Modifications of ion beam sputtered tantala thin films by secondary argon and oxygen bombardment
Amorphous tantala (Ta₂O₅) thin films were deposited by reactive ion beam sputtering with simultaneous low energy assist Ar⁺ or Ar⁺/O₂⁺ bombardment. Under the conditions of the experiment, the as-deposited thin films are amorphous and stoichiometric. The refractive index and optical band gap of thin films remain unchanged by ion bombardment. Around 20% improvement in room temperature mechanical loss and 60% decrease in absorption loss are found in samples bombarded with 100-eV Ar⁺. A detrimental influence from low energy O₂⁺ bombardment on absorption loss and mechanical loss is observed. Low energy Ar⁺ bombardment removes excess oxygen point defects, while O₂⁺ bombardment introduces defects into the tantala films.
© 2020 Optical Society of America. Received 17 September 2019; revised 19 November 2019; accepted 3 December 2019; posted 3 December 2019 (Doc. ID 377788); published 14 January 2020. Portions of this work were presented at the Optical Interference Coatings Conference in 2019, FA.6 "Optical properties and mechanical loss of amorphous Ta₂O₅ thin films bombarded with low energy assist ions." Funding: LIGO program, National Science Foundation (1710957). The authors declare no conflicts of interest.