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" Ga2O3 Growth and Characterization for Sensing Applications "
Alhalaili, Badriyah
Islam, Prof M Saif
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Latin Dissertation
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English
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| Record Number
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1105330
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| Doc. No
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TLpq2306563063
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| Main Entry
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Alhalaili, Badriyah
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Islam, Prof M Saif
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| Title & Author
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Ga2O3 Growth and Characterization for Sensing Applications\ Alhalaili, BadriyahIslam, Prof M Saif
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| College
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University of California, Davis
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| Date
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2019
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| student score
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2019
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| Degree
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Ph.D.
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| Page No
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133
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| Abstract
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In recent years, gallium oxide (Ga2O3), both thin films and nanowires, has been used in many scientific disciplines due to their unique properties including wide bandgap, resistance to high temperature and high radiation. Several applications have focused on incorporating gallium oxide nanowires in devices to improve their performance and efficiency. These distinctive structures bring new opportunities to several research fields and applications such as optoelectronics, electronics, and chemistry. This dissertation provides a basic overview of the properties of gallium oxide and the growth process of gallium oxide nanowires, with an emphasis on various applications and future challenges. Thermal oxidation is a simple and inexpensive technique that can produce growing self-assembled nanowires. It involves heating a material to a high temperature inside a furnace. The use of a catalyst that has the ability to sustain higher temperatures than its melting point could be a beneficial choice to increase the speed of the growth mechanism spontaneously. With silver catalysts, it is possible to change the morphology of nanowires, leading to longer and denser nanowire growth. Silver has a high diffusivity and solubility for oxygen and thus is able to catalyze the growth of nanowires by increasing the amount of oxygen available to react with Ga to form Ga2O3 through its affinity for oxygen. A simple and inexpensive thermal oxidation process was performed to synthesize Ga2O3 nanowires using Ag thin film as a catalyst at 800 °C and 1000 °C to understand the effect of the silver catalyst on the nanowire growth. The effects of doping and orientation of the substrates on the growth of Ga2O3 nanowires on single-crystal gallium arsenide (GaAs) wafers in an argon atmosphere were investigated. A comprehensive study of the oxide film and nanowire growth was performed using various characterization techniques including XRD, SEM, EDS, FIB and STEM. Based on the characterization results, we believe that Ag thin film produces Ag nanoparticles at high temperatures and enhances the reaction between oxygen and gallium, contributing to denser and longer Ga2O3 nanowires compared to those grown without a silver catalyst. This process can be optimized for large-scale production of high-quality, dense, and long nanowires. Interest in the use of Ga2O3 as a semiconductor for high power and high temperature devices as well as deep-UV sensors has grown. Ga2O3 has a very wide bandgap of 4.8 eV, which makes it well-suited for these applications. Nanowires have become more relevant in recent years as their unique advantages have been recognized. Compared to thin films, nanowires exhibit a higher surface-to-volume ratio, increasing their sensitivity for UV detection. Additionally, nanowire devices exhibit quantum effects not seen in bulk materials. Nanowires, because of inherent nanoscale geometries, can be grown on highly lattice mismatched substrates and still can release the mismatch strain. The nanowire growth process is completely different from that of thin films and the strain-energy relief is favorably accommodated for coherent growth of the axial nanowires with certain diameters. This allows for crystalline materials to be grown on arbitrary substrates in spite of lattice mismatch due to lattice strain relaxation at the interface. In this research, we explored a simple and inexpensive method of growing high-density gallium oxide Ga2O3 nanowires at high temperatures. Ga2O3 nanowire growth can be achieved by heating and oxidizing pure gallium at high temperatures (~1000 °C) in the presence of trace amounts of oxygen. We show the results of morphological, structural, electrical and optical characterization of Ga2O3 nanowires including the optical band gap, Schottky barrier height with metal contacts (gold), and photoconductance. The influence of the density of these Ga2O3 nanowires and their properties will be examined in order to determine the optimum configuration for the detection of UV light sensing. In addition, Ga2O3 nanowires have been successfully examined for sensing O2 gas at different temperatures. Different characterization techniques were performed such as scanning electron microscopy (SEM), focused ion beam (FIB) and transmission electron microscopy (TEM). Contacts for the sensor were deposited by sputtering of 200 nm of platinum (Pt). The electrical and gas sensing properties of Ga2O3 nanowires were characterized. At different temperatures (200 °C, 400 °C and 800°C) and varying concentrations of oxygen gas in nitrogen, the gas sensor showed a high variation in resistance. The results show that Ga2O3 nanowires have a great potential for high-sensitivity oxygen gas sensors and power electronics.
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Electrical engineering
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Nanoscience
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Nanotechnology
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