Optical properties of PLT films with various composition on quartz and modifications of their surfaces

Abstract

(Pb1-xLax)TiO3 (PLT) films with various compositions of La were deposited by using the sol-gel process on quartz substrates in order to study their optical properties. X-ray patterns indicated that the pseudocubic phase of the PLT film dominated with increased La concentration due to a decrease in the lattice constant of the c-axis. Three-dimensional atomic force microscopy images revealed that the grain size and root mean square (r.m.s) surface roughness were decreased by adding of La. The optical band gap of the as-deposited films became wider when Pb was replaced with La, which could be calculated from the transmittance of an UV-visible spectrometer. The addition of La increased the transparency of the PbTiO3 film and shifted the threshold to shorter wavelengths for initiation of absorption. In addition, we modified the surfaces of the PLT films with La concentrations of 5 % by using an oxygen-ion beam with an oxygen-ion energy of 1 kV at different doses. The optical band gap of the PLT film was changed by the oxygen-ion-beam modification although the XRD patterns and the transmittance values were not changed significantly. AFM measurements indicated that the surface morphology of the PLT film was changed slightly. These results suggested that the addition of La and the surface modification by using oxygen-ion-beam can affect the optical properties of PbTiO3 and PLT films.