## 2 Results
### Conversion of VO to VO\({}_{2}\) Defect Versus Ge Dopant Concentration  
Figure 6 shows the conversion ratio (a\({}_{\rm VO2}\)/a\({}_{\rm VO}\)) of the VO to VO\({}_{2}\) defect as a function of the Ge dopant concentration (information about the samples from Table 3). As observed, the ratio (a\({}_{\rm VO2}\)/a\({}_{\rm VO}\)) decreases with the increase in Ge content. This effect is attributed [127] to the influence of Ge on the main reactions that govern the annealing of VO pair, that is: VO + O\({}_{\rm i}\) \(\rightarrow\) VO\({}_{2}\) and VO + Si\({}_{\rm i}\) \(\rightarrow\) O\({}_{\rm i}\). As mentioned above, the sources of the self-interstitials are large defect clusters [144] formed in the course of irradiation. It has been argued [127] that the strains introduced into the Si lattice due to the presence of Ge facilitates the liberation of Si\({}_{\rm i}\)'s from the clusters, thus enhances the reaction VO + Si\({}_{\rm i}\)\(\rightarrow\) O\({}_{\rm i}\) and, therefore, suppresses the reaction VO + O\({}_{\rm i}\)\(\rightarrow\) VO\({}_{2}\), since less VO are available for the latter reaction. In essence, this leads to a decrease in the formation of VO\({}_{2}\) defect which is manifested by the decrease in the (a\({}_{\rm VO2}\)/a\({}_{\rm VO}\)) ratio. Notably, due to the temporary trapping of V by Ge atoms in the course of irradiation, the annihilation rate between vacancies and self-interstitials in the course of irradiation is reduced, which increases the availability of Si\({}_{\rm i}\)'s and, therefore, increases the reaction VO + Si\({}_{\rm i}\)\(\rightarrow\) O\({}_{\rm i}\). In fact, the latter reaction is the main reason for the partial transformation of VO pairs to VO\({}_{2}\) defects. Importantly, the behavior of the ratio (a\({}_{\rm VO2}\)/a\({}_{\rm VO}\)) is similar for the LC and the HC material (compare Figure 6a,b). Additionally, in the case of high Ge content, there is a slight increase in the (a\({}_{\rm VO2}\)/a\({}_{\rm VO}\)) ratio in both samples. This is related with the fact that the introduction of Ge in very large concentrations in the Si lattice leads [145] to the inhomogeneous distributions of Ge atoms, which generally affects [142] the balance between the reactions VO + O\({}_{\rm i}\)\(\rightarrow\) VO\({}_{2}\) and VO + Si\({}_{\rm i}\)\(\rightarrow\) O\({}_{\rm i}\), which mainly govern the VO to VO\({}_{2}\) transformation. This change may be reflected in the slight increase in the (a\({}_{\rm VO2}\)/a\({}_{\rm VO}\)) ratio in the high Ge concentration samples, as observed in Figure 6.  
The Effect of the Ge Dopant Concentration on the Tann of the VO and the Tform of the VO\({}_{2}\) Defects  
Figures 7 and 8 show the characteristic temperatures T\({}_{\rm ann}\) of the VO annealing and T\({}_{\rm form}\) of the VO\({}_{2}\) formation as a function of the Ge concentration (information about the samples from Table 3). It was observed that the annealing temperature T\({}_{\rm ann}\) of VO (Figure 7) and the consequent formation temperature T\({}_{\rm form}\) of VO\({}_{2}\) (Figure 8) decreased as the Ge concentration in the samples increased. The phenomenon can be explained as follows. In Ge-doped Si, the reaction VO + Si\({}_{\rm i}\)\(\rightarrow\) O\({}_{\rm i}\) involved in the VO annealing is enhanced [127]. Indeed, the presence of Ge facilitates the emission of Si\({}_{\rm i}\)'s from loosely bound self-interstitial clusters. This promotes an earlier onset of VO annealing' that is, the earlier annealing of the VO defect is mainly due to the reaction VO + Si\({}_{\rm i}\)\(\rightarrow\) O\({}_{\rm i}\), which is activated earlier in the Si lattice due to the Ge presence. The larger the Ge concentration the earlier the onset of the VO annealing. Regarding the now earlier growth of the VO\({}_{2}\) defect in the spectra, the following explanation can be offered [127].