Enhancement of graphene-related and substrate-related Raman modes through dielectric layer deposition

In this report, we demonstrate a method for the enhancement of Raman active modes of hydrogen-intercalated quasi-free-standing epitaxial chemical vapor deposition graphene and the underlying semi-insulating 6H-SiC(0001) substrate through constructive signal interference within atomic-layer-deposited amorphous Al2O3 passivation. We find that an optimum Al2O3 thickness of 85 nm for the graphene 2D mode and one of 82 nm for the SiC longitudinal optical A1 mode at 964 cm-1 enable a 60% increase in their spectra intensities. We demonstrate the method's efficiency in Raman-based determination of the dielectric thickness and high-resolution topographic imaging of a graphene surface.