Raman scattering from LayRxMnO3-δ compounds (single crystals, ceramics, films) was studied as a function of kind (R) and amount (x) of dopant as well as of oxygen deficit (δ). For x = 0.1 to 0.55, a nearly linear Raman shift of the Ag mode from 240 to 125 cm−1 was observed in Srdoped compounds. While the intensity of disorder-induced Raman bands was found to be sensitive to the oxygen content, the symmetry allowed related Raman modes exhibit the changes in the frequency. As an indication of deposition conditions, lowering of a symmetry of the film structures with respect to single crystals and ceramics was detected. We discuss the physical nature of the observed effects and show how Raman data can be used for the optical characterization of manganite samples.

We put forward the hypothesis that cations with 6s electrons (Hg,Tl,Pb,Bi) in the charge reservoir layers of high Tc cuprate superconductors actively participate in the pairing interaction as negative-U centers. We further argue that the Hg-cuprates are outstanding superconductors (Tc > 160 K) because they can exist as two-ion negative-U centers, . Their electrons are less localized than in single-site centers (negative-U or bipolaron) and can have a strong pairing interaction with a smaller increase in effective mass. The centers are oriented in the x and y directions and can have phase differences compatible with the d-wave symmetry of the CuO2 planes.

We present results of first principles calculations which indicate the simultaneous occurrence of ferromagnetism and ferroelectricity in perovskite structure bismuth manganite, BiMnO3.

BaZn1/3Ta2/3O3 (BZT) ceramics are widely used in current microwave communication applications due to the material's large-dielectric constant (εr > 25), ultra-low loss tangent (tan δ < 2×10−5 at 2 GHz) and a near-zero temperature-coefficient of resonant frequency (τf∼0). In this paper, we report the first growth of epitaxial BZT thin films. The films are grown on MgO substrates using pulsed laser deposition. X-ray diffraction data indicate the films have a disordered pseudocubic perovskite structure with a small tetragonal distortion (i.e. a = b = 4.100 Å; c = 4.088 Å). An optimized substrate temperature of 575°C results in films which are over 98% oriented in the (001) direction and are relatively smooth (rms roughness of 5.2 Å). X-ray diffraction Φ scans of off-axis (202) reflection show four-fold symmetry, indicating a high degree of in-plane epitaxy, albeit with small angle grain boundaries. The refractive index of epitaxial BZT films is inferred to be 5 from Fabry- Perot fringes in optical transmission spectra. Substrate temperatures during growth are limited to ∼600°C as a result of Zn loss.

Ni,Zn-ferrite (NZF) thin films are of interest for high frequency applications because of their high saturation magnetization compared to garnet films and their low eddy current losses compared to metal alloy films. Therefore there is an increasing need for methods to deposit single crystal ferrite thin films for incorporation into next generation microwave devices.

Epitaxial thin films of NZF have been deposited by liquid delivery metal-organic chemical vapor deposition onto (100) oriented MgO substrates. The morphology, orientation and magnetic properties of the as-deposited films were investigated as a function of deposition temperature and pressure. X-ray diffraction (XRD) reveals highly oriented films with a film strain of 1.01% compared to bulk lattice parameters. Films with well saturated magnetic hysteresis were obtained under a number of conditions with values of saturation magnetization up to 270 emu/cc (3400 gauss) with relatively low coercive fields ~100 Oe. The influence of metal cation ratio on magnetic properties is discussed.

We have grown thin films of La1-xCaxMnO3 using off-axis cosputtering for x ≤ 1/3 onto (001) NdGaO3 and (100) SrTiO3 substrates from individual targets of LaMnO3 and La2/3Ca1/3MnO3. As-deposited films of La2/3Ca1/3MnO3 on NdGaO3 have a peak resistance temperature of ≈ 260 K. We see a difference in the peak temperature between the two types of substrates of ≈ 15 K, with samples on NdGaO3 having higher peak temperatures. As the value of x is reduced from 1/3, the peak resistance temperature decreases until x ≈ 0.15, when the peak temperature has an upturn. Even down to x=0 we still observe a metal-insulator transition (at 185 K) for films on NdGaO3, while samples on SrTiO3 show only activated behavior. We also find a scaling relationship between the peak temperature and the resistivity activation energy of the films.

