Two-dimensional (2D) transition metal dichalcogenides (TMDs) are a distinct class of atomically thin materials assembled by weak van der Waals bonding. They exhibit 2D layer number-dependent bandgap tunability promising exciting applications in electronics and optoelectronics. Among them, there is a surge of interest in Platinum-based dichalcogenides (e.g., PtSe2 and PtTe2). 2D PtSe2 has a theoretically predicted carrier mobility of > 1000 cm2/(Vs), at room temperature, which is higher than that of most 2D TMDs. Additionally, 2D PtSe2 exhibits a semiconducting to metallic transition with an increasing number of layers. 2D PtTe2 is highly metallic in its few- layer form and exhibits electrical conductivity of > 106 S/m – superior to most of the previously reported 2D TMDs. These properties project the promise of Platinum-based dichalcogenides for photosensitive applications. This intrinsic superiority of Platinum-based dichalcogenides is improved further when they are merged with conventional three-dimensional (3D) semiconductors such as silicon (Si). We applied a novel chemical vapor deposition (CVD) technique to synthesize large-area 2D PtSe2 and 2D PtTe2 directly on various substrates with controlled 2D layer orientation and electronic property. With direct CVD synthesis of metallic 2D PtSe2 and PtTe2 on silicon (Si) wafer, we created 2D PtSe2/Si and 2D PtTe2/Si Schottky junction devices. We investigated their photovoltaic performance as well as viability as photodetectors in visible to mid-infrared (MIR) regimes. The PtTe2/Si photodetectors exhibit fast photoresponse time (~ 1µs) and high photodetectivity ( > 1013 Jones) in visible light and display photocurrent up to 7µm wavelength regime. Finally, we extended the application of Platinum-based dichalcogenides into flexible opto- electronics by directly synthesizing Platinum-based dichalcogenides on thin Si wafer or polyimide substrates, owing to their low synthesis temperature. These studies are a part of a new paradigm shift of using Pt-based TMDs with unique optical, electrical, and mechanical properties in unique photosensitive devices.
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Doctor of Philosophy (Ph.D.)
College of Engineering and Computer Science
Electrical and Computer Engineering
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Shawkat, Mashiyat Sumaiya, "Atomically Thin Platinum-based Dichalcogenide Materials for Multifunctional Photo-sensitive Applications" (2021). Electronic Theses and Dissertations, 2020-. 1345.