Characterizing Strain in Graphene on Cu(100) Substrate with Raman Spectroscopy

Chemical vapor deposition (CVD) grown graphene offers superior carrier mobility and minimal defects compared to mechanically transferred graphene onto Si/SiO2 substrates. Yet the performance of CVD-derived graphene films can vary across an array of wrinkles, folds, and transfer-related contaminations. Raman spectroscopy is a highly useful non-contact and non-destructive means of characterizing graphene owing to the nature of its band structure which provides strong and unique features stemming from physical effects such as resonant processes and strong electron-phonon coupling. Here, we present a detailed Raman analysis of uniquely grown defect-free graphene on Cu(100) substrate via low-pressure CVD. We observe the blue-shift and narrowing lineshapes of the 2D and G bands, as well as their intensity ratio indicating the graphene monolayer. Furthermore, a compressive strain and significant coupling of the graphene to the Cu substrate are observed with multiple laser excitations. Additionally, Raman is also used to monitor copper oxide at defect sites. We perform a combined electro-optical measurements in aqueous solutions to estimate the electrical material properties of graphene on Cu(100). The outcomes of this study will be used to establish quantitative Raman-based metrics on strain-doping for documentary standards on Gr/Cu compared to epitaxial Gr and other large-scale growth methods.