Structure of (Ba0.7Sr0.3)TiO3 films prepared by chemical solution deposition during crystallization on a sublayer

Barium strontium titanate (BST) films on Si-SiO₂-Ti-Pt substrates are prepared by chemical solution deposition upon crystallization on a sublayer. The structure of the BST films is investigated using transmission electron microscopy, high-resolution electron microscopy, and x-ray diffraction analysis.     

Nonlinear-optical and micro-Raman diagnostics of thin films and nanostructures of ABO3 ferroelectrics

Ferroelectric composite two-dimensional ferroelectric/aluminum oxide nanostructures were studied. A porous aluminum oxide matrix was used as a template into which a ferroelectric precursor was introduced, followed by annealing. The prepared nanostructures were studied using optical second harmonic generation and micro-Raman scattering.     

Laser Annealing of Thin-Film Ferroelectric Heterostructures

Preliminary experiments on laser annealing of ferroelectric samples by ultraviolet radiation of a KrF laser are carried out. In principle, laser annealing allows one to reduce appreciably the duration of thermal action, minimize the size of the samples treated, and control the crystallization processes in the samples. A special focussing system was employed to provide homogeneous irradiation of the spot with dimensions of ~1×1 cm² within a broad energy range from 0.1 to 10~J per pulse. The range of energy densities leading to phase transitions in thin films is determined.     

Leakage currents in thin ferroelectric films

The basic mechanisms of leakage current components of thin lead zirconate titanate (PZT) ferroelectric films grown by the sol-gel method have been studied. Characteristic regions of current-voltage characteristics with different charge transport mechanisms have been determined. It has been shown that there is an intermediate region which separates such regions. In one of them, the leakage current depends on properties of the contact of electrodes with PZT film at low voltages; in the other, the leakage current is controlled by intrinsic properties of the PZT film bulk, and the basic mechanism of charge transport is Poole-Frenkel emission. In the intermediate region, a stepwise change in the current has been observed, which is caused by relaxing breakdown of the Schottky barrier. Time dependences of the leakage currents have been determined. It has been shown that the leakage current decreases with increasing delay time before the Schottky barrier breakdown, and the dependence becomes opposite in character after the breakdown.     

Thin ORMOSIL Films with Different Organics

Structural, optical and electrical properties of silicate films modified by structure fragments containing different organic groups were studied. The ORMOSILs were produced by a cohydrolysis of tetraethoxysilane with different types of alkyl (aryl) substituted alkoxysilanes. Film structure and its evolution during heat treatment were studied by ellipsometry and IR spectroscopy. For methyl- and phenyl-modified silicate films the shrinkage is lower than for silicate ones in the range of annealing temperature from 200 to 500°C. The shrinkage of phenyl-modified silicate film is more than three times lower than of methyl- and trimethyl-modified ones. The presence of single or double C=C bonds in the organic chain leads to an increase in the film shrinkage due to the thermodestruction of the bond as it is confirmed by IR data. In the case of phenyl- and methyl-modified silicate films this process starts from 500°C and it is accompanied by abrupt film shrinkage. The dielectric constant and the loss tangent of methyl and phenyl groups decrease due to reduction of hydroxyl content and film density. Other groups are not effective due to their thermodestruction at lower temperatures.     

Porous silicon-based ferroelectric nanostructures

A procedure is suggested for the preparation of porous silicon-based ferroelectric nanostructures. It is demonstrated that the method of chemical deposition from solutions provides for the penetration of the initial components of the solution into the matrix pores, and subsequent annealing leads to the crystallization of the ferroelectric phase. The diagnostics of the ferroelectric properties is performed using the method of generation of second optical harmonic. The spectral characteristics of the prepared ferroelectric nanostructures are investigated.     

Nonlinear optical and electrostatic force microscopy for ferroelectric polarization imaging

Second-harmonic generation (SHG)-based nonlinear optical microscopy is used for spatially resolved imaging of the polarization switching in lead zirconium titanate ferroelectric thin films. The local SHG hysteresis loops reveal a strong dependence on film composition and structure. The SHG microscopy results are in good agreement with the efficiency of electrostatic force microscopy writing and allow us to predict the microscopic dielectric memory efficiency, both in contact and contact-less ways. Received: 15 January 2001 / Revised version: 27 March 2002 / Published online: 6 June 2002     

The Mechanisms of Absorption of Terahertz and Infrared Radiation in PZT Films

Physics of the Solid State - Terahertz and IR spectra of dielectric response of dense and porous Pb(Zr,Ti)O3 films deposited on single-crystal magnesia and alumina substrates and on silicon...     

Electrodynamic properties of lead Zirconate-Titanate thin films in the terahertz frequency range

The transmission/reflection spectra of bilayer structures consisting of thin amorphous and polycrystalline Pb(Zr_0.52Ti_0.48)O₃ ferroelectric films deposited on dielectric substrates of magnesium oxide MgO and sapphire α-Al₂O₃ were measured in the frequency range of 5–4000 cm^?1. Based on these spectra and using the dispersion analysis method, the spectra of complex dielectric permittivity ?*(ν) and dynamic conductivity σ′(ν) of the films were simulated, the electrodynamic parameters of the films were determined, and the dielectric dispersion responsible for the formation of static permittivity was found.     

Ferroelectric Thin Films of Bismuth Strontium Tantalate Prepared by Alkoxide Route

Study of the interactions in Bi(OR)3-Ta(OR)5-ROH (R = Me, Et, iPr) at 20°C show that metal ethoxides are the best of the investigated precursors for the production of bismuth tantalates via alkoxides. Polycrystalline SrBi2Ta2O9 (SBTO) and BiTaO4 films on Si-SiO2-Ti-Pt substrates with thicknesses of 0.4–0.5 m and 0.4 m, respectively, have been formed by sol-gel processing. The most stable solutions for film application were obtained by using mixed-metal Bi-Ta ethoxides and solutions of Sr carboxylate (2-ethylhexanoic acid derivative) in 2-ethylhexanoic acid. Films annealed at 700–750°C for 30 min were single-phased. SBTO films demonstrated good ferroelectric properties: remanent polarization ranged from 3.5 to 4.0 C/cm2 and coercive voltage 1.5–2.0 V, whereas BiTaO4 films showed dielectric behavior.