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

(Pb1-xLax)TiO3 (PLT) films with various compositions of La were deposited b y using the sol-gel process on quartz substrates in order to study their op tical properties. X-ray patterns indicated that the pseudocubic phase of th e PLT film dominated with increased La concentration due to a decrease in t he lattice constant of the c-axis. Three-dimensional atomic force microscop y 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-de posited films became wider when Pb was replaced with La, which could be cal culated from the transmittance of an UV-visible spectrometer. The addition of La increased the transparency of the PbTiO3 film and shifted the thresho ld to shorter wavelengths for initiation of absorption. In addition, we mod ified 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. Th e optical band gap of the PLT film was changed by the oxygen-ion-beam modif ication although the XRD patterns and the transmittance values were not cha nged significantly. AFM measurements indicated that the surface morphology of the PLT film was changed slightly. These results suggested that the addi tion of La and the surface modification by using oxygen-ion-beam can affect the optical properties of PbTiO3 and PLT films.