Title Formation of aluminium oxynitride thin films and their application for optical coatings /
Translation of Title Aliuminio oksinitrido plonų sluoksnių formavimas ir jų taikymas optinėse dangose.
Authors Kyžas, Naglis
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Pages 43
Keywords [eng] magnetron sputtering, optical coatings, aluminum oxynitride
Abstract [eng] The aim of this work is to investigate possible applications of aluminum oxynitride thin films in optical coatings. In order to reach the aim, several tasks must be done: 1) investigate reactive magnetron sputtering process with metallic aluminum target and two reactive gases; 2) characterize deposited aluminum oxynitride films with various nitride fractions; 3) model and characterize multilayer antireflective coating using aluminum oxynitride layers; 4) model quasi – Rugate filter consisting of alternating fraction aluminum oxynitride films. Investigation of reactive sputtering modes while changing reactive gases composition (oxygen and/or nitrogen) was done. It was determined that with the increase of nitrogen content in reactive gas, the moment of target poisoning is shifting to the higher flow values. Also high-rate, stable process optimized reactive gases flows were found. Samples with various nitrogen fraction in the films were prepared. Their refractive indices and extinction coefficients were modelled. It was shown that by varying oxygen and nitrogen flows as reactive gases during magnetron sputtering process it is possible to tune refractive index of deposited thin film from pure Al2O3 to pure AlN. Surface roughness and band gap values of the films were evaluated. Antireflective coatings with conventional high and low refractive index layers structure and aluminum oxynitride films gradual refractive index change structure were compared. It was shown that both coatings satisfy desired spectral specifications and maintain low roughness values of the coating. However, it was found that antireflective coatings using oxynitride thin films exhibit two times smaller coating stress than conventional high and low refractive index layers structure. Comparison of conventional high and low refractive index layers and quasi – Rugate filters showed that quasi – Rugate filter design enables opportunity to reach better spectral characteristics in high transmittance zone. Moreover, investigation of electric field distribution in the coatings suggests that quasi – Rugate filter should perform higher laser – induced damage threshold values than typical high and low refractive index layers coating.
Dissertation Institution Vilniaus universitetas.
Type Master thesis
Language English
Publication date 2020