Controllable synthesis of high quality monolayer WS2 on a SiO2/Si substrate by chemical vapor deposition

Abstract

Tungsten disulfide (WS₂), with its transformation from indirect to direct band transitions when scaled down to a monolayer, exhibits great potential for future micro-device applications. In this work, we report a controllable route for monolayer WS₂ synthesis. The high-quality of as-grown monolayer WS₂ was confirmed by optical microscopy, atomic force microscopy (AFM), high resolution scanning transmission electron microscopy (HRSTEM), Raman spectroscopy, and photoluminescence (PL). The impact of growth parameters (including gas flow rate and reaction temperature) on the morphology of the WS₂ domain was investigated. A growth mechanism is proposed based on the experimental analysis. Our results also provide some general guidelines for other two dimensional (2D) monolayer syntheses of transition metal dichalcogenides (TMD).