Role of gas flow direction on monolayer MoS2 growth on patterned surfaces via CVD

Abstract

The chemical vapor deposition (CVD) technique has been widely used to grow high quality single layer MoS2 crystals. However, there are still issues that need to be clarified in order to determine the appropriate conditions for the repeatable and scalable process. In this study, we experimentally investigated the effect of flow direction on the size distribution and optical signal of monolayer MoS2 flakes grown on microchannel arrayed surfaces. As an important parameter controlling the CVD process, the carrier gas flow was revealed to be highly sensitive to geometric orientation of the patterned surface. The flow direction parallel to the array yielded larger flakes with narrower size distribution, and enhanced photoluminescence (PL) peak intensities compared to the case with flow normal to the array while the Raman intensities for both the cases are almost the same. The size distributions were obtained as 6 +/- 13 and 37 +/- 4 mu m for the perpendicular and parallel cases, respectively. It was also found that the PL peak intensity increased by approximately 1.5 times when switching to parallel configuration. This study presents an experimental approach to understand the influence of the precursor stream reshaped by the growth surface geometry on the structural and optical properties of monolayer MoS2, which has great potential for use in optoelectronic applications.