Unraveling the Defect Emission and Exciton–Lattice Interaction in Bilayer WS2

• Published in: Journal of physical chemistry. C Vol. 123; no. 7; pp. 4433 - 4440
• Main Authors: Tan, Qing-Hai, Ren, Shu-Liang, Shen, Tao, Liu, Xue-Lu, Shi, Wei, Sun, Yu-Jia, Deng, Hui-Xiong, Tan, Ping-Heng, Zhang, Jun
• Format: Journal Article
• Language: English; Japanese
• Published: American Chemical Society 21.02.2019
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.8b11011

Defect states and exciton of two-dimensional semiconductors play an important role in fundamental research and device applications. Here, we reported the defect emissions and exciton–lattice interaction of bilayer WS2. These defect emissions show a very narrow linewidth, doublet peaks, spatial localization, saturation with pumping power and can survive up to 180 K. The behavior of these defect emissions means it should be a good candidate as a single photon source. Besides defect emissions, direct exciton and two indirect excitons due to band-to-band transition are identified. By analyzing the temperature-dependent photoluminescence (PL) spectra of excitons, we obtained the Debye temperature, exciton–phonon coupling constant, and pressure coefficient terms of all excitons. Combining the PL experiments and density functional theory calculations, we attributed two indirect excitons to the Λ–K and Λ–Γ transitions, respectively. Our study not only gives a better understanding of the defect emissions and energy band structure in multilayer materials, but also provides an opportunity for defect and band engineering in two-dimensional layered systems.