New Strategy for the Growth of Complex Heterostructures Based on Different 2D Materials

Tungsten disulfide (WS<inf>2</inf>) monolayers have been synthesized under ultra high vacuum (UHV) conditions on quasi-free-standing hexagonal boron nitride (h-BN) and gold deposited on Ni(111). We find that the synthesis temperature control can be used to tune the WS<inf>2</inf> structure. As documented by in situ core level and valence band photoemission and by ex situ Raman spectroscopy, the partially disordered WS<inf>2</inf> layer obtained at room temperature transforms to the 2H-WS<inf>2</inf> phase at about 400°C. Low energy electron diffraction confirms the existence of van der Waals epitaxy between WS<inf>2</inf> and h-BN and gold substrates. The measured band structure indicates that the WS<inf>2</inf> electronic structure is not affected by the interaction with the h-BN and gold substrates.