Vapor pressure-controllable molecular inorganic precursors for growth of monolayer WS2: Influence of precursor-substrate interaction on growth thermodynamics

Abstract

A chemical route for the growth of centimeter-scale and homogeneous WS2 monolayer has been developed using the penta-coordinated inorganic W complex, WOCl4. The relatively low melting point of WOCl4 compared to other conventional W precursors enables the use of WOCl4 as a vapor phase precursor. Consequently, the precise control of partial pressure during chemical vapor deposition (CVD) allows the optimization of growth conditions, synthesizing the entirely covered homogeneous monolayer WS2 film. The contamination of amorphous carbon, which is considered a demerit of metal–organic CVD, is highly reduced because of the carbon-free compositional characteristic of WOCl4. Additionally, the growth behavior of WS2 with respect to the growth parameters is systematically studied by investigating the thermodynamics of the molecular precursors compared with MoS2 growth using MoOCl4. This approach enables us to understand the effect of the growth temperature and partial pressure on the optimum growth conditions of WS2 monolayer.