Vapor-transport growth of high optical quality WSe2 monolayers

• Main Authors: Genevieve Clark, Sanfeng Wu, Pasqual Rivera, Joseph Finney, Paul Nguyen, David H. Cobden, Xiaodong Xu
• Format: Article
• Language: English
• Published: AIP Publishing LLC 2014-10-01
• Series: APL Materials
• Online Access: http://dx.doi.org/10.1063/1.4896591

Monolayer transition metal dichalcogenides are atomically thin direct-gap semiconductors that show a variety of novel electronic and optical properties with an optically accessible valley degree of freedom. While they are ideal materials for developing optical-driven valleytronics, the restrictions of exfoliated samples have limited exploration of their potential. Here, we present a physical vapor transport growth method for triangular WSe2 sheets of up to 30 μm in edge length on insulating SiO2 substrates. Characterization using atomic force microscopy and optical microscopy reveals that they are uniform, monolayer crystals. Low temperature photoluminescence shows well resolved and electrically tunable excitonic features similar to those in exfoliated samples, with substantial valley polarization and valley coherence. The monolayers grown using this method are therefore of high enough optical quality for routine use in the investigation of optoelectronics and valleytronics.