Structural, electrical and optical properties of sol-gel processed lead titanate thin films

Polycrystalline PbTiO3 thin films having layered perovskite structure were fabricated by a sol-gel (spin coating) processing method. The substrates used were fused silica and stainless-steel, Surface morphology of the films was studied with scanning electron microscopy (SEM). The effect of post-deposition annealing on the electrical and structural properties were analyzed. Crystalline phase of PbTiO3 can only be obtained when the annealing temperature is higher than 500 degrees C. The electrical measurements were conducted on metal-film-metal capacitors. Films annealed at 600 degrees C exhibited crystallinity with perovskite phase: a dielectric constant of 132 and a dissipation factor of 0.039 at 1kHz. I-V characteristics were found to be ohmic at low fields and space charge limited, controlled by traps at high fields. Transmission spectra of the films deposited on fused silica were recorded and from this, refractive index, extinction coefficient and thickness of the films were calculated. The standard deviation of the thickness was found to be 18.8 nm. The dispersion curve for the refractive index 'n' is fairly fiat beyond 500 nm and rises rapidly towards shorter wavelength region, showing the typical shape of dispersion curve near an interband transition. The refractive index was found to be in the range 2.00-2.20 for different wavelengths (300 to 900 nm).