directly excite the magnetization of the particles without heating the electrons. Results of the transport measurements on Co particles will be discussed, which demonstrate that electron tunneling through a ferromagnetic particle can induce magnetization excitations in that particle. A physical model regarding the mesoscopic fluctuations is presented to address the current driven magnetization noise. Numerical simulations based on that model are performed to explain the experimental data and validate the model. Electron transport measurements on Ni, Fe, and Ni??Fe?? are conducted. The hysteretic behaviors of the particles in presence of electron tunneling have strong material dependence, which is mainly due to the magnetic shape anisotropy. Electron tunneling is a main source of magnetization noise, while other sources still need to be identified. Some data we collected from literature will be included in this thesis as an appendix.
Advisors/Committee Members: Davidovic, Dragomir (advisor), First, Phillip (committee member), Jiang, Zhigang (committee member), Pustinik, Michael (committee member), Gokhale, Arun M. (committee member).
Subjects/Keywords: Electron transport; Nanoparticle
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APA (6th Edition):
Jiang, W. (2014). Spin dependent transport in ferromagnetic particles. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/52204
Chicago Manual of Style (16th Edition):
Jiang, Wenchao. “Spin dependent transport in ferromagnetic particles.” 2014. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/52204.
MLA Handbook (7th Edition):
Jiang, Wenchao. “Spin dependent transport in ferromagnetic particles.” 2014. Web. 10 Jul 2020.
Vancouver:
Jiang W. Spin dependent transport in ferromagnetic particles. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/52204.
Council of Science Editors:
Jiang W. Spin dependent transport in ferromagnetic particles. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/52204
Georgia Tech
8.
Gao, Yang.
Force microscopy of two-dimensional materials.
Degree: PhD, Physics, 2017, Georgia Tech
URL: http://hdl.handle.net/1853/59799
► Atomic Force Microscopy (AFM) is a powerful tool for the characterization and fabrication of two-dimensional materials, which are films of a few atomic layers with…
(more)
▼ Atomic Force Microscopy (AFM) is a powerful tool for the characterization and fabrication of two-dimensional materials, which are films of a few atomic layers with strong in-plane bonds and weak van der Waals interactions between the layers. The in-plane elasticity has been widely studied with nano-indentation where a suspended 2D film is bent substantially (~10nm to 1000nm). In this thesis we report on a novel AFM-based sub-Å-resolution indentation technique: Modulated nano-indentation (MoNI) or "Å-indentation". MoNI can allow for indentation below 1 Å, smaller than the inter-layer distance of most 2D materials. The perpendicular-to-the-plane elasticity of 2D materials can be detected with MoNI at extremely high precision while the in-plane covalent bonds are negligible. The inter-layer elasticity as well as intercalation properties of epitaxial graphene, graphene oxide and other 2D materials were carefully investigated. Furthermore, the fingerprint of a new ultra-hard phase of epitaxial graphene on SiC(0001), indicating possible diamondization at room temperature, has been observed and reported in this thesis.
Advisors/Committee Members: Riedo, Elisa (advisor), First, Phillip (committee member), Davidovic, Dragomir (committee member), Jiang, Zhigang (committee member), Degertekin, Levent (committee member).
Subjects/Keywords: AFM; Two-dimensional materials; van der Waals force; Elasticity
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APA (6th Edition):
Gao, Y. (2017). Force microscopy of two-dimensional materials. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/59799
Chicago Manual of Style (16th Edition):
Gao, Yang. “Force microscopy of two-dimensional materials.” 2017. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/59799.
MLA Handbook (7th Edition):
Gao, Yang. “Force microscopy of two-dimensional materials.” 2017. Web. 10 Jul 2020.
Vancouver:
Gao Y. Force microscopy of two-dimensional materials. [Internet] [Doctoral dissertation]. Georgia Tech; 2017. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/59799.
Council of Science Editors:
Gao Y. Force microscopy of two-dimensional materials. [Doctoral Dissertation]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/59799
Georgia Tech
9.
Deniz, Dogukan.
FABRICATION OF ARRAYS OF BALLISTIC EPITAXIAL GRAPHENE NANORIBBONS.
Degree: PhD, Physics, 2018, Georgia Tech
URL: http://hdl.handle.net/1853/61155
► Epitaxial graphene nanoribbons have recently demonstrated exceptional one dimensional ballistic transport where charge carriers can travel without scattering up to 16 m at room temperature…
(more)
▼ Epitaxial graphene nanoribbons have recently demonstrated exceptional one dimensional
ballistic transport where charge carriers can travel without scattering up to 16 m at
room temperature (STM probes in UHV). These transport properties are not yet fully understood,
and they can only be exploited if nanoribbons can be produced at large scale with
good properties in ambient conditions. Following up on these results, in this thesis I will
summarize my work on arrays of epitaxial graphene nanoribbons grown on the sidewalls
of trenches and steps of silicon carbide. I will discuss nanoribbon growth, nanofabrication,
factors that affect nanoribbon transport and how mean free paths larger than one micron are
consistently found at room temperature for thousands of nanoribbons.
Advisors/Committee Members: de Heer, Walter (advisor), Jiang, Zhigang (committee member), First, Phillip (committee member), Mourigal, Martin (committee member), Naeemi, Azad (committee member).
Subjects/Keywords: Graphene Nanoribbons; ballistic transport; pristine graphene;
contacting graphene
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APA (6th Edition):
Deniz, D. (2018). FABRICATION OF ARRAYS OF BALLISTIC EPITAXIAL GRAPHENE NANORIBBONS. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/61155
Chicago Manual of Style (16th Edition):
Deniz, Dogukan. “FABRICATION OF ARRAYS OF BALLISTIC EPITAXIAL GRAPHENE NANORIBBONS.” 2018. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/61155.
MLA Handbook (7th Edition):
Deniz, Dogukan. “FABRICATION OF ARRAYS OF BALLISTIC EPITAXIAL GRAPHENE NANORIBBONS.” 2018. Web. 10 Jul 2020.
Vancouver:
Deniz D. FABRICATION OF ARRAYS OF BALLISTIC EPITAXIAL GRAPHENE NANORIBBONS. [Internet] [Doctoral dissertation]. Georgia Tech; 2018. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/61155.
Council of Science Editors:
Deniz D. FABRICATION OF ARRAYS OF BALLISTIC EPITAXIAL GRAPHENE NANORIBBONS. [Doctoral Dissertation]. Georgia Tech; 2018. Available from: http://hdl.handle.net/1853/61155
Georgia Tech
10.
Wang, Feng.
Surface/interface modification and characterization of C-face epitaxial graphene.
Degree: PhD, Physics, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/53855
► Graphene has been one of the most interesting and widely investigated materials in the past decade. Because of its high mobility, high current density, inherent…
(more)
▼ Graphene has been one of the most interesting and widely investigated materials in the past decade. Because of its high mobility, high current density, inherent strength, high temperature stability and other properties, scientists consider it a promising material candidate for the future all-carbon electronics. However, graphene still exhibits a number of problems such as an unknown interface structure and no sizable band gap. Therefore, the purpose of this thesis is to probe and solve these problems to make graphene suitable for electronics. The work focuses on high-quality C-face epitaxial graphene, which is grown on the (000-1) face (C-face) of hexagonal silicon carbide using the confinement-controlled sublimation method. C-face epitaxial graphene has much higher mobility compared to Si-face graphene, resulting from its special stacking order and interface structure, the latter of which is not fully understood. Thus, the first part of the work consists of a project, which is to investigate and modify the interface and the surface of C-face graphene by silicon deposition and annealing. Results of this project show that silicon can intercalate into the graphene-SiC interface and form SiC by bonding carbon atoms on the graphene surface. Another crucial problem of graphene is the absence of a band gap, which prevents graphene from becoming an ideal candidate for traditional digital logic devices. Therefore, the second project of this work is devoted to introducing a wide band gap into the graphene electronic structure by growing from a nitrogen-seeded SiC. After successful opening of a band gap, a pre-patterning method is applied to improve graphene thickness variations, orientational epitaxy, and the gapped electronic structure.
Advisors/Committee Members: Conrad, Edward H. (advisor), Jiang, Zhigang (committee member), Alamgir, Faisal (committee member), de Heer, Walter A. (committee member), First, Phillip N. (committee member).
