Browsing by Author "Azcatl, Angelica"
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Item Al₂O₃ on WSe₂ by Ozone Based Atomic Layer Deposition: Nucleation and Interface StudyAzcatl, Angelica; Wang, Qingxiao; Kim, Moon J.; Wallace, Robert M.; 0000-0001-5566-4806 (Wallace, RM); Azcatl, Angelica; Wang, Qingxiao; Kim, Moon J.; Wallace, Robert M.In this work, the atomic layer deposition process using ozone and trimethylaluminum (TMA) for the deposition of Al₂O₃ films on WSe₂ was investigated. It was found that the ozone-based atomic layer deposition enhanced the nucleation of Al₂O₃ in comparison to the water/TMA process. In addition, the chemistry at the Al₂O₃ / WSe₂ interface and the surface morphology of the Al₂O₃ films exhibited a dependence on the deposition temperature. A non-covalent functionalizing effect of ozone on WSe₂ at low deposition temperatures 30 ⁰C was identified which prevented the formation of pinholes in the Al₂O₃ films. These findings aim to provide an approach to obtain high-quality gate dielectrics on WSe₂ for two-dimensional transistor applications.Item In Situ Study of E-Beam Al And Hf Metal Deposition on Native Oxide InP (100)Dong, Hong; Santosh, KC; Azcatl, Angelica; Cabrera, Wilfredo; Qin, Xiaoye; Brennan, Barry; Zhernokletov, Dmitry; Cho, Kyeongjie; Wallace, Robert M.The interfacial chemistry of thin Al (∼3 nm) and Hf (∼2 nm) metal films deposited by electron beam (e-beam) evaporation on native oxide InP (100) samples at room temperature and after annealing has been studied by in situ angle resolved X-ray photoelectron spectroscopy and low energy ion scattering spectroscopy. The In-oxides are completely scavenged forming In-In/In-(Al/Hf) bonding after Al and Hf metal deposition. The P-oxide concentration is significantly decreased, and the P-oxide chemical states have been changed to more P-rich oxides upon metal deposition. Indium diffusion through these metals before and after annealing at 250 °C has also been characterized. First principles calculation shows that In has lower surface formation energy compared with Al and Hf metals, which is consistent with the observed indium diffusion behavior.Item MoS₂ Functionalization for Ultra-Thin Atomic Layer Deposited DielectricsAzcatl, Angelica; McDonnell, Stephen; KC, Santosh; Peng, Xin; Dong, Hong; Qin, Xiaoye; Addou, Rafik; Mordi, Greg I.; Lu, Ning; Kim, Jiyoung; Kim, Moon J.; Cho, Kyeongjae; Wallace, Robert M.; 70133685 (Kim, J)The effect of room temperature ultraviolet-ozone (UV-O₃) exposure of MoS₂ on the uniformity of subsequent atomic layer deposition of Al₂O₃ is investigated. It is found that a UV-O₃ pre-treatment removes adsorbed carbon contamination from the MoS₂ surface and also functionalizes the MoS₂ surface through the formation of a weak sulfur-oxygen bond without any evidence of molybdenum-sulfur bond disruption. This is supported by first principles density functional theory calculations which show that oxygen bonded to a surface sulfur atom while the sulfur is simultaneously back-bonded to three molybdenum atoms is a thermodynamically favorable configuration. The adsorbed oxygen increases the reactivity of MoS₂ surface and provides nucleation sites for atomic layer deposition of Al₂O₃. The enhanced nucleation is found to be dependent on the thin film deposition temperature.