STM Morphology and Moire-pattern-resolved STS of CVD Grown MoS2 on HOPG
Date Issued
2014
Date
2014
Author(s)
Sun, Yung-Che
Abstract
Molybdenum disul de (MoS2) and tungsten diselenide (WSe2) are typical layered transition-metal dichalcogenide 2D materials with semiconductor properties. In this work, we investigate the topography of the chemical vapor deposition (CVD) grown MoS2 on HOPG by low temperature STM. In atomic force microscopy (AFM) data, MoS2 islands tend to form large domain triangular islands and show some preferred growing direction compared to the HOPG edge. From scanning tunneling microscopy (STM) atom-resolved image, the unit cell vector of the sulfur atoms and the superstructure moir e pattern can be determined. Through the symmetry analysis of the hexagonal array overlapping, we can figure out the angle of orientation di fference is small through the MoS2 domains we found, which means that MoS2 and HOPG lattice are almost parallel. Combining the edge orientation model analysis, the preferred direction of the triangular islands observed in AFM topography can be explained. Additionally, we obtain highly resolved scanning tunneling spectroscopy (STS) of monolayer MoS2 on HOPG in moir e-pattern resolution. The moir e pattern is mainly related to the corrugation of electronic states under this situation. A atom model of moir e pattern is made to reveal that the atomic arrangement between sulfur and carbon atoms causes the corrugation of electronic states. Moreover, we observe the state localized in the local maximum of moir e pattern, which may be originated from the orbital interaction between sulfur and carbon atoms.
Subjects
二硫化鉬
過渡金屬硫屬化合物
化學氣相沉積
掃描穿隧式顯微鏡
莫列條紋
掃描穿隧能譜
Type
thesis
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