Growth of continuous MoS2 film with large grain size by chemical vapor deposition

Abstract

In this work we present the growth of an inch size continuous MoS2 (molybdenum disulfide) film by chemical vapor deposition (CVD). The continuous film was formed by merging hexagonal and triangular MoS2 single-crystals with different sizes and various orientations. By separating the Mo source and the substrate and control their respective temperatures, we found out that the lower Mo source temperature could decrease the evaporation rate, while higher substrate temperature could reduce the nucleation density. All these factors are significantly beneficial to the increase of each single crystal grain. The average edge length of the single crystalline hexagons and triangles is approximately 200 µm. Besides, the gas flow rate also plays a significant role in enlarging the size of the subsequent continuous films. With the increased size of the single crystal, the grain boundary density has been notably reduced in the continuous MoS2 film. Most areas without small triangular crystals on top are monolayers, while other regions were comprised of about 2–4 layers where multilayer triangle crystals stack is formed. A bottom-gate transistor was then fabricated on the continuous MoS2 film, of which on/off current ratio is approximately 104, and field-effect mobility for the MoS2-channel is about 10 cm2/Vs. These results demonstrate a promising path towards the growth of high quality continuous layered MoS2 film with inch size and few grain boundaries.