title: Microscopic basis for the band engineering of Mo1-xWxS2-based heterojunction.
abstract: Transition-metal dichalcogenide layered materials, consisting of a transition-metal atomic layer sandwiched by two chalcogen atomic layers, have been attracting considerable attention because of their desirable physical properties for semiconductor devices, and a wide variety of pn junctions, which are essential building blocks for electronic and optoelectronic devices, have been realized using these atomically thin structures. Engineering the electronic/optical properties of semiconductors by using such heterojunctions has been a central concept in semiconductor science and technology. Here, we report the first scanning tunneling microscopy/spectroscopy (STM/STS) study on the electronic structures of a monolayer WS2/Mo1-xWxS2 heterojunction that provides a tunable band alignment. The atomically modulated spatial variation in such electronic structures, i.e., a microscopic basis for the band structure of a WS2/Mo1-xWxS2 heterojunction, was directly observed. The macroscopic band structure of Mo1-xWxS2 alloy was well reproduced by the STS spectra averaged over the surface. An electric field of as high as 80 × 10(6) Vm(-1) was observed at the interface for the alloy with x = 0.3, verifying the efficient separation of photoexcited carriers at the interface.
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573, Japan.
authors.forename: Shoji
authors.initials: S
authors.lastname: Yoshida
authors.affiliation: Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Kobayashi
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573, Japan.
authors.forename: Ryuji
authors.initials: R
authors.lastname: Sakurada
authors.affiliation: Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Mori
authors.affiliation: Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.|JST-PRESTO, Kawaguchi, 332-0012, Japan.
authors.forename: Yasumitsu
authors.initials: Y
authors.lastname: Miyata
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mogi
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573, Japan.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Koyama
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Takeuchi
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573, Japan.
authors.forename: Hidemi
authors.initials: H
authors.lastname: Shigekawa