Modifications of ion beam sputtered tantala thin films by secondary argon and oxygen bombardment.

Abstract

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.