Origin of Indirect Optical Transitions in Few-Layer MoS2, WS2, and WSe2

• Published in: Nano letters Vol. 13; no. 11; pp. 5627 - 5634
• Main Authors: Zhao, Weijie, Ribeiro, R. M, Toh, Minglin, Carvalho, Alexandra, Kloc, Christian, Castro Neto, A. H, Eda, Goki
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 13.11.2013
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Electron states; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic structure of nanoscale materials : clusters, nanoparticles, nanotubes, and nanocrystals; Exact sciences and technology; Excitons and related phenomena; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Physics; Thermal properties of condensed matter; Thermal properties of small particles, nanocrystals, nanotubes; strain; Transition metal dichalcogenides; indirect band gap; thermal expansion; exciton; photoluminescence spectroscopy; Conduction bands; Thermal expansion; Temperature dependence; Multilayers; Band structure; Electronic structure; Excitons; Semiconductor materials; Multilayer; Anisotropy; Photoluminescence; Optical transition

It has been well-established that single layer MX2 (M = Mo, W and X = S, Se) are direct gap semiconductors with band edges coinciding at the K point in contrast to their indirect gap multilayer counterparts. In few-layer MX2, there are two valleys along the Γ–K line with similar energy. There is lit...