Non-destructive and Rapid Evaluation of CVD Graphene by Dark Field Optical Microscopy

TL;DR

This paper demonstrates a fast, non-destructive method using dark field optical microscopy to evaluate CVD graphene directly on copper substrates, providing contrast comparable to electron microscopy without additional treatments.

Contribution

The study introduces dark field optical microscopy as a rapid, non-destructive technique for assessing graphene coverage and thickness on copper substrates immediately after growth.

Findings

Dark field microscopy provides high-contrast imaging of graphene on Cu.

Graphene adlayers can be distinguished by copper step height differences.

DF imaging contrast surpasses bright field optical microscopy.

Abstract

Non-destructive and rapid evaluation of graphene directly on the growth substrate (Cu foils) by dark field (DF) optical microscopy is demonstrated. Without any additional treatment, graphene on Cu foils with various coverages can be quickly identified by DF imaging immediately after chemical vapor deposition growth with contrast comparable to scanning electron microscopy. The improved contrast of DF imaging compared to bright field optical imaging was found to be due to Rayleigh scattering of light by the copper steps beneath graphene. Indeed, graphene adlayers are readily distinguished, due to the different height of copper steps beneath graphene regions of different thickness.