Giant increase of optical transparency for Zn-rich CaxZn1−xO on Al2O3 (0 0 0 1) grown by pulsed laser deposition

Abstract

In this study, CaxZn1−xO high quality films with different Ca ratios (from 0% to 10%) were grown on Al2O3 (0001) substrates by pulsed laser deposition for the first time. The optical properties for the grown films were studied over a wide spectral range from 200 to 3300nm using the reflectance and transmittance spectrum. It was found that the calculated optical energy gap values increases from 3.275 to about 3.340eV with increasing Ca concentrations from 0% to 10%. This opens a new stage in the study of the high quality optical films. The stoichiometry of the films was achieved using targets of the same intended film ratio. Two sample sets were grown at 650°C, one set with argon gas background at 10mTorr and the other one without any intentionally introduced gases. The structural properties for the grown films were studied using X-ray Diffraction. It was clear that by increasing Ca, the lattice parameter c is decreased and 2θ was shifted towards higher values from, while the FWHM was increased. These results indicated that the film crystallinity degrades as Ca content in the films increased.