Subjects/Keywords: SiC; Graphene; Graphite; Silicon carbide; Thin film
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APA (6th Edition):
Wang, F. (2015). Surface/interface modification and characterization of C-face epitaxial graphene. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53855
Chicago Manual of Style (16th Edition):
Wang, Feng. “Surface/interface modification and characterization of C-face epitaxial graphene.” 2015. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/53855.
MLA Handbook (7th Edition):
Wang, Feng. “Surface/interface modification and characterization of C-face epitaxial graphene.” 2015. Web. 10 Jul 2020.
Vancouver:
Wang F. Surface/interface modification and characterization of C-face epitaxial graphene. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/53855.
Council of Science Editors:
Wang F. Surface/interface modification and characterization of C-face epitaxial graphene. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/53855
Georgia Tech
11.
Hankinson, John H.
Spin dependent current injection into epitaxial graphene nanoribbons.
Degree: PhD, Physics, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/53884
► Over the past decade there has been a great deal of interest in graphene, a 2-dimensional allotrope of carbon with exceptional mechanical and electrical properties.…
(more)
▼ Over the past decade there has been a great deal of interest in graphene, a 2-dimensional allotrope of carbon with exceptional mechanical and electrical properties. Its outstanding mobility, minimal size, and mechanical stability make it an appealing material for use in next generation electronic devices. Epitaxial graphene growth on silicon carbide is a reliable, scalable method for the production of high quality graphene films. Recent work has shown that the SiC can be patterned prior to graphitization, in order to selectively grow graphene nanostructures. Graphene nanoribbons grown using this technique do not suffer from the rough edges caused by lithographic patterning, and recent measurements have revealed extraordinary transport properties. In this thesis the magnetic properties of these nanoribbons are investigated through spin polarized current injection. The sensitivity of these nanoribbons to spin polarized current is interesting from a fundamental physics standpoint, and may find applications in future spintronic devices.
Advisors/Committee Members: de Heer, Walter (advisor), First, Phillip (committee member), Conrad, Edward (committee member), Jiang, Zhigang (committee member), Haddon, Robert (committee member).
Subjects/Keywords: Graphene; Nanoribbons; Transport; Magnetism; Nanoelectronics; Spintronics
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APA (6th Edition):
Hankinson, J. H. (2015). Spin dependent current injection into epitaxial graphene nanoribbons. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53884
Chicago Manual of Style (16th Edition):
Hankinson, John H. “Spin dependent current injection into epitaxial graphene nanoribbons.” 2015. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/53884.
MLA Handbook (7th Edition):
Hankinson, John H. “Spin dependent current injection into epitaxial graphene nanoribbons.” 2015. Web. 10 Jul 2020.
Vancouver:
Hankinson JH. Spin dependent current injection into epitaxial graphene nanoribbons. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/53884.
Council of Science Editors:
Hankinson JH. Spin dependent current injection into epitaxial graphene nanoribbons. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/53884
Georgia Tech
12.
Palmer, James Matthew.
Pre-growth structures for high quality epitaxial graphene nanoelectronics grown on silicon carbide.
Degree: PhD, Physics, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/54293
► For graphene to be a viable platform for nanoscale devices, high quality growth and structures are necessary. This means structuring the SiC surface to prevent…
(more)
▼ For graphene to be a viable platform for nanoscale devices, high quality growth and structures are necessary. This means structuring the SiC surface to prevent graphene from having to be patterned using standard microelectronic processes. Presented in this thesis are new processes aimed at improving the graphene as well as devices based on high quality graphene nanoribbons. Amorphous carbon (aC) corrals deposited prior to graphene growth are demonstrated to control SiC step-flow. SiC steps are shown to be aligned by the presence of the corrals and can increase SiC terrace widths. aC contacts deposited and crystallized during graphene growth are shown as a way to contact graphene without metal lift-off. Observation of the Quantum Hall Effect demonstrates the high quality of the graphene grown alongside the nanocrystalline graphite contacts. Continuing the ballistic transport measurements on sidewall graphene nanoribbons, the invasive probe effect is observed using an atomic force microscope (AFM) based technique that spatially maps the invasive probe effect. Cleaning experiments demonstrate the role of scattering due to resist residues and environmental adsorbates on graphene nanoribbons. Finally, switches based on junctions formed in the graphene nanoribbons are shown as a route toward graphene based devices.
Advisors/Committee Members: de Heer, Walt A. (advisor), Jiang, Zhigang (committee member), Mani, Ramesh (committee member), Conrad, Edward H. (committee member), First, Phillip N. (committee member).
Subjects/Keywords: Graphene; Nanoelectronics; Condensed matter physics; Epitaxial graphene; Epitaxy; Silicon carbide; Tunneling; Step-flow; Amorphous carbon
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APA (6th Edition):
Palmer, J. M. (2014). Pre-growth structures for high quality epitaxial graphene nanoelectronics grown on silicon carbide. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54293
Chicago Manual of Style (16th Edition):
Palmer, James Matthew. “Pre-growth structures for high quality epitaxial graphene nanoelectronics grown on silicon carbide.” 2014. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/54293.
MLA Handbook (7th Edition):
Palmer, James Matthew. “Pre-growth structures for high quality epitaxial graphene nanoelectronics grown on silicon carbide.” 2014. Web. 10 Jul 2020.
Vancouver:
Palmer JM. Pre-growth structures for high quality epitaxial graphene nanoelectronics grown on silicon carbide. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/54293.
Council of Science Editors:
Palmer JM. Pre-growth structures for high quality epitaxial graphene nanoelectronics grown on silicon carbide. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/54293
Georgia Tech
13.
Chen, Xunchi.
A point contact spectroscopy study of topological superconductivity.
Degree: PhD, Physics, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/54874
► The study of topological superconductivity has been at the forefront of condensed matter physics for the past few years. Topological superconductors are predicted to have…
(more)
▼ The study of topological superconductivity has been at the forefront of condensed matter physics for the past few years. Topological superconductors are predicted to have odd parity pairing and host so called Majorana fermions, which are not only of fundamental importance, but also proposed to be building blocks for fault-tolerant quantum computing. In this dissertation, we use point contact spectroscopy to study the pairing symmetry of candidate topological superconducting materials. We study proximity induced superconductivity in the topological insulator Bi2Se3 by a superconducting niobium tip, and propose a model to explain its features in point contact spectra. We further study the nature of the superconductivity in highly doped superconducting topological insulators, including CuxBi2Se3 and Sn1-xInxTe, using both a normal metal gold tip and a superconducting niobium tip. For CuxBi2Se3, we observe a robust zero-bias conductance peak (ZBCP) in the differential conductance spectra with the gold point contact, while with the niobium point contact we find the height of the peak exhibiting unusual non-monotonic temperature dependence. We argue that both observations cannot be explained by Andreev reflection within the standard Blonder-Tinkham-Klapwijk (BTK) model, but signify unconventional superconductivity in the material. For Sn1-xInxTe samples, we observe ZBCP in the differential conductance spectra with the gold point contact, while with the niobium point contact, the temperature dependence of ZBCP is monotonic as expected from conventional theory, leaving the nature of the superconductivity of Sn1-xInxTe still an open question.
Advisors/Committee Members: Jiang, Zhigang (advisor), Zangwill, Andrew (committee member), First, Phillip (committee member), Mourigal, Martin (committee member), Bellissard, Jean (committee member).
Subjects/Keywords: Topological superconductor; Topological insulator; Point contact spectroscopy; Odd parity superconductivity
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APA (6th Edition):
Chen, X. (2015). A point contact spectroscopy study of topological superconductivity. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54874
Chicago Manual of Style (16th Edition):
Chen, Xunchi. “A point contact spectroscopy study of topological superconductivity.” 2015. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/54874.
MLA Handbook (7th Edition):
Chen, Xunchi. “A point contact spectroscopy study of topological superconductivity.” 2015. Web. 10 Jul 2020.
Vancouver:
Chen X. A point contact spectroscopy study of topological superconductivity. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/54874.
Council of Science Editors:
Chen X. A point contact spectroscopy study of topological superconductivity. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/54874
Georgia Tech
14.
Zhuo, Keenan.
Electronic, thermoelectric and vibrational properties of silicon nanowires and copper chalcogenides.
