Inert Gas Admixtures in PECVD of Titanium Dioxide Thin Films on Polymers—Influence on the UV Absorptance of the Films

A low pressure radio frequency discharge (200 W for 5 min) was operated in oxygen, nitrogen/oxygen and argon/oxygen with small admixtures of titanium(IV)isopropoxide (TTIP). By means of the O 2 ‐flow, the O 2 ‐to‐TTIP ratio q was varied in all the gas mixtures. Besides the growth rate, the absorptance of films deposited was determined in the range of 200–500 nm. Accordingly, their cut‐off wavelength increased with q for mixtures containing N 2 or Ar, while it was unaffected for O 2 /TTIP mixtures. At 310 nm, the absorption coefficient was a 310  = 13 µm −1 for q  ≈ 44 in Ar/O 2 /TTIP and marginally lower in N 2 /O 2 /TTIP as well as O 2 /TTIP. But, for decreasing q , a drastic decrease in a 310  ≈ 8 µm −1 was witnessed for O 2 /TTIP mixtures. In contrast, a 310 increased by 2 µm −1 for gas mixtures with Ar or N 2 .