Controlling sulphur precursor addition for large single crystal domains of WS2

Abstract

We show that controlling the introduction time and the amount of sulphur (S) vapour relative to the WO₃ precursor during the chemical vapour deposition (CVD) growth of WS₂ is critical to achieving large crystal domains on the surface of silicon wafers with a 300 nm oxide layer. We use a two furnace system that enables the S precursor to be separately heated from the WO₃ precursor and growth substrate. Accurate control of the S introduction time enabled the formation of triangular WS₂ domains with edges up to 370 μm which are visible to the naked eye. The WS₂ domains exhibit room-temperature photoluminescence with a peak value around ∼635 nm and a full-width at half-maximum (FWHM) of ∼12 nm. Selected area electron diffraction from different regions of the triangular WS₂ domains showed that they are single crystal structures.