Low-temperature electrical conduction of plasma-treated bilayer MoS 2
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Research Letter
Low-temperature electrical conduction of plasma-treated bilayer MoS2 Jakub Jadwiszczak, School of Physics, Trinity College Dublin, Dublin 2, Ireland; Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland; Advanced Materials and BioEngineering Research Centre (AMBER), Trinity College Dublin, Dublin 2, Ireland; School of Material Science and Engineering, Nanchang University, 999 Xuefu Road, Nanchang, Jiangxi 330031, China Yangbo Zhou, School of Material Science and Engineering, Nanchang University, 999 Xuefu Road, Nanchang, Jiangxi 330031, China Hongzhou Zhang, School of Physics, Trinity College Dublin, Dublin 2, Ireland; Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland; Advanced Materials and BioEngineering Research Centre (AMBER), Trinity College Dublin, Dublin 2, Ireland Address all correspondence to Hongzhou Zhang at [email protected] (Received 23 January 2018; accepted 4 April 2018)
Abstract We report on the low-temperature electrical characterization of bilayer MoS2 treated with increasing dose of oxygen:argon (1:3) plasma. We characterize the effective Schottky barrier heights as a function of plasma exposure time and observe a significant barrier lowering, with no accompanying p-type conduction in the negative bias region. Furthermore, we observe a crossover in the temperature-dependent conduction regimes below 181 K due to the plasma exposure. The Efros–Shklovskii (ES) hopping regime is seen to transform upon plasma exposure to a mixed ES/thermally-activated regime at high temperatures, and to a strongly short-range Arrhenius regime at low temperatures. We attribute the observed crossovers to a critical defect density created by the surface reaction with the plasma.
Introduction Two-dimensional (2D) MoS2 has attracted considerable attention in recent years in various areas of applied physics. As a layered semiconductor, it shows good promise in future ultra-thin nanoelectronic devices. However, the nature of the substrate, surface roughness, and charged impurity scattering centers have been shown to substantially degrade carrier mobility in layered 2D semiconductors[1,2], hampering their applications in novel electronics. Engineering of the contact interface and/ or top layer surface may open avenues for tailoring the electrical performance of MoS[23,4]. Plasma treatment is an effective and versatile method of modifying the properties of 2D materials, enabling a wide range of applications. In particular, oxygen plasma treatment has shown promise in effective surface doping of layered semiconductors in order to tune their electrical performance. This strategy has been used to implement rectifying diodes, multibit nonvolatile memory, electrocatalysts and ambipolar transistors based on 2D MoS[24–8]. Such an approach to nanofabrication offers large-scale, on-substrate, and rapid functionalization of 2D materials at low costs. However, to harness the potential applications of
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