In the pursuit of identifying improved amorphous oxide coatings for gravitational wave detector test masses, 44% Ti-doped ${\mathrm{GeO}}_2$ has emerged as a potential candidate due to its low mechanical loss [Vajente et al. Phys. Rev. Lett. 127, 071101 (2021)]. It has been proposed and experimentally demonstrated that a reduction in mechanical loss in amorphous oxides is associated with medium-range order (MRO) dominated by corner-sharing links in the amorphous network. In this work, we describe a combined experimental and theoretical approach to investigate the MRO of Ti-doped ${\mathrm{GeO}}_2$. Using atomistic modeling and simulations, we calculate the Raman spectrum of 44% Ti-doped ${\mathrm{GeO}}_2$, and we show that it predicts the main features observed in the experiments and further provides insight into the MRO, which would otherwise be hidden. It is shown that the amorphous oxide mixture exhibits a distribution of predominantly large ($>4$ member) rings formed by corner-shared tetrahedral Ge-O-Ti connections. It is also shown that the addition of Ti to $a\text{−}{\mathrm{GeO}}_2$ does not largely compromise corner-sharing connections, as the smaller populations of Ti-O-Ti and Ge-O-Ge links in the network are predominantly corner-shared. The mainly covalently bonded representation of the MRO of Ti-doped ${\mathrm{GeO}}_2$ revealed by this analysis validates the importance of the MRO network organization in influencing mechanical loss in amorphous oxides.

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• Amorphous materials
• Thin films
• First-principles calculations
• Raman spectroscopy