Strontium ruthenium oxide (SrRuO3) was deposited on Pt/(100)Si substrates at varying temperatures and 300 mTorr oxygen pressure using the pulsed laser deposition method and was found to be highly crystalline and textured when deposited over 450°C. After achieving highly crystalline SrRuO3 films, capacitors using the ferroelectric material - PZT (PbZr0.5Ti0.48O3) were successfully fabricated on Pt/(100)Si substrates. The ferroelectric properties of the films were determined by the RT66A Standardized Ferroelectric Test System. The structural properties of the films were analyzed by X-ray diffraction. Transmission electron microscopy was used to determine the crystallinity and quality of interfaces among different layers.

Vacancy type defects in bulk La1−xSrxCoO3−δ samples were investigated by positron lifetime spectroscopy. The effects of Sr-doping as well as the effect of oxygen deficiency were determined. Comparing the resolved lifetimes with calculated values permits defect identification.

Transition metal oxides with perovskite structure exhibit a wide range of electrical properties. SrRuO3 (SRO), a perovskite oxide with high conductivity, finds applications as an electrode layer in ferroelectric devices and as a barrier layer in superconductor-normal metal-superconductor (SNS) Josephson junctions involving high Tc superconductors. Here we report on the structure and properties of thin SRO films on SrTiO3 (100) substrates grown by pulsed laser deposition. AFM investigations revealed that the SRO films exhibit island growth. The island size increases with thickness, and at a typical thickness of about 20 nm a connected network of islands is formed. The resistivity of the SRO films grown at different substrate temperatures (700 °C - 850 °C) exhibits metallic behavior with a ferromagnetic transition at 150 K. The films with typical thicknesses of 20 nm, grown at a substrate temperature of 775 °C exhibited the lowest resistivity of 200 μΩ-cm at 300 K, whereas the films grown at lower (700 °C) and higher (850 °C) temperatures showed a much higher resistivity at 300 K. By AFM and high resolution TEM investigations, this behavior is correlated with the atomicscale structure of the films. The film with the lowest room temperature resistivity showed an almost defect-free orthorhombic structure, whereas the film grown at 850 °C contained structural defects in high density, such as SrO-rich antiphase boundaries and twins located at the boundaries between the islands. The films grown at 700 °C showed a cubic perovskite structure, which is obviously the reason for their high resistivity.

Pt/SrBi2Ta2O9(SBT)/CeO2/Si (MFIS) structures were investigated for observing the change of electrical properties and morphology of interface of Pt/SBT after post-annealing of Pt top electrodes. The morphology of Pt/SBT interface became smooth and Bi oxide was formed at the bottom of Pt top electrode after post-annealing Pt top electrode. In order to describe the origin of these changes, Bi-oxide/Pt/SiO2/Si structure was investigated with annealing temperatures about the reaction between Bi oxide and Pt. We can describe that the smooth interface of Pt/SBT and the consumption of metallic Bi, which the reason why electrical properties were drastically improved, is induced by the melting of Pt-Bi alloys and formation of Bi-oxide after post-annealing Pt top electrode.

Pulsed Laser Deposition (PLD) was used to deposit Pb(Zr,Ti)O3 thin films on high-grade steel Hastelloy. This material is suitable as substrate and electrode material as well. The deposited films were characterized with respect to their structural (XRD, RBS), topological (AFM) and their ferroelectric properties (P(E) hysteresis, retain and fatigue) which were found to be excellent. The ferroelectric properties in general, are sensitive to structural modifications and chemical doping and could therefore be influenced by ion implantation. Several species of ions (Ca+, O+) show different influence on the ferroelectric behavior and on the structural defects of the films. A subsequent annealing process can partially restore these modifications. The implanted Ca+ films were characterized by dielectric spectroscopy dependend on frequency and temperature to get information about ferroelectric domains.

