Surface Electron Accumulation and Electronic Transport in MoS2 Layer Semiconductors

• Main Authors: Ming-Deng Siao, 蕭名登
• Other Authors: Ruei-San Chen
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/8qzu62

碩士 === 國立臺灣科技大學 === 應用科技研究所 === 105 === Surface electron accumulation (SEA) and thickness-dependent electric properties in the molybdenum disulfide (MoS2) two-dimensional (2D) nanostructures have been observed and investigated. The MoS2 nanoflakes fabricated by mechanical exfoliation exhibit several orders of magnitude higher conductivity than their bulk counterparts. The carrier activation energy of nanostructures is lower than that of the bulk counterparts. The transfer length method was used to determine the current transport in MoS2 following a 2D behavior rather than the conventional 3D mode. Scanning tunneling microscopy measurements confirmed the presence of surface electron accumulation (SEA) in this layer material. Notably, the pronounced n-doping characteristic can be easily removed by producing a fresh surface through mechanical exfoliation. Long-term exposure to air can transform the intrinsic fresh surface into a metallic-like surface, indicating that SEA is not inherent. The FET measurement indicates that the MoS2 nanoflakes with fresh surface exhibit higher mobility and lower electron concentration compare to the nanoflakes with non-fresh surface. A more significant surface scattering in the non-fresh MoS2 nanoflakes was proposed.