We have prepared highly textured superconducting thin films from Bi1.5pb0.5Ca3Sr2Cu4Ox (2324) on (100) YS-ZrO2 (Yttria stabilized zirconia) and Bi1.5Pb0.5Ca2Sr2Cu3°x (2223) on LaAlC-3 (100) and MgO (100) substrates at 650°C by pulsed laser ablation method.These films showed 2212 type of phase of the (BiPb)2(Ca,Sr)n+1CunO2n+4+5 family with onset transition temperature ( Tc ) ~ 110 K, confirming our earlier observations of 110 K superconductivity in a n = 2 bulk material. Thin films deposited from 2324 bulk target on YS-Z1O2 showed zero resistance temperature (Tco ) of 68 K but post annealing for one hour at 400°C in oxygen improved Tco from 68 K to 82 K. Thin films from 2223 target on LaAlO3 ( 100 ) and MgO ( 100 ) exhibited a Tco of 65 K and 74 K respectively while onset remained the same at 110 K. Further annealing at 400°C for one hour in oxygen did not show any improvement in Tco. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Rutherford backscattering (RBS) channeling studies were performed on these films for correlation between crystal structure, microstructure and superconducting properties. X-ray diffraction patterns indicated 2212 type phase with a= 5.39 Å and c=30.76 Å; preferential orientation of c-axis perpendicular to the substrate was observed. The lattice parameter and x-ray diffraction patterns were found to be invariant with annealing treatments.

By using 1ayer-by-1ayer successive deposition method with excimer laser ablation, the distance between CuO2 planes in the Bi2Sr2Ca1Cu2Oy superconductor has been controlled and super lattices with concentration modulation of Y and Ca have been formed. From the properties of these ‘Tailored films’, it is suggested that there is an interaction between CuO2 layers across Ca layer to affect the Tc value, but there is a very weak interaction across Bi2O2 blocking layers.

Basic thin film deposition processes for the high-Tc superconductors of Bi-systems are described. There appear several superconducting phases including the low-Tc phase Bi2Sr2Ca1 Cu2Ox and the high-Tc phase Bi2Sr2Ca2Cu3Ox. Thin films with these superconducting phases are synthesized by a selection of the substrate temperature Ts during the deposition : the high-Tc phase with Tc=100K is synthesized at Ts>800 °C; the low-Tc phase with Tc=80K, at Ts<600°C. However, these films often comprise show structure comprizing the different superconducting phases.

The close control of the superconducting phase has been achieved by the layer-by-layer deposition in the atomic layer epitaxy process.

We have prepared in situ REBa2Cu3O7 (REBCO) (RE= Y, Pr, Dy) thin films and YBC0/Dy(Pr)BC0 superlattices by single target dc planar magnetron sputtering. YBCO/DyBCO superlattices have been realized with modulation wavelength as short as 24Å, i.e., a unit cell of YBCO alternates with a unit cell of DyBCO, on average. The superconducting properties of such superlattices are indistinguishable from those of single layers. Tco's (zero resistance) are between 85 and 89K, and the residual resistivity ratios are between 2.5 and 3. In contrast to these results, when YBCO is layered with PrBCO, which is insulating, a dramatic change in the superconducting properties is observed. We have been able to artificially vary the coupling between single 12Å unit cell of YBCO by interposing insulating planes of PrBCO. As the YBCO layer separation increases, T is reduced and the transition broadens showing evidence of 2‐D superconducting fluctuations.

We have prepared epitaxial thin films of Yy‐Pr1‐y‐Ba‐Cu‐O (y= 1 to 0) and superlattices of Y‐Ba‐Cu‐O/Yy‐Pr1‐y ‐Ba‐Cu‐O using pulsed laser deposition technique. The zero resistance transition temperatures of Yy‐Pr1‐y‐Ba‐Cu‐O bulk samples are reproduced in the films. The composition oscillations in the superlattices are observed by SIMS. The films and superlattices are found to have c‐axis orientations and good crystallinity.

Using our standard single target off-axis sputter deposition procedure[1], ultra-thin YBa2Cu3O7 superconducting films were made in-situ. We have studied the thickness dependence of superconducting properties (Tc, Jc) from 20 to 5000Å. Tc starts degrading below 125Å and falls to 50 K for the 30 Å film. Jc drops linearly with decreasing thickness below l000Å. We have grown YBa2Cu3O7/La2-xSrxCuO4 superconducting thin film multilayers in-situ by the same process. The modulation wavelength of the multilayers ranged from 45Å to 2000Å. X-ray diffraction and cross sectional TEM confirm the superlattice periodicity. The superconducting transition temperature drops in much the same way as the single layer ultra-thin films. Both the critical current density and its magnetic field dependence decrease as the modulation wavelength decreases.

