Surface analysis of carbon allotropes

Abstract

The spectroscopy of carbon is very important in surface analysis of solids, because its content indicates the grade of surface contamination. Adventitious carbon from air ambient is practically present on any solid material and the C 1s photoelectron spectrum is often used as a reference for the scale calibration of binding energy. Moreover, during the last two decades, new 2D carbon materials have been developed and intensively investigated: graphene, fullerenes, nanotubes and nanowalls, quantum dots, etc. Also, the growing applications of amorphous carbon (a-C), e.g. diamond-like carbon (DLC), carbon quantum dots (CQDs), etc., require the characterization of these materials.
This short overview is dedicated to the analysis of new carbon-based materials by widely used surface-sensitive techniques: X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The combination of XPS and AES techniques permits one to investigate the electron hybridization in carbon materials, i.e. to determine the ratio of sp2/sp3 configurations, which defines their main mechanical, electrical and optical properties. In addition, it was demonstrated that the same experimental approach could be successfully used for the investigation of bulk composite materials containing 2D carbon, e.g. graphene or nanotubes.