Nanocrystallite Formation in Amorphous Titania Coatings

The use of sophisticated optical elements is integral to the functionality of gravitational-wave-detecting interferometry. The mirrors in the interferometer, constituted by a Bragg multilayer coating, are one of the main sources of noise, particularly thermal and quantum. Furthermore, these coatings need to satisfy very tight requirements in terms of optical quality. In this project, we observe the crystallization process of the optical coating titania (TiO₂) when it undergoes a thermal treatment, and how these phenomena change with respect to temperature. Five different annealing temperatures were tested: 330°C, 340°C, 350°C, 380°C, and 390°C. We analyze the parameters recovered from the x-ray spectra of TiO₂ following heat treatment, and subsequently build a crystallization kinetics analysis from them. From this, we hope to understand how the crystallization process proceeds and use it to limit mirror-related noise in Virgo.