This study deals with the thermodynamic equilibrium theory of pyroelectric polycrystalline thin films. The unit cell of pyroelectric polycrystalline thin films in the ferroelectric phase to be considered is assumed as a dipole and is a nondipole at its paraelectric phase. The phase transition between ferroelectric and paraelectric phases is hypothesized as an equilibrium of the dipoles and the nondipole. Based on the thermodynamic equilibrium theory, an expression formula about the spontaneous polarization and temperature is suggested. Considering the sandwich structure of pyroelectric polycrystalline thin films, an equation about the relations between pyroelectric coefficient and temperature was established.

Dielectric nonlinearity is an important characteristic of ferroelectrics. Based on the characteristics of hysteresis loops and ε-E curves in ferroelectric materials, a model for dielectric nonlinearity of ferroelectrics is established. It is verified by the data of barium strontium titanate thin films.

BaxSr1-xTiO3 (x=0. 6 and 0. 8) thin films have been prepared on indium-doped tin oxide (ITO) coated quartz substrates using radio-frequency magnetron sputtering. Their structural properties and surface morphologies were examined by x-ray diffraction and atomic force microscopy, respectively. The BaxSr1-xTiO3 (BST) thin films with x=0. 6 and 0. 8 annealed at 650°C for 20 min exhibit good surface morphology and well-crystallized perovskite structure. High quality BST ferroelectric thin films were further investigated by electrical measurements, showing the remnant polarization (Pr) of 6. 75 μC/cm2 and the coercive field Ec of 43. 2 kV/cm. Optical transmittance measurement indicated that the Ba concentration has an effect on the band gap energy Eg structure of the BaxSr1-xTiO3 thin films. The Eg decreases linearly with the increase of the Ba content. The refractive index n and extinction coefficient k of the BST films with x=0. 6 and 0. 8 were obtained by fitting the spectroscopic ellipsometric data using a parametric dielectric function model. The refractive index n and extinction coefficient k increase with increasing wavelength. All of the results show that the BST/ITO/quartz heterostructure is promising for applications in integrated optical waveguide devices.

To be suitable for integrated optical devices, (Pb, La)(Zr, Ti)O3 PLZT ferroelectric thin films require high crystalline quality, low surface roughness, high optical index, and high transparency. In this paper, PLZT thin films have been grown in situ on indium tin oxide (ITO) coated quartz substrates by rf magnetron sputtering. X-ray diffraction, scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to investigate the structural properties of these PLZT films. The results show that the ferroelectric films exhibit satisfying crystallization with the highly 110-oriented growth from 550°C, and the surface roughness value (~3. 1 nm) in studied films is within the optimum range so that a low optical loss can be obtained. High quality PLZT ferroelectric thin films were further investigated by electrical measurements, showing that the remnant polarization Pr and coercive field Ec are approximately 11. 3 μC/cm2 and 56. 2 kV/cm, respectively. Spectroscopic ellipsometry (SE) was employed to characterize the depth profiles, the microstructural inhomogeneities (void and surface roughness), refractive index n, and extinction coefficient k of the PLZT film. In the analysis of the measured SE spectra, a three-layer Lorentz model with four oscillators was adopted to represent the optical properties of the PLZT film. In this model, the film was assumed to consist of two layers a bottom bulk PLZT and a surface layer composed of bulk PLZT as well as void. Good agreement was obtained between the measured spectra and the model calculations. The film thickness measured from SEM is consistent with that obtained by SE, while the root mean square roughness determined by AFM is also close to our fitted effective surface layer thickness obtained by SE. The PLZT thin film on ITO-coated quartz substrate is highly transparent in the visible near infrared wavelength region, and the band gap energy Eg is estimated to be 3. 54 eV. The experimental results above tend to demonstrate the suitability of the PLZT films in situ grown on ITO/quartz substrates for optical applications. @2006 American Institute of Physics.

(Pb, La)(Zr, Ti)O3 PLZT thin films were grown on Pt/Ti/SiO2/Si and fused quartz substrates by radio-frequency magnetron sputtering at 650