Yttria-stabilized ZrO2 (YSZ) and CeO2 thin films were deposited on patterned (001) YSZ and (001) LaAIO3 substrates, respectively, using ion beam assisted deposition (IBAD) at normal incidence and an ion beam energy of 500eV. All deposition took place at 600°C. An initial 1000Å thick layer was evaporated at 0.2Å/s before beginning IBAD at rates of 0.3Å/s for YSZ and between 0.8Å/s and 1.2Å/s for CeO2. X-ray diffraction shows the YSZ films to grow epitaxially. The planarization mechanism for IBAD YSZ is similar to that previously observed for if-bias sputtering. CeO2 grows epitaxially on LaA103 but a second polycrystalline phase grows preferentially over the surface steps and inhibits the planarization process. The emergence of this phase appears to be related to highly incoherent growth of CeO2 over the stepped edges, which in turn is a function of the large lattice mismatch between CeO2 and LaA1O3 in the [001] direction.

Yttria stabilized zirconia (YSZ), SrTiO3 and CeO2 thin films have been widely used as buffer layers in YBa2Cu3O7-x (YBCO) deposition on silicon substrates. YBCO superconducting properties are limited by lattice mismatches between YSZ and YBCO, and chemical interaction of CeO2 and SrTiO3 with silicon. In order to avoid these problems we have deposited CeO2/YSZ/Si(100) and SrTiO3/YSZ/Si(100) bilayers by laser ablation. Wide temperature and pressure ranges have been studied. The influence of the intermediate layer on the CeO2 and SrTiO3 films properties has been studied. Previous studies were performed on films of each material on Si(100) and YSZ(100) single crystals. The surface of the films and bilayers is smooth without microcracks and only few droplets are found. Only small interdiffusion is observed in all the cases. Texture of the films changes with deposition conditions. Epitaxial growth of CeO2 has been found both on YSZ(100) single crystals and YSZ buffers on Si(100).

Deposition of high quality superconducting thin films requires lattice-matched single crystal substrates. This greatly reduces the number of candidate materials to a few expensive substrates that are only available in small sizes. Inexpensive, low-dielectric constant amorphous or polycrystalline substrates would greatly enhance the feasibility of superconducting devices such as HTSC multichip modules. Deposition of HTSC films on aligned dielectric layers allows the use of amorphous and polycrystalline substrates in these structures. Biaxially aligned zirconia thin films have been deposited using ion beam assisted deposition (IBAD) on pyrex, quartz, and Hastelloy substrates. Deposition rate, substrate temperature, ion beam energy, and other processing parameters control the orientation of films deposited by ion beam assisted deposition. Biaxially aligned (200) oriented zirconia has been deposited by IBAD on all three substrates without active substrate heating. Biaxial alignment was not observed in films deposited at 400°C. Increased ion beam energy promotes polycrystalline nucleation at lower temperatures, which is important to the development of biaxial alignment. Other faster growing orientations begin to dominate as the temperature is increased. These results are consistent with a growth and extinction model.

We present investigations of YBa2Cu3O7-x, thin films deposited on Silicon on Sapphire (SoS) substrates by pulsed laser deposition and dc sputtering. A compound buffer system consisting of YSZ and CeO2 is used for improved YBa2Cu3O7-x growth characteristics. The critical thickness of YBa2Cu3O7-x on CeO2/YSZ/SoS is determined to be 280 nm.

An a-axis oriented YBa2Cu3O7-x (YBCO) thin film exhibiting zero resistance at 83 K and critical current density of 7.9x103 A/cm2 at 62 K was obtained on an 180 nm - thick PrBa2Cu3 O7-xx(PBCO) buffered SrTiO3(100) substrate by two step pulsed laser deposition (PLD). The volume fraction of a-axis orientation and the crystallinity(Xmin) of the 150 nm-thick YBCO thin films were increased with increasing the thickness of PBCO buffer layer, which was varied friom 0 nm to 180 nm. It is concluded that the thickness of PBCO buffer layer is one of the important parameters to control the structural and superconducting properties of the a-axis oriented YBCO thin films using the PBCO buffer layers.

