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

Tungsten disulfide (WS2) 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 WS2 structure. As documented by in situ core level and valence band photoemission and by ex situ Raman spectroscopy, the partially disordered WS2 layer obtained at room temperature transforms to the 2H-WS2 phase at about 400 degrees C. Low energy electron diffraction confirms the existence of van der Waals epitaxy between WS2 and h-BN and gold substrates. The measured band structure indicates that the WS2 electronic structure is not affected by the interaction with the h-BN and gold substrates.