Effects of the annealing of amorphous Ta2O5 coatings produced by ion beam sputtering concerning the effusion of argon and the chemical composition

We investigate the effects of thermal treatments in vacuum or air on amorphous Ta2O5 deposited crystalline Si by Ion Beam Sputtering, mimicking coatings mirrors gravitational-wave revealers Advanced Virgo and LIGO detectors. Argon is present whole thickness coating, likely introduced during synthesis, it can be released above 200°C vacuum, while less discharge Ar detected heating air. Formation sub-stoichiometric Ta oxides evidenced surface layers, after in-vacuum annealing. The macroscopic structure samples not affected treatments. However, length interference fringes, due to decreases both suggesting an increase ~1-2%, caused volume pores structure.