The Ta-doped PZT films (PTZT) were deposited on Pt/TiO2/SiO2/Si(001) substrates by pulsed laser deposition using La1-xSrxCoO3 buffer layers. The grain orientation of PTZT films is strongly influenced by the cation ratio of La1-xSrxCoO3. The PTZT films deposited using La0.75Sr0.25CoO3 with rhombohedral structure prefer (110)-orientaion, and those deposited using La0.25Sr0.75CoO3 with psuedo-cubic structure prefer (001)-orientation. It is found that the fatigue property of the PTZT capacitors can be improved enormously by using (001)-oriented La0.25Sr0.75CoO3 bottom electrodes. SEM morphology pattern for the surface of PTZT films and for the cross-section show that no obvious interdiffusion occurs across the interfaces. The ferroelectric capacitor La0.25Sr0.75CoO3/PTZT/La0.25Sr0.75CoO3/Pt/TiO2/SiO2/Si(001) shows almost no degradation in its polarization after 1.5×1010 switching cycles at an applied voltage 5 V and a frequency 1MHz.

The properties of Y2O3, ITO (indium tin oxide), and TaSi2 thin layers grown using a new in-situ ultraviolet (UV)-assisted pulsed laser deposition (UVPLD) technique have been studied. X-ray diffraction investigations showed that with respect to conventional PLD grown films under similar conditions, but without UV illumination, UVPLD grown films exhibited better crystallinity, especially for growth at low substrate temperatures, from 200 °C up to 450 °C, depending on the material. X-ray photoelectron spectroscopy investigations showed that UVPLD layers contained less physisorbed oxygen than the conventional PLD layers, exhibiting a better overall stoichiometry. These results suggest that during the ablation-growth process, UV radiation increases the surface mobility of adatoms and provides more reactive gaseous species. Both factors contribute to the crystalline growth and are especially effective at moderate processing temperatures, where the thermal energy available for the process is comparatively low.

A new wet chemical concept is presented for the preparation of electrically conducting SnO2:Sb (ATO) and In2O3:Sn (ITO) coatings. It is based on the deposition by spin, dip or spray techniques of a solution containing crystalline nanoscaled particles fully redispersable in a solvent. The particle synthesis is carried out in a solution at temperatures < 200 °C by a controlled growth reaction using SnCl4 and InCl3 as precursors and SbCl3 and SnCl4 as dopant, respectively. The aggregation of the particles is avoided by in-situ surface modification with bifunctional organic molecules. After drying the nanocrystalline particles can be fully redispersed in ethanol at pH < 6 (for ITO) or water at pH > 8 (for ATO) with solid contents up to 8.8 vol. %. Single layers with thickness up to 200 nm (ATO) and 400 nm (ITO) have been fabricated. Their sheet resistance decrease with the sintering temperature. Typical lowest values are 430 Ω□ (550 °C) for ATO and 90 Ω□ (900 °C) for reduced ITO. The resistivity of as fired ATO and ITO coatings is stable but it slightly increases with time for ITO in the reduced state. All coatings have a transmission in the visible range of about 90 %. Anti-glare conducting coatings on glass with 70 GU as well as antistatic coatings (R□ ≈ 1 MΩ□) on polycarbonate substrates have been obtained with chemically modified ITO suspensions.

Degenerately doped thin films of zinc oxide are useful in a variety of applications, including front transparent contacts to Cu(In,Ga)Se2 thin film solar cells and flat panel displays. To gauge the influence of the interface on the performance of sputter deposited ZnO:AI transparent electrodes, the structure and electrical properties of the interfacial region has been investigated during nucleation and growth of the thin films. RF magnetron sputter deposited films with thicknesses ranging from ∼20 to 1580 Å were characterized using Atomic Force Microscopy (AFM), Auger Electron Spectroscopy (AES), Hall measurements, and four point probe. AES spectra of the films with thickness between ∼20 and 60 Å exhibited clear Si (1619eV) peaks suggesting the thin films were discontinuous islands on the substrate. AFM micrographs indicated a distribution of hillocks on the surface which agrees with AES results, and suggest a Volmer-Webber nucleation and growth mechanism. Hall measurements indicated that the films had electron carrier concentrations on the order of 1019 to 1020/cm−3, mobilities of <10cm2V.s, and resistivities on the order of 10−2 to10−3Ω-cm depending on the film thickness. The possible impact of these results on solar cell performance is discussed.

