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Clemson University
1.
Raghu Srimathi, Indumathi.
Metaoptics for Spectral and Spatial Beam Manipulation.
Degree: PhD, Electrical and Computer Engineering, 2017, Clemson University
URL: https://tigerprints.clemson.edu/all_dissertations/1933 
► Laser beam combining and beam shaping are two important areas with applications in optical communications, high power lasers, and atmospheric propagation studies. In this dissertation,…
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▼ Laser beam combining and beam shaping are two important areas with applications in optical communications, high power lasers, and atmospheric propagation studies. In this dissertation, metaoptical elements have been developed for spectral and spatial beam shaping, and multiplexing. Beams carrying orbital angular momentum (OAM), referred to as optical vortices, have unique propagation properties. Optical vortex beams carrying different topological charges are orthogonal to each other and have low inter-modal crosstalk which allows for them to be (de)multiplexed. Efficient spatial (de)multiplexing of these beams have been carried out by using diffractive optical geometrical coordinate transformation elements. The spatial beam combining technique shown here is advantageous because the efficiency of the system is not dependent on the number of OAM states being combined. The system is capable of generating coaxially propagating beams in the far-field and the beams generated can either be incoherently or coherently multiplexed with applications in power scaling and dynamic intensity profile manipulations. Spectral beam combining can also be achieved with the coordinate transformation elements. The different wavelengths emitted by fiber sources can be spatially overlapped in the far-field plane and the generated beams are Bessel-Gauss in nature with enhanced depth of focus properties. Unique system responses and beam shapes in the far-field can be realized by controlling amplitude, phase, and polarization at the micro-scale. This has been achieved by spatially varying the structural parameters at the subwavelength scale and is analogous to local modification of material properties. With advancements in fabrication technology, it is possible to control not just the lithographic process, but also the deposition process. In this work, a unique combination of spatial structure variations in conjunction with the conformal coating properties of an atomic layer deposition tool has been utilized to create metal-oxide nano-hair structures that are compatible with high power laser systems. These devices are multifunctional – acting as resonant structures for one wavelength regime and as effective index structures in a different wavelength regime. Discrete and continuous phase functions have been realized with this controlled fabrication process. The design, simulation, fabrication and experimental characterization of these optical elements are presented.
Advisors/Committee Members: Dr. Eric G. Johnson, Committee Chair, Dr. Richard J. Watkins, Dr. Goutam Koley, Dr. Lin Zhu.
Subjects/Keywords: Diffractive Optics; Orbital Angular Momentum; Spatial Demultiplexing; Spatial Multiplexing; Spectral Beam Combining; Subwavelength Grating Structures
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APA (6th Edition):
Raghu Srimathi, I. (2017). Metaoptics for Spectral and Spatial Beam Manipulation. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/1933
Chicago Manual of Style (16th Edition):
Raghu Srimathi, Indumathi. “Metaoptics for Spectral and Spatial Beam Manipulation.” 2017. Doctoral Dissertation, Clemson University. Accessed January 18, 2021.
https://tigerprints.clemson.edu/all_dissertations/1933.
MLA Handbook (7th Edition):
Raghu Srimathi, Indumathi. “Metaoptics for Spectral and Spatial Beam Manipulation.” 2017. Web. 18 Jan 2021.
Vancouver:
Raghu Srimathi I. Metaoptics for Spectral and Spatial Beam Manipulation. [Internet] [Doctoral dissertation]. Clemson University; 2017. [cited 2021 Jan 18].
Available from: https://tigerprints.clemson.edu/all_dissertations/1933.
Council of Science Editors:
Raghu Srimathi I. Metaoptics for Spectral and Spatial Beam Manipulation. [Doctoral Dissertation]. Clemson University; 2017. Available from: https://tigerprints.clemson.edu/all_dissertations/1933
Clemson University
2.
Shah, Deepkumar Rameshchandra.
Electrical Characterization of Thin-Film Polymer Tantalum Capacitors.
