Solid-state electrochemical cells with dense oriented thin film electrodes of La 0.5 Sr 0.5 CoO 3Ϫ␦ (LSCO) were prepared on (100) surfaces of single-crystal disks of yttria-stabilized zirconia (YSZ) by the pulsed laser deposition technique. Oxygen exchange at the electrodes was studied with alternating current impedance spectroscopy under various temperature and oxygen partial pressure conditions. Three distinctive features were observed in the impedance spectra from high to low frequency corresponding to contributions from the ionic conduction of the YSZ electrolyte, ionic transfer at the LSCO/YSZ interface, and the oxygen exchange on the LSCO electrode surface. An equivalent circuit model of the electrode process is used to fit the impedance data. The time constant for the oxygen surface exchange was derived from the impedance simulation. The surface chemical exchange coefficients, k chem , were calculated from the time constants as a function of temperature and pO 2 . k chem is 7 ϫ 10 Ϫ4 cm/s at T ϭ 700ЊC and pO 2 ϭ 1 atm. The activation energy at pO 2 ϭ 1 atm is Ϸ1.1 eV. The interfacial conductivity data were also derived from the impedance simulations as a function of temperature and pO 2 . The activation energy for the interfacial transport at pO 2 ϭ 1 atm is Ϸ1.6 eV.

Dielectric Ba0.6Sr0.4TiO3 thin films were epitaxially grown on (001) MgO by using pulsed laser ablation. Microstructure studies from x-ray diffraction and electron microscopy suggest that the as-grown films are c-axis oriented with an interface relationship of 〈100〉BSTO//〈100〉MgO. A room temperature coupled microwave phase shifter has been developed with a phase shift near 250° at 23.675 GHz under an electrical field of 40 V/μm and a figure of merit of ∼53°/dB. The performance of the microwave phase shifter based on the epitaxial Ba0.6Sr0.4TiO3 thin films on (001) MgO is close to that needed for practical applications in wireless communications.

Highly conductive perovskite La0.5Sr0.5CoO3 thin films were grown on (012) LaAlO3 by pulsed-laser deposition at different substrate temperatures. Magnetoresistance (MR) measurements show only a negative effect for the films grown at a temperature of 800 °C. However, a positive MR effect was found for the films grown at lower temperatures of 400 and 500 °C. The sign of the magnetoresistance changed from positive to negative near 150 K under an applied magnetic field of 5.0 T, and the largest positive MR of 2.6% was obtained at a temperature of 4.2 K for the film grown at 500 °C. Low-temperature magnetic hysteresis of the films was also studied, and it is suggested that the scattering of the carrier at the domain boundary may lead to the positive-MR effect.

This paper will review the recent progress of the Texas Center for Superconductivity concerning the epitaxial growth of ferroelectric Bal-,Sr,Ti03 thin films on various substrates using pulsed laser ablation. Microstructure studies from X-ray diffraction and electron microscopy suggest that the as-grown films on (001) LaAIO, and (001) MgO are c-axis oriented with excellent single crystallinity. The Rutherford Back-Scattering Spectroscopic studies indicate that the films have excellent epitaxial behavior. Microwave property measurements showed that the room temperature dielectric constant could be tuned up to 33% at 2.33 V/Km applied electric field. The coupled microwave phase shifter has achieved a phase shift of over 200" at 23.675 GHz and a figure of merit of about 55"/dB at room temperature. These results demonstrate that the epitaxial Ba,-,Sr,Ti03 thin films are close to becoming used in the practical applications for the wireless rf communications.

Photocopying permitted by liceow only 0 2000 OPA (Over\ea\ Publisher< Association) N.V. Publishcd by licenrc under the Gordon and Breach Science Publishers imprint.Ferroelectric Ba(,.,)Sr,Ti03 (x = 0.5 and 0.25) thin films were grown on (001) LaAlOj.by using pulsed laser ablation. Extensive x-ray diffraction and selected area electron diffraction reveal that the as-grown films were (001) oriented with a good in-plane relationship of BSTO // < 1 0 0 >~~0 .Rutherford Backscattering Spectroscopy ion-channeling studies suggested that the films had excellent epitaxial quality and crystallinity with an ion beam minimum yield xmin of only 2.6%. Atomically sharp interfaces were seen by cross-sectional high-resolution electron microscopy, indicated that the density of misfit dislocations was consistent with the lattice mismatch from the theoretical calculation.

We have investigated the crystallization of amorphous Y–Ba–Cu–O films with pulsed laser irradiation. The Y–Ba–Cu–O films were prepared on Si (001) substrates by pulsed laser deposition at room temperature. The microstructure and surface morphology of the films during the crystallization process were studied by x-ray diffraction and scanning electron microscopy. Micro or submicro Y–Ba–Cu–O crystalline particles can be obtained with variant laser pulses and energy densities. The particles have half-spherical or even spherical shapes on the film surfaces, and the saturated particle sizes were found to be determined by the film thickness.

Thin films of doped perovskite manganites of the type R1-X AxMnO3-y are currently become the focus of intense theoretical and experimental research due to their promising technological implications. However, the microstructure of the film and the interface structure at the atomic level remains unclear. In this report, we will present the atomic structure of the film/substrate interface and the microstructure of the film using a combination of transmission electron microscopy (TEM), Z-contrast scanning transmission microscopy (STEM), and electron energy loss spectroscopy (EELS).The La0.67Ca0.33MnO3 (LCMO) samples were grown on (001) LaA1O3 (LAO) using pulsed laser deposition. X-ray diffraction indicated the films to be oriented with the [001] directions parallel to the <001> directions of the pseudo-cubic perovskite LAO. Rocking curve measurements using the (002) reflection from the film indicated a full width half maximum of less than 0.3°. A Philips EM-400 electron microscope at 100 kV and a VG HB603 STEM at 300 kV were employed for sample analysis.