A new decoupling strategy for strain and doping in wrinkled CVD graphene with total effective strain evaluation

The determination of strain levels in chemical vapor deposition (CVD) graphene is essential to maximize its electronic and optoelectronic applications. The combination of Raman shift effects with doping effects creates difficulties when attempting to precisely extract accurate deformation-related measurements. This research decouples strain from doping using Kelvin Probe Force Microscopy (KPFM), Raman spectroscopy, and high-resolution strain mapping. The research methodology allows precise mechanical strain measurement by properly distinguishing Raman shift effects from doping to enhance strain detection precision. Surface potential difference measured by KPFM enables determination of doping concentration values. Calibration factors applied to G-band and 2D-band Raman shifts enable the removal of doping effects so actual mechanical strain values become accessible. The Raman-derived in-plane strain measurement ranges from −0.34 % to −0.53 % for the G-band and −0.35 % to −0.67 % for the 2D-band. Substrate-induced distortions and wrinkle-induced out-of-plane deformations create compressive residual strain which is confirmed through curvature analysis and AFM topography measurements. The analysis from polarized Raman spectroscopy demonstrates that strain components for tension and compression follow the orientations of the wrinkles and deformations in the material. This advanced strain-doping decoupling method creates an exact measurement method to determine true graphene strain which may help accelerate use of strained graphene in electronic and optoelectronic devices and flexible systems as well as sensors.