Crystallite growth limits in amorphous oxides

doi:10.1088/1361-6382/ad14b7

Crystallite growth limits in amorphous oxides

2023-12-22

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DOI：10.1088/1361-6382/ad14b7

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Post deposition thermal annealing of amorphous coatings improves optical properties of dielectric mirrors. However, excessive temperatures cause crystallization, resulting in a degradation of mechanical and optical properties. Therefore, annealing is limited to temperatures 'below' the crystallization threshold. The threshold is determined by x-ray diffraction (XRD) measurement which requires a significant amount of crystallized material for detection, yet it has been shown that a population of crystallites may exist in otherwise amorphous coatings below the threshold temperature. In this study XRD measurements show crystallites that grow during annealing within amorphous oxide coatings to a limited and predictable size predicated on the difference in density between the crystal and the surrounding amorphous phase and the average material's Young's modulus. These crystallites may be the point-like, extremely weak scatterers revealed in the LIGO test masses when imaged off-axis.

Keywords:

crystallites

gravitational waves

optical coatings

scatter

zirconia

titania

XRD

Crystallite growth limits in amorphous oxides

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