Universal Substrate-Trapping Strategy to Grow Strictly Monolayer Transition Metal Dichalcogenides Crystals

Monolayer transition metal dichalcogenides (TMDs) possess great potential in the electronic and optoelectronic devices on account of their unique electronic structure as well as outstanding characteristics. However, presented growth approaches are hardly to avoid multilayers and the root cause of this thermodynamic growth process lies on the overflowing transition metal sources. Here, a novel substrate-trapping strategy (STS) is developed to achieve monolayer TMDs crystals over the whole substrate surface. A designed substrate with appropriate reaction activity to fix the extra precursors is the key, for which the dominance of the dynamics will be established, thus leading to strict self-limited monolayer growth behavior. The high-quality nature of the synthesized monolayer MoS2 crystals is also clarified by transmission electron microscopy characterizations and field-effect transistors performance. Excellent tolerance to variations in growth parameters of STS is therefore exhibited and, moreover, it is also verified in achieving strictly monolayer WS2 crystals, thus demonstrating the universality of this approach. The facile strategy opens up a new avenue in growth of monolayer TMDs and may facilitate their industrial applications.