Exploration of the key parameters in sol-gel preparation of Ta2O5 films with high laser damage resistance

Ta2O5 films were prepared by using TaCl5 as the precursor with different contents of H2O2, HNO3 and acetylacetone (ACAC). The particle size, photoluminescence spectra and optical transmittance of the sols, as well as the surface morphology, weak absorption, laser -induce damage threshold (LIDT) and damage morphology of the films were studied. It was shown that the hydrolysis process in the sol was very slow when H2O2 was absent. With the H2O2 content increase, the nanoparticles grew faster in the sol. However, with the HNO3 content increase, the hydrolysis process decreased and the sol became stable. The ACAC showed the inhibition effect similar to that of HNO3 on the sol evolution. With the ACAC content increase, the LIDT of the films decreased after the first rising, which showed an opposite trend compared with the weak absorption. Moreover, based on the experimental results, a pseudo-ternary phase diagram of H2O2-HNO3-ACAC system was proposed that is helpful for the high LIDT Ta2O5 film preparation.