PLZT thin films from a stoichiometric (9/65/35) commercial target were laser deposited using the second and third harmonics of a nanosecond Nd:YAG laser. The films were grown on oriented sapphire substrates and analysed by X-ray diffraction, SEM and EDX techniques. The influence of the deposition parameters laser fluence and substrate temperature on the physical characteristics of the films is presented.

High quality epitaxial BaTiO3 and SrTiO3 have been grown on MgO, stabilized at a one unit cell height, and grown to film thicknesses of 0.5 - 0.7 μm. These relatively thick films remain adherent when thermally cycled between growth temperatures and room temperature, are crack free with high optical quality, and have both in-plane and out-of-plane X-ray rocking curves of 0.3–0.5°. These films have been grown using molecular beam epitaxy (MBE) methods starting with the TiO2 layer of the perovskite structure. The TiO2-Iayer/MgO interface uniquely satisfies electrostatic requirements for perovskite heteroepitaxy and provides the template structure that leads to the high quality films that are obtained. Wavelength dependence of optical loss has been characterized between 475 nm and 705 nm with loss coefficients < 1dB/cm being obtained at the He-Ne wavelength.

Raman spectroscopy was used to examine the structure of polycrystalline and epitaxial barium titanium oxide thin films grown by metal-organic chemical vapor deposition. The Raman spectra confirmed the presence of the tetragonal ferroelectric phase of BaTiO3 and also revealed several other Ba-Ti-O phases. These films were also characterized by X-ray diffraction and TEM imaging. The structural information provided by the Raman spectra was qualitatively consistent with the X-ray and TEM results. The temperature dependencies of the Raman spectra of two films were examined in the range 25°C-175°C. Raman peaks due to tetragonal BaTiO3 were observed at temperatures well above 132°C, which is the tetragonal-cubic phase transition temperature for bulk single-crystal BaTiO3. This may indicate stabilization of the tetragonal phase by an anisotropic film-substrate interaction or by inter-grain stresses.

Iron-doped sapphire thin films have been successfully epitaxially grown onto sapphire single crystal substrates by electron beam deposition and subsequent thermal annealing. Amorphous A12O3 thin films, about 280–390 nm thick, cation doped with iron have been deposited on [0001] oriented sapphire substrates. Iron doping with cation concentrations (a ratio of Fe content to total cation content) up to 5 at.% can be incorporated into the octahedral sites of Al-cation sublattice during the epitaxial regrowth process at 1000–1400 C, as determined by Rutherford Backscattering Spectrometry and ion channeling measurements. Cross-sectional Transmission Electron Microscopy shows the presence of two distinct regions in the annealed films. One exhibits the epitaxial relationship with the sapphire substrate and the second region has amorphous type of contrast. External optical transmittance measurements in the ultra violet and visible light range have exhibited the absorption associated with Fe3+. This study has demonstrated a simple method of incorporating dopants into single crystal sapphire, which has potential in the fabrications of thin film planar optical waveguiles.

Hetero-epitaxial PbTiO3 films have been grown on different oxidic substrates. The orientation (the c or a axis being perpendicular to the substrate surface) and the morphology of the PbTiO3 film have been studied with transmission electron microscopy and X-ray diffraction. For non-volatile memory applications ferroelectric capacitors consisting of PbZrxTi1-xO3 films and Pt electrodes are most commonly used. The microstructure of PbZrxTi1-xO3 films (x=0.36 and x=0.71) grown on oxidized silicon provided with a Ti/Pt electrode, will be discussed in relation to the ferrroelectric properties. Finally, the use of La0.5Sr0.5CoO3 as an oxidic electrode is considered.

Studies performed by our group on orientation-microstructure-property relationships of Pb(ZrxTil1-x)O3 (PZT) / metal or metal-oxide layered heterostructure are reviewed. The work discussed is related to the synthesis and characterization of ferroelectric PZT and conductive Pt, RuO2, and Lao.5Sr0.5CoO3 layers and their integration into heterostructure capacitors suitable for non-volatile memories. The main objective of our research was to determine the influence of deposition techniques and their related parameters and layer processing on the orientation, microstructure, and properties of PZT-based capacitors, with the goal of controlling electrical properties such as polarization fatigue, retention, and imprint effects, in order to produce commercial non-volatile ferroelectric memories. The work discussed relates to the synthesis of films by ion beam sputter-deposition (IBSD), and pulsed laser ablation deposition (PLAD), where the heterostructures are grown in-situ without exposing the interfaces to uncontrollable atmospheric conditions. Comparisons are presented between orientation and microstructural characteristics and properties of PZT heterostructure capacitors produced by IBSD and PLAD and those synthesized by the sol-gel technique. The work reviewed indicates that substrate and template layers (at the ferroelectric/bottom electrode interface) and/or bottom electrode material type contribute to the control of orientation and/or microstructure, and properties of PZT-based capacitors.

Epitaxial PbTiO3 thin films have been grown on single-crystal MgO (100) substrates using metalorganic chemical vapor deposition technique. The energy gap was determined from optical absorption data to be Eg= 3,425 eV. Secondary ion mass spectrometry data showed uniform distribution of Pb, Ti and O atoms with no traces of carbon contamination. Atomic force microscopy studies showed different surface morphology for different film growth rates. In-situ X-ray diffraction data indicate that the tetragonal-to-cubic structural phase transition occurs at about 500–520°C. Above 750 °C the films exhibit multi-phase character, the textured PbTiO3 phase co-existing with a polycrystalline Pb2Ti2O6 structure and a possible Mg-containing impurity phase.

