  The nucleation and growth of single-layer molybdenum disulfide single domain
islands is investigated by in situ low-energy electron microscopy. We study the
growth of micron-sized flakes and the correlated flattening process of the gold
surface for three different elevated temperatures. Furthermore, the influence
of surface step edges on the molybdenum disulfide growth process is revealed.
We show that both island and underlying terrace grow simultaneously by pushing
the surface step in the expansion process. Our findings point to an optimized
growth procedure allowing for step-free single-domain single-layer islands of
several micrometers in size, which is likely transferable to other transition
metal dichalcogenides.
