Observation of biexcitonic emission at extremely low power density in tungsten disulfide atomic layers grown on hexagonal boron nitride.
Monolayer transition metal dichalcogenides (TMDCs) including WS2, MoS2, WSe2and WS2, are two-dimensional semiconductors with direct bandgap, providing an excellent field for exploration of many-body effects in 2-dimensions (2D) through optical measurements. To fully explore the physics of TMDCs, the prerequisite is preparation of high-quality samples to observe their intrinsic properties. For this purpose, we have focused on high-quality samples, WS2grown by chemical vapor deposition method with hexagonal boron nitride as substrates. We observed sharp exciton emissions, whose linewidth is typically 22~23 meV, in photoluminescence spectra at room temperature, which result clearly demonstrates the high-quality of the current samples. We found that biexcitons formed with extremely low-excitation power (240 W/cm2) at 80 K, and this should originate from the minimal amount of localization centers in the present high-quality samples. The results clearly demonstrate that the present samples can provide an excellent field, where one can observe various excitonic states, offering possibility of exploring optical physics in 2D and finding new condensates.
Department of Chemistry, Nagoya University, Nagoya, 464-8602, Japan.
Mitsuhiro
M
Okada
Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan.
Yuhei
Y
Miyauchi
Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan.
Kazunari
K
Matsuda
National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan.
Takashi
T
Taniguchi
National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan.
Kenji
0000-0003-3701-8119
K
Watanabe
Department of Chemistry, Nagoya University, Nagoya, 464-8602, Japan. noris@nagoya-u.jp.
Hisanori
H
Shinohara
Department of Chemistry, Nagoya University, Nagoya, 464-8602, Japan. r.kitaura@nagoya-u.jp.
Ryo
R
Kitaura