Optical properties of electron beam evaporated ZrO₂:10 %SiO₂ thin films: dependence on structure

Abstract

ZrO₂:10 %SiO₂ thin films have been deposited on fused silica substrate by reactive electron beam co-evaporation technique at different oxygen partial pressure. The structural analysis shows tetragonal phase with distortion of the lattice in the films. The intensity of the tetragonal t(110) phase are found increasing with increasing oxygen pressure. The optical band gap is found increasing from 5.06 to 5.28 eV with increasing oxygen pressure because of increasing crystalinity of monoclinic phase. No crystallite size or grain size effect on the optical properties of the films has been observed. The film surface roughness decreases from 3.51 to 2.25 nm with increasing oxygen pressure. The dispersion of the refractive index is discussed in terms of single oscillator Wimple–DiDomenico model. The film with least lattice distortion shows maximum value of refractive index and vice versa. The dispersion energy E _d better known as structural order parameter is found increasing from 20.3 to 23.97 eV with the intensity of tetragonal t(110) phase. The film surface roughness is found decreasing with increasing dispersion energy, which concludes that the local microstructure ordering can predominantly influence the grain morphology which in turn can lead to better surface.