Characteristics of ion-beam-sputtered high-refractive-index TiO2-SiO2 mixed films

The ion-beam-sputtering method was used to deposit TiO2-SiO2 mixed films on silica substrates. The SiO2 concentration ranged from 9 to 17%, and the re fractive index ranged from similar to 2.7 to similar to 2.3 in visible wave length. All the structures of the as-deposited films were amorphous. The re fractive index and the extinction coefficient decreased with increased SiO2 concentration. High temperature annealing reduced the optical absorption f or all films. There was a phase transition from amorphous to polycrystallin e anatase at high temperature. Surface roughness, and thus optical scatteri ng, increased drastically with the appearance of the phase transition. The phase transition temperature was higher for films with higher SiO2 concentr ation. The ion-beam-sputtered TiO2-SiO2 mixed film could sustain higher tem perature annealing, resulting in lower extinction coefficient, than that of the ion-beam-sputtered pure TiO2 film. The phase diagram of the mixed film system was given. (C) 1999 Optical Society of America [S0740-3232(99)03005 -7] OCIS code: 310.3840.