Atomic Structure of Amorphous Optical Coatings of TiO$_2$-doped GeO$_2$ by Grazing-Incidence Total X-ray Scattering Measurements
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| Autores principales: | , , , , , , , , , , , , , , , |
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| Formato: | Preprint |
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2026
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| author | Prasai, K. Jiang, J. Lee, K. Yang, L. Chicoine, M. Khadka, S. Markosyan, A. Mehta, A. Menoni, C. S. Patel, S. Schiettekatte, F. Shyam, B. Vajente, G. Cheng, H-P Fejer, M. M. Bassiri, R. |
| author_facet | Prasai, K. Jiang, J. Lee, K. Yang, L. Chicoine, M. Khadka, S. Markosyan, A. Mehta, A. Menoni, C. S. Patel, S. Schiettekatte, F. Shyam, B. Vajente, G. Cheng, H-P Fejer, M. M. Bassiri, R. |
| contents | Reducing coating thermal noise in future gravitational-wave detectors requires identifying the atomic motifs that control mechanical loss in amorphous optical coatings. We combine grazing-incidence X-ray pair distribution function measurements with atomic-structure modeling to study amorphous TiO$_2$-doped GeO$_2$ films over Ti cation concentrations from $\sim$11 % to $\sim$48 %, before and after annealing. The structural analysis reveals systematic composition- and annealing-dependent changes in short- and intermediate-range order. Increasing Ti content raises the average Ti coordination and promotes edge- and face-sharing polyhedral connections, while Ge remains predominantly fourfold coordinated. Annealing reduces these compact shared-polyhedron motifs and sharpens the first sharp diffraction peak, indicating a more relaxed intermediate-range network. Among the structural descriptors examined, the clearest correlation with the annealing-induced reduction in mechanical loss is the decrease in edge- and face-sharing polyhedra. These results connect composition, annealing, atomic structure, and mechanical dissipation in TiO$_2$-doped GeO$_2$, providing microscopic guidance for optimizing low-noise mirror coatings. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_27462 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Atomic Structure of Amorphous Optical Coatings of TiO$_2$-doped GeO$_2$ by Grazing-Incidence Total X-ray Scattering Measurements Prasai, K. Jiang, J. Lee, K. Yang, L. Chicoine, M. Khadka, S. Markosyan, A. Mehta, A. Menoni, C. S. Patel, S. Schiettekatte, F. Shyam, B. Vajente, G. Cheng, H-P Fejer, M. M. Bassiri, R. Materials Science Reducing coating thermal noise in future gravitational-wave detectors requires identifying the atomic motifs that control mechanical loss in amorphous optical coatings. We combine grazing-incidence X-ray pair distribution function measurements with atomic-structure modeling to study amorphous TiO$_2$-doped GeO$_2$ films over Ti cation concentrations from $\sim$11 % to $\sim$48 %, before and after annealing. The structural analysis reveals systematic composition- and annealing-dependent changes in short- and intermediate-range order. Increasing Ti content raises the average Ti coordination and promotes edge- and face-sharing polyhedral connections, while Ge remains predominantly fourfold coordinated. Annealing reduces these compact shared-polyhedron motifs and sharpens the first sharp diffraction peak, indicating a more relaxed intermediate-range network. Among the structural descriptors examined, the clearest correlation with the annealing-induced reduction in mechanical loss is the decrease in edge- and face-sharing polyhedra. These results connect composition, annealing, atomic structure, and mechanical dissipation in TiO$_2$-doped GeO$_2$, providing microscopic guidance for optimizing low-noise mirror coatings. |
| title | Atomic Structure of Amorphous Optical Coatings of TiO$_2$-doped GeO$_2$ by Grazing-Incidence Total X-ray Scattering Measurements |
| topic | Materials Science |
| url | https://arxiv.org/abs/2605.27462 |