Degree: PhD, Physics, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/54878
► Silicon nanowires (SiNWs) and the copper chalcogenides, namely copper sulfide (Cu2S) and selenide Cu2Se, have diverse applications in renewable energy technology. For example, SiNWs which…
(more)
▼ Silicon nanowires (SiNWs) and the copper chalcogenides, namely copper sulfide (Cu2S) and selenide Cu2Se, have diverse applications in renewable energy technology. For example, SiNWs which have direct band gaps unlike bulk Si, have the potential to radically reduce the cost of Si based photovoltaic cells. However, they degrade quickly under ambient conditions. Various surface passivations have therefore been investigated for enhancing their stability but it is not yet well understood how they affect the electronic structure of SiNWs at a fundamental level. Here, we will explore, from first-principles simulation, how fluorine, methyl and hydrogen surface passivations alter the electronic structures of [111] and [110] SiNWs via strain and quantum confinement. We also show how electronic charge states in [111] and [110] SiNWs can be effectively modelled by simple quantum wells. In addition, we address the issue of why [111] SiNWs are less influenced by their surface passivation than [110] SiNWs. Like SiNWs, Cu2S and Cu2Se also make excellent photovoltaic cells. However, they are most well known for their exceptional thermoelectric performance. This is by virtue of their even more unique solid-liquid hybrid nature which combines the low thermal conductivity and good electrical characteristics required for a high thermoelectric efficiency. We use first-principles molecular dynamics simulations to show that Cu diffusion rates in Cu2S and Cu2Se can be as high as 10-5cm2s-1. We also relate their phonon power spectra to their low thermal conductivities. Furthermore, we evaluate the thermoelectric properties of Cu2S and Cu2Se using a combination of Boltzmann transport theory and first-principles electronic structure calculations. Our results show that both Cu2S and Cu2Se are capable of maintaining high Seebeck coefficients in excess of 200μVK-1 for hole concentrations as high as 3x1020cm-3.
Advisors/Committee Members: Chou, Mei-Yin (advisor), Zangwill, Andrew (committee member), Landman, Uzi (committee member), Jiang, Zhigang (committee member), Wang, Xiao-Qian (committee member).
Subjects/Keywords: Thermoelectric; Silicon nanowire; Copper chalcogenide; Cu2s; Cu2se; Molecular dynamics; First-principles; Ab-initio; Density functional theory; Electronic structure; Diffusion; Superionic; Solid-liquid hybrid; Quantum confinement
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APA ·
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APA (6th Edition):
Zhuo, K. (2015). Electronic, thermoelectric and vibrational properties of silicon nanowires and copper chalcogenides. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54878
Chicago Manual of Style (16th Edition):
Zhuo, Keenan. “Electronic, thermoelectric and vibrational properties of silicon nanowires and copper chalcogenides.” 2015. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/54878.
MLA Handbook (7th Edition):
Zhuo, Keenan. “Electronic, thermoelectric and vibrational properties of silicon nanowires and copper chalcogenides.” 2015. Web. 10 Jul 2020.
Vancouver:
Zhuo K. Electronic, thermoelectric and vibrational properties of silicon nanowires and copper chalcogenides. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/54878.
Council of Science Editors:
Zhuo K. Electronic, thermoelectric and vibrational properties of silicon nanowires and copper chalcogenides. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/54878
Georgia Tech
15.
Li, Yuntao.
Nanostructured graphene on Si-terminated SiC and its electronic properties.
Degree: PhD, Physics, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/54964
► Graphene nanostructures directly grown on SiC are appealing for their potential application to nano-scale electronic devices. In particular, epitaxial sidewall graphene nanoribbons have been a…
(more)
▼ Graphene nanostructures directly grown on SiC are appealing for their potential application to nano-scale electronic devices. In particular, epitaxial sidewall graphene nanoribbons have been a promising candidate in ballistic transport and band gap engineering. In this thesis, we study graphene nanoribbons by utilizing both nano-lithography and natural step bunching to control the step morphology of the SiC(0001) surface in order to guide the growth of graphene which initiates at step edges, and study their respective characteristics. With scanning tunneling microscopy and spectroscopy (STM/STS), we explore the local atomic and electronic structures of the graphene nanoribbons down to atomic scale. It is found that nanoribbon formation depends critically on nanofacet orientation, nanofacet density, and growth conditions. Under some conditions, nanoribbons grow predominantly on the nanofacet. Significant electronic density-of-states features, resolved by STS, are found to depend strongly on proximity to strained graphene near the step edge. Experimental results are compared to Molecular Dynamics simulations to better understand the origin of the discrete electronic states.
Advisors/Committee Members: First, Phillip N (advisor), Jiang, Zhigang (committee member), Conrad, Edward H (committee member), Kindermann, Markus (committee member), Orlando, Thomas (committee member).
Subjects/Keywords: Graphene; Nanoribbon; STM; Epitaxy; Strain; Sidewall
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APA (6th Edition):
Li, Y. (2016). Nanostructured graphene on Si-terminated SiC and its electronic properties. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54964
Chicago Manual of Style (16th Edition):
Li, Yuntao. “Nanostructured graphene on Si-terminated SiC and its electronic properties.” 2016. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/54964.
MLA Handbook (7th Edition):
Li, Yuntao. “Nanostructured graphene on Si-terminated SiC and its electronic properties.” 2016. Web. 10 Jul 2020.
Vancouver:
Li Y. Nanostructured graphene on Si-terminated SiC and its electronic properties. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/54964.
Council of Science Editors:
Li Y. Nanostructured graphene on Si-terminated SiC and its electronic properties. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/54964
Georgia Tech
16.
Zhang, Siyuan.
Controlled doping of organic semiconductors and 2d materials with molecular reductants and oxidants.
Degree: PhD, Chemistry and Biochemistry, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/55616
► New air-stable dimeric n-dopants are synthesized and studied in detail with respect to the kinetics of both their redox reaction in solution with and their…
(more)
▼ New air-stable dimeric n-dopants are synthesized and studied in detail with respect to the kinetics of both their redox reaction in solution with and their doping in the solid-state of various organic semiconductor acceptors. Detailed mechanistic studies are necessary to recognize the strengths and limitations of existing dimers to inform future dopant design. The newly synthesized n-dopants together with other redox-active n- and p-dopants are then used to surface modify mono- and multi-layer graphene, which shows a large decrease in the sheet resistance and tunable work function shifts. A subset of these molecules is applied to MoS2 and WSe2 to realize controllable n- and p-doping, respectively, to improve their electrical properties. Other experimental techniques, especially UPS and XPS, are coupled with the electrical measurements to give information about work function shifts, surface coverage, charge transfer efficiency, and etc. Finally, organic diodes, solar cells, and field-effect transistors with doped graphene electrodes were fabricated, where the work function engineering of graphene electrodes via doping proved to be important in reducing the carrier-injection barriers.
Advisors/Committee Members: Marder, Seth R. (advisor), Collard, David M. (advisor), Reynolds, John (committee member), Jiang, Zhigang (committee member), Brédas, Jean-Luc (committee member).
Subjects/Keywords: Doping; Organic semiconductor; Graphene; TMDCs; 2D
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APA ·
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APA (6th Edition):
Zhang, S. (2016). Controlled doping of organic semiconductors and 2d materials with molecular reductants and oxidants. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/55616
Chicago Manual of Style (16th Edition):
Zhang, Siyuan. “Controlled doping of organic semiconductors and 2d materials with molecular reductants and oxidants.” 2016. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/55616.
MLA Handbook (7th Edition):
Zhang, Siyuan. “Controlled doping of organic semiconductors and 2d materials with molecular reductants and oxidants.” 2016. Web. 10 Jul 2020.
Vancouver:
Zhang S. Controlled doping of organic semiconductors and 2d materials with molecular reductants and oxidants. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/55616.
Council of Science Editors:
Zhang S. Controlled doping of organic semiconductors and 2d materials with molecular reductants and oxidants. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/55616
Georgia Tech
17.
Ramos Alvarado, Bladimir.
The effect of wetting transparency on the interfacial phenomena between water and solid surfaces: An atomistic modeling investigation.
