Semiconductor and Optical Materials Commons^™

Complementary Metal-Oxide Semiconductor-Compatible Detector Materials With Enhanced 1550 Nm Responsivity Via Sn-Doping Of Ge/Si(100), Richard T. Beeler, Jay Mathews, Mee-Yi Ryu, Yung-Kee Yeo, Jose Menendez, John Kouvetakis

Faculty Publications

Previously developed methods used to grow Ge_1−ySn_y alloys on Si are extended to Sn concentrations in the 10¹⁹−10²⁰ cm⁻³ range. These concentrations are shown to be sufficient to engineer large increases in the responsivity of detectors operating at 1550 nm. The dopant levels of Sn are incorporated at temperatures in the 370–390 °C range, yielding atomically smooth layers devoid of threading defects at high growth rates of 15–30 nm/min. These conditions are far more compatible with complementary metal-oxide semiconductor processing than the high growth and processing temperatures required to achieve the same …

Plasmonic Effect On The Photoluminescence Of Inas Quantum Dot Nanostructures, David Fryauf

Electrical Engineering Undergraduate Honors Theses

New materials for thin film photovoltaic applications are being explored worldwide, and one of the most popular new implementations is the introduction of an intermediate band gap in the semiconductor energy structure. Careful manipulation of semiconductor lattice material can form nanostructures such as quantum dots, which can be tuned to control specific intermediate energy levels. The introduction of an intermediate band in photovoltaic devices has a theoretical potential sunlight-toelectricity efficiency of roughly 63%. However, a specific material challenge of these thin film devices is limited absorption of long wavelengths of light. To increase absorption of the sun's visible spectrum, plasmonic …

Pigments For Improving Plant Health In Organic Systems, Gregory Keith Bartley Jr.

Gregory Keith Bartley Jr.

Photosynthesis, arguably the most important biological process on earth, solely relies on the ability of pigments to capture, utilize, and convert the sun‟s energy to form life. The adequate conversion of light into harvestable food, fuel, and fiber regulates rates of population and economic growth. In order to meet the expanding needs of humanity with the earth‟s potential for agricultural production, new sustainable techniques for increased photosynthetic efficiency in plants must be implemented. The earth's pattern of light exposure is extremely dynamic, exhibiting constant changes in quantity and quality throughout time and space. For photosynthetic organisms, this meant evolving various …

Fabrication And Characterization Of Graphene Hydrogel Via Hydrothermal Approach As A Scaffold For Preliminary Study Of Cell Growth, Huang Nay Ming

Huang Nay Ming

Three-dimensional assembly of graphene hydrogel is rapidly attracting the interest of researchers because of its wide range of applications in energy storage, electronics, electrochemistry, and waste water treatment. Information on the use of graphene hydrogel for biological purposes is lacking, so we conducted a preliminary study to determine the suitability of graphene hydrogel as a substrate for cell growth, which could potentially be used as building blocks for biomolecules and tissue engineering applications. A three-dimensional structure of graphene hydrogel was prepared via a simple hydrothermal method using two-dimensional large-area graphene oxide nanosheets as a precursor. The concentration and lateral size …

Electronically Enhanced Surface Diffusion During Ge Growth On Si(100), Ali Orguz Er, Hani E. Elsayed-Ali

Physics Faculty Publications

The effect of nanosecond pulsed laser excitation on surface diffusion during the growth of Ge on Si(100) at 250 °C was studied. In situ reflection high-energy electron diffraction was used to measure the surface diffusion coefficient while ex situ atomic force microscopy was used to probe the structure and morphology of the grown quantum dots. The results show that laser excitation of the substrate increases the surface diffusion during the growth of Ge on Si(100), changes the growth morphology, improves the crystalline structure of the grown quantum dots, and decreases their size distribution. A purely electronic mechanism of enhanced surface …

Self-Pulsing And Chaos In Distributed Feedback Bistable Optical Devices, Herbert G. Winful, Gene D. Cooperman

Gene D. Cooperman

We show that the light transmitted by a nonlinear distributed feedback structure can be steady (time independent), periodic, or chaotic depending on the intensity of the input cw beam. The feasibility of an experimental demonstration of such behavior is discussed.

Corrections To Enhanced Optical Nonlinearity Of Superlattices, Gene D. Cooperman, L. Friedman, W. L. Bloss

Gene D. Cooperman

In recent publications, a large enhancement of the third order nonlinear optical susceptibility was predicted for GaAs-GaAIAs superlattices, as a result of the band nonparabolicities introduced by the additional periodicity of the superlattice. These predictions, based on the tight binding model, are here extended to the more realistic Kronig-Penney model. Results show that corrections to tight binding are non-negligible; however, enhancements of χ⁽³⁾ are still large, but reduced by approximately 30%-50% over previous estimates.

