Thickness-dependent Transport Properties and Ohmic Contacts in MoS₂ and WS₂ Layer Nanostructures
Wei-Chu Shen (沈韋竹)1*, Ruei-San Chen (陳瑞山)2, Ying-Sheng Huang (黃鶯聲)1
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:沈韋竹,
The electrical properties of the layer semiconductors including MoS₂ and WS₂ grown by chemical vapor transport method (CVT) have been investigated. The two-terminal MoS₂ and WS₂ multilayer devices with good ohmic contact property were fabricated by focused-ion beam (FIB) deposition using platinum (Pt) as the contact metal. A common thickness-dependent conductivity was observed for these two layer materials. The conductivity of MoS₂ multilayers increases for two orders of magnitude from 7 to 890 Ω-1cm-1 when the thickness decreases from 380 to 6 nm. Meanwhile, the WS₂ multilayers show a similar behavior, of which the conductivity increases from 7 to 210 Ω-1cm-1 with the decrease of thickness from 260 to 6 nm. The temperature-dependent conductivities also indicate that the layer nanostructures exhibit lower activation energy than those of their bulk counterparts. The probably higher surface conductivity or surface electron accumulation in the layer semiconductors is proposed.

Keywords: molybdenum disulfide and tungsten disulfide, layer semiconductor, electrical properties, conductivity, ohmic contact