Person: Jayaraman, Ashwin
Loading...
Email Address
AA Acceptance Date
Birth Date
Research Projects
Organizational Units
Job Title
Last Name
Jayaraman
First Name
Ashwin
Name
Jayaraman, Ashwin
6 results
Search Results
Now showing 1 - 6 of 6
Publication Electrostatically Doped Silicon Nanowire Arrays for Multispectral Photodetectors(American Chemical Society (ACS), 2019-10-02) Um, Han-Don; Solanki, Amit; Jayaraman, Ashwin; Gordon, Roy; Habbal, FawwazNanowires have promising applications as photodetectors with superior ability to tune absorption with morphology. Despite their high optical absorption, the quantum efficiencies of these nanowire photodetectors remain low due to difficulties in fabricating a shallow junction using traditional doping methods. As an alternative, we report non-conventional radial heterojunction photodiodes obtained by conformal coating of indium oxide layer on silicon nanowire arrays. The indium oxide layer has a high work function which induces a strong inversion in the silicon nanowire and creates a virtual p-n junction. The resulting nanowire photodetectors show efficient carrier separation and collection leading to an improvement of quantum efficiency up to 0.2. In addition, by controlling the nanowire radii, the spectral response of the In2O3/Si nanowire photodetectors are tuned over several visible light wavelengths, creating a multispectral detector. Our approach is promising for the development of highly-efficient wavelength selective photodetectors.Publication Obtaining a Low and Wide Atomic Layer Deposition Window (150-275 °C) for In2O3 Films Using an InIII Amidinate and H2O(Wiley, 2018-06-05) Zheng, Shao-Liang; Jayaraman, Ashwin; Chua, Danny; Davis, Luke M.; Zhao, Xizhu; Lee, Sunghwan; Gordon, RoyIndium oxide is a major component of many technologically important thin films, most notably the transparent conductor indium tin oxide (ITO). Despite being pyrophoric, homoleptic indium(III) alkyls do not allow atomic layer deposition (ALD) of In2O3 using water as a co‐precursor at substrate temperatures below 200 °C. Several alternative indium sources have been developed, but none allows ALD at lower temperatures except in the presence of oxidants such as O2 or O3, which are not compatible with some substrates or alloying processes. We have synthesized a new indium precursor, tris(N,N′‐diisopropylformamidinato)indium(III), compound 1, which allows ALD of pure, carbon‐free In2O3 films using H2O as the only co‐reactant, on substrates in the temperature range 150–275 °C. In contrast, replacing just the H of the anionic iPrNC(H)NiPr ligand with a methyl group (affording the known tris(N,N′‐diisopropylacetamidinato)indium(III), compound 2) results in a considerably higher and narrower ALD window in the analogous reaction with H2O (225–300 °C). Kinetic studies demonstrate that a higher rate of surface reactions in both parts of the ALD cycle gives rise to this difference in the ALD windows.Publication Atomic layer deposition of Al-incorporated Zn(O,S) thin films with tunable electrical properties(AIP Publishing, 2014) Park, Helen; Jayaraman, Ashwin; Heasley, Rachel Lenox; Yang, Chuanxi; Hartle, Lauren; Mankad, Ravin; Haight, Richard; Mitzi, David B.; Gunawan, Oki; Gordon, RoyZinc oxysulfide, Zn(O,S), films grown by atomic layer deposition were incorporated with aluminum to adjust the carrier concentration. The electron carrier concentration increased up to one order of magnitude from 1019 to 1020 cm−3 with aluminum incorporation and sulfur content in the range of 0 ≤ S/(Zn+Al) ≤ 0.16. However, the carrier concentration decreased by five orders of magnitude from 1019 to 1014 cm−3 for S/(Zn+Al) = 0.34 and decreased even further when S/(Zn+Al) > 0.34. Such tunable electrical properties are potentially useful for graded buffer layers in thin-film photovoltaic applications.Publication Front and back contact modification as a route to increasing open circuit voltage in CZTS,Se devices(2015) Haight, Richard; Gunawan, Oki; Gershon, Talia; Lee, Yun; Ek, Bruce; Gokmen, Ravin; McCandless, Brian; Bishop, Doug; Lloyd, Mike; Gordon, Roy; Jayaraman, Ashwin; Vogel, Mike; Chua, Danny; Kummel, Andy; Sardashti, Kasra; Chagarov, EvguenyPublication Atomic layer depositied Indium oxy-sulfide on CZT(S,Se) absorbers(2015) Jayaraman, Ashwin; Kim, Sang Bok; Gordon, RoyPublication Study of the Crystal Structure of SnS Thin Films by Atomic Layer Deposition(AIP Publishing, 2021-03-01) Zhao, Xizhu; Davis, Luke M.; Lou, Xiabing; Kim, Sang Bok; Uličná, Soňa; Jayaraman, Ashwin; Yang, Chuanxi; Schelhas, Laura T.; Gordon, RoyTin monosulfide, SnS, absorbs visible light and holds promise for thin-film photovoltaics. However, the optoelectronic properties of this material vary among the different structural phases, and control over the phase of vapor deposited SnS thin films is not well understood. In order to study the phases and crystallographic orientations of SnS films, films with thicknesses of 90 nm to 750 nm were prepared by atomic layer deposition (ALD) at temperatures between 80 and 200 °C on amorphous silicon dioxide (a-SiO2) and single-crystal sodium chloride (NaCl). We show that the crystal structures and orientations of the ALD-SnS thin films vary with deposition temperature, film thickness, and substrate. We confirm the presence of metastable cubic π-SnS in co-existence with the thermodynamically stable orthorhombic α-SnS, and find that the π phase is more prevalent at lower deposition temperatures. The films grown on a-SiO2 are textured and the degree of texturing increases with lower temperature or higher thickness, and the deposited phase is also thickness dependent. Upon annealing, which is known to promote SnS grain growth, all films revert to orthorhombic α-SnS. The films grown on the NaCl(100) substrate exhibit a much higher degree of texturing and show different preferred orientations dependent on the phase: π-(400) and α-(111) or (040). In addition, we demonstrate a proof-of-concept device made from the highly oriented SnS grown on NaCl.