Tungsten disulfide on Au(111)

Transition metal dichalcogenides (TMDCs) are a rising star among other two-dimensional materials, in view of a possible usage in building new electronic devices that exploit the spin-valley degree of freedom.
The sample was grown at the SuperESCA beamline of Elettra Synchrotron in Trieste, by evaporating W atoms with the UHV chamber backfilled with H₂S. The preparation was performed monitoring the W 4f and S 2p core levels with fast x-ray photoelectron spectroscopy, which allowed a precise tuning of the deposition conditions (temperature, H₂S pressure, W evaporation rate). We observed that the growth of a single crystalline orientation is triggered by choosing a low W evaporation rate and performing the process with a high temperature of the substrate. Information about the single orientation of the layer was obtained by acquiring XPD patterns, revealing a 1H polytype for the WS₂ layer and, moreover, determining the structural parameters and registry

with the substrate.
These measurements were complemented by low-energy electron microscopy (LEEM) measurements, performed at the University of Bremen, Germany, which provided further details about the morphology of the WS₂ crystalline domains.