Characterization of plasma-deposited and dip-coated films for critical optical applications

Two types of coatings were evaluated with respect to their suitability for optical applications in which low scattering is required. The plasma-deposition technique produces dense pinhole-free films of refractory materials from a glow discharge plasma at typical substrate temperatures of 200-300 degrees C. Plasma-deposited films of SiO(2) and Si(3)N(4), produced from reactions of SiH(4) with N(2)O and NH(3), respectively, were evaluated in this study. SiO(2) films were also produced from metal-organic precursor solutions using dipping and spinning application techniques followed by pyrolysis at 600 degrees C. Coatings were deposited on the highest quality substrates available, which were characterized prior to deposition so that the effects of the coatings could be separated from those of the substrates. Nomarski microscopy, surface profiling, total integrated scattering, ellipsometry, and photon backscattering techniques were used for characterization. The properties of these coatings and information on how the quality depends on coating conditions are reported in this paper.