## 2 Results
### Production of VO Defect Versus C Concentration
It is important to note that the thermal annealing of the dicarbon center is uncertain [16; 159] and is not completely understood. Although destruction is the main annealing mechanism, photoluminescence (PL) studies [160] have shown that the dicarbon center may also capture a mobile atom to form another center responsible for the 7686 cm\({}^{-1}\) line growing in the PL spectra as the G line of the C\({}_{\text{i}}\)C\({}_{\text{s}}\) center decay. The origin of the latter line is not certain [160]. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **Dopant** & **Fluence** & **[C\({}_{\text{i}}\)\({}_{\text{h}}\)\(\times\) 10\({}^{\text{th}}\)** & **[O\({}_{\text{i}}\)\({}_{\text{h}}\)\(\times\) 10\({}^{\text{th}}\)** & **[O\({}_{\text{i}}\)\({}_{\text{h}}\)\(\times\) 10\({}^{\text{th}}\)** & **[C\({}_{\text{i}}\)C\({}_{\text{s}}\)]\(\times\) 10\({}^{\text{th}}\)** \\  & **(cm\({}^{-3}\))** & **(cm\({}^{-3}\))** & **(cm\({}^{-3}\))** & **(cm\({}^{-3}\))** & **(cm\({}^{-3}\))** \\ \hline Cz-Si & \(\cdots\) & \(5\times 10^{17}\) & 16 & 10 & 3.7 & 0.15 \\ Sn\({}_{\text{h}}\) & \(3\times 10^{17}\) & \(1\times 10^{18}\) & 47 & 9.6 & 6.9 & 0.26 \\ Sn\({}_{\text{H}}\) & \(9\times 10^{18}\) & \(1\times 10^{18}\) & 20 & 9.2 & 5.5 & 0.29 \\ Pb & \(1\times 10^{18}\) & \(1\times 10^{18}\) & 19 & 2.1 & 2.0 & 0.17 \\ SnPb & \(2\times 10^{17}\), \(1\times 10^{18}\) & \(1\times 10^{18}\) & 40 & 6.2 & 5.8 & 0.29 \\ Ge\({}_{\text{c}}\) & \(1\times 10^{18}\) & \(5\times 10^{17}\) & 3 & 10 & 2.0 & 0.13 \\ Ge\({}_{\text{H}}\) & \(1\times 10^{19}\) & \(5\times 10^{17}\) & 20 & 6.74 & 4.3 & 0.13 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Initial concentrations of O\({}_{\text{i}}\) and C\({}_{\text{s}}\) impurities and the C\({}_{\text{i}}\)O\({}_{\text{i}}\) and C\({}_{\text{i}}\)C\({}_{\text{s}}\) concentrations for the samples used, irradiated with 2 MeV electrons, as well as the respective fluencies for each sample [158]. Figure 19: The conversion ratio of the C\({}_{\text{i}}\)O\({}_{\text{i}}\) to C\({}_{\text{s}}\)O\({}_{\text{2}}\) defect for various isovalent dopants. Reproduced with permission from [155]. American Institute of Physics, 2013. Figure 20: Evolution with temperature of the C\({}_{\rm i}\)O\({}_{\rm i}\) defect for various isovalent dopants. For (**a**) Cz-Si, (**b**) Sn\({}_{\rm L}\) and Sn\({}_{\rm H}\), (**c**) SnPb and Pb, and (**d**) Ge\({}_{\rm L}\) and Ge\({}_{\rm H}\) Si samples. Reproduced with permission from [158]. Comparing Figures 20 and 21, we observed that the annealing temperature \(\rm T_{ann}\) of both of the \(\rm C_{i}O_{i}\) and \(\rm C_{i}C_{s}\) centers was slightly affected, depending not only on the isovalent dopant covalent radius but also on the concentration of the isovalent dopant in the Si material. These small variations of \(\rm T_{ann}\) for the samples in Table 6 are clearly illustrated in Figure 22. Taking as a reference point the \(\rm T_{ann}\) of a \(\rm Cz\)-Si sample, the main finding, as clearly seen comparing Figure 22a, for \(\rm C_{i}O_{i}\), and Figure 22b, for \(\rm C_{i}C_{s}\), is that  
Figure 21: Evolution with temperature of the \(\rm C_{i}C_{s}\) defect for various isovalent dopants. For (**a**) \(\rm Cz\)-\(\rm Si\), (**b**) \(\rm Sn_{L}\) and \(\rm Sn_{H}\), (**c**) \(\rm SnPb\) and \(\rm Pb\), and (**d**) \(\rm Ge_{L}\) and \(\rm Ge_{H}\)\(\rm Si\) samples. Reproduced with permission from [158]. isovalent dopants differently affect the T\({}_{\rm amn}\). More specifically, as a general characteristic, the annealing temperature decreased in the case of C\({}_{\rm i}\)O\({}_{\rm i}\), although it increased in the case of C\({}_{\rm i}\)C\({}_{\rm s}\). Both C\({}_{\rm i}\)O\({}_{\rm i}\) and C\({}_{\rm i}\)C\({}_{\rm s}\) annealed out mainly [16] by dissociation expressed, respectively, by the reactions (C\({}_{\rm i}\)O\({}_{\rm i}\)\(\rightarrow\) C\({}_{\rm i}\) +O\({}_{\rm i}\)) and (C\({}_{\rm i}\)C\({}_{\rm s}\)\(\rightarrow\) C\({}_{\rm i}\) +C\({}_{\rm s}\)).