Degree: MS, Electrical and Computer Engineering (Holcomb Dept. of), 2017, Clemson University
URL: https://tigerprints.clemson.edu/all_theses/2760
► Polymer Hermetic Sealed (PHS) Tantalum capacitors are advanced Polymer Tantalum capacitors with moisture sealed in the capacitor via hermetically sealing the device inside a…
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▼ Polymer Hermetic Sealed (PHS) Tantalum capacitors are advanced Polymer Tantalum capacitors with moisture sealed in the capacitor via hermetically sealing the device inside a package. Their attractive features include high volumetric efficiency, leakage current stability, and low weight as compared to wet and solid-state polymer Ta capacitors. Moreover, recent studies have observed certain interesting properties in PHS Ta capacitors like Breakdown Voltage (BDV) being greater than Formation Voltage, anomalous transient currents, and Capacitance Stability issues. In this thesis, a technique to accurately perform the electrical characterization of thin-film MIS polymer Ta capacitors is established in order to understand the properties observed in PHS Ta capacitors. BDV greater than Formation Voltage is observed in these thin-film MIS capacitors which bolsters our hypothesis that this amazing phenomenon is primarily due to the material layers and their interactions, as opposed to being primarily due to the complex structure of KEMET’s PHS Ta capacitors. Moreover, Capacitance Stability is observed in thin-film MIS devices. The C(T) results are observed to be closely following the dielectric constant k(T) for almost the entire range of temperature, i.e., -55˚C to 150˚C. This result suggests that the thin-film MIS capacitors have capacitance dependence on temperature primarily due to the natural dependence of its dielectric material. In addition, Poole-Frenkel leakage mechanism is observed in some of the thin-film MIS capacitors. Thin-film MIS capacitors are established as viable, inexpensive, and easily fabricated models of KEMET PHS Ta capacitors to improve the Capacitance Stability and Breakdown Voltages of existing PHS Ta capacitors.
Advisors/Committee Members: Dr. William R. Harrell, Committee Chair, Dr. Yuri P. Freeman, Dr. Goutam Koley.
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APA (6th Edition):
Shah, D. R. (2017). Electrical Characterization of Thin-Film Polymer Tantalum Capacitors. (Masters Thesis). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_theses/2760
Chicago Manual of Style (16th Edition):
Shah, Deepkumar Rameshchandra. “Electrical Characterization of Thin-Film Polymer Tantalum Capacitors.” 2017. Masters Thesis, Clemson University. Accessed January 18, 2021.
https://tigerprints.clemson.edu/all_theses/2760.
MLA Handbook (7th Edition):
Shah, Deepkumar Rameshchandra. “Electrical Characterization of Thin-Film Polymer Tantalum Capacitors.” 2017. Web. 18 Jan 2021.
Vancouver:
Shah DR. Electrical Characterization of Thin-Film Polymer Tantalum Capacitors. [Internet] [Masters thesis]. Clemson University; 2017. [cited 2021 Jan 18].
Available from: https://tigerprints.clemson.edu/all_theses/2760.
Council of Science Editors:
Shah DR. Electrical Characterization of Thin-Film Polymer Tantalum Capacitors. [Masters Thesis]. Clemson University; 2017. Available from: https://tigerprints.clemson.edu/all_theses/2760
Clemson University
3.
Mallineni, Sai Sunil Kumar.
Two-dimensional Nanomaterials for Renewable Energy Generation and Sensing Applications.
Degree: PhD, Physics and Astronomy, 2018, Clemson University
URL: https://tigerprints.clemson.edu/all_dissertations/2124
► Two-dimensional (2D) materials have been intriguing physicists and material scientists for more than two decades due to their unique physical properties that emerge from phenomena…
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▼ Two-dimensional (2D) materials have been intriguing physicists and material scientists for more than two decades due to their unique physical properties that emerge from phenomena such as charge confinement, heat flow in a 2D plane, etc. For example, graphene exhibits room temperature quantum Hall effect, quantized optical transmittance, non-local hot carrier transport, and Klein tunneling. Building on such fundamental phenomena, my work focuses on biomolecular sensing, energy generation, and storage using 2D materials such as graphene, graphene oxide, boron nitride, and 2D titanium carbide. Chapter 1 provides an introduction to 2D materials and their current status and their applications. In Chapter 2, the effects of nitrogen dopants in graphene are investigated for its possible applications as a selective permeable membrane. Specifically, I investigated theoretically and confirmed experimentally the influence of nitrogen dopant configuration (viz., graphitic, pyridinic, and pyrrolic) on selective gas permeability of graphene. The N-dopants in non-graphitic configurations (pyridinic and pyrrolic) showed selective permeability to O2 unlike graphitic N-dopants. These results implied that N-doped graphene could potentially be used as an O2 selective permeable membrane in devices such as Li-air batteries. In addition to the use of high surface area 2D materials in energy storage as discussed in Chapter 2, I also demonstrated the use of 2D materials (particularly, graphene and titanium carbide) for energy generation as described in Chapter 3 using novel “triboelectric nanogenerators (TENGs)”. Notably, in Chapter 3 I provide blueprints for flexible and wearable TENGs that can be directly integrated with textiles, automobiles, and ocean wave energy harvesters. Lastly, in Chapter 3 I demonstrate new strategies for additive manufacturing of 2D material-based TENGs that convert mechanical energy into electricity and wirelessly transmit it for storage in batteries and capacitors. In Chapter 4, the use of novel 2D nanomaterials such as graphene, graphene oxide, and boron nitride for bio-sensing applications is demonstrated. In particular, the fundamental interactions of aromatic amino acids viz., tyrosine, tryptophan, and phenylalanine with 2D materials were studied using a comprehensive array of tools including Raman spectroscopy, cyclic voltammetry, and photoluminescence spectroscopy. In summary, my work epitomizes the unique electronic and optical properties of 2D materials and their use in a variety of sensors and sustainable energy devices.
