Confocal laser scanning microscopy for rapid optical characterization of graphene

Vishal Panchal,Albert F Rigosi,Jiuning Hu,Olga Kazakova,Christos Melios,Angela R Hight Walker,Mattias Kruskopf,David B Newell,Randolph E Elmquist,Chieh-I Liu,Guangjun Cheng,Yanfei Yang

doi:10.1038/s42005-018-0084-6

Abstract

Two-dimensional (2D) materials such as graphene have become the focus of extensive research efforts in condensed matter physics. They provide opportunities for both fundamental research and applications across a wide range of industries. Ideally, characterization of graphene requires non-invasive techniques with single-atomic-layer thickness resolution and nanometer lateral resolution. Moreover, commercial application of graphene requires fast and large-area scanning capability. We demonstrate the optimized balance of image resolution and acquisition time of non-invasive confocal laser scanning microscopy (CLSM), rendering it an indispensable tool for rapid analysis of mass-produced graphene. It is powerful for analysis of 1–5 layers of exfoliated graphene on Si/SiO2, and allows us to distinguish the interfacial layer and 1–3 layers of epitaxial graphene on SiC substrates. Furthermore, CLSM shows excellent correlation with conventional optical microscopy, atomic force microscopy, Kelvin probe force microscopy, conductive atomic force microscopy, scanning electron microscopy and Raman mapping.

Highlights

Two-dimensional (2D) materials such as graphene have become the focus of extensive research efforts in condensed matter physics
We believe that confocal laser scanning microscopy (CLSM) is the tool that meets all of the aforementioned requirements with applications in real-time observation of graphene growth[34] and nanomaterials in biological systems[35,36]
We demonstrate that reflection mode CLSM is a superior tool for rapid characterization of large-area graphene and graphene nanostructures on Si/SiO2 and SiC, compared to conventional optical microscopy (OM), Raman spectroscopy, atomic force microscopy (AFM), conductive AFM (C-AFM), Kelvin probe force microscopy (KPFM), and scanning electron microscope (SEM) methods

Summary

Introduction

Two-dimensional (2D) materials such as graphene have become the focus of extensive research efforts in condensed matter physics. We demonstrate the optimized balance of image resolution and acquisition time of non-invasive confocal laser scanning microscopy (CLSM), rendering it an indispensable tool for rapid analysis of mass-produced graphene. It is powerful for analysis of 1–5 layers of exfoliated graphene on Si/SiO2, and allows us to distinguish the interfacial layer and 1–3 layers of epitaxial graphene on SiC substrates. We demonstrate that reflection mode CLSM is a superior tool for rapid characterization of large-area graphene and graphene nanostructures on Si/SiO2 and SiC, compared to conventional optical microscopy (OM), Raman spectroscopy, AFM, conductive AFM (C-AFM), KPFM, and scanning electron microscope (SEM) methods. We apply CLSM to EG on SiC demonstrating the speed, accuracy, and versatility of CLSM compared to OM, SEM, AFM, KPFM, C-AFM, and Raman microscopy

Methods

Results

Conclusion