Comparison of thin films deposited by magnetron sputtering from oxide targets for sub-ps high-power laser applications

The aim of this work is to investigate the properties of oxide materials deposited as thin films with magnetron sputtering as candidates for the fabrication of multilayer mirrors or multilayer dielectric (MLD) gratings in the framework of high-power laser applications. We compare the refractive index, bandgap and laser-induced damage threshold (LIDT) of thin films of oxide materials deposited from either pure oxide or mixed oxide targets with precise control of the oxygen supply in the plasma. Refractive index and optical bandgap are correlated with laser-induced damage threshold and compared with literature. It reveals that a mixture of SiO 2 /Sc 2 O 3 (Si/Sc = 76/24 at. %) exhibits very good performance in terms of LIDT and refractive index. It might be a good alternative to SiO 2 and Sc 2 O 3 /SiO 2 (Sc/Si = 76/24 at. %) as an intermediate refractive index material between the refractive index of SiO 2 and HfO 2 . A physicochemical surface analysis by X-ray photoelectron spectroscopy (XPS) was carried out in order to complete the LIDT results. The stoichiometry of the films composed of SiO 2 /Sc 2 O 3 mixtures was derived from XPS measurements and compared to those of the targets. XPS also provides information about bond energies. Among the studied materials, the presence of elemental silicon or variations in the proportion of oxygen bonds related with the addition of oxygen in the plasma is shown.