Multitechnique investigation of Ta2O5 films on SiO2 substrates: comparison of optical, chemical and morphological properties

Ta2O5 mechanical losses seem to be the main cause of mirror thermal noise, limiting current interferometric gravitational wave detectors sensitivity in the 50-300 Hz frequency range. Work is in progress for the identification of these relaxation processes probably related with lattice defects and impurities that are distributed both in the mirror bulk and at the surface, in order to introduce step by step the suitable modifications in the samples until a stable “optimum performance” is obtained both from the optical and the thermo-mechanical point of view. Here we present our first results of a multitechnique characterization of Ta2O5 films deposited on SiO2 substrates. Optical, chemical and morphological properties have been investigated by means of Spectroscopic Ellipsometry, X-ray Photoelectron Spectroscopy and Atomic Force Microscopy. Measurements carried out on pure bulk Ta2O5 samples will be also reported for comparison.