The surface morphology of Yba2Cu3O7 thin films formed on (001)-oriented LaAlO3 substrates by pulsed-laser deposition has been examined using electron and scanning probe microscopies. The observed surface features can be divided into two types: particles formed as a result of material (often molten) ejected from the target and outgrowths formed as a result of nucleation and growth processes on the substrate and/or the film surface. Where both types of surface feature occur on a particular film the outgrowths are always more numerous. The density of outgrowths is strongly related to the deposition parameters and, as a consequence, with the film growth mechanism.

An arrangement for large area PLD on 3-inch wafers is proposed. In order to get a homogeneous stoichiometry and thickness distribution and small variations of superconducting properties on the 3-inch diameter, the substrate is foreseen to be rotated and additionally laterally moved up to 45 mm during deposition whereas the laser plume remains fixed.

YSZ buffer layers showed thickness homogeneity of 1% within 10 mm, of 4% within 2 inch and of 8% within 3 inch diameter, respectively. For in-situ deposited YBCO thin films on r-plane sapphire with YSZ buffer layer we inductively measured within 3 inch diameter values of the critical temperature Tc(90%) from 85.9 K to 86.7 K and values of the critical current density jc(77 K) from 1 × 106 to 2 × 106 A/cm2. However, up to now the degree of epitaxy of the YBCO thin films on r-plane sapphire with YSZ buffer layer is lower compared to YBCO on MgO(100) as determined by Raman spectroscopy. Nevertheless, large area PLD seems to be a very promising technique for homogeneous coating of 3-inch wafers by epitaxial oxide thin films.

We tried to deposit (Sr1−xCax)0.9CuO2-δ films, so-called “the infinite-layer” structure, of (100) SrTiO3 substrates by using radio-frequency thermal plasma evaporation. The crysta structure of these films was confirmed by X-ray diffraction to consist of the (00l) oriented infinite-layer structure. However, the temperature dependence of resistivity showed no superconductivity in spite of varying ratios of Sr/Ca. A description is given of attempts to induce superconductivity in the infinite-layer films by the introduction of holes, namely by O2 plasma annealing and Na-doping.

We report theoretical studies on oxygen excess defect structure of lanthanum cuprate, La2CuO4+δ, using the Local Density formalism. The self-consistent Discrete Variational method has been used to find energy levels, densities of states, charge transfer, wavefunctions and potentials for a fragment consisting of N atoms embedded in the infinite crystal. Various possible interstitial oxygen positions and relative stability have been studied, including the structure suggested by Chaillout, et al. on the basis of neutron diffraction. Calculated electronic structures have been used to predict defect-related spectroscopic consequences.

Ion-assisted, ion-beam sputter deposition is used to obtain (00l) biaxially oriented films of cubic yttria-stabilized-zirconia (YSZ) on polycrystalline metal substrates. Yttrium-barium-copper-oxide (YBCO) is then heteroepitaxially-pulse-laser deposited onto the YSZ. Phi scans of the films show the full-width-half maxima of the YSZ (202) and the YBCO (103) reflections to be 14° and 10° respectively. Our best dc transport critical current density measurement for the YBCO is 800,000 A/cm2 at 75K and 0T. At 75K, the total dc transport current in a 1 cm wide YBCO film is 23 A.

The research focused upon generating new substrate materials for the deposition of superconducting yttrium barium cuprate (YBCO) has yielded several new hosts in complex perovskites, modified perovskites, and other structure families. New substrate candidates such as Sr(Al1/2Ta1/2)O3 and Sr(Al1/2Nb1/2)O3, Ba(Mg1/3Ta2/3)O3 in complex oxide perovskite structure family and their solid solutions with ternary perovskite LaAlO3 and NdGaO3 are reported. Conventional ceramic processing techniques were used to fabricate dense ceramic samples. A laser heated molten zone growth system was utilized for the test-growth of these candidate materials in single crystal fiber form to determine crystallographic structure, melting point, thermal, and dielectric properties as well as to make positive identification of twin free systems. Some of those candidate materials present an excellent combination of properties suitable for microwave HTSC substrate applications.