The effect of various electrode materials on the ferroelectric properties of SrBi2Ta2O9 (SBT) thin films has been investigated for non-volatile memory applications. Two sets of electrode structures, viz., Pt-Ir based and Pt-Rh based, were sputter deposited in-situ on Si substrates. SBT thin films were deposited on these electrodes using a metal-organic solution deposition technique followed by a post-deposition anneal at 750 °C in oxygen. Structural characterization revealed a polycrystalline nature with predominant perovskite phase in SBT thin films. Ferroelectric properties were studied in capacitor mode by depositing top electrodes, where the top electrode material is identical to that of the bottom electrode. Extensive analysis of the ferroelectric properties signify the important role played by the electrode material in establishing the device applicability is reported in this work.

We report on the use of Ti1−xAlxN as an electrically conductive barrier layer from the viewpoint of its oxidation kinetics and electrical properties. Auger electron spectroscopy depth profile analysis revealed the improvement of oxidation resistance with Al incorporation. At 650 °C, an oxygen diffusion coefficient and an activation energy of Ti0.47AI0.53N were determined to be 5.85×10−1 Å 2/sec and 2.51 eV respectively. Compared with TiN, this corresponds to an oxide gowth rate reduction of about two orders of magnitude. An Al-rich oxide layer, which gew near the Ti1−XAlxN surface, is believed to act as a passivation layer to oxidation. Furthermore, current-voltage characteristics showed that the oxidation resistant Ti1−xAlxN minimized the increase of electrical resistance after heat treatment in an oxidizing atmosphere. These results suggest that Ti1−xAlxN is an attractive candidate for an electrically conductive barrier layer for advanced memory device applications.

We have investigated the electrode-barrier properties of Ir for PZT-based nonvolatile memories. Ir layer was rf-sputtered onto a poly-Si coated Si wafer. PZT thin films were deposited on Ir/poly-Si/SiO2/Si by means of sol-gel spin coating. Highly c-axis oriented perovskite PZT thin films were obtained, which might be due to the interface-controlled growth. We found that Ir in itself acted as an oxygen barrier, which was confirmed from the measurement of P-E hysteresis loops with the electrical contact between top-electrode and bottom-poly-Si. Remanent polarization and coercive field of 1rO2/PZT/Ir/poly-Si capacitor were 20 μC/cm2and 30 kV/cm, respectively and the capacitor showed negligible polarization fatigue up to 1011 switching repetitions. However, the leakage current density at the field of larger than 80 kV/cm was high, which was believed to be related to the unknown phase in PZT caused by the reaction of PbO with bottom-Ir. Such high leakage current behavior could be successively improved by the insertion of vacuum-annealed IrOx buffer layer between PZT/Ir. The electrical properties of IrOx/PZT/annealed-IrO2Ir/poly-Si capacitors are also discussed.

Bismuth-based layer-structured ferroelectric oxides are gaining much attention for ferroelectric thin film applications due to their low fatigue. Epitaxial thin films of these layered ferroelectric oxides grown on epitaxial perovskite-type conducting oxide electrodes such as LaNiO3 are known to further improve the fatigue resistance. In this paper the ferroelectric properties of BaBi4Ti4O15films grown by pulsed laser deposition on epitaxial LaNiO3/SrTiO3(100) and LaNiO3/YSZ/Si(100) substrates are presented. BaBi4Ti4O15thin films with mixed a - and c - orientation exhibit ferroelectric hysteresis loops with a remanent polarization Pr of 2 μC/cm2and a coercive field Ec of about 75 kV/cm. The effect of the deposition parameters on thin film orientation, morphology and the ferroelectric properties of BBiT are discussed.

A systematic study is presented of the resulting SBT films deposited by PLD at substrate temperatures from 300 to 600°C. The characteristics of the film as-deposited are determined. Special attention is focused on the compositional and structural properties. XRD, SEM, and TEM analyses are reported.

