Effect of inter-layer heat treatment on two-layer SiO2/ZrO2 films

Two-layer SiO2/ZrO2 thin films were deposited on K9 glass by Sol-Gel dip-coating method. The colloidal suspension of ZrO2 and SiO2 were prepared using Zr(OPr)4 and TEOS as precursors, respectively. For sample 1, the ZrO2 film was directly deposited on the pre-deposited SiO2 film. For sample 2, the ZrO2 film was deposited on the pre-deposited and heat-treated SiO2 film. Atomic force microscopy(AFM), ellipometry and UV-VIS spectroscopy were used to characterize the thin films. The samples were simulated with three-layer Cauchy theoretical model. The simulated ellipsometric parameters curves were perfectly consistent with the experimental ones. The results showed that the thickness of infiltrated layer of sample 2 was reduced by 23 nm by using heat treatment compared with that of sample 1. As a result, the heat treatment improved the tramsmittance of the two- layer film. The laser-induced damage threshold(LIDT) of the two kinds of films was measured. The LIDTs (1.064 μm, 8.1 ns) of sample 1 and 2 were 13.6 J/cm2 and 14.18 J/cm2, respectively. The damage morphologies were mainly ablation and desquamation according to optical microscopy. (authors)