Single-Layer MoS Grown on Atomically Flat SrTiO Single Crystal for Enhanced Trionic Luminescence.

The elaborate interface interactions can be critical in determining the achievable functionality of a semiconductor heterojunction (SH), particularly when two-dimensional material is enclosed in the system and its thickness is at an atomic extreme. In this work, we have successfully constructed a SH model system composed of typical transition-metal chalcogenide (TMDs) and transition metal oxides (TMO) by directly growing molybdenum sulfide (MoS) nanosheets on atomically flat strontium titanate (SrTiO) single crystal substrates through a conventional chemical vapor deposition (CVD) synthetic method. Multiple measurements have demonstrated the uniform monolayer thickness and single crystallinity of the MoS nanosheets as well as the atomic flatness of the heterojunction surface, both characterizing an extremely high quality of the interface. Clear evidence have been obtained for the electron transfer from the MoS adlayer to the SrTiO substrate which varies against the interface conditions. More importantly, the photoluminescence of MoS is significantly tailored, which is correlated with both the cleanness of the interface and the crystal orientation of the SrTiO substrate. These results not only shed fresh lights on the structure-property relationship of the TMDs/TMO heterostructures but also manifest the importance of the ideal interface structure for a hybridized system.