The ability to fabricate sensitive and stable gas sensors which can detect low concentrations of gaseous species is necessary for many critical applications such as environmental safety monitoring. Although highly sensitive gas sensors have been produced by dispersion of catalytic metals on oxide sensing films, fouling of catalysts can cause instability in sensor performance. We have examined an approach which involves fine tuning the microstructure of tin oxide sensing films by vapor depositing an ultra-thin film of seed layer metals prior to tin oxide deposition. Metals including Fe, Sn and Pt have been investigated for their influence on tin oxide growth. Systematic studies of the growth mechanism and microstructure of CVD tin oxide using four-element arrays of “microhotplates” have revealed a number of different film morphologies which result from seeding. Enhancements in sensitivity for seeded growth relative to unseeded growth suggest a method of producing sensitive gas sensors which may not require the addition of surface catalytic layers. In this study we also demonstrate the use of microhotplates not only as sensing devices, but as excellent platforms for materials research.

Low energy density in conventional capacitors severely limits efforts to miniaturize power electronics and imposes design limitations on electronics in general. We have successfully applied physical vapor deposition technology to greatly increase capacitor energy density. The high dielectric breakdown strength we have achieved in alumina thin films allows high energy density to be achieved with this moderately low dielectric constant material. The small temperature dependence of the dielectric constant, and the high reliability, high resistivity, and low dielectric loss of Al2O3, make it even more appealing. We have constructed single dielectric layer thin film capacitors and shown that they can be stacked to form multilayered structures with no loss in yield for a given capacitance. Control of film growth morphology is critical for achieving the smooth, high quality interfaces between metal and dielectric necessary for device operation at high electric fields. Most importantly, high rate deposition with extremely low particle generation is essential for achieving high energy storage at a reasonable cost. This has been achieved by reactive magnetron sputtering in which the reaction to form the dielectric oxide has been confined to the deposition surface. By this technique we have achieved a yield of over 50% for 1 cm2 devices with an energy density of 14 J per cubic centimeter of Al2O3 dielectric material in 1.2 kV, 4 nF devices. By further reducing defect density and increasing the dielectric constant of the material, we will be able to increase capacitance and construct high energy density devices to meet the requirements of applications in power electronics.

Bismuth-doped rare-earth iron garnet thick films have become the material of choice for a wide variety of magnetooptic applications including optical isolators and circulators. Garnet compositional design and liquid phase epitaxial growth have been adapted to the requirements of these devices. Properties such as optical absorption, specific Faraday rotation, temperature dependence of Faraday rotation, saturation magnetization and temperature dependence of saturation magnetization can be controlled to a high degree. Introduction of nucleation induced coercivity has even allowed the elimination of a permanent bias magnet. However, in optimizing device performance and film growth, there are often tradeoffs among these properties. Material design is therefore a compromise based on the requirements of device designers.

We have been proposing the use of RMnO3 (R: rare earth elements) films for metalferroelectric- semiconductor field effect transistor (MFSFET)-type ferroelectric random access memories (Ferroelectric RAMs). This report describes the progress of YMnO3 and YbMnO3 films for FET type FeRAM application. Although highly (0001)-oriented YMnO3 films are easily obtained on a MgO, ZnO/Sapphire, Pt/Sapphire and Pt/Si substrates, it was very hard to obtain the crystalline films directly on Si or on SiO2/Si substrate. A Y-Mn-O buffer layer improved the crystallinity of the YMnO3 films on Si, and we got the C-V curve with ferroelectric hysteresis. The real ferroelectric component responsible for the C-V hysteresis was calculated to be just 8.4 nC/cm2 by pulse measurements. On the other hand, Y2O3 buffer layer drastically improved the dielectric properties. The window width of the C-V hysteresis does not change by changing the sweep rate and measurement frequency.

