Raman spectra evaluation of the carbon layers with Voigt profile

Purpose: Recent use of Raman spectroscopy as the valuable tool for investigations of the content and state of different material samples is rapidly growing especially in the area of the DLC (Diamond-Like Carbon) layers investigation. Not only qualitative analysis but also quantitative is in the scope of this method which in turn demands use of precise mathematical tools for describing spectrograms. Design/methodology/approach: So-called Voigt profile establish basis for the relatively most precise shape-functions used for describing spectrogram shape. Voigt profile is the convolution of the very well known distribution functions: Gaussian distribution and Cauchy distribution (Lorentz distribution). Gaussian distribution is traditionally recognized as a tool for modeling multi-causal phenomena due to the Central Limit Theorem results. Cauchy distribution is recognized as modeling influence of the Fabry-Pérot interferometer (etalon) used for detection of the Raman spectrum. Findings: We present successful decomposition of the Raman spectra into elements: base function, peaks’ determination and etalon influence on spectral peaks’ shapes. Thorough numerical simulation of the Fabry-Pérot interferometer has been performed and identification of its accuracy parameter has been done when matching Voigt profile based function to the experimental data. Research limitations/implications: Good computational tools for generation of the Voigt profile, being not an analytical function itself and good understanding of mutual relationships between the Voigt profile and the Fabry-Pérot interferometer is of main interest for not only practical but also precise use this tool for quantitative analysis of Raman spectra. Practical implications: The main goal of our work has been the thorough preparation for future works with spectrum deconvolution allowing better resolution in determining Raman spectrum components. Originality/value: So far no proper attention has been paid to precise, quantitative analysis of the Raman spectra of the DLC layers.