Browsing by Author "Peng, Xin"
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Item Atomically Thin Resonant Tunnel Diodes Built from Synthetic van der Waals Heterostructures(Nature Pub. Group) Lin, Yu-Chuan; Ghosh, Ram Krishna; Addou, Rafik; Lu, Ning; Eichfeld, Sarah M.; Zhu, Hui; Li, Ming-Yang; Peng, Xin; Kim, Moon J.; Li, Lain-Jong; Wallace, Robert M.; Datta, Suman; Robinson, Joshua A.; A-5283-2008 (Wallace, RM); A-2297-2010 (Kim, MJ)Vertical integration of two-dimensional van der Waals materials is predicted to lead to novel electronic and optical properties not found in the constituent layers. Here, we present the direct synthesis of two unique, atomically thin, multi-junction heterostructures by combining graphene with the monolayer transition-metal dichalcogenides: molybdenum disulfide (MoS₂), molybdenum diselenide (MoSe₂) and tungsten diselenide (WSe₂). The realization of MoS₂-WSe₂-graphene and WSe₂-MoS₂-graphene heterostructures leads to resonant tunnelling in an atomically thin stack with spectrally narrow, room temperature negative differential resistance characteristics.;Item Creating a Single Twin Boundary between Two CdTe (111) Wafers with Controlled Rotation Angle by Wafer BondingSun, Ce; Lu, Ning; Wang, Jinguo; Lee, Jihyung; Peng, Xin; Klie, R. F.; Kim, Moon J.The single twin boundary with crystallographic orientation relationship (1‾ 1‾ 1 ‾)//(111) [0 1‾1]// [011‾] was created by wafer bonding. Electron diffraction patterns and high-resolution transmission electron microscopy images demonstrated the well control of the rotation angle between the bonded pair. At the twin boundary, one unit of wurtzite structure was found between two zinc-blende matrices. High-angle annular dark-field scanning transmission electron microscopy images showed Cd- and Te-terminated for the two bonded portions, respectively. The I-V curve across the twin boundary showed increasingly nonlinear behavior, indicating a potential barrier at the bonded twin boundary.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.