## 3 Results and Discussion
Significantly, the 700 \({}^{\circ}\)C sample consistently exhibits lower absorption coefficient values than the 650 \({}^{\circ}\)C sample across both models. In fact, the CL model yields near-zero \(\alpha\) values (\(\leq\)1 cm\({}^{-1}\)) for the 700 \({}^{\circ}\)C sample, comparable to those of the measured SiO\({}_{2}\) reference. Tauc's optical bandgap (\(E_{g,Tauc}\)) is determined from the absorption data using a linear fit in Tauc's relation \(\left(\alpha E\right)^{1/2}=B\left(E-E_{g,Tauc}\right)\), where \(E\) is the photon energy, \(B\) is the slope, and \(\alpha\) is the absorption coefficient [57; 58]. Figure 4E shows these plots for the 650 \({}^{\circ}\)C and 700 \({}^{\circ}\)C AD films based on the absorption data from both the CL and TL models. Each fit yielded consistent \(E_{g,Tauc}\) values of \(\sim\)2.1 eV, which lie within the expected range for amorphous SiC 1.6-2 eV [59] and are slightly higher than the \(E_{g}\) values obtained directly from the SE models (1.8-2.0 eV, see Tables S1 and S2). Figure 5A presents these \(E_{g}+E_{t}\) and \(E_{04}\) values from both TL and CL models for the 650 \({}^{\circ}\)C and 700 \({}^{\circ}\)C AD thin films before and after the sequential annealing to A3. Also shown are the \(E_{g}+E_{t}\) values obtained from the CL fits for both samples, which align closely with the corresponding \(E_{04}\) values. \(E_{g}+E_{t}\) in the CL model is associated with the transition into the band-to-band absorption region, and thus, related to \(E_{04}\) as the onset of strong absorption. In this context, \(E_{g}+E_{t}\) may approximate the energy near the mobility edge (Figure 4A). \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Deposition** & **NameName** & **Model** & **Tauc’s Optical** & **\(E_{04}\)(eV)** & **\(n\) @ 1550 nm** & **\(k\) @ 1550 nm** & **Abs. Coeff.@** \\  & & & **Cap (eV)** & & & & **1550 nm (cm\({}^{-1}\))** \\ \hline \multirow{4}{*}{650} & \multirow{4}{*}{AD} & TL & 2.0 & 2.3 & 2.57 & 0 & 0 \\  & & CL & 2.1 & 2.3 & 2.56 & \(1.5\times 10^{-3}\) & 121 \\  & & Cauchy & NA & NA & 2.56 & \(11.8\times 10^{-3}\) & 957 \\  & & TL & 2.1 & 2.4 & 2.66 & 0 & 0 \\  & & CL & 2.1 & 2.4 & 2.67 & \(4.0\times 10^{-6}\) & 0 \\  & & Cauchy & NA & NA & 2.59 & \(6.6\times 10^{-3}\) & 539 \\ \hline \multirow{4}{*}{650} & \multirow{4}{*}{A1} & TL & 2.1 & 2.4 & 2.65 & 0 & 0 \\  & & CL & 2.0 & 2.4 & 2.65 & \(5.1\times 10^{-4}\) & 41 \\  & & Cauchy & NA & NA & 2.65 & \(4.8\times 10^{-3}\) & 389 \\  & & TL & 2.0 & 2.3 & 2.76 & 0 & 0 \\  & & CL & 2.1 & 2.3 & 2.76 & \(6.3\times 10^{-5}\) & 5 \\  & & Cauchy & NA & NA & 2.66 & \(2.2\times 10^{-3}\) & 182 \\ \hline \multirow{4}{*}{650} & \multirow{4}{*}{A2} & TL & 2.0 & 2.3 & 2.73 & 0 & 0 \\  & & CL & 2.0 & 2.3 & 2.73 & \(3.4\times 10^{-4}\) & 27 \\  & & Cauchy & NA & NA & 2.72 & \(19.1\times 10^{-3}\) & 1546 \\  & & TL & 2.0 & 2.3 & 2.73 & 0 & 0 \\  & & CL & 2.1 & 2.4 & 2.73 & \(2.6\times 10^{-5}\) & 2 \\  & & Cauchy & NA & NA & 2.58 & \(1.3\times 10^{-3}\) & 105 \\  & & TL & 2.0 & 2.4 & 2.73 & \(0\) & 0 \\
650 & & CL & 2.0 & 2.4 & 2.73 & \(5.0\times 10^{-5}\) & 4 \\  & & Cauchy & NA & NA & 2.72 & \(14.0\times 10^{-3}\) & 1135 \\  & & TL & 2.1 & 2.5 & 2.69 & 0 & 0 \\
700 & & CL & 2.0 & 2.4 & 2.68 & \(1.9\times 10^{-3}\) & 160 \\  & & Cauchy & NA & NA & 2.64 & \(28.2\times 10^{-3}\) & 2200 \\ \hline \end{tabular}
\end{table} 
Table 1: Summary analysis of AD and annealed samples deposited at 650 \({}^{\circ}\)C and 700 \({}^{\circ}\)C.  
Figure 5B presents a comparative analysis of the absorption at 1550 nm for the AD and annealed 650 \({}^{\circ}\)C and 700 \({}^{\circ}\)C samples. For samples deposited at 650 \({}^{\circ}\)C, absorption values derived from the CL model monotonically decrease with increasing annealing steps, exhibiting an approximate 30-fold decrease following A3 annealing, from \(\sim\)120 cm\({}^{-1}\) for the AD to \(\sim\)4 cm\({}^{-1}\) for the A3 sample. The CU model analysis yields overall higher absorption, with \(\alpha\) values of around 10\({}^{3}\) cm\({}^{-1}\).