Transmission electron microscopy(TEM) and scanning electron microscopy (SEM) have been used to study the microstructural features of YBa2Cu3O7 (hereafter referred to as Y123) films grown on various single crystal substrates by electron beam deposition. The films are all of high quality with the best observed Jc value being 10 A.cm‐2 at 7K. Cross‐sectional views in TEM have shown that the morphology of the film depends on its thickness. Thinner films (2500 Å) have a single layer of Y123 oriented with its c‐axis perpendicular to the substrate while thicker films(8000 Å) have this same c‐axis perpendicular layer closest to the interface with a c‐axis parallel layer above it. The interface between the film and the substrate is well defined in all cases with no amorphous region at the interface. Chemical analysis shows evidence of interdiffusion between the film and substrate.

Thin films of nominal composition YBa2Cu3O7‐x (YBCO) were produced on (100) SrTiO3 substrates by coevaporation and furnace annealing. Film thicknesses in the range of 0.2 to 2.4/μm were analyzed. Microstructural investigations by cross sectional transmission electron microscopy (TEM) reveal a continuous layer of about 0.4 μm thickness adjacent to the substrate with c‐axis normal to the substrate plane. In thicker films the remaining top portion has the c‐axis in the film plane. The critical current density (J ) at 77 K decreases with increasing thickness in the thickness range exceeding 0.4 μm, qualitatively consistent with the microstructural observations, but quantitatively inconsistent with a simple model based on the microstructural data.

The effect of in‐situ cooling conditions on surface roughness and superconducting properties have been studied. Bi‐Sr‐Ca‐Cu‐0 thin films were grown in‐situ on (100) MgO substrates at 700°C by activated reactive co‐evaporation. The films cool‐down in 760 Torr oxygen showed a transition temperature (Tc(onset)) of 100 K and zero resistance temperature (Tc (zero)) of 65 K. Smooth surface was obtained for the sample cooled‐down in oxygen plasma.

The in situ epitaxial growth of Bi‐Sr‐Ca‐Cu‐O films by molecular beam epitaxy (MBE) is reported. The suitability of ozone to the MBE growth of cuprate superconductors is discussed. Molecular beams of the constituents were periodically shuttered to grow various Bi2Sr2Can‐1CunOx phases, including 2201, 2212,2223,2245, and layered mixtures of these phases. Using these techniques a superconducting film with TConset near 100 K and Tc (ρ=0) of 81 K was achieved under entirely MBE conditions (Pchamber≤xl0‐4 Torr during growth and cooling). The films are smooth on an atomic scale. The results demonstrate the ability of shuttered MBE growth to selectively grow Bi2Sr2Can‐1CunOx phases.

Elementary steps of the oxide formation on a Si(001) substrate surface have been studied by means of RHEED, LEED, XPS and UPS. A Bi monolayer on Si (001 ) terminates with a surface dangling bond. Oxide formation on to this surface was studied one by one. Oxidation of Bi overlayered system with oxygen and N2O revealed that the surface Si was inactive to NoO exposure unless Sr was evaporated on. Bi overlayer was easily oxidized with O2 but not with N2O. Further oxidation of surface with Sr and Cu coevaporated system has also been studied.

The simple cubic perovskite crystal structure of superconducting (Rb,Ba)BiO3 makes it an ideal system for the study of perovskite heteroepitaxy. We report novel growth phenomena which have been observed in (Rb,Ba)BiO3 films grown by molecular beam epitaxy (MBE). For growth on MgO, the orientation of the film is observed to depend on the substrate temperature during growth, changing from (1 1 0) to (1 0 0) with increasing temperature. For films on SrTiO3, the large (10%) lattice mismatch appears to cause small grain rotations, resulting in a film with many low angle grain boundaries. In at least one growth regime, (2 2 1) oriented grains nucleate and grow on Ʃ3 coincidence boundaries on a faceted (1 0 0) oriented film.

High Tc superconducting YBa2Cu3O7 films have been prepared by the Liquid Phase Epitaxial (LPE) technique. The x‐ray diffraction patterns displayed a high degree of (00l) preferred orientations with c‐axes perpendicular to the film surfaces. The in‐situ grown YBa2Cu3O7 films showed zero‐resistivity at 76*K. Examination of the film cross sections by SEM revealed a growth mechanism.

Superconducting Y‐Ba‐Cu‐0 film can be prepared by a liquid phase growth method without crucible on 96 % and 99 % alumina substrates. A buffer layer of sputtered gold or platinum was necessary for the formation of Yba2Cu3Ox phase. The flux of Ba2Cu3O10. was appropriate for this purpose. For a film of 10 mm x 20 mm x 10 micron, 0.6 to 0.8 gm initial weight was optimal, the optimum melting temperature was 1090 to 1110 °C for 20 ‐ 30 minutes. In order to obtain films with superconducting transition, an additional Y2BaCuO5‐underlayer was necessary. The resultant optimal films had Tc‐onset of above 80 % and Tc ‐zero of typically around 60 K.

Partial melting followed by recrystallization at lower temperatures during high temperature treatment of superconducting Ba2YCu3O7-δ films is associated with texture development In these films, partial melting is induced by rapid thermal annealing at a temperature slightly above the peritectic melting temperature of Ba2YCu3O7-δ. Short firing duration prevents segregation of liquid and permits recrystallization of the correct phase at around 920°C.

Research has been performed on the use of chemical spray pyrolysis for depositing films of YBCO. The effects of reagent concentration, deposition rate, substrate temperature and substrate type were investigated. Films from less than 2 to more than 10 microns thick were deposited on single crystal strontium titanate, polycrystalline alumina and type 304 stainless steel.