Many defects in high Tc superconducting films propagate from the substrate through to the film surface, disturbing the epitaxy at the interface and adversely affecting the physical properties of the film, particularly Jc. In this study the surface of Magnesium Oxide (100) single crystal substrates with different preparative treatments have been investigated using optical cathodoluminescence microscopy (CL), with a view to establishing its effect on the deposition of thin films of YBa2Cu3O7-δ superconductors.

CL excitations due to mechanically and chemically induced defects in the MgO substrate crystals are observed by optical CL microscopy. Several pre-deposition treatments have been compared in this way to determine the best preparation route for the substrates. Jc measurements indicate that the substrate surface quality is an important parameter in the production of high quality thin films especially for the fabrication of devices.

It is concluded that CL provides a powerful and rapid tool for MgO quality assessment before thin film deposition.

We have grown epitaxial thin films of various isotropic metallic oxides such as Sr1-xCaxRuO3 and La8-xSrxCu8O2Oin situ by 90° off-axis sputtering. These metallic oxides are pseudo-cubic perovskites with essentially isotropic properties, which could be ideal normal metals for SNS junctions in superconducting devices and for electrodes in ferroelectric devices. We have fabricated epitaxial ferroelectric heterostructures [SrRuO3/Pb(Zr0. 52 Ti0.4 8) O3 /SrRuO3] employing isotropic metallic oxide (SrRuO3) electrodes on substrates of (100) SrTiO3 and (100) Si with an yttria stabilized zirconia buffer layer. They exhibit superior fatigue characteristics over those made with metal electrodes, showing little degradation over 10 cycles, with a large remnant polarization (27 μC/cm2 ). We have also grown epitaxial superconducting heterostructures (YBa2Cu3O7 / La8-xSrxCu8O2O / YBa2Cu3O7 ) with a copper-oxide-based isotropic metallic oxide (La8-xSrxCu8O20) normal metal barrier. X-ray diffraction and cross-sectional transmission electron microscopy reveal these heterostructures to have high crystalline quality and clean interfaces. This material will facilitate fabrication of ideal SNS Josephson junctions with low boundary resistance due to its excellent chemical compatibility and lattice match with cuprate superconductors and will be useful for determining the source of interface resistance in such heterostructures.

Many approaches to fabrication of nonlinear optical and electro-optical thin-film materials are currently under investigation including: epitaxial inorganic films; polycrystalline inorganic materials; organic nonlinear moieties poled in polymer hosts; and poled amorphous inorganic materials. For each of these approaches there are a variety of characteristics and constraints that impact the ultimate uses. These are discussed in the context of signal processing and transmission applications such as optical interconnects and integrated optics. Almost universally, integration with the Si materials and processing that dominates current computer technology, or with the III-V materials that dominate optoelectronics technology, are major factors in the attractiveness of a technology direction. A relatively recent development is the observation of a strong nonlinearity in fused silica, χ(2) ∼ 1 pm/V, poled by modest temperature and electric-field stress. Temperature-dependent dynamic and spectroscopic measurements suggest that mobile-ion species such as Na+, as well as non-bridging oxygen bond re-orientation under a strong field, play a role in the nonlinearity.