Advisors/Committee Members: Dr. Apparao M Rao, Committee Chair, Dr. Ramakrishna Podila, Co-Chair, Dr. Terry M Tritt, Dr. Goutam Koley.
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APA (6th Edition):
Mallineni, S. S. K. (2018). Two-dimensional Nanomaterials for Renewable Energy Generation and Sensing Applications. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/2124
Chicago Manual of Style (16th Edition):
Mallineni, Sai Sunil Kumar. “Two-dimensional Nanomaterials for Renewable Energy Generation and Sensing Applications.” 2018. Doctoral Dissertation, Clemson University. Accessed January 18, 2021.
https://tigerprints.clemson.edu/all_dissertations/2124.
MLA Handbook (7th Edition):
Mallineni, Sai Sunil Kumar. “Two-dimensional Nanomaterials for Renewable Energy Generation and Sensing Applications.” 2018. Web. 18 Jan 2021.
Vancouver:
Mallineni SSK. Two-dimensional Nanomaterials for Renewable Energy Generation and Sensing Applications. [Internet] [Doctoral dissertation]. Clemson University; 2018. [cited 2021 Jan 18].
Available from: https://tigerprints.clemson.edu/all_dissertations/2124.
Council of Science Editors:
Mallineni SSK. Two-dimensional Nanomaterials for Renewable Energy Generation and Sensing Applications. [Doctoral Dissertation]. Clemson University; 2018. Available from: https://tigerprints.clemson.edu/all_dissertations/2124
4.
Hossain, Md Maksudul.
Metal Oxide Semiconductor / Graphene Heterojunction Based Sensors.
Degree: MS, Electrical and Computer Engineering (Holcomb Dept. of), 2017, Clemson University
URL: https://tigerprints.clemson.edu/all_theses/2754
► Graphene, a two-dimensional material with very high carrier mobility, has drawn much attention for sensing chemical species. It is atomically thin hexagonal arrangement of…
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▼ Graphene, a two-dimensional material with very high carrier mobility, has drawn much attention for sensing chemical species. It is atomically thin hexagonal arrangement of carbon where each atom is attached to 3 neighboring carbon atoms. The presence of π* and π bonds can be attributed for it many remarkable properties. Some of these properties are high mobility, modulation of carrier concentration and Fermi level by electrical, optical, and chemical means, low 1/f and thermal noise, and very high surface to volume ratio to name a few making graphene a potential candidate for sensing material. However, to utilize these amazing properties for practical applications a reliable synthesis of high quality, large area graphene is needed. Chemical Vapor Deposition (CVD) based synthesis offers reliable, scalable, and inexpensive method to make low defect, continuous, large area, and thinner graphene with the ability to transfer graphene on any desirable substrate. In this work, high quality single layer graphene has been synthesized by CVD for sensing applications. The growth process was optimized to produce good quality monolayer graphene as characterized by Raman spectroscopy. CH4 has been used as precursor gas for the growth at 1035°C. Since graphene work function can be varied electrically or chemically, the Schottky Barrier Height (SBH) at Graphene/Semiconductor interface also varies accordingly affecting the carrier transport across the barrier. In this work, we used transition metal oxide (e.g. WO3, In2O3, and ZnO) along with graphene to study the behavior of graphene/metal oxide heterojunction in sensing NO2 and NH3 because both of these metal oxides and graphene are individually very sensitive to NO2 and NH3. Our motivation was to see if the sensitivity and response time improves in case we use them together.
Advisors/Committee Members: Dr. Goutam Koley, Committee Chair, Dr. William Rod Harrell, Dr. Rajendra Singh.
