Low temperature vacuum ultraviolet annealing of ZrO2 optical coatings grown by laser ablation

The effect of post-deposition low temperature annealing treatment of ZrO2 thin films, grown by laser ablation using vacuum ultraviolet (VUV) radiation emitted by an excimer lamp, was investigated. The optical absorption coefficient of the films was reduced by more than one order of magnitude after annealing while the refractive index increased, reaching values similar to those recorded for the bulk material. The treatment was especially effective for films grown at modest substrate temperatures. After VUV annealing for 1 h at 350 degrees C, films deposited at only 300 degrees C exhibited a lower optical absorption than films grown at 550 degrees C.