Detailed study on MOCVD of wafer-scale MoS2 monolayers: From nucleation to coalescence

Abstract

Metal–organic chemical vapour deposition (MOCVD) has become one of the most promising techniques for the large-scale fabrication of 2D transition metal dichalcogenide (TMDC) materials. Despite efforts devoted to the development of MOCVD for TMDC monolayers, the whole picture of the growth process has not been fully unveiled yet. In this work, we employ a commercial AIXTRON CCS MOCVD tool for the deposition of MoS2 on sapphire using standard precursors and H2 as carrier gas. Adsorption and diffusion of Mo adatoms on the substrate are found to be decisive for nucleation. By lowering temperature from 650 to 450 °C, a uniform distribution of nuclei on sapphire terraces is achieved. Full coalescence of MoS2 monolayers with limited bilayer formation (~ 15%) is then realized at 700 °C. This study highlights the importance of understanding the details of film formation mechanisms and developing multi-stage MOCVD processes for 2D TMDC films.Graphical abstract