Graphene layer number characterization using scanning kelvin probe force microscopy

Abstract

As the importance of material surfaces and interfaces for industrial applications is ever increasing, a need for accuratemeasurement of their properties and functionalities with traceability and reproducibility through unbroken chain ofmeasurements and their reference materials for proficiency testing has become very important. Carbon and its allotropeshave several industrial applications and recently graphene which is a two dimensional layered material of carbon has provento have great potential, and its characterization for layer number has become very important. A need for quantitativemeasurement apart from existing qualitative techniques is very much required for accurate determination of layer number.Under the aegis of Versailles Project on Advanced Materials and Standards (VAMAS), technical working area (TWA-2) aninternational round robin test is conducted among 13 laboratories for establishing a protocol for accurate measurement ofgraphene layer number and generating reference material. CSIR-NPL being NMI of India participated and contributed to theproject which got recognition from VAMAS for its participation. Scanning Kelvin Probe Force Microscopy (SKPFM) ofgraphene layers on Au/SiO2/Si and SiO2/Si substrates is performed and their CPD data is compared. Graphene onAu/SiO2/Si has shown consistent CPD data for different modulation voltages with least uncertainty. From the comparativeanalysis it is found that SKPFM has potential to be an international standard technique to determine graphene layer numberand can generate certified reference material.