In La0.7Sr0.3MnO3/SrTiO3/Co tunnel junctions, the half-metallic nature of La0.7Sr0.3MnO3 allows probing the spin polarization of Co. For applied voltage bias around zero volts, an inverse tunnel magnetoresistance is found, indicating the negative spin polarization of Co at the Fermi level as expected from the density of states of the “d” band in Co. The bias dependence of the magnetoresistance reflects the structure of the “d” band density of states of Co. In this article we underline the important consequences for the knowledge of the spin-dependent tunneling in solids brought by these results and describe in detail the effect of temperature and high magnetic field on the magnetoresistance.

Using pulsed laser ablation, we have grown epitaxial bilayers of strontium titanate (STO) and yttrium barium copper oxide (YBCO) on (110) neodymium gallate (NGO) substrates. Using a selective acid etch, we have removed the YBCO from the middle of the bilayer and lifted off the STO films from their parent substrates. Using coplanar interdigital capacitors patterned on the surface of the films, we have measured the capacitance and loss as a function of frequency (from 10 kHz to 1 GHz), temperature (from 300 K to 4 K), and applied electric field (up to roughly 2 V/μm). We have seen frequency dependent loss peaks in the films that indicate thermally activated behavior, and an improvement in the tuning quality.

Highly (0001)-oriented films of YMnO3 were grown on n-type Si(100) substrates by a chemical solution deposition with a modified precursor solution. Spin-coated films were crystallized by rapid thermal annealing at 650 °C, and showed improved structural and electrical properties. Capacitance-voltage (C-V) measurements at 1 MHz showed a counterclockwise hysteresis, with a memory window of 1.9 V at 9 V, due to ferroelectric polarization, and a dielectric constant of 25. The effects of mobile ionic charge and effective interface charge in the C-V measurements were found to be small by investigating the bias sweep rate dependence and flat-band voltage shift, respectively. The interface trap density near the Si midgap was obtained to be about 1.3 × 1011 cm−2eV−1 through conductance measurements. Current-voltage characteristics showed a leakage current density of 16 nA/cm2 at 3 V. An asymmetric polarization-voltage (P-V) hysteresis curve became symmetric one with a remanent polarization value of 0.1 μ C/cm2 under He-Ne laser illumination. The depolarization field in the ferroelectric film and charge compensation by the light-generated minority carriers may be responsible for the observed P-V characteristics. The low temperature fabrication of this YMnO3 film showed good structural and electrical properties for application to nonvolatile ferroelectric memory devices.

We successfully deposited high quality biaxially oriented BaxSr1-xTiO3 thin films on polycrystalline yttrium iron garnet substrates using both the metal-organic chemical liquid deposition and pulsed laser deposition methods with biaxially oriented MgO and yttriumstabilized- zirconia buffer layers. The dielectric losses of the films range from 0.005 to 0.015 while 25% of dielectric constant change was observed with 40V bias voltage up to 10 MHz. Both the dissipation and dielectric constant of the films remained nearly constants over a wide temperature range. A dual-tuning microwave phase shifter using a BST film grown on an MgO buffered polycrystalline YIG substrate was fabricated. A significant phase shift was observed in a wide frequency range when an electric bias or a magnetic field was applied to the device.

We propose the application of ZnO:X (X = Li, Mg, N, In, Al, Mn, Gd, Yb etc.) films for a monolithic Optical Integrated Circuit (OIC). Since ZnO exhibits excellent piezoelectric effect and has also electro-optic and nonlinear optic effects and the thin films are easily obtained, it has been studied as one of the important thin film wave guide materials especially for an acoustooptic device[1]. In terms of electro-optic and nonlinear optic effects, however, LiNbO3 or LiTaO3 is superior to ZnO. The most important issue of thin film waveguide using such ferroelectrics is optical losses at the film/substrate interface and the film surface, because the process window to control the surface morphology is very narrow due to their high deposition temperature. Since ZnO can be grown at extremely low temperature, the roughness at the surface and the interface is expected to be minimized. This is the absolute requirement especially for waveguide using a blue or ultraviolet laser. Recently, lasing at the wavelength of ultraviolet, ferroelectric and antiferromagnetic behaviors of ZnO doped with various exotic elements (exotic doping) have been reported. This paper discusses the OIC application of ZnO thin films doped with exotic elements.

