Characterization of optical properties of nanocrystalline doped PZT thin films

High optical transmittance and refractive index together with strong electro-optic Kerr effect of the ferroelectric lead-zirconate-titanate (PZT) films can be utilized in various active optical applications like optical shutters, modulators and waveguides. Pulsed laser deposition (PLD) with XeCl-excimer laser with a wavelength of 308 nm and Nd-modified PZT target were used for the optical thin film fabrication. The films were deposited on single-crystal MgO (1 0 0) substrates. The crystal structure and grain size distribution were studied using XRD technique. The optical transmission spectra of the films were measured at UV–vis–NIR wavelengths, which was utilized to obtain the refraction index n dispersion, extinction coefficient k, and the value of the band gap E_g. Electro-optic coefficients were determined by ellipsometric technique. In the case of polycrystalline films, mean grain size was between 9 and 20 nm. At the wavelength of 633 nm the refractive index varied from 2.28 to 2.46 as a function of mean grain size. Also, the electro-optic coefficient showed dependence on grain size distribution increasing from 0.37 × 10⁻¹⁸ to 2.49 × 10⁻¹⁸ m²/V² with increasing mean grain size.