Facile Preparation of Single MoS2 Atomic Crystals with Highly Tunable Photoluminescence by Morphology and Atomic Structure

To prepare atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDs) single atomic crystals with highly tunable photoluminescence (PL) is of special importance in 2D photonics and optoelectronics. However, to control the PL in 2D TMDs atomic crystals is still a big challenge due to the atomically thin 2D nature which induces far more complicated and variable PL behaviors than normal semiconductors. In this report, triangular and tetragonal MoS2 atomic crystals are prepared simultaneously on one single growth substrate for the first time in a single chemical vapor deposition process. Through manipulating the growth dynamics to reduce nucleation density and enhance lateral growth with mixture precursor and other growth parameters, both the morphology and PL of the MoS2 atomic crystals can be efficiently modulated. The PL of the optimized triangular MoS2 atomic crystals can be over one to two orders higher than the PL of other triangular morphology modulated by different growth dynamics. In addition, position-dependent PL and a gradient decrease in PL intensity from the center toward edge region are found in both triangular and tetragonal MoS2 atomic crystals, which show 1-2 orders of magnitude of decrease in the PL and imply the strong influences of atomic structure disorders and edges considering the high-resolution transmission electron microscopy observations and first-principles calculations. These results indicate a facile way to tune the PL of TMDs by morphology and atomic structure.