*3.3. Raman Spectroscopy*

Figure 5 shows the results of Raman spectroscopy used to identify the bonds present in the films. The Raman spectra for the SiC films deposited at 200 W in both substrates (with and without the AlN layer) are presented in Figure 5a, showing a very visible and well-defined Si peak at 519.41 cm<sup>−</sup>1. Since the difference in thickness between both films was small, the substrate had an accentuated influence. In addition to Si, the SiC film deposited on the AlN layer showed (i) a peak relative to AlN at ~652.20 cm<sup>−</sup>1; (ii) peaks for SiC and Si in the regions between 741–894 cm<sup>−</sup><sup>1</sup> and 906–1109 cm<sup>−</sup>1, respectively; (iii) and a broad carbon band at 1370–1625 cm<sup>−</sup>1. Except for the AlN peak, the SiC/Si spectrum exhibited signals at similar regions to that of the SiC/AlN/Si spectrum. However, the regions relative to SiC and Si were more visible, and the C band region had a more explicit separation in two peaks (D and G bands), but with a low definition of the disorder band. The D band was attributed to the disorder or polycrystalline carbon and the G band to the graphite-like carbon [19,50].

**Figure 5.** Raman spectra of SiC thin films on both substrates: (**a**) as-deposited at 200 W and (**b**) as-deposited at 400 W.

For 400 W (Figure 5b), both substrates exhibited similar behavior following the deposition of SiC films. In these spectra, the substrate signal was not detected and only peaks corresponding to carbon at 1457 and 1462 cm<sup>−</sup><sup>1</sup> were evident. With the exception of the spectrum of the SiC film at 200 W of SiC/Si, where the peak of the C band was not overlapped, all spectra of the "as-deposited" SiC film showed

overlapping C, D, and G bands between ~1457 and 1462 cm<sup>−</sup>1. Ferrari and Robertson [51] reported that for C–C bands, the Raman spectrum was influenced by factors such as disorder, clustering of the sp<sup>2</sup> phase, the presence of sp<sup>2</sup> C-rings or C-chains, and the ratio of sp<sup>2</sup> to sp<sup>3</sup> (I(D)/I(G)). Thus, with an increasing disorder of the C phase, the G peak position can be moved, and the D and G peaks will therefore overlap [19,50,51].
