Preparation of Er₂O₃ and TiO₂ Multilayer Films as Optical Filter Using Magnetron Sputtering Deposition

Dispersion relations of refractive indexes and extinction coefficients of constituent materials were obtained by comparing the experimental and simulated transmission spectra of single-layer Er₂O₃ and TiO₂ films. We designed multilayer thin films of [Er₂O₃/TiO₂]⁶/[Er₂ O₃]²/[TiO₂/Er₂O₃]⁶ such that they can act as photonic crystals exhibiting a resonance wavelength of 514 nm. We prepared single-layer TiO₂ and Er₂O₃ thin films on quartz glass substrates by employing a magnetron sputtering deposition method. Uniform films exhibiting very high transmittance values were obtained. Deposition rates of the TiO₂ and Er₂O₃ films were 0.44 and 0.82 nm/s, respectively. [Er₂O₃/TiO₂]⁶/[Er₂ O₃]²/[TiO₂/Er₂O₃]⁶ multilayer films, to be used for optical bandpass filter applications, were also prepared using a multitarget sputtering deposition method. Uniform and transparent films were obtained; however, the wavelength corresponding to the highest transmittance was observed around 490 nm through ultraviolet-visible near-infrared spectroscopic measurements. The shift in the wavelength can be attributed to the low crystallinity and variations in the thicknesses of Er₂O₃ and TiO₂ films.