In this paper we describe the fabrication of oxide based devices similar in architecture to a conventional FET with source, drain, and gate electrodes and a channel. This distinctive characteristic of our device is the use of a channel material capable of undergoing a field-induced Mott insulator-metal transition at room temperature. Lithographic techniques developed for oxide materials have been combined with pulsed laser deposition of perovskite materials onto single-crystal strontium titanate (STO) substrates to fabricate these devices. Materials chosen for the Mott transition channel include La2CuO4 (LCO) and YBCO, p-type; and Nd2CuO4, n-type.

We report on ferroelectric/giant magnetoresistive Na0.5K0.5NbO3/La0.6Sr0.2Mn1.2O3 (NKN/LSMO) heterostructures grown onto LaAlO3 (001) single crystal using KrF pulsed laser ablation of stoichiometric ceramic target. Main processing parameters have been optimized to obtain smooth LSMO template layer, avoid NKN-LSMO interdiffusion, preserve NKN stoichiometry against the lost of volatile potassium and sodium and achieve reasonable reliability of NKN film performance. X-ray diffraction θ- 2θ scans and rocking curves evidence for single-phase content and high c-axis orientation both in template LSMO and top NKN layers. Ferroelectric measurements yield remnant polarization Pr of 1.5 [C/cm2 and spontaneous polarization Ps of 7 μC/cm2 at electric field strength of 130 kV/cm. At room temperature, dielectric permittivity ε′ and dissipation factor tan δ have been found to vary from 595 to 555 and 0.046 to 0.029 respectively in the frequency range of 0.4 to 20 kHz. At 10 kHz dielectric permittivity linearly increases from 410 to 650 in the temperature range 77 K to 415 K while the dissipation factor below 320 K does not exceed 3%.

We report on the fabrication and analysis of silicon-oxynitride (SiON) as core material for silicon-based planar photonic waveguide circuits. Features of devices made of this particular SiON material are: (1) a silicon-compatible technology (low-cost perspective), (2) a waveguide structure with high dielectric index contrast, allowing a very compact device layout (approximately 10× smaller radius of curvature than conventional doped SiO2 technology), (3) a low optical loss < 0.15 dB/cm, in the 1550 nm telecommunication window and (4) a negligible polarization dependence. The materials aspects and resulting analyses of the SiON layers as well as particular device properties are described.

A comprehensive understanding of the transport properties of interfaces in high-Tc cuprates been obtained by considering their microstructure, the possibility of bending of the electronic band structure in these materials, and the predominant dx2-y2 -symmetry of the order parameter in most high-Tc cuprates. These factors are of central importance for the critical current density and the normal state resistivity of grain boundaries and their dependencies on boundary misorientation and on applied magnetic and electrical fields. In addition, some of these factors play an important role for the transport properties of other interfaces involving high-Tc superconductors, such as superconductors-normal metal contacts.

Based on the improved understanding of the mechanisms controlling interface transport properties, we have been able to meet a long-standing challenge in high-Tc superconductivity and have increased the critical current densities of grain boundaries by large factors, using appropriate doping.

Doped manganite trilayer junction provides a model system for the study of spin-dependent transport across an artificial interface between manganites. Large interface magnetoresistance is observed in manganite trilayer junctions. Further studies reveal a strongly temperature and junction-bias dependent magnetoresistance, as well as a large interaction between the spin-polarized current and the ferromagnetic moment. The physical and materials origin of these and other junction properties are discussed in this brief review.

The present paper proposes a simple method which may be able to provide true single-crystal films of complex oxides on large substrates including semiconductors like silicon or gallium arsenide. The method describes a layer transfer process using layer splitting by hydrogen implantation and direct wafer bonding (DWB) to obtain single-crystal oxide films on different substrates. Alternatively, a fabrication process of ferroelectric-semiconductor heterostructures based on direct wafer bonding and layer transfer is also described. This process is an alternative method to the direct deposition of oxides films (ferroelectric, high-k) on silicon and allows fabrication of metal oxide-silicon heterostructures with an interface having a good structural quality as well as a low trap density.