Epitaxial growth of highly-aligned MoS2 on c-plane sapphire

Abstract

The ability to grow high-quality, single-crystal transition metal dichalcogenides (TMDCs) is important for the application of electronic and optoelectronic devices. Here, we report the epitaxial growth of highly-aligned molybdenum disulfide (MoS2) on c-plane sapphire by chemical vapor deposition (CVD). The base edge of MoS2 flakes is mainly along the [11−20] crystallographic orientation of c-plane sapphire. Structural characterization indicates that coupling between sapphire step edges and MoS2 zigzag edges gives rise to epitaxial growth. We find that photoluminescence (PL) intensity of aligned MoS2 is much weaker than that of randomly orientated MoS2 flakes, attributing to the strong MoS2-substrate interaction and thus introducing strain in aligned MoS2. The ratio of sulfur and molybdenum trioxide (MoO3) precursor in the CVD process also plays an essential role in the orientation of MoS2 triangular flakes. In addition, the morphology of aligned MoS2 flakes shows great growth temperature dependence and high growth temperature leads to the formation of trapezoid MoS2 flakes.