We demonstrated a low magnetic field response in 2D array of weakly coupled ferromagnets created by bi-epitaxial growth of La0.7Sr0.3MnO3 film on multilayer template of MgO seed and CeO2 buffer layer deposited on SrTiO3 substrate. To form the array we etched the MgO seed layer into a chess board pattern. The chess board fields, where the substrate surface is disclosed, initiate a 45° in-plate rotated growth of the CeO2 buffer layer while it does not rotate on the neighboring fields covered by MgO seed layer. The La0.7Sr0.3MnO3 film inherits the template orientation of the buffer layer forming misoriented at 45° domains and a well defined 2D array of 45° grain boundaries is created. The size of the domains, correspondingly the number of grain boundaries, can be varied by changing the dimensions of the chess board fields. The multilayer structures were investigated by θ–2θ and φ-scan x-ray diffraction. A magnetoresistance of 25% by 0.5 T was measured and ascribed to the properties of the 2D array of grain boundaries.

We have studied structures used in MOM capacitors including Ta2O5/TiN/Ti, Ta2O5/Ti, Ta2O5/TaN/Ti, Ta2O5/WN/Ti, and Ta2O5/M where M = Ta, Pt, W, Al, and Si using X-Ray Photoelectron Spectroscopy. We find that Ti and Al are able to reduce the Ta2O5 to Ta, forming oxides of Ti and Al, respectively. The diffusion barrier TiN hampers the diffusion of oxygen and therefore postpone the reduction of Ta2O5 to higher temperatures. The oxygen migrates from the Ta2O5 layer and through the TIN layer to the Ti layer during the heat treatment. As judged by the temperatures at which the reduction of Ta2O5 occurs, TaN and WN are more effective oxygendiffusion barriers than TiN. Leakage current observed in AI/Ta2O5/TaN/Ta capacitors is one to two orders of magnitude lower than that observed in Al/Ta2O5/TiN/Ti capacitors.

YBa2Cu3Oy/SrTiO3/La2/3Sr1/3MnO3 heterostructures have been deposited on LaAlO3(001) and SrTiO3(001) substrates by pulsed laser deposition. First, the influence of deposition conditions on crystallinity and morphology of single LSMO films was examined. Results were used for preparation of heterostructures in tri-layer and cross-strip geometry. Cross-strip geometry was defined by direct shadow mask patterning. Different characterization techniques have been used to determine and correlate the heterostructure properties. A complete analysis of the crystal structure has been carried out with a four-circle difractometer. Morphology has been studied by scanning electron microscopy and atomic force microscopy in order to determine surface roughness and droplet density. Basic electrical properties of films have been determined.

Effective pattern transfer into (Pr,Ba,Ca)MnO3 and (La,Sr)MnO3 has been achieved using Cl2/Ar discharges operated under Inductively Coupled Plasma conditions. Etch rates up to 900 Å-min−1 for (La,Sr)MnO3 and 300 Å-min−1 for (Pr,Ba,Ca)MnO3 were obtained, with these rates being a strong function of ion flux, ion energy and ion-to-neutral ratio. The etching is still physically-dominated under all conditions, leading to significant surface smoothing on initially rough samples. Sub-micron (0.35 μm) features have been produced in both materials using SiNx as the mask.

Barium titanate (BaTiO3) 0–3 ceramic/ceramic composite thick films (∼16μm) for ultrasonic transducer applications were fabricated by a modified sol-gel process. Nano-sized BaTiO3 powder was dispersed in a sol-gel matrix of BaTiO3 to form a 0–3 composite solution. Films were prepared by spin coating and then annealed at various temperatures. The crystallization of the composite film was studied by X-ray diffraction. The dielectric permittivity and the ferroelectric properties of the film were also measured.