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APA (6th Edition):
Hossain, M. M. (2017). Metal Oxide Semiconductor / Graphene Heterojunction Based Sensors. (Masters Thesis). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_theses/2754
Chicago Manual of Style (16th Edition):
Hossain, Md Maksudul. “Metal Oxide Semiconductor / Graphene Heterojunction Based Sensors.” 2017. Masters Thesis, Clemson University. Accessed January 18, 2021.
https://tigerprints.clemson.edu/all_theses/2754.
MLA Handbook (7th Edition):
Hossain, Md Maksudul. “Metal Oxide Semiconductor / Graphene Heterojunction Based Sensors.” 2017. Web. 18 Jan 2021.
Vancouver:
Hossain MM. Metal Oxide Semiconductor / Graphene Heterojunction Based Sensors. [Internet] [Masters thesis]. Clemson University; 2017. [cited 2021 Jan 18].
Available from: https://tigerprints.clemson.edu/all_theses/2754.
Council of Science Editors:
Hossain MM. Metal Oxide Semiconductor / Graphene Heterojunction Based Sensors. [Masters Thesis]. Clemson University; 2017. Available from: https://tigerprints.clemson.edu/all_theses/2754
5.
Chinnam, Shiva Kumar.
Characterization of Polymer Hermetic Sealed Tantalum Capacitors Using Thin-film Devices.
Degree: MS, Electrical Engineering, 2017, Clemson University
URL: https://tigerprints.clemson.edu/all_theses/2610
► Polymer Hermetic Sealed (PHS) capacitors are advanced polymer capacitors with a hermetic seal enclosing the materials inside a metal enclosure. Their primary features include leakage…
(more)
▼ Polymer Hermetic Sealed (PHS) capacitors are advanced polymer capacitors with a hermetic seal enclosing the materials inside a metal enclosure. Their primary features include leakage current stability, high volumetric efficiency, and low weight compared to both wet and solid-state polymer tantalum capacitors. However, Life Tests performed on these capacitors have revealed a failure to withstand their rated voltage in a working temperature range over the long-term. There are also other interesting properties which have been observed such as Breakdown voltage (BDV) exceeding the Formation Voltage (Vf), anomalous transient currents, and a larger than expected capacitance dependence on temperature, C(T). A primary goal in this research is to understand whether the observed characteristics of PHS capacitors are a result of their complex structure or due more to the nature of interactions between the organic and inorganic material layers present. C(T) and BDV measurements were performed on thin-film MIS capacitors representing the material layers of PHS capacitors. Measurements were performed in the voltage range (0V-100V), a temperature range (-550C to 1250C), with varying frequency (20-10kHz), under both humid and dry conditions. Furthermore, one sample went through a curing process referred to as "Heat Treatment", which is thought to improve device stability. Results from these measurements show that thin-film devices can be reasonable representatives of discrete PHS capacitors, and the properties observed in PHS capacitors are significantly dependent on the material layers in the capacitors. Thus, the thin-film MIS capacitor is shown to be a useful test structures for investigating physical phenomena observed in the more complex polymer Ta capacitor structure.
Advisors/Committee Members: Dr. William R. Harrell, Committee Chair, Dr. Yuri Freeman, Dr. Goutam Koley.
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APA (6th Edition):
Chinnam, S. K. (2017). Characterization of Polymer Hermetic Sealed Tantalum Capacitors Using Thin-film Devices. (Masters Thesis). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_theses/2610
Chicago Manual of Style (16th Edition):
Chinnam, Shiva Kumar. “Characterization of Polymer Hermetic Sealed Tantalum Capacitors Using Thin-film Devices.” 2017. Masters Thesis, Clemson University. Accessed January 18, 2021.
https://tigerprints.clemson.edu/all_theses/2610.
MLA Handbook (7th Edition):
Chinnam, Shiva Kumar. “Characterization of Polymer Hermetic Sealed Tantalum Capacitors Using Thin-film Devices.” 2017. Web. 18 Jan 2021.
Vancouver:
Chinnam SK. Characterization of Polymer Hermetic Sealed Tantalum Capacitors Using Thin-film Devices. [Internet] [Masters thesis]. Clemson University; 2017. [cited 2021 Jan 18].
Available from: https://tigerprints.clemson.edu/all_theses/2610.
Council of Science Editors:
Chinnam SK. Characterization of Polymer Hermetic Sealed Tantalum Capacitors Using Thin-film Devices. [Masters Thesis]. Clemson University; 2017. Available from: https://tigerprints.clemson.edu/all_theses/2610
6.
