title: Growth and Optical Properties of High-Quality Monolayer WS2 on Graphite.
abstract: Atomic-layer transition metal dichalcogenides (TMDCs) have attracted appreciable interest due to their tunable band gap, spin-valley physics, and potential device applications. However, the quality of TMDC samples available still poses serious problems, such as inhomogeneous lattice strain, charge doping, and structural defects. Here, we report on the growth of high-quality, monolayer WS2 onto exfoliated graphite by high-temperature chemical vapor deposition (CVD). Monolayer-grown WS2 single crystals present a uniform, single excitonic photoluminescence peak with a Lorentzian profile and a very small full-width at half-maximum of 21 meV at room temperature and 8 meV at 79 K. Furthermore, in these samples, no additional peaks are observed for charged and/or bound excitons, even at low temperature. These optical responses are completely different from the results of previously reported TMDCs obtained by mechanical exfoliation and CVD. Our findings indicate that the combination of high-temperature CVD with a cleaved graphite surface is an ideal condition for the growth of high-quality TMDCs, and such samples will be essential for revealing intrinsic physical properties and for future applications.
authors: †Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
authors: Yu
authors: Y
authors: Kobayashi
authors: †Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
authors: Shogo
authors: S
authors: Sasaki
authors: †Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
authors: Shohei
authors: S
authors: Mori
authors: ‡NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa 243-0198, Japan.
authors: Hiroki
authors: H
authors: Hibino
authors: §Nanotube Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan.
authors: Zheng
authors: Z
authors: Liu
authors: ⊥National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
authors: Kenji
authors: K
authors: Watanabe
authors: ⊥National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
authors: Takashi
authors: T
authors: Taniguchi
authors: §Nanotube Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan.
authors: Kazu
authors: K
authors: Suenaga
authors: †Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
authors: Yutaka
authors: Y
authors: Maniwa
authors: †Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.|∥JST, PRESTO, Kawaguchi, Saitama 332-0012, Japan.
authors: Yasumitsu
authors: Y
authors: Miyata
keywords: CVD growth; WS2; exciton; graphite; line width; photoluminescence