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Atomically thin transition metal dichalcogenides (TMDCs) have attracted considerable interest owing to the spin-valley coupled electronic structure and possibility in next-generation devices. Substrates are one of the most important factors to limit physical properties of atomic-layer materials, and among various substrates so far investigated, hexagonal boron nitride (hBN) is the best substrate to explore the intrinsic properties of atomic layers. Here we report direct chemical vapor deposition (CVD) growth of WS2 onto high-quality hBN using a 3-furnace CVD setup. Triangular-shaped WS2 grown on hBN have shown limited crystallographic orientation that is related to that of the underlying hBN. Photoluminescence spectra of the WS2 show an intense emission peak at 2.01 eV with a quite small fwhm of 26 meV. The sharp emission peak indicates the high quality of the present WS2 atomic layers with high crystallinity and clean interface.
Okada et al. (2014) studied this question.