Characterization And Fabrication Of Active Matrix Thin Film Transistors For An Addressable Microfluidic Electrowetting Channel Device, Seyeoul Kwon

Doctoral Dissertations

The characterization and fabrication of active matrix thin film transistors (TFTs) has been studied for an addressable microfluidic electrowetting channel device as application. A new transparent semiconductor material, Amorphous Indium Gallium Zinc Oxide (a-IGZO), is used for TFT, which shows high electrical performance rather than amorphous silicon based TFT; higher mobility and even higher transparency. The purpose of this dissertation is to optimize each TFT process including the optimization of a-IGZO properties to achieve robust device for application. To minimize hysteresis of TFT curves, the gate dielectric is discussed extensively in this dissertation. By optimizing gas ratio of NH3SiH4, it …

Thin Film Combinatorial Synthesis Of Advanced Scintillation Materials, Jonathan Daniel Peak

Doctoral Dissertations

The development and application of a combinatorial sputtering thin film technique to screen potential scintillation material systems was investigated. The technique was first benchmarked by exploring the binary lutetium oxide-silicon oxide material system, which successfully identified the luminescence phases of the system, Lu2SiO5 (LSO) and Lu2Si2O7 (LPS). The second application was to optimize the activator concentration in cerium doped LSO. The successfully optimized cerium concentration in the thin film LSO of 0.34 atomic percent was much greater than the standard cerium concentration in single crystal LSO. This lead to an intensive study based on temperature dependent steady-state and lifetime photoluminescence …

Chemical And Electronic Structure Of Surfaces And Interfaces In Compound Semiconductors, Sujitra Pookpanratana

UNLV Theses, Dissertations, Professional Papers, and Capstones

The interface formation between two different materials is important in applications for optoelectronic devices. Often, the success or performance of these devices is dependent on the formation of these heterojunctions. In this work, the surface and interfaces in such materials for optoelectronic devices are investigated by a suite of X-ray analytical techniques including X-ray photoelectron (XPS), X-ray excited Auger electron (XAES), and X-ray emission (XES) spectroscopies to provide novel insight.

For the group III-nitrides (e.g., AlxGa1-xN) used in many light emitting devices, a significant challenge exists to form an Ohmic contact. The electron affinities and band gaps of GaN and …

Photoelectrochemical Properties Of N,S,And Cl Modified Nano Tio_2 Thin Films, Hong Yun, Chang-Jian Lin, Jing Li, Rong-Gui Du

Journal of Electrochemistry

The nitrogen(N),sulfur(S) and chlorine(Cl) modified nano TiO2 thin films were prepared by adding Ti(O-n-Bu)4 as the precursor into concentrated HNO3,H2SO4 and HCl Solutions,respectively,on different substrates in a sol-gel process.The photoelectrochemical performances of N,S and Cl modified nano TiO2 thin films have been studied by UV-vis(DRS),photocurrent curves,EIS and OCP-time curves.N-modified TiO2 nano films show better surface structure,which helps to improve the quantum efficiency of nano TiO2 thin films.

Effect On The Processing Characteristics Of Zno Varistors Produced Using Vibratory Milling, Maura Kelleher, M.S.J. Hashmi

Conference Papers

Abstract. Each manufacturing stage in the production of zinc oxide varistors from powder preparation to the final encapsulated device is important not only for the formation of the varistor component with optimum microstructure and thus electrical characteristics but also for avoiding the introduction of flaws and reduced yield. In this paper the authors describe and discuss the effect of multi-elemental oxide additives having been milled for different durations using a vibratory mill with cylindrical zirconia media on the powder characteristics of the subsequent processing stages. A commercial ZnO varistor formulation was used. The subsequent processing stages that are given particular …

Regulating Factors In Anthocyanin Biosynthesis, Gregory Keith Bartley Jr.

Gregory Keith Bartley Jr.

No abstract provided.

