## 2 Results  
Figure 1 presents the IR spectra of Si samples doped with isovalent impurities and recorded after irradiation, at various characteristic temperatures in the course of isochronal anneals (complementary information is also given in Figure 1 of [102] and [127]). Information about the considered samples is presented in Table 1. We observed numerous signals from O-related and C-related defects. Regarding O-related defects, there were  
well-known bands [9; 10; 11; 127; 128; 129; 130; 131] such as those of VO\({}_{\rm n}\) (n = 1-5) defects: VO (830 cm\({}^{-1}\)), VO\({}_{2}\) (888 cm\({}^{-1}\)), VO\({}_{3}\) (904, 968, 1000 cm\({}^{-1}\)), VO\({}_{4}\) (985, 1010 cm\({}^{-1}\)), VO\({}_{5}\) (1037, 1051 cm\({}^{-1}\)), and some very weak bands originating [102; 127] from either VO\({}_{6}\) or V\({}_{\rm n}\)O\({}_{\rm m}\) and VO\({}_{\rm n}\)C defects (762, 967, 1005 cm\({}^{-1}\), respectively). Notably, the 762 cm\({}^{-1}\) band appeared clearly only in the higher fluence irradiated samples. Regarding C-related defects, there were well-known bands [16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41] such as those of C\({}_{\rm i}\)O\({}_{\rm i}\) (860 cm\({}^{-1}\)), C\({}_{\rm i}\)C\({}_{\rm s}\) (546 cm\({}^{-1}\)) and C\({}_{\rm i}\)O\({}_{\rm i}\)(Si\({}_{\rm I}\)) (936, 1020 cm\({}^{-1}\)). Furthermore, a band at 806 cm\({}^{-1}\) appeared in the spectra only in the Cz-Si:Sn\({}_{\rm H}\) sample, upon annealing out of the VO defect. It had a similar evolution behavior as the VO\({}_{2}\) defect which was also formed upon the annealing of the VO defect. The 806 cm\({}^{-1}\) band had previously been attributed to the SnVO complex [142].  
Figure 1: \(Cont.\)  
We will first consider oxygen-vacancy related defects.  
Figure 2 (refer also to complementary Figures 2 and 3 of [102; 127]) presents the evolution of the various VO\({}_{\text{n}}\) bands which appear in Figure 1. In the following, we shall mainly deal with the effect of isovalent dopants on the properties of the first two members of the VO\({}_{\text{n}}\) family of defects, that is, the VO and the VO\({}_{2}\) centers.  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Sample** & **[Ge] \(\times\) 10\({}^{20}\)** & **[Pb] \(\times\) 10\({}^{17}\)** & **[Sn] \(\times\) 10\({}^{17}\)** & **[O]\({}_{\text{n}}\)\(\times\) 10\({}^{17}\)** & **[C]\({}_{\text{n}}\)\(\times\) 10\({}^{16}\)** & **Fluence** \\
**Name** & **[cm\({}^{-3}\))** & **[cm\({}^{-3}\))** & **[cm\({}^{-3}\))** & **[cm\({}^{-3}\))** & **[cm\({}^{-3}\))** & **[cm\({}^{-3}\))** & **[cm\({}^{-3}\))** \\ \hline Cz-Si0 & \(\dots\) & \(\dots\) & \(\dots\) & 9.56 & \(<\)2.0 & \(5\times 10^{17}\) \\ Cz-Si1 & \(\dots\) & \(\dots\) & \(\dots\) & 10.00 & 16.0 & \(5\times 10^{17}\) \\ Ge-8 & 2 & \(\dots\) & \(\dots\) & 7.70 & 18.0 & \(5\times 10^{17}\) \\ Cz-Si:Pb & \(\dots\) & \(\dots\) & 2.1 & 1.9 & \(1\times 10^{18}\) \\ Cz-Si:SnPb & \(\dots\) & \(\dots\) & 90 & 9.2 & 2.0 & \(1\times 10^{18}\) \\ Cz-Si:SnPb & \(\dots\) & \(\dots\) & 10 & 2 & 6.2 & 4.0 & \(1\times 10^{18}\) \\ \hline \end{tabular}
\end{table}
Table 1: The O\({}_{\text{i}}\), C\({}_{\text{s}}\), Ge, Sn and Pb concentrations of the used samples for Figure 1 [102; 127].  
Figure 1: IR spectra of the Ge-8 sample (**a**), after irradiation at a fluence of \(5\times 10^{17}\) cm\({}^{-2}\), and the Cz-Si:Pb (**b**), Cz-Si:Sn\({}_{\text{H}}\) (**c**), and Cz–Si:SnPb (**d**) samples, after irradiation at a fluence of \(1\times 10^{18}\) cm\({}^{-2}\), at characteristic temperatures of the isochronal anneal sequence. Reproduced with permission from [102; 127]. American Institute of Physics.  
Figure 2: Thermal evolution of the various VO\({}_{\rm n}\) defects for the Ge-8 sample (**a**), and the Cz–Si:Pb (**b**), Cz–Si:Sn\({}_{\rm H}\) (**c**), and Cz–Si:SnPb (**d**) samples. Reproduced with permission from [102; 127]. American Institute of Physics.