Interference effect on Raman spectrum of graphene on SiO_2/Si

TL;DR

This study demonstrates that interference effects significantly influence the Raman intensity ratio of graphene on SiO_2/Si, affecting the interpretation of intrinsic properties from Raman spectra.

Contribution

It provides a detailed analysis of how dielectric layer thickness impacts Raman intensity ratios through interference effects, highlighting the need to consider these effects in graphene characterization.

Findings

Raman intensity ratio varies by 370% with dielectric thickness changes

Interference effects explain the large variation in Raman ratios

Accounting for interference is essential for accurate graphene property analysis

Abstract

The intensity ratio between two major Raman bands in graphene is one of the most important information for physics of graphene and has been believed to represent various intrinsic properties of graphene without critical assessment of extrinsic effects. We report a micro Raman spectroscopy study on the Raman intensity ratio of the 2D band to the G Raman band of graphene varying the thickness of dielectric layers (SiO_2) underneath it. The ratio is shown to change by almost 370% when the thickness is varied by 60%. The large variation in the ratio is well explained by theoretical calculations considering multiple Raman scattering events at the interfaces. Our analysis shows that the interference effect is critical in extracting the intrinsic 2D to G intensity ratio and therefore must be taken into account in extracting various physical properties of graphene from Raman measurements.