Quantitative Analysis of Hydrogenated DLC Films by Visible Raman Spectroscopy

TL;DR

This study investigates how visible Raman spectroscopy can reliably predict key properties of hydrogenated diamond-like carbon films, correlating spectral features with parameters like hydrogen content, hardness, and optical gap.

Contribution

It demonstrates the effectiveness of visible Raman spectroscopy in estimating multiple properties of DLC films and discusses discrepancies with other measurement techniques.

Findings

Raman spectra correlate with hydrogen content and sp$^3$ content.

Visible Raman spectroscopy can predict hardness and optical gap.

Discrepancies between Raman and other techniques are analyzed.

Abstract

The correlations between properties of hydrogenated diamond like carbon films and their Raman spectra have been investigated. The films are prepared by plasma deposition technique, keeping different hydrogen to methane ratio during the growth process. The hydrogen concentration, sp$^3$ content, hardness and optical Tauc gap of the materials have been estimated from a detail analysis of their Raman spectra. We have also measured the same parameters of the films by using other commonly used techniques, like sp$^3$ content in films by x-ray photoelectron spectroscopy, their Tauc gap by ellipsometric measurements and hardness by micro-hardness testing. The reasons for the mismatch between the characteristics of the films, as obtained by Raman measurements and by the above mentioned techniques, have been discussed. We emphasize on the importance of the visible Raman spectroscopy in reliably predicting the above key properties of DLC films.