Cui, Yan.
Radio-Frequency Sensors for Detection and Analysis of Chemical and Biological Substances.
Degree: PhD, Electrical and Computer Engineering (Holcomb Dept. of), 2017, Clemson University
URL: https://tigerprints.clemson.edu/all_dissertations/2021
► Dielectric spectroscopy (DS) is an important technique for scientific and technological investigations in various areas. DS sensitivity and operating frequency ranges are critical for many…
(more)
▼ Dielectric spectroscopy (DS) is an important technique for scientific and technological investigations in various areas. DS sensitivity and operating frequency ranges are critical for many applications, including lab-on-chip development where sample volumes are small with a wide range of dynamic processes to probe. In this dissertation, the design and operation considerations of radio-frequency (RF) interferometers that are based on power-dividers (PDs) and quadrature-hybrids (QHs) is presented. The effective quality factor (Qeff) of the sensor is as high as ∼3.8×10
6 with 200 μL of water samples. Such interferometers are proposed to address the sensitivity and frequency tuning challenges of current DS techniques. A high-sensitivity and stable QH-based interferometer is demonstrated by measuring glucose-water solution at a concentration level that is ten times lower than some recent RF sensors and DNA solution at ~3×10
-15 mol/mL that is close to the previously reported lowest result while the sample volume is ~1 nL. Composition analysis of ternary mixture solutions are also demonstrated with a PD-based interferometer. Using a tunable liquid attenuator by accurately changing its liquid volume, the sensitivity of a RF interferometer is tuned automatically. The obtained Qeff of the interferometer is up to 1×10
8 at ~5 GHz, i.e., ~100 times higher than previously reported results. When material-under-test, i.e., methanol-water solution in this work, is used for the tuning, a self-calibration and measurement process is demonstrated from 2 GHz to 7.5 GHz at a methanol concentration level down to 5×10
-5 mole fraction, which is 100 times lower than previously reported results. A microwave scanning technique is reported for the measurement of floating giant unilamellar vesicles (GUV) in a 25 μm wide and 18.8 μm high microfluidic channel. The measurement is conducted at 2.7 GHz and 7.9 GHz, at which a split ring resonator (SRR) operates at odd modes. A 500 nm wide and 100 μm long SRR split gap is used to scan GUVs that are slightly larger than 25 μm in diameter. The smaller fluidic channel induces flattened GUV membrane sections, which make close contact with the SRR gap surface. The used GUVs are synthesized with POPC (16:0-18:1 PC 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine), SM (16:0 Egg Sphingomyelin) and cholesterol at different molecular compositions. It is shown that SM and POPC bilayers have different dielectric permittivity values, which also change with measurement frequencies. The obtained membrane permittivity values, such as 73.64-j6.13 for POPC at 2.7 GHz, are more than 10 times larger than previously reported results. The discrepancy is likely due to the measurement of dielectric polarization responses that are parallel with, other than perpendicular to, the membrane surface. POPC and SM-rich GUV surface sections are also clearly identified from scanning measurement results. Further work is needed to enable accurate analysis of membrane composition and dynamics at high spatial…
Advisors/Committee Members: Dr. Pingshan Wang, Committee Chair, Dr. Emil Alexov, Dr. Eric G. Johnson, Dr. Goutam Koley, Dr. Guigen Zhang.
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APA ·
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APA (6th Edition):
Cui, Y. (2017). Radio-Frequency Sensors for Detection and Analysis of Chemical and Biological Substances. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/2021
Chicago Manual of Style (16th Edition):
Cui, Yan. “Radio-Frequency Sensors for Detection and Analysis of Chemical and Biological Substances.” 2017. Doctoral Dissertation, Clemson University. Accessed January 18, 2021.
https://tigerprints.clemson.edu/all_dissertations/2021.
MLA Handbook (7th Edition):
Cui, Yan. “Radio-Frequency Sensors for Detection and Analysis of Chemical and Biological Substances.” 2017. Web. 18 Jan 2021.
Vancouver:
Cui Y. Radio-Frequency Sensors for Detection and Analysis of Chemical and Biological Substances. [Internet] [Doctoral dissertation]. Clemson University; 2017. [cited 2021 Jan 18].
Available from: https://tigerprints.clemson.edu/all_dissertations/2021.
Council of Science Editors:
Cui Y. Radio-Frequency Sensors for Detection and Analysis of Chemical and Biological Substances. [Doctoral Dissertation]. Clemson University; 2017. Available from: https://tigerprints.clemson.edu/all_dissertations/2021
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