Influence of oxygen partial pressure on the properties of pulsed laser deposited nanocrystalline zirconia thin films

ZrO2 thin films were deposited at various oxygen partial pressures (2.0 × 10−5–3.5 × 10−1 mbar) at 973 K on (1 0 0) silicon and quartz substrates by pulsed laser deposition. The influence of oxygen partial pressure on structure, surface morphology and optical properties of the films were investigated. X-ray diffraction results indicated that the films are polycrystalline containing both monoclinic and tetragonal phases. The films prepared in the oxygen partial pressures range 2.0 × 10−5–3.5 × 10−1 mbar contain nanocrystals of sizes in the range 54–31 nm for tetragonal phase. The peak intensity of the tetragonal phase decreases with the increase of oxygen partial pressures. Surface morphology of the films examined by AFM shows the formation of nanostructures. The RMS surface roughness of the film prepared at 2.0 × 10−5 mbar is 1.3 nm while it is 3.2 nm at 3.5 × 10−1 mbar. The optical properties of the films were investigated using UV–visible spectroscopy technique in the wavelength range of 200–800 nm. The refractive index is found to decrease from 2.26 to 1.87 as the oxygen partial pressure increases from 2.0 × 10−5 to 3.5 × 10−1 mbar. The optical studies show two different absorption edges corresponding to monoclinic and tetragonal phases.