# Correlated evolution of structure and mechanical loss of a sputtered silica film

## TL;DR

This study investigates how the structure of sputtered silica films influences their mechanical loss, revealing that three-membered rings and chain-like structures play key roles in energy dissipation mechanisms.

## Contribution

It provides new insights into the correlation between structural features and mechanical loss in sputtered silica, highlighting the impact of thermal treatment on metastable states.

## Key findings

- Loss correlates with three-membered Si-O rings.
- Thermal treatment reduces metastable states with ~0.5 eV energy.
- Three-fold rings are involved in relaxation within chain-like structures.

## Abstract

Energy dissipation in amorphous coatings severely affects high-precision optical and quantum transducers. In order to isolate the source of coating loss, we performed an extensive study of Raman scattering and mechanical loss of a thermally-treated sputtered silica coating. Our results show that loss is correlated with the population of three-membered rings of Si-O$_4$ tetrahedral units, and support the evidence that thermal treatment reduces the density of metastable states separated by a characteristic energy of about 0.5 eV, in favour of an increase of the states separated by smaller activation energies. Finally, we conclude that three-fold rings are involved in the relaxation mechanisms only if they belong to more complex chain-like structures of 10 to 100 tetrahedra.