van der Waals interaction-induced photoluminescence weakening and multilayer growth in epitaxially aligned WS.

Recently, transition metal dichalcogenides (TMDCs) have attracted great interest due to their unique electronic and optical properties. Chemical vapor deposition (CVD) has been regarded as the most promising method for the synthesis of large-area TMDCs with high reproducibility. Having similar hexagonal crystal structures with many TMDCs, c-plane sapphire is commonly used as a growth substrate in CVD.

Surface-Mediated Aligned Growth of Monolayer MoS and In-Plane Heterostructures with Graphene on Sapphire.

Aligned growth of transition metal dichalcogenides and related two-dimensional (2D) materials is essential for the synthesis of high-quality 2D films due to effective stitching of merging grains. Here, we demonstrate the controlled growth of highly aligned molybdenum disulfide (MoS) on c-plane sapphire with two distinct orientations, which are highly controlled by tuning sulfur concentration. We found that the size of the aligned MoS grains is smaller and their photoluminescence is weaker as compared with those of the randomly oriented grains, signifying enhanced MoS-substrate interaction in the aligned grains.

Two-step synthesis and characterization of vertically stacked SnS-WS and SnS-MoS p-n heterojunctions.

We demonstrate the synthesis of unique heterostructures consisting of SnS and WS (or SnS and MoS) by two-step chemical vapor deposition (CVD). After the first CVD growth of triangular WS (MoS) grains, the second CVD step was performed to grow square SnS grains on the same substrate. We found that these SnS grains can be grown at very low temperature with the substrate temperature of 200 °C.