Degree: PhD, Mechanical Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/56233
► Experimental and numerical investigations indicate that surface effects govern the transport phenomena in nanoconfined liquids. The wettability of solid surfaces, usually characterized by the static…
(more)
▼ Experimental and numerical investigations indicate that surface effects govern the transport phenomena in nanoconfined liquids. The wettability of solid surfaces, usually characterized by the static contact angle, has been used to correlate the hydrodynamic boundary condition and the thermal transport at solid-liquid interfaces. Recent investigations suggest the existence of quasiuniversal laws correlating the hydrodynamic slip length and the contact angle in nanoconfined liquid flows. Likewise, a correlation between the work of adhesion and the thermal boundary conductance has been consistently reported in previous investigations. Classical molecular dynamics simulations and a physically sound theoretical background were used to critically assess the effects of wettability on the interfacial momentum and thermal energy transport at solid-liquid interfaces. In particular, the silicon-water interface was investigated due to the rising importance of silicon-based sensors and devices operating in aqueous environments. The wettability of the Si(100) and Si(111) planes was theoretically and numerically characterized. Additionally, the recently discovered wettability transparency phenomenon was considered in this investigation in order to provide a broader perspective of the wettability effects on interfacial transport phenomena. The results indicated that although the wettability of a given surface can be of practical use to describe the hydrodynamic boundary condition and thermal transport in nanoconfined liquids, the interfacial liquid structure properties give a universal description of these phenomena which is being reported here for the first time. These groundbreaking results provide the foundations to theoretically tackle the challenging task of describing interfacial transport in nanoconfined liquids; likewise, these results suggest the possibility of developing highly efficient nanofluidics devices with applications in the biomedical sciences, the energy sector, ultrafast flow delivery systems, low friction nano- and microgap bearings, etc., by means of tailoring the properties of the interfaces in order to achieve low friction flows or highly conductive solid-liquid interfaces.
Advisors/Committee Members: Peterson, G. P. (advisor), Kumar, Satish (committee member), Zhang, Zhuomin (committee member), Alexeev, Alexander (committee member), Jiang, Zhigang (committee member).
Subjects/Keywords: Wettability; MD; Nanoscale; Thermal transport; Graphene; Slip
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APA (6th Edition):
Ramos Alvarado, B. (2016). The effect of wetting transparency on the interfacial phenomena between water and solid surfaces: An atomistic modeling investigation. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/56233
Chicago Manual of Style (16th Edition):
Ramos Alvarado, Bladimir. “The effect of wetting transparency on the interfacial phenomena between water and solid surfaces: An atomistic modeling investigation.” 2016. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/56233.
MLA Handbook (7th Edition):
Ramos Alvarado, Bladimir. “The effect of wetting transparency on the interfacial phenomena between water and solid surfaces: An atomistic modeling investigation.” 2016. Web. 10 Jul 2020.
Vancouver:
Ramos Alvarado B. The effect of wetting transparency on the interfacial phenomena between water and solid surfaces: An atomistic modeling investigation. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/56233.
Council of Science Editors:
Ramos Alvarado B. The effect of wetting transparency on the interfacial phenomena between water and solid surfaces: An atomistic modeling investigation. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/56233
Georgia Tech
18.
Joiner, Corey Alexander.
Impact of materials disorder on graphene heterostructure devices.
Degree: PhD, Materials Science and Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/56243
► This work is focused on characterizing the impact of material based disorder on the properties of graphene based vertical tunneling heterostructures. The motivation and challenges…
(more)
▼ This work is focused on characterizing the impact of material based disorder on the properties of graphene based vertical tunneling heterostructures. The motivation and challenges for replacing silicon for low power digital electronics has been presented. The status of the research on graphene based digital electronics is critically reviewed. Scalable methods for synthesizing large area two dimensional materials including graphene, molybdenum disulfide, and hexagonal boron nitride are integrated into a complex CMOS fabrication process to investigate the impact of disorder on the properties of vertical graphene based heterostructures for low power digital electronics. The CMOS fabrication process was found to introduce contaminants in the form of polymeric residues that reduced the lateral conduction of the graphene. Thermal decomposition of the residues resulted in the introduction of defects in the graphene. A chemical etching method utilizing a sacrificial titanium layer removed via HF etching effectively removed the contaminants without damaging the graphene.
Dielectric tunneling barriers were deposited by atomic layer deposition (ALD). The composition of the tunneling barrier was experimentally shown to alter the electrical performance of the graphene heterostructure and allows barrier engineering for tailoring the electrical properties of the device. The thickness of the tunneling barrier was shown to control the dominant tunneling mechanism with barriers less than ~3 nm required for direct tunneling. The impact of the graphene on the electrical performance of the device was investigated by using graphene of various domain sizes. No dependence was found on the graphene domain size suggesting the tunneling barrier dielectric or device substrate is limiting the device performance.
Following recent reports utilizing exfoliated materials, two dimensional materials (molybdenum disulfide and hexagonal boron nitride) complimentary to graphene were utilized as tunneling dielectrics to further improve the device performance over conventional dielectric materials. The direct synthesis of complimentary two dimensional materials on graphene was shown to introduce defects into the graphene structure and to suppress the electrical properties of the device. Trapping of electrons in the MoS2 defect states was shown to drastically suppress the tunneling current compared to less defective exfoliated materials. Decreasing the synthesis temperature of the MoS2 was shown as a potential pathway for reducing the induced defects in the graphene.
A large area synthesized hexagonal boron nitride buffer layer was shown to improve the lateral conduction of the graphene. Contrary to reports of exfoliated materials, the introduction of a hexagonal boron nitride tunneling barrier was shown to reduce the mobility of the graphene due to increased scattering as a result of defects in the hexagonal boron nitride as well as contamination introduced during the transfer process. The lateral conductance of the graphene was shown to be improved…
Advisors/Committee Members: Vogel, Eric M. (advisor), Tsukruk, Vladimir V. (committee member), Alamgir, Faisal M. (committee member), Lin, Zhiqun (committee member), Jiang, Zhigang (committee member).
Subjects/Keywords: Tunneling field effect transistor; Graphene; Molybdenum disulfide; Hexagonal boron nitride; Field effect transistor; TFET; FET; CMOS
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APA (6th Edition):
Joiner, C. A. (2016). Impact of materials disorder on graphene heterostructure devices. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/56243
Chicago Manual of Style (16th Edition):
Joiner, Corey Alexander. “Impact of materials disorder on graphene heterostructure devices.” 2016. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/56243.
MLA Handbook (7th Edition):
Joiner, Corey Alexander. “Impact of materials disorder on graphene heterostructure devices.” 2016. Web. 10 Jul 2020.
Vancouver:
Joiner CA. Impact of materials disorder on graphene heterostructure devices. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/56243.
Council of Science Editors:
Joiner CA. Impact of materials disorder on graphene heterostructure devices. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/56243
19.
Hahn, David Gil.
Viscoelastic polymer-assisted mechanical exfoliation of large area highly oriented pyrolytic graphite.
Degree: MS, Mechanical Engineering, 2017, Georgia Tech
URL: http://hdl.handle.net/1853/58235
► There is a growing demand for a cost-effective, scalable, and reliable production method for 2D van der Waals materials such as graphene and pyrolytic graphite…
(more)
▼ There is a growing demand for a cost-effective, scalable, and reliable production method for 2D van der Waals materials such as graphene and pyrolytic graphite sheets, because of their attractive thermal/electrical/physical properties. This thesis reports on the study of a viscoelastic polymer stamp-based mechanical exfoliation technique capable of yielding large area (~square centimeters or larger) thin (<1 micron) graphite sheets from a highly ordered pyrolytic graphite (HOPG) substrate by tailoring the properties of a Polydimethylsiloxane (PDMS) stamp and other key exfoliation process parameters. Experiments show that the exfoliated layers consist of a range of layer thicknesses, surface areas, and several topographical features such as bubbles, wrinkles, and compressed regions. Several hypotheses are put forth to reduce the thickness of the exfoliated layers and to eliminate the abovementioned defect structures while preserving the large surface area. In particular, the effect of PDMS stamp curing time, the effect of surface roughness, the effect of high frequency shear oscillation, and the effect of PDMS stamp thickness are studied systematically. The results of these studies show that the PDMS stamp based mechanical exfoliation process can produce high quality, large area, thin sheets of pyrolytic graphite. This work serves as the first step toward developing a scalable, top-down production method for large area graphite sheets and other 2D van der Waals materials of interest.