Measurement And Modeling Of Infrared Nonlinear Absorption Coefficients And Laser-Induced Damage Thresholds In Ge And Gasb, Torrey J. Wagner, Matthew J. Bohn, Ronald A. Coutu Jr., L. P. Gonzales, J. M. Murray, K. L. Schepler, S. Guha

Faculty Publications

Using a simultaneous fitting technique to extract nonlinear absorption coefficients from data at two pulse widths, we measure two-photon and free-carrier absorption coefficients for Ge and GaSb at 2.05 and 2.5 µm for the first time, to our knowledge. Results agreed well with published theory. Single-shot damage thresholds were also measured at 2.5 µm and agreed well with modeled thresholds using experimentally determined parameters including nonlinear absorption coefficients and temperature dependent linear absorption. The damage threshold for a single-layer Al₂O₃ anti-reflective coating on Ge was 55% or 35% lower than the uncoated threshold for picosecond or nanosecond …

Optimization Of P3ht-Pcbm Polymer Solar Cells Through Device Simulation And Manufacturing, James Boom

Computer Engineering

Given a good model and implementation of that model, computer simulation can be used to reduce the time and material costs of research. To this end I worked with other students to manufacture, test and simulate the single layer P3HT-PCBM solar cell. Using the data collected from this project, future work can then be done with the project's simulator to further optimize these types of solar cell devices.

Feasibility Of Manipulating Correlated Color Temperatures With A Phosphor Converted High-Powered Light Emitting Diode White Light Source, Matthew Michael Little

Master's Theses

In this thesis we examine the feasibility of developing a white light source capable of producing colors between 2500 and 7500 Kelvin on the black-body radiator spectrum by simply adjusting amperage to a blue and ultraviolet (UV) light emitting diode (LED). The purpose of a lighting source of this nature is to better replicate daylight inside a building at a given time of day. This study analyzes the proposed light source using a 385 nm UV LED, a 457 nm blue LED, a 479 nm blue LED, a 562 nm peak cerium doped yttrium aluminum garnet (YAG:Ce) phosphor, and a …

Enhanced Light Extraction Efficiency From Gan Light Emitting Diodes Using Photonic Crystal Grating Structures, Simeon S. Trieu

Master's Theses

Gallium nitride (GaN) light emitting diodes (LED) embody a large field of research that aims to replace inefficient, conventional light sources with LEDs that have lower power, higher luminosity, and longer lifetime. This thesis presents an international collaboration effort between the State Key Laboratory for Mesoscopic Physics in Peking University (PKU) of Beijing, China and the Electrical Engineering Department of California Polytechnic State University, San Luis Obispo. Over the course of 2 years, Cal Poly’s side has simulated GaN LEDs within the pure blue wavelength spectrum (460nm), focusing specifically on the effects of reflection gratings, transmission gratings, top and bottom …

Ultrathin, Ultrasmooth And Low-Loss Silver Films Via Wetting And Annealing, Weiqiang Chen, Kuo-Ping Chen, Mark Daniel Thoreson, Alexander Kildishev, Vladimir M. Shalaev

Weiqiang Chen

We have demonstrated that a thermal annealing treatment can reduce the optical losses in ultrathin, ultrasmooth, silver films deposited on a Ge wetting layer to values as low as the bulk material value and at the same time maintain an ultrasmooth surface. The annealing effect is sensitive to the annealing temperature and time, both of which should be carefully controlled. This annealing treatment is also effective for Ag–SiO2 multilayer composite films.

Toward Superlensing With Metal-Dielectric Composites And Multilayers, Rasmus Bundgaard Nielsen, Mark Thoreson, Weiqiang Chen, Anders Kristensen, Jørn Hvam, Vladimir M. Shalaev, Alexandra Boltasseva

Weiqiang Chen

We report on the fabrication of two types of adjustable, near-field superlens designs: metal–dielectric composites and metal–dielectric multilayer films. We fabricated a variety of films with different materials, thicknesses and compositions. These samples were characterized physically and optically to determine their film composition, quality, and optical responses. Our results on metal–dielectric composites indicate that although the real part of the effective permittivity generally follows effective medium theory predictions, the imaginary part does not and substantially higher losses are observed. Going forward, it appears that multilayer metal–dielectric designs are more suitable for sub-diffraction imaging applications because they could provide both tunability …

Fabrication And Optical Characterizations Of Smooth Silver-Silica Nanocomposite Films, Weiqiang Chen, Mark Daniel Thoreson, Alexander V. Kildishev, Vladimir Shalaev

Weiqiang Chen

We have studied the surface-smoothing effect of an ultrathin germanium (Ge) layer on silver (Ag)-silica (SiO2) nanocomposite films for superlensing applications. Our experimental results indicate that inserting a thin Ge layer below the silver-silica composite films can reduce the final surface root-mean-squared (RMS) roughness to under 1 nm. Additionally, the metal nanostructure plays a role in both the smoothing effect and the optical properties of the nanocomposite films. Our experimental results show that the Bruggeman effective medium theory (EMT) is not sufficiently accurate to describe some properties of our nanocomposite films. In addition to the constituent materials and their filling …