A spray pyrolysis system has been developed in which the use of airless atomisation and optical heating permits the deposition of thin film superconductors at growth surface temperatures exceeding 650*C. A comparison between centrifugal and hydrodynamic atomisation techniques shows that each possesses advantages and disadvantages for the deposition of thin films by this technique. The presence of a corona discharge has been found to be an essential ingredient for growth at high substrate temperatures.

Decomposition of metal‐organic precursors to Ba2Ycu3O7‐X films is difficult because of the high reaction temperature required to decompose the BaCO3 intermediate. The recently proposed use of metal trifluoroacetate (TFA) solutions offers an alternative path to barium‐containing superconducting films. The TFA salts decompose to the metal fluorides forming BaF2, eliminating BaCO3 from the system. Ultimate conversion to BYC, however, is shown not only to depend on hydrolysis of the BaF2 at high temperatures, but also hydrolysis of copper trifluoracetate at low temperatures to prevent the volatilization of Cu(TFA)2. These processes result in unique microstructural behavior which can be characterized by electon microscopy and Auger spectroscopy. Effects due to substrate interactions have been eliminated by use of a chemically inert substrate material, BaZrO3.

A nitrate solution of Y, Ba and Cu was atomized and introduced into an inductively coupled argon ‐ oxygen plasma operated at 4.4 kW and 13.56 MHz under atmospheric pressure. As‐deposited superconducting films were grown on (100) YSZ substrates heated to 650°C. Critical temperatures of 85 K and critical current densities of 7.0 x 104 amp/cm2 at 77 K have been achieved. X‐ray diffraction shows the films to be oriented with the c‐axis perpendicular to the substrate surface. The effects of process parameters, solution composition, and aerosol concentration on the superconducting properties and microstructures will be discussed.

Highly oriented Bi2Sr2CaCu2O8+x films were prepared on MgO and SrTiO3 substrates by the solution sol ‐ gel (SSG) method. The tetra phasic sol containing bismuth, strontium, calcium and copper oxides was coated on the substrate by spin casting and calcined at 870*C for 10 minutes. X‐ ray diffraction patterns of the films showed the formation of the superconducting phase with preferential orientation along the C‐ axis. The microwave absorbtion data as a funtion of temperature revealed the onset temperature to be 90*K for the film coated on MgO substrate.

Thin films in the Bi‐Sr‐Ca‐Cu‐O system have been synthesized from liquid ethyl hexanoate precursors by spin pyrolysis. An extensive solid solution range was determined for the two Cu‐layer phase through the study of c‐axis oriented, single‐phase thin films fabricated on single‐crystal MgO (100). Extensive cation non‐stoichiometry was observed in all cases. The variation of important thin film properties with composition within the solid solution range have been described.

Utilising the results from the thin film study together with data relating to liquid formation in mixtures of bulk material a working model describing the formation of the two‐layer phase has been formulated. The two‐layer phase is formed as the result of precipitation from a fugitive liquid at temperatures exceeding 730 *C.

Thick films of high-temperature superconductors have been deposited electrophoretically using techniques developed for office copier toning. The resultant films are dense because of the high charge density per particle and the high fields during deposition. Orientation by electrostatic and magnetic fields has been demonstrated.

Z-contrast scanning transmission electron microscopy (STEM) is a fundamentally new approach to high-resolution imaging which provides unambiguous, compositionally sensitive images on the atomic scale. Such images are intuitively interpretable, even in thick regions of the sample, tremendously simplifying determination of the structure and chemistry of defects and interfaces. To illustrate this, examples are presented of commonly observed planar defects in laser-ablated thin films of YBa2Cu3O7-x. Film/substrate interfaces are shown to be chemically diffuse on the atomic scale and steps or undulations in the substrate need not result in defects in the film. Low-angle grain boundaries are found to be chemically clean, the drastic reductions in critical currents with tilt angle being due to the array of intrinsic structural defects comprising the boundary.

Grain boundaries in thin films of high Tc YBa2Cu3O7-x superconductors have been investigated with high resolution scanning transmission electron microscope (STEM) imaging and nanoprobe energy dispersive x-ray (EDX) analysis. Atomic resolution images indicate that the grain boundaries are mostly clean, i.e., free of a boundary layer of different phase or of segregation, and are often coherent. EDX microanalysis with a 10 Å spatial resolution also indicates no composition deviation at the grain boundaries.

Since the discovery of superconductivity in certain classes of cuprates, there has been much research activity aimed at understanding the structure, microstructure, electrical and other physical properties of these materials. In this paper, we present a summary of the current status of on-going research on structural and microstructural characterization of the Bi cuprates and cationically substituted derivatives of these superconducting compounds. High resolution structural imaging together with conventional and analytical electron microscopy is used to examine the structure[l]. The overall aim of these studies is to characterize the structural and microstructural evolution and ultimately to determine the effect on the superconducting properties.

Cross-sectioned TEM specimens of thin TIBaCaCuO superconducting films on MgO and LaAlO3 substrates have been obtained using special ceramic holders. The superconductor/substrate interface as well as grain boundaries and defects in the superconductor have been characterized by means of analytical and high-resolution electron microscopy. EDX analysis and lattice images confirm that interdiffusion and the formation of an amorphous layer takes place at the interface between the LaA1O3 substrate and the superconducting film, while no indication for such reactions has been found in the case of the MgO substrates. The presence of intergrowth and defects in the superconducting film have been demonstrated by high-resolution electron microscopy. The chemical nature of such defects has been determined by a quantitative evaluation of high-resolution micrographs.