Advisors/Committee Members: Melkote, Shreyes (advisor), Saldana, Christopher (committee member), Jiang, Zhigang (committee member).
Subjects/Keywords: Graphite; HOPG; PDMS; Mechanical exfoliation
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APA (6th Edition):
Hahn, D. G. (2017). Viscoelastic polymer-assisted mechanical exfoliation of large area highly oriented pyrolytic graphite. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/58235
Chicago Manual of Style (16th Edition):
Hahn, David Gil. “Viscoelastic polymer-assisted mechanical exfoliation of large area highly oriented pyrolytic graphite.” 2017. Masters Thesis, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/58235.
MLA Handbook (7th Edition):
Hahn, David Gil. “Viscoelastic polymer-assisted mechanical exfoliation of large area highly oriented pyrolytic graphite.” 2017. Web. 10 Jul 2020.
Vancouver:
Hahn DG. Viscoelastic polymer-assisted mechanical exfoliation of large area highly oriented pyrolytic graphite. [Internet] [Masters thesis]. Georgia Tech; 2017. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/58235.
Council of Science Editors:
Hahn DG. Viscoelastic polymer-assisted mechanical exfoliation of large area highly oriented pyrolytic graphite. [Masters Thesis]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/58235
Georgia Tech
20.
Shams Mousavi, Seyed Hamed.
Plasmonic Nanostructures and Metamaterials for Nanoscale Light-Matter Interaction.
Degree: PhD, Electrical and Computer Engineering, 2018, Georgia Tech
URL: http://hdl.handle.net/1853/62184
► The objective of this dissertation is to study the light-matter interaction phenamena at nanoscale in the presence of plasmonic nanostructures and metamaterials. Using the principles…
(more)
▼ The objective of this dissertation is to study the light-matter interaction phenamena at nanoscale in the presence of plasmonic nanostructures and metamaterials. Using the principles of nano-optics, a range of plasmonic nanodevices are developped for molecular sensing, nonlinear optics and surface plasmon lasing. This theoretical and experimental investigation is further extended by studying the effect of plasmon tunneling in sub-nanometer distances and light-matter interaction in atomically thin semiconductors adjacent to plasmonic nanostructures.
More specifically, chemically synthesized plasmonic nanocube dimers and chains are studied for ultrasensitive molecular sensing using the wavelength shift of their localized surface plasmon resonance. The effect of interparticle spacing and relative orientation of the nanocubes in the nanocube chains has also been analyzed. The band-edge lattice plasmon waves in plasmonic nanoantenna arrays have been studied and utilized for surface-enhanced Raman spectroscopy. Superchiral spectroscopy at the molecular level is demonstrated using a novel three-dimensional chiral metamaterial. Furthermore, surface-enhanced second harmonic generation in coupled plasmonic nanostructures that support sharp Fano-type resonance features, is studied theoretically and experimentally. Finally, a plasmonic nanolaser incorporating a plasmonic nanocavity and a monolayer of transition metal dichalcogenide is developed.
Advisors/Committee Members: Adibi, Ali (advisor), El-Sayed, Mostafa A. (committee member), Cai, Wenshan (committee member), Klein, Benjamin (committee member), Jiang, Zhigang (committee member), Harutyunyan, Hayk (committee member).
Subjects/Keywords: Plasmonics; Photonics; Metamaterials; Nonlinear Optics; Biosensing; Lasing
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APA (6th Edition):
Shams Mousavi, S. H. (2018). Plasmonic Nanostructures and Metamaterials for Nanoscale Light-Matter Interaction. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/62184
Chicago Manual of Style (16th Edition):
Shams Mousavi, Seyed Hamed. “Plasmonic Nanostructures and Metamaterials for Nanoscale Light-Matter Interaction.” 2018. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/62184.
MLA Handbook (7th Edition):
Shams Mousavi, Seyed Hamed. “Plasmonic Nanostructures and Metamaterials for Nanoscale Light-Matter Interaction.” 2018. Web. 10 Jul 2020.
Vancouver:
Shams Mousavi SH. Plasmonic Nanostructures and Metamaterials for Nanoscale Light-Matter Interaction. [Internet] [Doctoral dissertation]. Georgia Tech; 2018. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/62184.
Council of Science Editors:
Shams Mousavi SH. Plasmonic Nanostructures and Metamaterials for Nanoscale Light-Matter Interaction. [Doctoral Dissertation]. Georgia Tech; 2018. Available from: http://hdl.handle.net/1853/62184
21.
Benjamin, Daniel.
Thermal transport and photo-induced charge transport in graphene.
Degree: PhD, Physics, 2011, Georgia Tech
URL: http://hdl.handle.net/1853/42746
► The electronic material graphene has attracted much attention for its unique physical properties such as, linear band structure, high electron mobility, and room temperature ballistic…
(more)
▼ The electronic material graphene has attracted much attention for its unique physical properties such as, linear band structure, high electron mobility, and room temperature ballistic conduction. The possibilities for device applications utilizing graphene show great variety, from transistors for computing to chemical sensors. Yet, there are still several basic physical properties such as thermal conductivity that need to be determined accurately.
This work examines the thermal properties of graphene grown by the chemical vapor deposition technique. The thermoelectric power of graphene is studied in ambient and vacuum environments and is shown to be highly sensitive to surface charge doping. Exploiting this effect, we study the change in thermoelectric power due to introduction of gaseous species. The temperature dependent thermal conductivity of graphene is measured using a comparison method. We show that the major contribution to the thermal conductivity is the scattering of in-plane phonons.
Graphene also shows promise as an optoelectronic material. We probe the Landau level structure of graphene in high magnetic fields using a differential photoconductivity technique. Using this method we observed the lifting of spin and valley degeneracies of the lowest Landau level in graphene.
Advisors/Committee Members: Jiang, Zhigang (Committee Chair), Conrad, Edward (Committee Member), First, Phillip (Committee Member), Graham, Samuel (Committee Member), Zangwill, Andrew (Committee Member).
Subjects/Keywords: Thermal properties; Photoconductivity; Graphene; Graphene; Heat Transmission; Charge transfer
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APA (6th Edition):
Benjamin, D. (2011). Thermal transport and photo-induced charge transport in graphene. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/42746
Chicago Manual of Style (16th Edition):
Benjamin, Daniel. “Thermal transport and photo-induced charge transport in graphene.” 2011. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/42746.
MLA Handbook (7th Edition):
Benjamin, Daniel. “Thermal transport and photo-induced charge transport in graphene.” 2011. Web. 10 Jul 2020.
Vancouver:
Benjamin D. Thermal transport and photo-induced charge transport in graphene. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/42746.
Council of Science Editors:
Benjamin D. Thermal transport and photo-induced charge transport in graphene. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/42746
22.
Wong, Tsz Chun.
Single-shot measurements of complex pulses using frequency-resolved optical gating.
Degree: PhD, Physics, 2013, Georgia Tech
URL: http://hdl.handle.net/1853/50335
► Frequency-resolved optical gating (FROG) is the standard for measuring femtosecond laser pulses. It measures relatively simple pulses on a single-shot and complex pulses using multi-shot…
(more)
▼ Frequency-resolved optical gating (FROG) is the standard for measuring femtosecond laser pulses. It measures relatively simple pulses on a single-shot and complex pulses using multi-shot scanning and averaging. However, experience from intensity autocorrelation suggests that multi-shot measurements may suffer from a coherent artifact caused by instability in the laser source. In this thesis, the coherent artifacts present in modern pulse measurement techniques are examined and single-shot techniques for measuring complex pulse(s) are proposed and demonstrated. The study of the coherent artifact in this work shows that modern pulse measurement techniques also suffer from coherent artifacts and therefore single-shot measurements should be performed when possible. Here, two single-shot experimental setups are developed for different scenarios. First, an extension of FROG is developed to measure two unknown pulses simultaneously on a single-shot. This setup can measure pulses that have very different center wavelengths, spectral bandwidths, and complexities. Second, pulse-front tilt is incorporated to extend the temporal range of single-shot FROG to tens of picoseconds which traditionally can only be attained by multi-shot scanning. Finally, the pulse-front tilt setup is modified to perform a single-shot measurement of supercontinuum, one of the most difficult pulses to measure due to its long temporal range, broad spectral bandwidth, and low pulse energy.
