Substrate-induced strain and charge doping in CVD-grown monolayer MoS2

Abstract

Due to its electronic-grade quality and potential for scalability, two-dimensional (2D) MoS2 synthesized by chemical vapor deposition (CVD) has been widely explored for electronic/optoelectronic applications. As 2D MoS2 can be considered a 100% surface, its unique intrinsic properties are inevitably altered by the substrate upon which it is grown. However, systematic studies of substrate-layer interactions in CVD-grown MoS2 are lacking. In this study, we have analyzed built-in strain and charge doping using Raman and photoluminescence spectroscopy in 2D MoS2 grown by CVD on four unique substrates: SiO2/Si, sapphire, Muscovite mica, and hexagonal boron nitride. We observed decreasing strain and charge doping in grown MoS2 as the substrates become less rough and more chemically inert. The possible origin of strain was investigated through atomic force microscopy roughness measurements of the as-grown layer and substrate. Our results provide direction for device optimization through careful selection of the growth substrate and pave the way for further investigations to unravel the complex nature of the 2D monolayer-substrate interface.