The stoichiometric La-Ti doped strontium-barium niobate ceramic system was obtained for different concentrations of Titanium ions (Ti=1,3,5,10,30,50 %), where the Nb5− was substituted by Ti4+ according to the following expression Sr0.255 La0.03Bao0.7Nb2−yTiyO6−y/2 (LSBN-BST). The oxygen vacancies thus created which, together with the vacancies in the A sites of the tetragonal tungsten-bronze (TTB) material structure, have an important influence on their texture and dielectric properties, due to the crucial role of the occupancy of the crystallographic sites. X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and thermoelectric analyses are reported. We report the first results for thin films of LSBNT- 7 % obtained by the PLD technique. The diffraction pattern reveals the presence of the LSBNT structure without annealing.

A new chemical route using an alkanolamine chelating agent for synthesis of ferroelectric Sro0.8Bi2.3Ta2O9 (SBT) thin films is investigated. The addition of alkanolamine provided stability to the SBT solution by retarding the hydrolysis and condensation rates. This solution could be stored for 30 days without any appreciable change of the properties. The crystallinity and the microstructure of the SBT thin films improved with increasing annealing temperature, and strongly influenced the ferroelectric properties. This alkanolamine modified films annealed at 800 °C exhibited low voltage saturation, high remanent polarization and resistance to fatigue after 1010 switching cycles. These electrical properties are favorable for non-volatile memory applications.

SrBi2Ta2O9thin films doped with barium ions were studied, in which Ba/(Sr+Ba) = 0.3 and 0.5, meanwhile the content of (Sr+Ba) remains unity to keep the stoichiometry of SrBi2Ta2O9. Films were deposited using metalorganic decomposition method with spin-on coating. Crystallinity, surface morphology, and ferroelectric properties of prepared thin films were investigated. From X-ray diffraction (XRD) analysis, barium ions substituted strontium ions in the SrBi2Ta2O9 lattice. Shift of diffraction peaks was observed, indicating a slight distortion of the lattice while barium ions incorporated into. The observation of prepared films indicated that the grain size of films annealed at 750 °C was about 0.7∼0.8 μm. Such barium incorporated SrBi2Ta2O9 thin films exhibited higher remanent polarization than the intrinsic SrBi2Ta2O9thin films.

Effects of off-stoichiometry and Nb substitution on the dielectric anomaly and ferroelectric properties have been investigated for SrBi2Ta2O9(SBT) thin films. Local atomic environment for the stoichiometric and off-stoichiometric SBT films has been also measured. The features of the dielectric anomaly, the Curie temperature (Tc), and the temperature dependence of the spontaneous polarization (Ps) are independent of the film thickness, and are governed by the nature of the crystal. For the stoichiometric Sr content SBT films, the grain size increases and the temperature dependence of the remanent polarization (Pr) decreases with increasing thickness. For the films with Sr/Bi/Ta = 0.8/2/2 and 0.8/2.2/2, Sr deficient local structure was observed, and such lattice structure probably leads to higher Tc than the stoichiometric crystal. Nb substitution for Ta also raises Tc, and makes the dielectric anomaly sharper. The phase transition associated with the dielectric anomaly for these films is thought to be first-order.

The polarization suppression and electrical properties directly associated with the electrical polarization fatigue in SrBi2Ta2O9system were systematically investigated using Pt/SBT/Pt capacitors. Three general observations were made after 109 switching cycles: (i) ∼95% of the remanent polarization was conserved, (ii) both high and zero bias field capacitance decreased, and (iii) leakage current density increased from approximately 10−7 to 10−5 A/cm2at ∼30kV/cm2. In addition, the “knee” field, at which the leakage abruptly increases, assumed smaller values with cumulative switching cycles. Temperature dependent leakage data was collected for both as-deposited and field-cycled samples. Based on these results, we propose the possibilities of enhanced concentration of charge carriers or additional reductions in interfacial conduction barriers. Motion of oxygen vacancies to less-shallow energy levels near electrode/ferroelectric interface may allow this mechanism to occur.