Thin films of La123 and their superlattice with Y123 are deposited on various substrates for the first time. Thin films of La123 can be made semiconducting or superconducting within a small range of oxygen stoichiometry. A multiple target holder has been used for insitu processing of superlattice thin films. The ability of the La123 compound to exhibit either semiconductivity or superconductivity has been utilized to construct semiconductor / superconductor superlattice structures with Y123- X-ray diffraction studies have shown clearly the presence of two distinct type of layers in the superlattice films with a individual layer thickness of ∼ 120 and 300 Å, although this did not happen for ∼ 24 Å thickness of the individual layers. Rutherford backscattering experiments showed good quality of the films with channeling yields < 10%. Resistivity measurements showed a Tc (onset) = 90 K and Tc(zero) = 85 K for the La123 as well as superlattice thin films.

Grazing angle ion-beam milling of c-axis oriented YBa2Cu3O7 films is shown to give smooth films which have metallic-like resistance transitions and superconduct at thicknesses approaching a lattice constant. The zero resistance transition temperature decreases uniformly with increased milling with most of the change occurring for thicknesses less than 100Å. The crossover to non-superconducting behavior occurs at “electrical” thicknesses near 10 Å with a sheet resistance above the onset of the superconducting transition having a value near h/4e2 = 6450Ω, a combination of fundamental constants predicted by theory and observed previously in low-Tc superconductors. Continued milling beyond this limit results in semiconducting behavior without a superconducting transition.

High‐Tc superconducting Y‐Ba‐Cu‐O films were prepared on Mg0(100) substrate by MO‐CVD technique without post annealing. The highest Tc obtained was 85K. The film was made up of dense matrix and dispersed fine particles. The Y‐Ba‐Cu composition of matrix was nearly equal to the 1:2:3 superconducting phase. The film was highly oriented with c‐axis perpendicular to the substrate. The lattice constant of the film was 11.68A.

High quality Y‐Ba‐Cu‐O thin films were produced by metal‐organic chemical vapor deposition (MOCVD) using metal chelates of P‐diketonate ligands. The films were grown in a cold‐wall CVD reactor at a reactor pressure of 10 torr and substrate temperature in the range 450‐550°C. Characterization studies were performed using Rutherford Backscattering (RBS), Auger electron spectroscopy (AES), scanning electron microscopy (SEM), and energy‐dispersive x‐ray spectroscopy (EDXS). These studies showed that the films were uniform, continuous, adherent and highly pure—carbon and fluorine contents were below the detection limits of the techniques used. Four point resistivity measurements showed that the films had a sharp superconducting transition at 9OK and exhibited current densities of ‐3x105 A/cm2 (B=0, T=65K) . The Y‐Ba‐Cu‐0 films thus grown were subsequently compared to radio‐frequency (rf) sputtered Y‐Ba‐Cu‐O films. It was found that the MOCVD‐produced films were superior in terms of uniformity, adherence, and electrical properties.

Superconducting thin films of YBa2Cu307‐x were grown on MgO (100) and YSZ(IOO) substrates without post‐annealing by metal organic chemical vapor deposition using vertical, high‐speed (1100 rpm) rotating disk reactor. The source materials were Y(tmhd)3, Ba(tmhd)2, and Cu(tmhd)2, which were kept at 135 °C, 240 °C, and 120 °C respectively. The precursors were transported using nitrogen as the carrier gas and introduced separately into the cylindrical stainless steel reaction chamber, which was maintained at 60 torr. The oxygen partial pressure was 30 Torr. The substrates were heated resistively at 800°C. After growth, the films were cooled down at a rate of 5 °C/min under 1 atmospheric pressure of pure oxygen. The X‐ray diffraction pattern of the films showed primarily an orientation of c‐axis perpendicular to the substrates, with weak peaks of (hoo) corresponding to a‐axis orientation. Scanning Electron Microscopy of the films showed a well‐developed a‐axis and c‐axis plate‐like structure which appeared as rectangular micron‐sized features on the MgO surface. On the YSZ substrates a‐axis and c‐axis plate‐like projections were also observed, with the dense plate‐like c‐axis orientation dominant. Four probe resistance measurements showed Tc(R=0) at 91.8 K(△TC=2.2 K) and 85 K (△TC=7 K) on YSZ and MgO substrates respectively.

A rapid, controllable process for CVD of superconducting Yba2Cu30x has been developed. The new process relies on slowly feeding and pneumatically transporting powdered solid reagents directly into the CVD furnace; vaporizers are not used. Deposition rates two orders of magnitude greater than those achievable by reagent sublimation have been obtained using a powder feed mixture of Y, Ba, and Cu tmhd complexes (tmhd is tetramethylheptanedionate). Potentially, the process is applicable to thermally unstable, less volatile, lower cost reagents such as the acetylacetonates.

