## 3 Results and Discussion  
Synoptically, FTIR spectroscopy shows that SiC thin films deposited at T\({}_{\rm D}\)\(\leq\) 750 \({}^{\circ}\)C exhibit a strong peak at -760 cm\({}^{-1}\), shifting to \(\sim\)780 cm\({}^{-1}\) after A3 annealing--indicating Si-C bonding (Figure 1B). A3 annealing effectively transforms amorphous a-SiC into polycrystalline 3C-SiC, as confirmed by FTIR and high-resolution scanning transmission electron microscopy (HRSTEM) studies (Figure S1A). Additionally, XPS results agree well with the FTIR data across all samples. The Si 2p binding energy (\(\sim\)100.3 eV) matched with that of 3C- and 4H-SiC reference samples, confirming that the chemical bonding in the synthesized SiC thin films is Si-C (Figure 1C). The absence of peaks near \(\sim\)98.5 eV and \(\sim\)103 eV--corresponding to Si-Si and Si-O bonds, respectively--rules out the presence of silicon nanodomains or oxidation in the films [6, 37]. The highly controlled growth rate yields exceptionally smooth surfaces, exhibiting a root-mean-square (RMS) roughness of \(\sim\)5 A for samples deposited at \(T_{\rm D}\)\(\leq\) 700 \({}^{\circ}\)C, as measured by AFM (Figure 1D). However, increased surface roughness (\(\sim\)15 A RMS) was observed in the A3-annealed samples compared to their as-deposited (AD) counterparts and for the 800 \({}^{\circ}\)C--grown thin films (Figure 1D,E). Figure 1: Chemical vapor deposition (CVD) system and characterization of film growth, composition, and morphology. **(A)** (**i**) Schematic of the custom hot-wall quartz tube CVD and annealing system. **(ii)** SiC film growth rate as a function of deposition temperature under process-specific pressures (0.2 T, 0.4 T, and 1.5 T). **(iii)** Thermal annealing transforms amorphous SiC (a-SiC) deposited at 650 \({}^{\circ}\)C (green) into cubic crystalline SiC (3C-SiC). **(B)** Evolution of the Si–C stretching mode FTIR peak from the AD to A3 annealing, reflecting changes in crystallinity and peak position. **(C)** XPS spectra of the Si 2p peak for the deposited SiC film (black) compared to reference spectra (3C-SiC (red dashed), Si (green dashed), and SiO\({}_{2}\) (purple dotted)) showing a binding energy near \(\sim\)100.3 eV that matches the 3C-SiC reference and confirms Si–C bonding. **(D)** SEM and AFM images of **(i)** AD and **(ii)** A3 annealed SiC films deposited at 650 \({}^{\circ}\)C, and **(E)** corresponding SEM and AFM analysis for **(i)** AD and **(ii)** A3 annealed films deposited at 800 \({}^{\circ}\)C.  
Additionally, we have used the same deposition parameters to grow films of various thicknesses on different substrates, including Si (111) and SiO\({}_{2}\)-on-Si (650 \({}^{\circ}\)C \(\leq T_{\rm D}\leq\) 700 \({}^{\circ}\)C). As shown in Figure 2A and summarized in Figure 2B, film uniformity and surface roughness remained consistent (5-8 A) across Si (100), Si (111), and SiO\({}_{2}\) substrates for similarly thick films, indicating no observable substrate dependence in surface roughness or morphology under the investigated processing conditions. FTIR studies revealed a prominent absorption peak at ~760 cm\({}^{-1}\) for SiC films deposited at T\({}_{\rm D}\leq\) 750 \({}^{\circ}\)C, and a shift to ~785 cm\({}^{-1}\) for samples deposited at 800 \({}^{\circ}\)C, corresponding to Si-C stretching mode (Figure 3(Ai,Aii)) [6; 38]. To quantify the relative contributions of amorphous and crystalline phases, we deconvoluted the FTIR spectra of the AD and annealed films using Gaussian (G) and/or Lorentzian (L) components, corresponding to amorphous and crystalline phases, respectively, and the degree of crystallinity was then estimated using the ratio L/(L + G) [6; 38]. For example, the line shape of the Si-C stretching mode in the AD SiC thin films (T\({}_{\rm D}\leq\) 750 \({}^{\circ}\)C) was best fit with a Gaussian function characteristic of an amorphous phase with short-range structural order [6; 38; 39].