Thin films of ferroelectric (SrBi2Ta2O9)x(Bi3TiNbO9)1−x layered structure were prepared for x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0, by metal organic solution deposition method on Pt/TiO2/SiO2/Si substrates. The micro-Raman studies reveal that the samples are mostly homogeneous. The Raman sprectrum for the film with x = 0 shows bands around 60, 170, 232, 256, 337, 569, and 839 cm−1, which indicate Bi3TiNbO9 (BTN) formation. The prominent band around 839 cm−1, which is an A1g mode of the orthorombic symmetry, corresponds to symmetric stretching of the BO6 octahedra. The frequency of this band is found to shift significantly as SrBi2Ta2O9(SBT) material is added to the BTN compound. In this paper, the evolution of the Raman bands with the inclusion of SBT material are presented and discussed. Finally, The Raman spectra of SBT- BTN films are compared with those obtained in SBT-BTN bulk ceramics.

Ferroelectric layered perovskite strontium bismuth niobium oxide SrBi2Nb2O9(SBN) ceramics and films were made by sol-gel processing. A multiple step hydrolysis-condensation process was applied to the synthesis of the SBN sol by using inorganic salts as precursors with citric acid as a complexing agent. Single phase polycrystalline SBN was obtained after heat-treatment at 650°C. It was found that the dielectric constants of SBN ceramics were dependent on heat-treatment. SEM, XPS, TGA/DTA and XRD analyses indicated that bismuth-deficiency may contribute to the relatively low dielectric constants. While a prolonged firing time at high temperatures may lead to a lattice expansion resulting in a significant decrease of the dielectric constant. C-oriented SBN films were obtained by dip-coating onto SrTiO3 substrates and the films are dense and crack-free with a thickness of 900 nm.

We describe Chemical Solution Deposition (CSD) processes by which Strontium Bismuth Tantalate (SBT) thin films can be prepared at temperatures as low as 550°C. In this paper, we will present strategies used to optimize the properties of the films including solution chemistry, film composition, the nature of the substrate (or bottom electrode) used, and the thermal processing cycle. Under suitable conditions, ∼1700 Å films can be prepared which have a large switchable polarization (2Pr >10μC/cm2), and an operating voltage, defined as the voltage at which 0.80 × 2Prmax is switched, 2.OV. We also describe an all-alkoxide route to SBT films from which SBT can be crystallized at 550°C.

The imprint behavior of CSD processed SrBi2Ta2O9 (SBT) thin films has been investigated as a function of time, applied bias, illumination with band gap light and post anneal under different oxygen partial pressures. Applying a bias in the direction of the polarization enhances the tendency of the capacitor to exhibit a voltage shift as well as illuminating the poled capacitor with band gap light. Post anneal after top electrode deposition and patterning under slightly reducing atmospheres does not affect the imprint rate. From these experimental results, a model is presented which explains the imprint behavior of SBT films by transport of electronic charges from the electrodes into the film and subsequent trapping of these charges near the interface.

SrxBiyTa2O5+x+3y/2 (SBT) is a promising material for ferroelectric random access memories (FeRAM's) because of its inherently high resistance to fatigue and imprint. Metalorganic chemical vapor deposition (MOCVD) offers the ability to produce high quality, conformal SBT films for both high and low density memory applications. An MOCVD process based on liquid delivery and flash vaporization has been developed which allows precise control of film stoichiometry and thickness. In this study, wavelength dispersive x-ray fluorescence and x-ray diffractometry have been used to survey composition and preferred crystallographic orientation (texture) relationships. It is shown that as-deposited film composition can be used to influence the texture of the Aurivillius phase in the annealed film. The polarization of the films increases with increasing (115) and (200)/(020) peak intensity due to the relationship of the electric field direction with the polarization direction in the film. The highest values of polarization are found with Sr content, x<0.8 and Bi content, 2.1 <y<2.6.