Thin YBa2Cu307‐xfilms were grown by thermal and plasma enhanced MOCVD, and the effects of growth teiperature on the film properties were studied. The crystal Iinity of the fills deteriorated with growth teiperature, so superconductity decreased with growth teiperature. Thin fills grown by therial MOCVD at 600°C, 650°C, 700°C and 750°C had zero‐resistivity at 10K, 71K, 83K and 84K, respectively. The growth teiperature for superconducting fids is decreased by plasia enhancement. Thin films grown by plasma enhanced MOCVD at 515°C and 580 °C had zero‐resistivity at 60K and 85K. The critical current density of fills grown by plasia enhanced MOCVD at 580°C was 105A/cm2 at 77K.

We report here a plasma‐enhanced organometallic chemical vapor deposition process for the preparation of YBa2Cu3O7‐x thin films using two rf plasma coupling configurations. For the films grown under a direct plasma glow, the YBa2Cu3O7‐x phase is not found in the as‐deposited state. However, by employing plasma‐activated nitrous oxide as the reactant gas, superconducting YBa2Cu3O7‐x films having a low carbon content and a mirror‐like surface have been prepared in‐situ at a substrate temperature of 610°C using an organometallic chemical vapor deposition process.

By using N2O for oxygen source, Y‐Ba‐Cu‐O films prepared at 650” C on the SrTiO3 substrates showed zero resistance at 79K. The deposition rate of Y‐Ba‐Cu‐0 films on MgO(l00) substrates by using N2O gas was nearly half of that using 02 gas. X‐ray diffraction patterns of Y‐Ba‐Cu‐0 films grown on SrTiO3(100) and MgO(l00) substrates indicate c‐axis orientation.

Superconducting YBa2Cu307_x thin films were prepared by chemical vapor deposition using beta‐diketonate chelates on various oxide substrates and metal substrates. According to X‐ray diffraction patterns, the existence of a well‐oriented orthorhombic YBagCUgO^x structure has been confirmed in all specimens. The temperature of complete superconducting transition were observed at 89K on single‐crystalline oxide substrate, and 84K on metal substrate. Reduced critical current density of the film on single‐crystalline substrate in magnetic fields up to 600mT at 77K remained one or two order of magnitude higher than that of the film on metal substrate.

Thin film production by aerosol deposition is a simple, non‐vacuum method, which under certain conditions of the process parameters, can be considered as a chemical vapor deposition (CVD) process. In this paper we describe the formation of superconducting thin films by aerosol deposition in the CVD regime by using metal‐organic precursors. The best results were obtained with the metal β‐diketonates of Y, Ba and Cu dissolved in butylacetate. This solution was nebulized and sprayed on a heated Si‐substrate with a Zr02‐buffer layer at a temperature of 450 C. After deposition a final heat treatment at a temperature of 800 C was applied. The resulting superconducting film has a Tc>2ero of 75 K.

Films of the high‐Tc undoped and Pb‐doped Bi‐Sr‐Ca‐Cu‐O (BSCCO) superconductors have been prepared by low pressure organometallic chemical vapor deposition (OMCVD) using the volatile metal‐organic precursors Cu(acetylacetonate)2, Sr(dipivaloylmethanate)2, Ca(dipivaloylmethanate)2, and triphenyl bismuth. Factors which influence texture and morphology of the OMCVD‐derived films have been investigated, including the effects of annealing, doping, and substrates.

Bi‐Sr‐Ca‐Cu‐0 superconducting thin films have been prepared on MgO substrates by a Metalorganic Chemical Vapor Deposition technique using an infrared lamp. It was found in this study that the film composition ratio could be precisely controlled by using this technique. A zero resistance at 81K was obtained for Bi1Sr1.3Ca0.9Cu1.8Ox film grown at 850°C. The critical current density of this film was 1.0xl03A/cm2 at 77K.

CVD‐grown Bi‐Sr‐Ca‐Cu‐0 thin films on (OOl)MgO with T at 110 K have been investigated by transmission electron microscopy. The films are found to consist of large domains oriented along the c‐axis, with diameters of 15‐100 um. These domains exhibit incommensurate superstructures along the fa‐axis. In addition, we have observed similar superstructure spots in two equivalent directions normal to each other. It has also been found that the interface between the thin film and the substrate is very abrupt. Five different perovskite‐related layers along the c‐axis with different thickness are present. In the thin film, 80K phases are dominant and 110 K phases are less likely. Three other phases are very rarely observed. Furthermore, boundaries where the layered structure is different on both sides are often found.