Electronic Transport Properties in MoS2 2D Layer Semiconductors: Surface Effect
Ming-Deng Siao2*, Wei-Chu Shen1, Ruei-San Chen2, Ying-Sheng Huang1
1Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan
2Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei, Taiwan
* presenting author:Ming-Deng Siao, email:m10422602@mail.ntust.edu.tw
Thickness-dependent electronic transport properties in the molybdenum disulphide (MoS2) two-dimensional (2D) nanostructures beyond quantum confinement scale were observed and investigated. It is found that the nanoflakes produced by simple mechanical exfoliation exhibit several orders of magnitude higher conductivity than their bulk counterparts. The smaller activation energies of carrier were also observed for the MoS2 nanoflakes in comparison to the bulk counterparts. The analysis of transfer length method (TLM) indicates the current transport in MoS2 following a two-dimensional (2D) behavior rather than conventional 3D mode. These results imply the presence of higher surface conductivity or electron surface accumulation in the layer semiconductor systems. In addition, the potential artificial effects, that could result in a high electron density at the surface, including electron injection from the substrate and surface damage by ion bombardment, were excluded. This result further indicates the proposed surface electron accumulation is an inherent characteristic, which might be generally applicable to the transition metal dichalcogenide (TMD) layer semiconductors. The finding provides a probable explanation to the consistent observations of anomalously high conductive nature in the TMD 2D layer materials and is also crucial for development of next-generation ultrathin, flexible and transparent electronics and optoelectronics.

Keywords: molybdenum disulphide, nanostructure, conductivity