The effect of low temperature thermal treatment on structural and chemical composition of a-C film with nc-G admixture studied by Raman spectroscopy

Abstract Extensive Raman spectroscopy studies combined with scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were applied to investigate structural changes in amorphous carbon film upon its annealing to 300 °C and cooling. The results show the variation in the carbon structure within the sample and the presence of nanocrystalline graphite features, as well as minor inclusion of sp 1 linear chains. The studies on the behaviour of characteristic D and G bands upon annealing to 300 °C and cooling reveal structural changes in amorphous carbon (a-C) as well as nanocrystalline graphite (nc-G). The intensity ratio I D /I G , FWHM and position of the G band indicates irreversible structural ordering of a-C annealed to 300 °C, which is also confirmed by XPS measurements. Additionally, Raman spectrum of nc-G is decomposed into 4 bands D 1 , D 2 , G 1 , G 2 and similar behaviour of G 2 band's parameters is observed. SEM measurements reveal a-C aggregates of spherical structures, however before annealing the smallest counterparts of these structures resemble chains, which is also supported by the presence of sp 1 features in the Raman and XPS spectra.