Influence of Epitaxial Graphene Substrate Morphology on the Orientation of CVD-Grown MoS2 Monolayers

Abstract

In this work, we analyze the growth of monolayer MoS₂ islands on two different epitaxial graphene substrates: graphene on off-axis SiC and graphene on on-axis SiC. The aim is to understand the effect of substrate steps and surface lattice directions on the growth of MoS₂ islands, determining their orientation with respect to the epitaxial graphene lattice and the SiC surface morphology. We combine statistical analysis of the preferred orientation of MoS₂ islands with atomic resolution imaging through STM and conductive AFM to determine the precise lattice orientation of MoS₂ relative to the substrate. Our study reveals that MoS₂ islands tend to align with the epitaxial graphene lattice on both substrates and that the uniform step-terrace structure of off-axis substrates reduces the number of mirror-twin domains. These results demonstrate that substrate morphology plays a crucial role in directing the evolution of monolayer MoS₂, marking an important step toward wafer-scale growth of single-crystal transition metal dichalcogenides on epitaxial graphene for 2D electronics applications.