Reactive evaporation in ionized gases

Area of Science:

• Materials Science
• Thin Film Deposition
• Optical Coatings

Background:

• Conventional reactive evaporation often results in films with non-stoichiometric compositions.
• Non-stoichiometric films exhibit increased absorptance and dielectric losses, limiting their performance.
• Improved deposition techniques are needed for high-quality optical films.

Purpose of the Study:

• To enhance the reactivity of residual gases during thin film deposition.
• To produce high-quality silicon dioxide (SiO2), silicon oxynitride (SiOxNy), and titanium dioxide (TiO2) films.
• To evaluate the optical properties of deposited films, specifically absorptance and refractive index.

Main Methods:

• Utilized a discharge tube with a high current density region for gas ionization within a bell jar.
• Introduced ionized gas directly into a high vacuum region via a nozzle.
• Optimized production parameters for SiO2, SiOxNy, and TiO2 film deposition on unheated substrates.

Main Results:

• Achieved a considerable increase in reactivity through residual gas ionization.
• Produced SiO2 films with negligible absorptance down to 190 nm.
• Obtained TiO2 films with high refractive indices up to 2.3.

Conclusions:

• Residual gas ionization is an effective method for improving thin film deposition quality.
• The developed technique enables the production of low-loss SiO2 and high-refractive-index TiO2 films.
• This approach offers a pathway to enhanced optical coatings with superior performance.