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.
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