Visualizing Band Profiles of Gate-Tunable Junctions in MoS<sub>2</sub>/WSe<sub>2</sub> Heterostructure Transistors.

Sun, Xinzuo; Chen, Yan; Li, Zhiwei; Han, Yu; Zhou, Qin; Wang, Binbin; Taniguchi, Takashi; Watanabe, Kenji et al. · ACS Nano · 2021

basic_science · Level V

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Abstract

Heterostructure devices based on two-dimensional materials have been under intensive study due to their intriguing electrical and optical properties. One key factor in understanding these devices is their nanometer-scale band profiles, which is challenging to obtain in devices. Here, we use a technique named contact-mode scanning tunneling spectroscopy to directly visualize the band profiles of MoS<sub>2</sub>/WSe<sub>2</sub> heterostructure devices at different gate voltages with nanometer resolution. The long-held view of a conventional p-n junction in the MoS<sub>2</sub>/WSe<sub>2</sub> heterostructure is reexamined. Due to strong inter- and intralayer charge transfer, the MoS<sub>2</sub> layer in contact with WSe<sub>2</sub> is found to convert from n-type to p-type, and a series of gate-tunable p-n and p-p<sup><i>+</i></sup> junctions are developed in the devices. Highly conductive edges are also discovered which could strongly affect the device properties.