Improvement of a dual frequency sputtering device for higher deposition rates of protective zirconium oxide films on ceramics

Zirconium thin films have been applied as protective coating films on ceramics by dual frequency oxygen plasma sputtering [Y. Ohtsu et al., Surf Coat Technol, 196 (2005) 81], where they were certified to be effective in modifying the surface state of china and porcelain with the water-repellency and the stoichiometric value of atomic ratio O/Zr in films. However, the deposition rate with the former device was about 0.6 nm/min, lower compared with a conventional radio frequency magnetron plasma device. Improvement of the deposition rate has been investigated by optimization of the geometry in a dual frequency plasma-sputtering device using O2 and Ar mixture gases. That is, the ratio of plasma volume to that of the vacuum chamber was changed from 8 to 44%. The high-deposition rate of about 7 nm/min was attained at O2 gas concentration of 10%, under the optimization of the geometry. The films have also kept the high transparency of 90%. These results indicate that the advanced dual frequency plasma-sputtering device is an effective plasma source for producing protective layers for ceramics.