The physical and optical properties of KNbO3 layers grown on (001) oriented spinel and MgO substrates by planar rf-sputter deposition were studied. Rutherford Backscattering measurements showed that stoichiometric films could be obtained by using K2CO3 enriched targets and 100% argon as a sputtering gas. The x-ray diffraction spectra showed that single crystalline tetragonal films could be obtained at temperatures in the range of 580–610°C. Furthermore, channelling experiments indicated good crystal quality with a χmin of 40%. High resolution Transmission Electron Microscopy of the films revealed epitaxial growth, but also domains with a typical width of 10–20 nm. Moreover, it was possible to excite waveguide modes with losses of only 1.1 dB/cm at λ = 632.8 nm. The nonlinear optical coefficient d31 was determined by the Maker-fringe technique using the 1.06 μm Nd:YAG laser fundamental wavelength. This yielded a d31 value of 5 pm/V. The electro-optic properties was investigated by phase modulation technique in a Michelson interferometer.

KNbO3 possesses high nonlinear optical coefficients making it a promising material for frequency conversion of infrared light into the visible wavelength range using integrated optical devices. While epitaxial thin films of KNbO3 have previously been grown using ion beam sputtering, defects (i.e. grain boundaries, domains, surface roughness) in these films resulted in high optical losses and no measurable in-plane birefringence. Previous films were grown on MgO substrates, which have a >4% lattice mismatch with KNbO3. In the work reported here, we have grown films on MgO, MgA12O4, NdGaO3, and KTaO3 to investigate the role of lattice mismatch on the resulting film quality. Films have also been grown with and without oxygen ion assistance. The orientations, morphologies, and defects in the films were examined using x-ray diffraction and AFM to determine their relationships to the growth conditions and substrate lattice mismatch.

Epitaxial, single phase (110) KnbO3 films were grown on (100) MgO substrates using a sol-gel process employing ethoxide precursors in methanol. The degree of epitaxy was dependent on both the annealing temperature and the amount of potassium in the film. Excess potassium in the sol-gel solution (K/Nb = 1.2) was necessary to produce single phase films. An amorphous or polycrystalline MgO interfacial layer was observed in some films, postulated to have developed after nucleation of KnbO3 and due to a highly defective surface layer.

The growth of thin films of LiNbO3 and Er:LiNbO3 on LiNbO3 single crystals produced by pulsed laser deposition (PLD) was studied. Samples were characterized by RBS/Channeling Spectrometry, X-ray diffraction measurements, Secondary Ion Mass Spectroscopy (SIMS) and photoluminescence (PL) measurements. Film preparation is performed in a two-step process including deposition and in-situ-annealing. Buried Er doped layers of approx. 800 nm thickness were grown.

Thin-film waveguides of LiNbO3 have been grown on Al2O3-c by off-axis rf magnetron sputtering. The films have been characterized optically by prism coupling measurements, crystallographically by x-ray diffraction, and morphologically by atomic force microscopy. We find that optical losses can be dominated by scattering from large outgrowths that litter the surface of the film. These outgrowths are c− grains imbedded in a c+ matrix. Although some grains nucleate c−, others have their polarity reversed from c+ to c− after nucleation. A model will be presented to explain the preferential nucleation of c+ grains on Al2O3-c. The c− grains grow much faster than the c+ ones because of attractive coulombic forces between the c− grains and the ionized Li and Nb species in the sputter plume.

Epitaxial PbTiOM3 films were prepared by metal-organic chemical vapor deposition (MOCVD) on MgO(001), SrTiO3 (001) and LaAlO3 (001) surfaces. Four-circle X-ray diffraction and optical waveguiding experiments were performed to characterize the deposited films. The films on all three substrates were single-crystal; however, the domain structure of the films was strongly dependent on the substrate material. Films on MgO and LaAlO3 substrates showed a large amount of 90° domain structures, whereas, the degree of twinning was greatly suppressed for films on SrTiO3. The refractive indices and optical birefringence of the films were measured as a function of wavelength using the film-prism coupling method. We found that for films on LaAlO3 (001), the ordinary index and for films on MgO(001) both the ordinary and extraordinary refractive indices were higher than those of bulk single-crystal PbTiO3. For films grown on SrTiO3 (001), the ordinary refractive index was very close to that of single crystal PbTiO3. We correlate the increased refractive index and the reduced birefringence to the degree of epitaxial strain and twinning in the samples, respectively.