High contrast imaging and thickness determination of graphene with in-column secondary electron microscopy

TL;DR

This paper introduces a high contrast imaging method using in-column secondary electron microscopy for precise, quantitative measurement of graphene layer thicknesses and structural features on insulating substrates.

Contribution

A novel quantitative imaging technique using secondary electron attenuation for accurate graphene thickness estimation and structural analysis.

Findings

Achieved high contrast for thickness estimation up to several layers.

Enabled structural characterization of graphene, identifying faults and multilayer patches.

Analyzed factors affecting image contrast such as surface charging and electron beam effects.

Abstract

We report a new method for quantitative estimation of graphene layer thicknesses using high contrast imaging of graphene films on insulating substrates with a scanning electron microscope. By detecting the attenuation of secondary electrons emitted from the substrate with an in-column low-energy electron detector, we have achieved very high thickness-dependent contrast that allows quantitative estimation of thickness up to several graphene layers. The nanometer scale spatial resolution of the electron micrographs also allows a simple structural characterization scheme for graphene, which has been applied to identify faults, wrinkles, voids, and patches of multilayer growth in large-area chemical vapor deposited graphene. We have discussed the factors, such as differential surface charging and electron beam induced current, that affect the contrast of graphene images in detail.