Depth-resolved study of hydrogen-free amorphous carbon films on stainless steel

Abstract

A method to obtain depth-resolved structural information from hydrogen-free amorphous carbon films of high roughness, high thickness and grown on unpolished substrates was developed. The characterization was based on combining secondary ion mass spectrometry (SIMS) sputtering for craters at defined depth with X-ray photoelectron spectroscopy (XPS) and visible Raman spectroscopy analysis. After determination of the etching rate for the carbon film, areas with a defined end position corresponding to different known depths of the films were obtained. The SIMS etching process used did not significantly affect the structure of the amorphous carbon layer. XPS measurements of the crater bottoms provided information about the composition of the films. Visible Raman spectroscopy measurements inside of the craters were correlated with the XPS results taking into account the penetration depths of both techniques, and models aimed at predicting the sp2/sp3 ratio from Raman measurements were evaluated.