*3.2. Structural Analysis*

Figures 2–4 show the patterns of grazing incidence angles of 1.0◦, 1.5◦, and 2.0◦, respectively. The Bragg reflections sugges<sup>t</sup> the existence of α and β SiC nanocrystalline structures. Although the patterns exhibit the SiC phase, it is not possible to determine which of the SiC phases are present because some diffraction peaks of α and β SiC might overlap [45]. The carbon phase at ~25◦ was also visible and confirmed the RBS results indicating an excess of C (Table 1). Lastly, two broad peaks at ~47◦ and 55◦ were assigned as unidentified. While some studies have attributed these peaks to the SiC polymorph phase [46,47], others often define them as being C or Si phases [48–50]. When comparing the results from the GIXRD with an incidence angle of 2◦ (Figure 4) with the smaller angle results, the variation of the crystalline phases with the depth of the film was clearly noted.

**Figure 2.** Grazing incidence X-ray diffraction (GIXRD) patterns of the SiC thin films at a grazing angle of 1.0◦.

In addition, Figure 2 suggests the existence of SiC nanocrystalline structures achieved without substrate heating. By varying the GIXRD incidence angle, the resulting film could be analyzed in depth. A comparison of the patterns between SiC/Si and SiC/AlN/Si for both angles of incidence (1◦ and 1.5◦), revealed that the phase observed at approximately 36◦, using the 1.5◦ GIXRD as the incidence angle, no longer existed in the pattern obtained with the smallest angle (1.0◦). This result pointed to the existence of phase and crystallinity variations with depth.

The film deposited on the AlN layer showed dislocation of the SiC peak between 35 and 36◦ in the GIXRD patterns. This dislocation may be attributed to the following reasons: (i) film stress; (ii) interference of the substrate (SiC/Si and SiC/AlN interface); or (iii) residual stress. More studies are necessary to better understand this observation.

**Figure 3.** GIXRD patterns of the SiC thin films at a grazing angle of 1.5◦.

**Figure 4.** GIXRD patterns of the SiC thin films at a grazing angle of 2◦.
