ANNEALING EFFECT ON ION-BEAM-SPUTTERED TITANIUM-DIOXIDE FILM

We found that the extinction coefficient of ion-beam-sputtered titaniu m dioxide films first decreased with increasing annealing temperature then increased drastically when annealing temperature was increased ab ove similar to 200 degrees C for 24 h of annealing time. The decreasin g extinction coefficient with annealing temperature was attributed to a reduction in absorption owing to oxidation of the film by annealing. The film structure remained amorphous to 200 degrees C annealing temp erature. The drastic increase of extinction coefficients above similar to 200 degrees C was associated with the appearance of an anatase pol ycrystalline structure and was attributed to scattering by the polycry stalline structure. With shorter annealing time the transition tempera ture from amorphous to polycrystalline anatase was higher. Guidance fo r reducing the optical loss of laser mirrors is proposed. (C) 1998 Opt ical Society of America.