title: Probing the electron states and metal-insulator transition mechanisms in molybdenum disulphide vertical heterostructures.
abstract: The metal-insulator transition is one of the remarkable electrical properties of atomically thin molybdenum disulphide. Although the theory of electron-electron interactions has been used in modelling the metal-insulator transition in molybdenum disulphide, the underlying mechanism and detailed transition process still remain largely unexplored. Here we demonstrate that the vertical metal-insulator-semiconductor heterostructures built from atomically thin molybdenum disulphide are ideal capacitor structures for probing the electron states. The vertical configuration offers the added advantage of eliminating the influence of large impedance at the band tails and allows the observation of fully excited electron states near the surface of molybdenum disulphide over a wide excitation frequency and temperature range. By combining capacitance and transport measurements, we have observed a percolation-type metal-insulator transition, driven by density inhomogeneities of electron states, in monolayer and multilayer molybdenum disulphide. In addition, the valence band of thin molybdenum disulphide layers and their intrinsic properties are accessed.
authors.affiliation: Department of Physics and the William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Physics and the William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Zefei
authors.initials: Z
authors.lastname: Wu
authors.affiliation: Department of Physics and the William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Shuigang
authors.initials: S
authors.lastname: Xu
authors.affiliation: Department of Condensed Matter Physics, Group of Applied Physics, University of Geneva, 24 Quai Ernest Ansermet, CH1211 Geneva, Switzerland.
authors.forename: Lin
authors.initials: L
authors.lastname: Wang
authors.affiliation: 1] Department of Physics and the William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China [2] Department of Physics and Electronic Engineering, Hanshan Normal University, Chaozhou, Guangdong 521041, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Huang
authors.affiliation: Department of Physics and the William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Han
authors.affiliation: Department of Physics and the William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Weiguang
authors.initials: W
authors.lastname: Ye
authors.affiliation: Department of Physics and the William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Xiong
authors.affiliation: Department of Physics and the William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Tianyi
authors.initials: T
authors.lastname: Han
authors.affiliation: Department of Physics and the William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Gen
authors.initials: G
authors.lastname: Long
authors.affiliation: Department of Physics and the William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Physics and the William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Yuheng
authors.initials: Y
authors.lastname: He
authors.affiliation: Department of Physics and the William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Cai
authors.affiliation: Department of Physics and the William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Sheng
authors.affiliation: Department of Physics and the William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Wang