Abstract
To improve optical lens transmission characteristics, anti-reflection film is applied to a lens surface. The substrate temperature strongly affects optical thin film durability and determines the thin film structure. Therefore, substrate temperature fluctuation from 25 ℃ to 400 ℃ during deposition was verified to improve mechanical properties while maintaining optical properties. As anti-reflection films, SiO2 and Nb2O5 were used. Each single-layer thin film was prepared using high-density plasma assisted vapor deposition at different substrate temperatures. Then, each single-layer film was evaluated using a falling sand test. The amount of transmittance change during testing after production at high temperatures was small for each film. Behaviors of refractive index and film stress demonstrated that these films were dense and stable after production at high temperatures. Furthermore, their surface roughness revealed that SiO2 films had small values and that Nb2O5 films had large values under high substrate temperatures. For these analyses, cross-sections of the tested films were observed using SEM（Scanning Electron Microscope）. Both thin films' hardness was measured by nanoindentation. These tests revealed high brittleness of the SiO2 thin film. Actually, Nb2O5 thin film tends to be plastically deformed: different heights of damage during extrusion affect the surface roughness. XPS（X-ray Photoelectron Spectroscopy）results showed differences in films from the bonding state according to the substrate temperature. Various measurement results obtained at various temperatures and fluctuation patterns revealed that the most durable films of each thin film type are produced at high temperatures.
