CaCu3Ti4O12 CCTO thin films are prepared by a sol-gel method on LaNiO3-coated silicon and Pt/TiO2/SiO2/Si substrate. Compared with the films on Pt, the CCTO on LaNiO3 exhibits a 400 orientation. Dielectric loss of CCTO on LaNiO3 is lower than 0.25 within 100 Hz-10 kHz, lower than the reported value of CCTO grown on Pt/TiO2/SiO2/Si by pulse laser deposition. Possible reason is that LaNiO3 acts as seed layer for the growth of CCTO. The crystallinity of CCTO is improved and the dielectric properties are enhanced. Complex impedance spectrum of CCTO on LaNiO3 is discussed according to grain boundary barrier layer capacitance model.

Ferroelectric BaTiO3 nanocrystalline films (BTNFs) with the crystalline sizes of about 30 nm were grown on Pt/Ti/SiO2/Si substrates by a modified sol-gel method. Spectroscopic ellipsometry (SE) was used to characterize the films in the photon energy range of 1.5-5.0 eV with a five-phase layered model (air/surface rough layer/BaTiO3/interface layer/Pt). The optical properties in the transparent and absorption regions have been investigated with the Forouhi Bloomer dispersion relation. With the aid of the structural and dielectric function models, the microstructure and electronic structure of the BTNFs can be readily obtained. It was found that the refractive index reaches the value of 2.20 in the transparent region. Based on the Sellmeier dispersion analysis, the single-oscillator energy is about 4.7 eV for the BTNFs. The long wavelength refractive index n(0) can be estimated to about 2.00 at zero point. The direct optical band gap energy approaches approximately 4.2 eV and Urbach band tail energy is 262

Optical response of rutile TiO2 films grown under different laser energy by pulsed laser deposition has been investigated by Raman scattering and spectral transmittance. Dielectric functions in the photon energy range of 1.24-6.5V have been extracted by fitting the experimental data with the Adachi's model [S. Adachi, Phys. Rev. B35, 7454(1987)]. The refractive index dispersion in the transparent region is mainly ascribed to the higher A1-A2 electronic transitions for the rutile TiO2 films. Owing to slightly different crystalline structures and film densities, the optical band gap linearly increases with increasing packing density. The phenomena were confirmed by different theoretical evaluation methods.