Electrical and thermoelectric transport properties in few-layer MoS2

• Main Authors: Chiu, Ta-Wei, 邱達偉
• Other Authors: Jian, Wen-Bin
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/he8p4k

碩士 === 國立交通大學 === 電子物理系所 === 105 === In recent years, many studies have concentrated on electrical and optoelectronic properties of few-layer MoS2. The thermoelectric properties are, however, still not well studied yet. In this study, we designed a pattern of current leads integrated with heater to investigate electrical and thermoelectric transport properties in few-layer MoS2 flakes in the temperature range from 80 to 600 K. The transport properties are different in different temperature regimes. We separated temperature behaviors into three different regimes for detailed discussions. At temperatures below 200 K, the temperature behavior of resistance (R) and Seebeck coefficient (S) can be described by the equations of R~exp⁡(〖(T_0/T)〗^(1/3)) and S~T^(1/3), respectively, indicating that both electrical and thermoelectric transport satisfies with the two-dimensional variable-range hopping (2D-VRH) transport. In the temperature range from 300 to 460 K, the electron transport behavior changes from 2D-VRH to thermally activated transport and the thermoelectric transport changes to linear behavior as described by the equation S~T^1. At temperatures above 460 K, the electron transport behavior changes from insulating to metallic behavior whereas the thermoelectric transport still follows the relation of S~T^1. Additionally, we observed hysteresis and step-like feature in current-voltage loops in both electrical and thermoelectric data. The thickness-dependent and gate-dependent thermoelectric power factor (PF=S^2 σ) are studied and a maximum PF of 1.7 mW/m·K2 is measured at VG= 60 V in single layer MoS2 flakes. Our research results help to understand the electrical and thermoelectric characteristics in MoS2, and to show a high PF value that has potential for future applications of thermoelectric devices.