The in-situ reactive sputter deposition of PbTiO3 on Pt/Ti/SiO2/Si from two metallic targets was investigated. A minimal lead oxide flux of two to three times the titanium oxide flux is needed in order to obtain stoichiometric films with the perovskite structure. For higher fluxes, the Pb/Ti ratio in the film stays at the stoichiometric value 1; the orientation changes from random to <100>; and the film morphology transforms from a rough to a smooth polycrystalline film. The obtained dielectric constants vary between 40 and 150, the losses between 2 and 4 % (10 kHz). The method could be extended to PbZrxTi1-xO3 for x ≤0.7. The orientation is lost when the Pt electrodes are replaced by RuO2 electrodes.

Multilayer epitaxial ferroelectric PbTiO3 and SrTiO3 thin films were grown alternatively on single crystal SrTiO3 (001) substrate by the sol-gel technique in this study. Lead titanium double metal alkoxide and strontium titanium double metal alkoxide were used for dip coating. By controlling the dip coating speed and the concentration of sol-gel solution, different thickness of films was obtained. The average thickness of each PbTiO3 or SrTiO3 layer was 120 Å which was measured by SEM method. By using XRD the structure of the epitaxial multilayer films was examined. The epitaxial PbTiO3 and SrTiO3 thin films could be obtained at 700°C and 800°C respectively. The change of transmittance with wavelength on 12( 6×[SrTiO3/PbTiO3]) layer films was measured. The structure and the optical properties of the films were discussed.

The nature of ferroelectric aging of epitaxial BaTiO3YBa2Cu3O7 heterostructures grown by laser deposition was investigated as a function of rricrostructure in the dielctric layer. Molar amounts of SrTiO3 were then substitutionally added to analyze the effect on the rnicrostructure and electrical properties. Corresponding shifts in c/a ratio and curie temperature were correlated to changes in aging rate (%δC/decade time). Microstructural analysis was provided by high-resolution x-ray diffraction (HRXRD), and Rutherford backscattering spectroscopy (RBS). Results indicate a moderate upward shift in c/a ratios from theoretical values due to increasing lattice strain across the bilayer interface. Minimum channel yields in RBS spectra were maintained between 6–8% for BaTiO3 purities above 60 %. Dielectric measurements were conducted using an impedance analyzer equipped with an isothermal chamber capable of maintaining ±1°C. The dielectric properies were consistent with c-axis oriented BaTiO3 values (k=120, D=.02)Minimum aging rates are observed at the lower c/a ratio compositions to be as low as .07%δC/decade.

Thin films of pure barium titanate have been prepared by the sol-gel process from organomettalic sols containing titanium alkoxides and barium acetate (molar ratio [Ba]/[Ti]=l). It leads to transparent, homogeneous and adherent coatings. The influence of various parameters such as chemical concentration, viscosity, withdrawal speed and temperature of densification on film thickness is described. The films were characterized by X-ray diffraction during their heat treatment. Their crystallization temperature was observed to be around 450°C. No variations in the optical properties were observed during the crystallization, and it occurred without the appearance of cracks or pinholes. Tetragonal BaTiO3 structure was observed, and the ferroeletric properties were investigated as functions of thickness and grain size.

A new time-of-flight ion scattering and recoil spectroscopy (TOF-ISARS) technique has been developed and is now used to perform in situ, real-time analysis of ferroelectric and conductive oxide layers during growth. Initial results presented here show various major effects, namely: (a) RuO2 films on MgO substrates appear to be terminated in O atoms on the top layer located in between Ru atoms lying in the layer underneath (This effect may have major implications for the explanation of the elimination of polarization fatigue demonstrated for RuO2/PZT/RuO2 heterostructure capacitors); (b) deposition of a Ru monolayer on top of a Pb monolayer results in surface segregation of Pb until a complete Pb layer develops over the Ru monolayer; and (c) a Pb/Zr/Ti layered structure yields a top Pb layer with first evidence of the existence of Pb vacancies, which also may have major implications in relation to the electrical characteristics of PZT-based capacitors.

LaNiO3 thin films were utilized as metallic contact layers in ferroelectric capacitors. The LaNiO3 films were probably epitaxial when deposited atop (100) LaAlO3 substrates. They exhibited metallic resistivity over a wide range of temperature and oxygen partial pressure. Subsequent deposition of PZT and LaNiO3 thin films atop LaNiO3/LaAlO3 allowed realization of parallel-plate ferroelectric capacitor structures. The suitability of such devices for nonvolatile memory applications was surveyed through pulsed voltage testing. The observed 1-second remanent polarization exceeded 18 μC/cm2. Long-term memory was demonstrated for up to sixteen hours. No decrease in remanent polarization was apparent after more than 109 switching cycles.

Thin films of Bi2VO5.5 (BVO), a vanadium analog of the n = I member of the Aurivillius family, have been prepared by pulsed laser deposition. The BVO films grow along the [001] direction on LaNiO3(LNO) and YBa2Cu3O7 (YBCO) electrode buffer layers on LaA- IO3(LAO) substrates as obtained from X-ray diffraction studies. The microstructure of the films and of the interfaces within the film and between the film and the substrate were characterized using transmission electron microscopy. The in-plane epitaxial relationship of the rhombohedral LNO on perovskite LAO was [100] LNO // [100] LAO and [001] LNO // [001] LAO. High resolution lattice images showed a sharp interface between LNO and LAO. However, the LNO film is twinned with a preferred orientation along the growth direction. The BVO layer is single crystalline on both LNO/LAO and YBCO/LAO with the caxis parallel to the growth direction except for a thin layer of about 400 Å at the interface which is polycrystalline.