Advisors/Committee Members: Trebino, Rick (advisor), Curtis, Jennifer (committee member), Jiang, Zhigang (committee member), Buck, John (committee member), Adibi, Ali (committee member).
Subjects/Keywords: Ultrafast optics; Ultrafast measurement; Laser pulses, Ultrashort Measurement
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APA (6th Edition):
Wong, T. C. (2013). Single-shot measurements of complex pulses using frequency-resolved optical gating. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/50335
Chicago Manual of Style (16th Edition):
Wong, Tsz Chun. “Single-shot measurements of complex pulses using frequency-resolved optical gating.” 2013. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/50335.
MLA Handbook (7th Edition):
Wong, Tsz Chun. “Single-shot measurements of complex pulses using frequency-resolved optical gating.” 2013. Web. 10 Jul 2020.
Vancouver:
Wong TC. Single-shot measurements of complex pulses using frequency-resolved optical gating. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/50335.
Council of Science Editors:
Wong TC. Single-shot measurements of complex pulses using frequency-resolved optical gating. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/50335
23.
Turmaud, Jean-Philippe.
Variable range hopping conduction in the epitaxial graphene buffer layer on SiC(0001).
Degree: PhD, Physics, 2018, Georgia Tech
URL: http://hdl.handle.net/1853/60254
► The properties of epitaxial graphene grown by thermal decomposition of hexagonal silicon carbide (SiC) have been the focus of extensive research for several decades now.…
(more)
▼ The properties of epitaxial graphene grown by thermal decomposition of hexagonal silicon carbide (SiC) have been the focus of extensive research for several decades now. In this thesis I am interested in the electronic transport properties of the first graphene layer grown on the (0001) of SiC, referred to as the buffer layer. It has been shown previously that the buffer layer is structurally a continuous graphene layer subject to periodic interactions with the underlying substrate. Electronically, the band structure presents a gap around the Fermi level. While much effort has been devoted to the surface science of the buffer layer, little is known about the actual dynamics of its charge carriers. To shed light on its properties as an electronic material, I performed temperature and bias voltage dependent electronic transport measurements on buffer layer devices. The buffer layer is found to display an insulating behavior with the conductivity following a 2D Mott variable range hopping model between 80K and 420K. At lower temperatures, the hopping can also be activated by a strong bias electric field. An effective temperature can be defined to take into account both temperature and electric field, which gives an estimate for the localization length of electrons in the buffer layer between 1 and 2 nm. A model of localization based on the image potential experienced by charges in the corrugation of the buffer layer is presented to explain the observed transport properties.
Advisors/Committee Members: First, Phillip N. (committee member), Jiang, Zhigang (committee member), Mourigal, Martin (committee member), Yoder, Paul D. (committee member).
Subjects/Keywords: Epitaxial graphene; Buffer layer; Variable range hopping conduction; Silicon carbide; Electronic transport; Image charge
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Export
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APA (6th Edition):
Turmaud, J. (2018). Variable range hopping conduction in the epitaxial graphene buffer layer on SiC(0001). (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/60254
Chicago Manual of Style (16th Edition):
Turmaud, Jean-Philippe. “Variable range hopping conduction in the epitaxial graphene buffer layer on SiC(0001).” 2018. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/60254.
MLA Handbook (7th Edition):
Turmaud, Jean-Philippe. “Variable range hopping conduction in the epitaxial graphene buffer layer on SiC(0001).” 2018. Web. 10 Jul 2020.
Vancouver:
Turmaud J. Variable range hopping conduction in the epitaxial graphene buffer layer on SiC(0001). [Internet] [Doctoral dissertation]. Georgia Tech; 2018. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/60254.
Council of Science Editors:
Turmaud J. Variable range hopping conduction in the epitaxial graphene buffer layer on SiC(0001). [Doctoral Dissertation]. Georgia Tech; 2018. Available from: http://hdl.handle.net/1853/60254
24.
Kubista, Kevin Dean.
Local measurements of cyclotron states in graphene.
Degree: PhD, Physics, 2011, Georgia Tech
URL: http://hdl.handle.net/1853/39592
► Multilayer epitaxial graphene has been shown to contain "massless Dirac fermions" and is believed to provide a possible route to industrial-scale graphene electronics. We used…
(more)
▼ Multilayer epitaxial graphene has been shown to contain "massless Dirac fermions" and is believed to provide a possible route to industrial-scale graphene electronics. We used scanning tunneling microscopy (STM) and spectroscopy (STS) in high magnetic fields to obtain local information on these fermions. A new STS technique was developed to directly measure graphene's energy-momentum relationship and resulted in the highest precision measurement of graphene's Dirac cone. STS spectra similar to ideal graphene were observed, but additional anomalies were also found. Extra peaks and an asymmetry between electron and hole states were shown to be caused by the work function difference between the Iridium STM tip and graphene. This tip effect was extracted using modeled potentials and performing a least square fit using degenerate perturbation theory on graphene's eigenstates solved in the symmetric gauge. Defects on graphene were then investigated and magnetic field effects were shown to be due to a mixture of potential effect from defects and the tip potential. New defect states were observed to localize around specific defects, and are believed to interact with the STM tip by Stark shifting in energy. This Stark shift gives a direct measurement of the capacitive coupling between the tip and graphene and agrees with the modeled results found when extracting the tip potential.
Advisors/Committee Members: First, Phillip (Committee Chair), Jiang, Zhigang (Committee Member), Kindermann, Markus (Committee Member), Stroscio, Joseph, (Committee Member), Zangwill, Andrew (Committee Member).
Subjects/Keywords: Graphene; Defect; Scanning tunneling spectroscopy; STS; Tip induced band bending; TIBB; Landau level; Scanning tunneling microscopy STM; Energy levels (Quantum mechanics); Electronics Materials; Fermions
…institutions such as Georgia Tech,14 IBM,7 and research
collaborations like NRI15 strive to control…
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APA (6th Edition):
Kubista, K. D. (2011). Local measurements of cyclotron states in graphene. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/39592
Chicago Manual of Style (16th Edition):
Kubista, Kevin Dean. “Local measurements of cyclotron states in graphene.” 2011. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/39592.
MLA Handbook (7th Edition):
Kubista, Kevin Dean. “Local measurements of cyclotron states in graphene.” 2011. Web. 10 Jul 2020.
Vancouver:
Kubista KD. Local measurements of cyclotron states in graphene. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/39592.
Council of Science Editors:
Kubista KD. Local measurements of cyclotron states in graphene. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/39592
25.
Gartland, Patrick.
Effects of the spin-orbit interaction on electron tunneling in single ferromagnetic nanoparticles.
Degree: PhD, Physics, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/56154
► Recent technological innovations such as giant magnetoresistance and spin-transfer torque, along with a desire for researching the emergence of magnetism from a fundamental level, has…
(more)
▼ Recent technological innovations such as giant magnetoresistance and spin-transfer torque, along with a desire for researching the emergence of magnetism from a fundamental level, has led to much interest in understanding nanometer scale ferromagnets. In this dissertation, I use sequential electron tunneling to study the differential conductance spectra and magnetic properties of single cobalt and nickel particles below 5 nm in diameter, and observe a wealth of material-dependent effects. The spin-orbit interaction is a key mechanism in the observation of a variety of effects, including giant electron spin g-factors and shifts in the anisotropy energy of the magnetic particle upon the addition of a single electron. I show how such effects can lead to an effective magnetization blockade, which allows for the voltage control of magnetic hysteresis. I model the quantum mechanical system characteristics using master equations, and propose a new type of spin-transfer torque device that relies on the magnetization blockade effect.
Advisors/Committee Members: Davidovic, Dragomir (advisor), Jiang, Zhigang (committee member), Mourigal, Martin (committee member), Pustilnik, Michael (committee member), Anderson, David (committee member).
Subjects/Keywords: tunneling; ferromagnets; nanoparticles; hysteresis
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APA (6th Edition):
Gartland, P. (2015). Effects of the spin-orbit interaction on electron tunneling in single ferromagnetic nanoparticles. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/56154
Chicago Manual of Style (16th Edition):
Gartland, Patrick. “Effects of the spin-orbit interaction on electron tunneling in single ferromagnetic nanoparticles.” 2015. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/56154.
