Deconvolution process approach in Raman spectra of DLC coating to determine the sp3 hybridization content using the ID/IG ratio in relation to the quantification determined by X-ray photoelectron spectroscopy

Abstract

Raman spectroscopy has contributed to many fields of materials science, for example, in studies addressing Diamond-Like Carbon coatings. In the literature, discussions have arisen due to the various interpretations of Raman spectra and some studies have not recommended using it to measure sp2 and sp3 hybridization contents. This article addresses the deconvolution process in Raman spectra, manipulating the Raman shift interval, the presence of Savitzky-Golay smoothing and the appearance of additional bands. X-ray photoelectron spectroscopy was used to quantify the sp2 and sp3 contents, which are discussed below in relation to the ID/IG ratio and the prediction of the amorphization trajectory of graphite. In an attempt to find a relationship between these characterization techniques, a polynomial equation was developed from thirty-three experimental results researched in the literature. The results indicated a coating belonging to the a-C:H class containing 18% of sp3. The relationship between the spectroscopies was complementary and the graphite amorphization trajectory was assertive. The coefficient of determination and the standard deviation proved to be useful parameters for selecting the representative spectrum of the coating. Neglecting or not the appearance of an additional band can provide modifications to the ID/IG ratio at the level of 52%. Representative results of the ID/IG ratio indicated the hypothesis of considering the intensity of the bands only as a function of height. The sp3 content predicted by the equation was maximized to any selected ID/IG value when the G Band was centered at approximately 1559 cm−1. It was observed that the equation can be used qualitatively with less errors in conditions where the deconvolutions present parameters similar to the experimental results whose sp3 content is between 20% and 39.9%.