## 3 Results and Discussion
In this phase, bond lengths and angles are distributed randomly, as evidenced by the broad full width at half maximum (FWHM) of approximately 170 cm\({}^{-1}\). After A2 annealing, however, the Si-C peak of the SiC films grown at 700 \({}^{\circ}\)C is best fit using a combination of Lorentzian and Gaussian functions, indicating approximately 50% crystallinity (Figure 3(Aii)). In contrast, the line shape for the AD sample grown at 800 \({}^{\circ}\)C is well described by a Lorentzian function with a FWHM of approximately 80 cm\({}^{-1}\)  
Figure 2: Surface morphology and substrate dependency of a-SiC films with different thicknesses: (**A**) SEM images and corresponding 2D AFM scans of films below 100 nm on Si (100), Si (111), and SiO\({}_{2}\) substrates ((**i**)–(**iii**)), and films above 200 nm on Si (111) **(iv**). AFM scans highlight substrate-independent morphology variations. (**B**) **(i**) RMS roughness values for a-SiC films deposited on different substrates (Si (100), Si (111), SiO\({}_{2}\)) vary between ~5–8 Å, indicating minimal impact of substrate choice and thickness on the film quality. Transformation of a- to c-SiC after A3 annealing slightly increases the roughness to ~15 Å. All films were deposited at temperatures of 650 \({}^{\circ}\)C and 700 \({}^{\circ}\)C. (**ii**) Optical image of the sample deposited at 650 \({}^{\circ}\)C showing uniformity of the thickness of the film. indicating a higher degree of medium-range order consistent with the onset of crystallinity (Figure 3(Aiv)) [40,41]. In the spectral range of 2000-2300 cm\({}^{-1}\), a low-intensity absorption peak centered around 2080 cm\({}^{-1}\) was detected in the 650 \({}^{\circ}\)C and 700 \({}^{\circ}\)C-deposited sample (Figure 3(Bi)). This is attributed to Si-H or Si-H\({}_{2}\) stretching modes [38,42]. The intensity of this hydrogen-related peak decreased monotonically with increasing T\({}_{\rm D}\), becoming negligible at 800 \({}^{\circ}\)C. Furthermore, in situ post-deposition A2 annealing effectively removed residual hydrogen. FTIR also confirmed the absence of C-H\({}_{\rm n}\) absorption in the 2800-3100 cm\({}^{-1}\) region for all samples within our investigated conditions (Figure 3(Bii)) [38,42]. Furthermore, hydrogen desorption upon in situ annealing leads to film densification and a corresponding reduction in thickness, as determined by SE and cross-sectional SEM analysis (Figure S1B). For example, the 650 \({}^{\circ}\)C-grown films showed a \(\sim\)22% thickness reduction following A3 annealing. To complement the FTIR findings, XPS depth profiling was conducted to assess the chemical environment of Si 2p, C 1s, and O 1s states. Binding energy shifts due to charging were corrected using the Ar 2p doublet reference peaks at \(\sim\)242 eV and \(\sim\)244 eV. For the AD film deposited at 800 \({}^{\circ}\)C, the Si:C atomic ratio was 50:50 with an experimental uncertainty of \(\sim\)1% (Figure 3C). A decrease of \(\pm\)1% in carbon content, approaching the XPS detection limit, was observed with decreasing T\({}_{\rm D}\) from 800 \({}^{\circ}\)C to 650 \({}^{\circ}\)C.  
Figure 3: FTIR compositional analysis of the films deposited at different temperatures. (**A**) Normalized absorption spectra of the Si––C stretching mode for (**i**) as-deposited and (**ii**) A3-annealed SiC samples grown at 650 \({}^{\circ}\)C and 800 \({}^{\circ}\)C, highlighting spectral shifts and intensity variations. Deconvolution of the Si–C absorption band for (**iii**) A2 annealed 700 \({}^{\circ}\)C sample applying Lorentz-Gaussian fit indicates the presence of both amorphous and crystalline phases, and (**iv**) A3 annealed sample using Lorentz fit indicates the cubic crystalline phase. (**B**) Quantitative presence of (**i**) Si–H (2000–2300 cm\({}^{-1}\)) and (**ii**) C-H bonds (2800–3100 cm\({}^{-1}\)) in A1- and A2-annealed SiC thin films. (**C**) XPS atomic concentrations for C1s and Si2p in as-deposited SiC films grown at 650 \({}^{\circ}\)C and 800 \({}^{\circ}\)C, showing stoichiometry.