MLA Handbook (7th Edition):
Gartland, Patrick. “Effects of the spin-orbit interaction on electron tunneling in single ferromagnetic nanoparticles.” 2015. Web. 10 Jul 2020.
Vancouver:
Gartland P. Effects of the spin-orbit interaction on electron tunneling in single ferromagnetic nanoparticles. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/56154.
Council of Science Editors:
Gartland P. Effects of the spin-orbit interaction on electron tunneling in single ferromagnetic nanoparticles. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/56154
26.
Ruan, Ming.
Structured epitaxial graphene for electronics.
Degree: PhD, Physics, 2012, Georgia Tech
URL: http://hdl.handle.net/1853/45596
► After the pioneering investigations into graphene-based electronics at Georgia Tech, great strides have been made developing epitaxial graphene on silicon carbide (EG) as a new…
(more)
▼ After the pioneering investigations into graphene-based electronics at
Georgia Tech, great strides have been made developing epitaxial graphene on silicon carbide (EG) as a new electronic material. EG has not only demonstrated its potential for large scale applications, it also has become an important material for fundamental two-dimensional electron gas physics. Graphene is generally considered to be a strong candidate to succeed silicon as an electronic material. However, to date, it actually has not yet demonstrated capabilities that exceed standard semiconducting materials. One disadvantage of conventionally fabricated graphene devices is that nanoscopically patterned graphene tends to have disordered edges that severely reduce mobilities thereby obviating its advantage over other materials. The other disadvantage is that pristine graphene does not contain a band gap, which is critical for standard field effect transistor to operate. This thesis will show that graphene grown on structured silicon carbide surfaces overcomes the edge roughness and promises to provide an inroad into nanoscale patterning of graphene. High-quality ribbons and rings can be made using this technique.
Advisors/Committee Members: de Heer, Walt (Committee Chair), Conrad, Edward (Committee Member), Cressler, John (Committee Member), First, Phillip (Committee Member), Jiang, Zhigang. (Committee Member).
Subjects/Keywords: Ballistic transport; Structured growth; Epitaxial graphene; Graphene; Hydrocarbons; Electronics Materials; Semiconductors
…investigations into graphene-based electronics at Georgia Tech,
great strides have been made developing… …Georgia Tech group ([18], [19]) reported the electron transport… …sublimate growth technique at Georgia Tech[20] . Details of this technique will
be…
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APA (6th Edition):
Ruan, M. (2012). Structured epitaxial graphene for electronics. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/45596
Chicago Manual of Style (16th Edition):
Ruan, Ming. “Structured epitaxial graphene for electronics.” 2012. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/45596.
MLA Handbook (7th Edition):
Ruan, Ming. “Structured epitaxial graphene for electronics.” 2012. Web. 10 Jul 2020.
Vancouver:
Ruan M. Structured epitaxial graphene for electronics. [Internet] [Doctoral dissertation]. Georgia Tech; 2012. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/45596.
Council of Science Editors:
Ruan M. Structured epitaxial graphene for electronics. [Doctoral Dissertation]. Georgia Tech; 2012. Available from: http://hdl.handle.net/1853/45596
27.
Hu, Yike.
Production and properties of epitaxial graphene on the carbon terminated face of hexagonal silicon carbide.
Degree: PhD, Physics, 2013, Georgia Tech
URL: http://hdl.handle.net/1853/48705
► Graphene is widely considered to be a promising candidate for a new generation of electronics, but there are many outstanding fundamental issues that need to…
(more)
▼ Graphene is widely considered to be a promising candidate for a new generation of electronics, but there are many outstanding fundamental issues that need to be addressed before this promise can be realized. This thesis focuses on the production and properties of graphene grown epitaxially on the carbon terminated face (C-face) of hexagonal silicon carbide leading to the construction of a novel graphene transistor structure. C-face epitaxial graphene multilayers are unique due to their rotational stacking that causes the individual layers to be electronically decoupled from each other. Well-formed C-face epitaxial graphene single layers have exceptionally high mobilities (exceeding 10,000 cm ²/Vs), which are significantly greater than those of Si-face graphene monolayers. This thesis investigates the growth and properties of C-face single layer graphene. A field effect transistor based on single layer graphene was fabricated and characterized for the first time. Aluminum oxide or boron nitride was used for the gate dielectric. Additionally, an all graphene/SiC Schottky barrier transistor on the C-face of SiC composed of 2DEG in SiC/Si₂O ₃ interface and multilayer graphene contacts was demonstrated. A multiple growth scheme was adopted to achieve this unique structure.
Advisors/Committee Members: de Heer, Walter A. (advisor), Conrad, Edward H. (committee member), First, Philip N. (committee member), Jiang, Zhigang (committee member), Graham, Samuel (committee member).
Subjects/Keywords: Epitaxial graphene; C-face silicon carbide; High mobility FET; Unconventional quantum Hall effect; Schottky barrier transistor; Graphene; Epitaxy; Silicon carbide
…until two
independent electrical measurement results were published in 2004. The Georgia Tech… …confinement controlled sublimation method developed
at Georgia Tech (de Heer, et al., 2011)…
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APA (6th Edition):
Hu, Y. (2013). Production and properties of epitaxial graphene on the carbon terminated face of hexagonal silicon carbide. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/48705
Chicago Manual of Style (16th Edition):
Hu, Yike. “Production and properties of epitaxial graphene on the carbon terminated face of hexagonal silicon carbide.” 2013. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/48705.
MLA Handbook (7th Edition):
Hu, Yike. “Production and properties of epitaxial graphene on the carbon terminated face of hexagonal silicon carbide.” 2013. Web. 10 Jul 2020.
Vancouver:
Hu Y. Production and properties of epitaxial graphene on the carbon terminated face of hexagonal silicon carbide. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/48705.
Council of Science Editors:
Hu Y. Production and properties of epitaxial graphene on the carbon terminated face of hexagonal silicon carbide. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/48705
28.
Lee, Yi-Che.
Development of III-nitride transistors: heterojunction bipolar transistors and field-effect transistors.
Degree: PhD, Electrical and Computer Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/53472
► The fabrication processes development for on III-nitride (III-N) heterojunction bipolar transistors (HBTs), heterojunction field-effect transistors (HFETs) and metal-insulator-semiconductor field-effect transistors (MISFETs) were performed. D.c, microwave…
(more)
▼ The fabrication processes development for on III-nitride (III-N) heterojunction bipolar transistors (HBTs), heterojunction field-effect transistors (HFETs) and metal-insulator-semiconductor field-effect transistors (MISFETs) were performed. D.c, microwave and quasi-static I-V and C-V measurements were carried out to characterize the fabricated III-N transistors and diodes. The GaN/InGaN direct-growth HBTs (DG-HBTs) grown on free-standing GaN (FS-GaN) substrates demonstrated a high current gain (hfe) > 110, high current density (JC) > 141 kA/cm2, and high power density (Pdc) > 3 MW/cm2. The first III-N DG-HBT showing fT > 8 GHz and fmax > 1.3 GHz were also demonstrated on sapphire substrates. Recessed-gate AlGaN/AlN/GaN HFETs demonstrated Vth = 0 V with 0.17 V deviation across the sample. Baliga's figure of merit is 240 MW/cm2 was achieved. Current collapse was eliminated and the dynamic on-resistance was reduced by 67% after using a remote-oxygen-plasma treatment. Normally-off recessed-gate AlGaN/AlN/GaN MISFETs with Vth = 0.9 V were also fabricated with the remote-oxygen-plasma treatment. Low leakage current (< 1 pA/mm), high on-off ratio (> 2.2E11) are achieved. These achievements suggest that high-performance III-N transistors are very promising for high-power switching and microwave amplification. Findings concerning remaining process issues and implications for future research are also discussed.
Advisors/Committee Members: Shen, Shyh-Chiang (advisor), Dupuis, Russell D. (committee member), Yoder, Paul Douglas (committee member), Doolittle, William Alan (committee member), Jiang, Zhigang (committee member).
Subjects/Keywords: III-nitride; Heterojunction; Bipolar transistor; Field-effect transistor; Fabrication process
…insulator-semiconductor field-effect transistors (MISFETs) developed at
Georgia Tech for… …HBTs and MISFETs at Georgia Tech. The results not
only indicated the great potential of III-N… …performance at Georgia Tech for III-N HBTs, HFETs
and MISFETs will be discussed.
