Layer-resolved Raman imaging and analysis of parasitic ad-layers in transferred graphene.

In this report, we demonstrate an applied protocol for layer-resolved Raman imaging and analysis of undesirable ad-layers found in Chemical Vapor Deposition graphene grown on copper foil and transferred onto an oxidized silicon substrate. The method assumes that the intensity of the silicon-related Raman-active mode at 520 cm-1 is attenuated by 2.3 % each time the light passes through a single graphene layer. Upon normalization with respect to a reference graphene-free area, the 520 cm-1 mode relative intensity r-I Si measured in a back-scatter mode follows a univalent function of the number of the graphene layers N. Since N is treated as a continuous argument, it can be ascribed a fractional value and considered statistically. Importantly, the r-I Si offers higher layer differentiation capability and unambiguity than non-functional indicators, including the 2D band width or the 2D-to-G band intensity ratio, thus providing unequivocal evaluation. [Display omitted] • Method for high-resolution Raman imaging of CVD graphene. • Truly functional and univalent protocol for layer-resolved analysis. • Applicable to multilayer graphene. • Useful extension for the Graphene Flagship technical standard. [ABSTRACT FROM AUTHOR]