Two-step growth of 4-inch multilayer MoS₂ wafers

Molybdenum disulfide (MoS₂) is an emerging two-dimensional (2D) semiconductor and has great potential for high-end applications beyond the traditional silicon-based electronics. Compared to the monolayers, multilayer MoS₂ has improved electron mobility and current density, and therefore provides a more promising platform in terms of thin-film transistors, flexible electronic devices, etc. However, the synthesis of large-area, high-quality multilayer MoS₂ films with controlled layer number remains a challenge. Here, we develop a two-step oxygen-assisted chemical vapor deposition (OA-CVD) methodology for the synthesis of 4-inch MoS₂ films from monolayer to trilayer on sapphire substrates. The influence of critical growth parameters on the growth of multilayer MoS₂ is systematically explored, such as the evaporation temperature of MoO₃ and the flow rate of O₂. Flexible field-effect transistor (FET) devices fabricated from bilayer/trilayer MoS₂ show substantial improvements in mobility compared with flexible FETs based on monolayer films.