5
1.3
GaN/InGaN… …during
fabrication processes [47].
At Georgia Tech, the research work was focused on…
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APA (6th Edition):
Lee, Y. (2014). Development of III-nitride transistors: heterojunction bipolar transistors and field-effect transistors. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53472
Chicago Manual of Style (16th Edition):
Lee, Yi-Che. “Development of III-nitride transistors: heterojunction bipolar transistors and field-effect transistors.” 2014. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/53472.
MLA Handbook (7th Edition):
Lee, Yi-Che. “Development of III-nitride transistors: heterojunction bipolar transistors and field-effect transistors.” 2014. Web. 10 Jul 2020.
Vancouver:
Lee Y. Development of III-nitride transistors: heterojunction bipolar transistors and field-effect transistors. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/53472.
Council of Science Editors:
Lee Y. Development of III-nitride transistors: heterojunction bipolar transistors and field-effect transistors. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/53472
29.
Guo, Zelei.
Mono-layer C-face epitaxial graphene for high frequency electronics.
Degree: PhD, Physics, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/52268
► As the thinnest material ever with high carrier mobility and saturation velocity, graphene is considered as a candidate for future high speed electronics. After pioneering…
(more)
▼ As the thinnest material ever with high carrier mobility and saturation
velocity, graphene is considered as a candidate for future high speed electronics. After
pioneering research on graphene-based electronics at
Georgia Tech, epitaxial graphene
on SiC, along with other synthesized graphene, has been extensively investigated for
possible applications in high frequency analog circuits. With a combined effort from
academic and industrial research institutions, the best cut-off frequency of graphene
radio-frequency (RF) transistors is already comparable to the best result of III-V
material-based devices. However, the power gain performance of graphene transistors
remained low, and the absence of a band gap inhibits the possibility of graphene in
digital electronics. Aiming at solving these problems, this thesis will demonstrate
the effort toward better high frequency power gain performance based on mono-layer
epitaxial graphene on C-face SiC. Besides, a graphene/Si integration scheme will
be proposed that utilizes the high speed potential of graphene electronics and logic
functionality and maturity of Si-CMOS platform at the same time.
Advisors/Committee Members: de Heer, Walter A. (advisor), Jiang, Zhigang (committee member), Conrad, Edward H. (committee member), First, Phillip N. (committee member), Cressler, John D. (committee member).
Subjects/Keywords: SiC; RF; SOI; Epitaxial graphene; High frequency; Maximum oscillation frequency; Dielectric; Top gate; Transistor; Wafer bonding; Smart-cut; Nanoribbon
…pioneering research on graphene-based electronics at Georgia Tech, epitaxial graphene
on SiC, along…
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APA ·
Chicago ·
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to Zotero / EndNote / Reference
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APA (6th Edition):
Guo, Z. (2014). Mono-layer C-face epitaxial graphene for high frequency electronics. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/52268
Chicago Manual of Style (16th Edition):
Guo, Zelei. “Mono-layer C-face epitaxial graphene for high frequency electronics.” 2014. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/52268.
MLA Handbook (7th Edition):
Guo, Zelei. “Mono-layer C-face epitaxial graphene for high frequency electronics.” 2014. Web. 10 Jul 2020.
Vancouver:
Guo Z. Mono-layer C-face epitaxial graphene for high frequency electronics. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/52268.
Council of Science Editors:
Guo Z. Mono-layer C-face epitaxial graphene for high frequency electronics. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/52268
30.
Zhang, Yun.
Development of III-nitride bipolar devices: avalanche photodiodes, laser diodes, and double-heterojunction bipolar transistors.
Degree: PhD, Electrical and Computer Engineering, 2011, Georgia Tech
URL: http://hdl.handle.net/1853/42703
► This dissertation describes the development of III-nitride (III-N) bipolar devices for optoelectronic and electronic applications. Research mainly involves device design, fabrication process development, and device…
(more)
▼ This dissertation describes the development of III-nitride (III-N) bipolar devices for optoelectronic and electronic applications. Research mainly involves device design, fabrication process development, and device characterization for Geiger-mode gallium nitride (GaN) deep-UV (DUV) p-i-n avalanche photodiodes (APDs), indium gallium nitride (InGaN)/GaN-based violet/blue laser diodes (LDs), and GaN/InGaN-based npn radio-frequency (RF) double-heterojunction bipolar transistors (DHBTs). All the epitaxial materials of these devices were grown in the Advanced Materials and Devices Group (AMDG) led by Prof. Russell D. Dupuis at the
Georgia Institute of Technology using the metalorganic chemical vapor deposition (MOCVD) technique.
Geiger-mode GaN p-i-n APDs have important applications in DUV and UV single-photon detections. In the fabrication of GaN p-i-n APDs, the major technical challenge is the sidewall leakage current. To address this issue, two surface leakage reduction schemes have been developed: a wet-etching surface treatment technique to recover the dry-etching-induced surface damage, and a ledged structure to form a surface depletion layer to partially passivate the sidewall. The first Geiger-mode DUV GaN p-i-n APD on a free-standing (FS) c-plane GaN substrate has been demonstrated.
InGaN/GaN-based violet/blue/green LDs are the coherent light sources for high-density optical storage systems and the next-generation full-color LD display systems. The design of InGaN/GaN LDs has several challenges, such as the quantum-confined stark effect (QCSE), the efficiency droop issue, and the optical confinement design optimization. In this dissertation, a step-graded electron-blocking layer (EBL) is studied to address the efficiency droop issue. Enhanced internal quantum efficiency (ɳi) has been observed on 420-nm InGaN/GaN-based LDs. Moreover, an InGaN waveguide design is implemented, and the continuous-wave (CW)-mode operation on 460-nm InGaN/GaN-based LDs is achieved at room temperature (RT).
III-N HBTs are promising devices for the next-generation RF and power electronics because of their advantages of high breakdown voltages, high power handling capability, and high-temperature and harsh-environment operation stability. One of the major technical challenges to fabricate high-performance RF III-N HBTs is to suppress the base surface recombination current on the extrinsic base region. The wet-etching surface treatment has also been employed to lower the surface recombination current. As a result, a record small-signal current gain (hfe) > 100 is achieved on GaN/InGaN-based npn DHBTs on sapphire substrates. A cut-off frequency (fT) > 5.3 GHz and a maximum oscillation frequency (fmax) > 1.3 GHz are also demonstrated for the first time. Furthermore, A FS c-plane GaN substrate with low epitaxial defect density and good thermal dissipation ability is used for reduced base bulk recombination current. The hfe > 115, collector current density (JC) > 141 kA/cm², and power density > 3.05 MW/cm² are achieved at RT, which are…
Advisors/Committee Members: Shen, Shyh-Chiang (Committee Chair), Dupuis, Russell (Committee Member), Jiang, Zhigang (Committee Member), Mukhopadhyay, Saibal (Committee Member), Yoder, Douglas (Committee Member).
Subjects/Keywords: Fabrication; GaN; Avalanche photodiode; Gallium nitride; Laser diode; Heterojunction bipolar transistors; Bipolar transistors; Heterojunctions; Avalanche photodiodes; Gallium nitride; Epitaxial growth
Record Details
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Record Details
Similar Records
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Zhang, Y. (2011). Development of III-nitride bipolar devices: avalanche photodiodes, laser diodes, and double-heterojunction bipolar transistors. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/42703
Chicago Manual of Style (16th Edition):
Zhang, Yun. “Development of III-nitride bipolar devices: avalanche photodiodes, laser diodes, and double-heterojunction bipolar transistors.” 2011. Doctoral Dissertation, Georgia Tech. Accessed July 10, 2020.
http://hdl.handle.net/1853/42703.
MLA Handbook (7th Edition):
Zhang, Yun. “Development of III-nitride bipolar devices: avalanche photodiodes, laser diodes, and double-heterojunction bipolar transistors.” 2011. Web. 10 Jul 2020.
Vancouver:
Zhang Y. Development of III-nitride bipolar devices: avalanche photodiodes, laser diodes, and double-heterojunction bipolar transistors. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2020 Jul 10].
Available from: http://hdl.handle.net/1853/42703.
Council of Science Editors:
Zhang Y. Development of III-nitride bipolar devices: avalanche photodiodes, laser diodes, and double-heterojunction bipolar transistors. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/42703
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