Optical and Structural Properties of Tantalum Pentoxide Thin Films by Ion Assisted Deposition Method with Radio Frequency Ion Source

抄録

Ion assisted deposition has been applied widely in present optical industry, to obtain more dense films, but it is often required to attain longer filament lifetime of the ion source particularly in the case of successively reactive oxidation processes under an additional oxygen gas inlet such as in oxide films for laser mirror application. It is the reason why radio frequency ion source is keenly interested at the present moment. Therefore we have investigated the optical and structural properties of Ta₂O₅ films as the functions of ion energy (300-750eV), substrate temperature (ambient or 300°C ), arrival ratio (0.2-0.8 atoms/ion), and providing the oxygen ions by RF ion source to bombardment. Typically, Ta₂O₅ thin films with refractive index larger than 2.25 and extinction coefficient less than 6×10^-4 in visible region have been obtained under the conditions of oxygen ion energy of 500 eV, at the substrate temperature of 300°Cand with the arrival ratio of 0.4 atoms/ion. Their cross sections of the films are shown the amorphous-like, amorphous columnar, and polycrystalline columnar structures by SEM and XRD. Several results of surface roughness of these films by AFM and OP, and the packing densities of these films by spectrometer (OPM-V1) are also presented.