Temperature effect on the nanosecond laser-induced damage of TiO2 films with two additives

TiO2 films were prepared using a very stable sol with two additives of diethanolamine (DEA) and polyethylene glycol (PEG) and remained intact without carbonization and cracking at high annealing temperature. It was shown that the laser-induced damage threshold (LIDT) at the wavelength of 1064 nm and the effective pulse duration of 12 ns of the films decreased with the annealing temperature increase. Because of the three-dimensional network structure and the low defect density, the annealing temperature of 353 K led to the highest LIDT of 14.3 J/cm(2). After annealed at 423 K, the ordered film structure was damaged to some extent and the inner defects emerged, contributing to the slight reduce of LIDT. Continually, the increasing annealing temperature of 523 K resulted in the gradual increase of the defect density and surface roughness and the significant decrease of the LIDT. When the annealing temperature increased further to 623 K, the film surface became much rougher, and more defects including the grain boundaries and the holes appeared which caused the lowest LIDT. According to the LIDT results and damage morphologies, a structure evolution model of the films at different temperatures was proposed.