Ferroelectric SrBi2(Ta1-xNbx)2O9 (SBTN) thin films are under evaluation for IC memory applications. It has been reported that SrBi2(Ta1-xNbx)2O9 has higher fatigue endurance and imprint resistance than other common ferroelectric materials such as lead zirconate titanate (PZT). One of the most important technical issues for integrating ferroelectric oxide materials into IC memory applications is the degradation of ferroelectric capacitor properties from the oxide reduction from hydrogen. Hydrogen annealing processes performed to terminate dangling bonds in silicon, or, elevated temperature processes, which dissociate hydrogen, are expected to reduce the ferroelectric oxide thereby degrading the dielectric properties. Therefore, in this work, we have investigated reducing degradation of Pt/SBTN/Pt capacitors due to hydrogen exposure by evaluating the compositional dependence of the Ta/Nb ratio and incorporating TiN as a hydrogen diffusion barrier. To investigate compositional dependence, the Pt/SBTN/Pt capacitors with the desired composition were fabricated from enhanced metal organic decomposition solutions that were spin deposited and delineated with a conventional patterning and etching techniques. Post annealing the samples in H2 (1%)-N2 ambient at 200°C for 10–60min, hysteresis and current-voltage measurements were conducted to evaluate any degradation to pre-anneal measurements. This experimental condition revealed that the best electrical characteristics were obtained with the Ta/Nb ratio of 1.5/0.5. Therefore, Pt/SBTN/Pt capacitors with a Ta/Nb ratio of 1.5/0.5 were evaluated using a TiN barrier and its effect characterized. After depositing a TiN film on the Pt/SBTN/Pt capacitors, the samples were annealed in H2 (5%)-N2 at 400°C for 10–60 min. The TiN was removed with NH4OH: H2O2: H2O = 1: 3: 1, respectively, at 60 - 70°C and the hysteresis and current-voltage characteristics of the capacitors measured. It was found that the degradation was extremely reduced by incorporating a TiN barrier. Moreover, the degradation effects decreased with increased density of the deposited TiN film. TiN densities greater than 3.8g/cm3 in these experiments kept the leakage current degradation to less than 10−6A/cm2 while the degradation in remanent polarization is less than 20%.

YbMnO3 (Yb/Mn = 0.96) thin films were prepared on Y2O3(111)/Si(111). Although the sample exhibited ferroelectric type C-V hysteresis, the window width changed depending on the applied bias voltage. Hence, the ferroelectric type hysteresis might include the effect of space charge. To make clear the C-V behavior caused by only ferroelectricity, and to obtain the optimal relationship between ferroelectric and insulator layer thicknesses, the C-V behavior at high frequency was computed for MFIS structure. Relationships between the counter bias voltage applied to the ferroelectric layer and the thickness of dielectric layer were also demonstrated. Compared with the calculated results, experimental C-V characteristics are discussed.

We report measurements of low frequency 1/f excess noise for the series of La0.75Sr0.25MnO3 (LSMO) giant magnetoresistive thin epitaxial films with thickness of 42, 50, 100, and 600 Å. Fabricated manganite films experience semiconductor-normal metal (paramagnetic-ferromagnetic) phase transition with the temperature change. The transition manifests itself by the sharp change of resistivity and characteristic peak of magnetoresistivity. Thickness decrease results in lowering the transition temperature and increasing of resistivity. The noise spectra has 1/fa behavior with a ≈ 1± 0.2. The voltage fluctuations spectral density shows quadratic dependence on current indicating that observed noise is caused by the resistance fluctuations. Noise level, temperature coefficient of resisistvity and magnetoresistance increase for thin films. Therefore, the operation point (transition temperature) can be tailored from 330 K to 220 K by changing only the film thickness while the performance of temperature and magnetic field LSMO sensors can be maintained almost constant in thickness range down to 100 Å.

This paper reviewed work to date on multicomponent oxides deposited, utilizing openatmosphere Combustion Chemical Vapor Deposition for electronic applications. Epitaxial barium strontium titanate and strontium titanate thin films were deposited on (100) MgO single crystal substrates. They were patterned to form interdigitated structures for electrically tunable devices, namely, coupled microstripline phase shifters (CMPS). The undoped, as-deposited perovskite dielectrics exhibited a figure of merit of 53°/dB at 20 GHz and 23°C, indicating high degree of tunability and fairly low loss. High-permittivity (ε=263), polycrystalline BST and SrTiO3 were studied for dynamic random access memory, and leakage current density of 10−7 A/cm2 was measured. Intended for non-volatile ferroelectric memory, lead zirconium titanate was deposited onto a seed layer of perovskite structure to prevent the growth of the unwanted pyrochlore phase. To function as buffer layers for superconductor applications, epitaxial CeO2, YSZ, SrTiO3, LaAlO3, Y2O3, and Yb2O3 coatings on single crystal and textured nickel substrate were investigated. Electronic analyses and characterization, using SEM, EDS, XRD, and X-ray pole figures, were presented.