Determination of the Number of Graphene Layers: Discrete Distribution of the Secondary Electron Intensity Derived from Individual Graphene Layers

TL;DR

This paper presents a novel SEM-based method to accurately determine the number of graphene layers by analyzing the discrete secondary electron intensity distribution, outperforming optical techniques especially for small-area samples.

Contribution

The study introduces a practical SEM approach that correlates secondary electron intensity with graphene layer count, enabling precise characterization of graphene on insulating substrates.

Findings

Discrete secondary electron intensity distribution correlates with graphene layers.

Linear relationship between electron intensity and layer number at low voltages.

Method outperforms optical techniques for small-area graphene samples.

Abstract

Using a scanning electron microscope, we observed a reproducible, discrete distribution of secondary electron intensity stemming from an atomically thick graphene film on a thick insulating substrate. The discrete distribution made it possible to uniquely relate the secondary electron intensity to the number of graphene layers. Furthermore, we found a distinct linear relationship between the relative secondary electron intensity from graphene and the number of layers, provided a low primary electron acceleration voltage was used. Based on these observations, we propose a practical method to determine the number of graphene layers in a sample. This method is superior to the conventional optical method in its capability to characterize graphene samples with sub-micrometer squares in area on various insulating substrates.