Effects of nitrogen partial pressure on titanium oxynitride films deposited by reactive RF magnetron sputtering onto PET substrates

Titanium oxynitride (TiNxOy) films have been deposited onto polyethylene terephthalate (PET) substrates by reactive radio frequency (RF) magnetron sputtering. The influence of the nitrogen (N2) partial pressure in the discharge atmosphere, with a set pressure of 0.133 Pa, was examined. Other deposition conditions were held constant. The deposition rate of the films, which exhibit an island-type morphology, was found to decrease with increasing N2 partial pressure. This concurred with an increase in the surface roughness at higher N2 partial pressure. The TiNxOy films deposited at N2 partial pressures from 0.26 × 10− 1 Pa to 0.8 × 10− 1 Pa possess Ti:N:O ratio of about 1:0.9:0.8 to 1:1.2:0.7. At the lowest N2 partial pressure of 0.26 × 10− 1 Pa, the water vapor (WV) and oxygen transmission rates (OTR) of the TiNxOy films reached values as low as 0.31 g/m2-day-atm and 0.62 cc/m2-day-atm, respectively; these values are about 16 and 50 times lower than those of the uncoated PET substrate.