Large-area synthesis of WSe sub(2) from WO sub(3) by selenium-oxygen ion exchange

Few-layer tungsten diselenide (WSe sub(2)) is attractive as a next-generation electronic material as it exhibits modest carrier mobilities and energy band gap in the visible spectra, making it appealing for photovoltaic and low-powered electronic applications. Here we demonstrate the scalable synthesis of large-area, few-layer WSe sub(2) via replacement of oxygen in hexagonally stabilized tungsten oxide films using dimethyl selenium. Cross-sectional transmission electron microscopy reveals successful control of the final WSe sub(2) film thickness through control of initial tungsten oxide thickness, as well as development of layered films with grain sizes up to several hundred nanometers. Raman spectroscopy and atomic force microscopy confirms high crystal uniformity of the converted WSe sub(2), and time domain thermo-reflectance provide evidence that near record low thermal conductivity is achievable in ultra-thin WSe sub(2) using this method.