Superconducting thin films of Tl‐Ba‐Ca‐Cu‐0 have been prepared by a unique hybrid technique that combines electron beam evaporation with organometallic chemical vapor deposition (OMCVD). Multilayer thin films of Ba‐Ca‐Cu‐O are prepared by sequential electron beam evaporation of BaF2, CaF2, and Cu sources onto single crystal MgO (100) or yttria‐stabilized zirconia (YSZ) substrates followed by annealing in a water vapor‐saturated oxygen atmosphere. Thallium is then incorporated into these films in either of two ways: (1) via OMCVD using thallium(cyclopentadienide) as the source, or (2) rapid annealing of the Ba‐Ca‐Cu‐O film in the presence of bulk thallium superconductor. The resultant films primarily consist of single phase TlBa2Ca2Cu3Ox with the Cu‐O planes preferentially oriented parallel to the substrate surface. Resistivity measurements indicate superconducting onset temperatures above 120 K with zero resistance by 104 K. By eliminating the water vapor anneal, residual fluoride, originating from the sources, may be left in the film. This leads to formation of predominantly c‐axis oriented crystallites of the TlBa2CaCu2Ox phase.

Films of the Tl‐Ba‐Ca‐Cu‐O high‐Tc superconductor can be prepared by several organometallic chemical vapor deposition routes. Two of these involve Ba‐Ca‐Cu‐0 films that are first prepared using the volatile metal‐organic precursors Ba(heptafluorodimethyloctanedionate)2, Ca(dipivaloylmethanate)2, and Cu(acetylacetonate)2‐ Deposition is carried out at a pressure of 5 Torr with argon as the carrier gas and water vapor as the reactant gas. Thallium is next incorporated into these films either by organometallic chemical vapor deposition using Tl(cyclopentadienide) as the source, or by vapor diffusion using bulk Tl‐Ba‐Ca‐Cu‐O as the source. Thallium deposition is carried out at atmospheric pressure with an argon carrier and water‐saturated oxygen reactant gas, followed by rapid thermal annealing. Both procedures yield films that consist primarily of the TlBa2Ca2Cu3Ox phase, have preferential orientation of the Cu‐O planes parallel to the substrate surface, and exhibit onset of superconductivity at ∼125 K with zero resistance by 100 K.

The synthesis parameters have been systematically examined for the in situ growth of high temperature superconducting Y‐Ba‐Cu‐0 thin films from a stoichiometric target by rf magnetron sputtering. By properly adjusting the deposition temperature, the total sputtering (O2+Ar)‐pressure and the O2‐partial pressure, we have reproducibly obtained 123 YBCO films with a zero resistivity temperature Tcz = 84 K and a transition width of 3 K°. The films so obtained have excellent surface morphology and a surface roughness better than ∼ 5 nm.

Superconducting Y‐Ba‐Cu‐0 thin films on (100)GaAs substrate have been successfully prepared by the high pressure DC sputtering process without further post‐annealing treatment. The target was compound Y1Ba2Cu3Ox made by solid‐state reaction. The sputtering gas was Ar‐50%02, and total pressure was 1.5 torr. The substrate temperature was lower than 450°C. The best superconductivity of the film is Tc(onset) = 95K and Tc(R=0) = 40K. There are no mi‐crocracks on the film surface. The interdiffusion between the film and GaAs is limited.

The Y‐Ba‐Cu‐0 (YBCO) films were grown on (100)Mg0 substrate by the high pressure DC diode sputtering process. The targets were YBCO compounds made by solid‐state reaction. The sputtering gas was Ar‐50%02, and total pressure was 1.5 torr. As‐deposited superconducting YBCO films can be prepared at low substrate temperature at high discharge current. For Y1Ba2Cu30x target, the atomic ratio Ba/Y in the films almost remains constant (Ba/Y = 1.7) and Cu content monotonically increases with increasing discharge current. The Cu content in the film approaches to that of the target at low discharge current. Concentrations of 0 and 02 + in plasma markedly increase during increase of discharge current. High Cu content at large discharge current may be caused by action of electrical field on Ba+ and Y+.

Superconducting YBa2Cu3O7‐ δ (YBCO) films 100‐300nm thick have been grown in‐situ on (100) SrTiO3 at 650°C by ion beam sputtering. Targets of Cu, CuO, Y, Y2O3, BaF2, BaCO3 and YBa2Cu3O7‐ δ have been studied. Uniform composition throughout the film thickness has been achieved by co‐sputtering. Films are metallic (p300=300μΩcm) and textured, with Tc onsets at 92K and Tco=82K. Jc(77K) exceeds 105 Acm‐2. Films grown in‐situ on Si with ZrOx/Y2O3 and In2O3(10 at.%SnO2) buffer layers show Tc onsets at about 90K and Tco at about 50K, annealing improves Tco to 60K with resistivities p30o=2000μΩcm and 4000μΩcm respectively.

High Tc superconducting thin films have been deposited on sapphire by means of RF‐sputtering from a single stoichiometric target of YBa2Cu3O7 ‐ x composition. The YBa2Cu3O7 ‐ x films were deposited in an argon‐oxygen atmosphere on a substrate which reached a temperature of s 400°C during deposition. The study of stoichiometry and homogeneity of the as‐deposited films, by means of electromicroprobe analysis (EMPA), was used to optimize the sputtering parameters of the system. To achieve superconductivity, with an onset of s 90 K, a high‐temperature, post‐deposition thermal treatment in oxygen was necessary. Resistivity measurements show that, with respect to the bulk samples, zero resistivity is lowered as a result of substrate interaction. The use of buffer layers can improve the quality of the superconducting thin films.

Thin films of Y‐Ba‐Cu‐O were produced by RF sputtering of YBa2Cu3O7‐x ceramic targets, using a variety of plasma compositions, RF power levels, and substrate temperatures. Post annealing of these films in oxygen produced superconducting films with Tc values between 40‐60 K, broad transition widths and semiconductor‐like electrical behavior above Tc. Subsequent annealing at 850°C in an inert gas with a residual oxygen partial pressure of ≤10 ppm followed by an oxygen anneal produced high quality thin films: Tc> 85 K with narrow transition widths. The structure and morphology of these films during reduction‐oxidation processing were monitored using X‐ray diffraction and electron microscopy.

Highly oriented films of YBa2Cu3O7‐x have been reproducibly prepared with the correct metal stoichiometry by dc magnetron sputtering from a single target of stoichiometric composition. To circumvent the resputtering effects, the magnetron used an unbalanced magnetic field configuration to direct the plasma away from the substrate. Typical films have sharp superconducting transitions with Tc up to 93 K and △TC(90%.‐10%.)=0.5 K, metallic resistivity above the transition with ρ300/ρ100=2‐4, and Jc>1.5xl06 A cm‐2 at 4.2 K. The temperature dependence of J,. obeys the flux creep model with activation energy U(0)=75 meV.

Thin films of YBaCuO were prepared on MgO and SrTi03/Al2 03 substrates by rf magnetron sputtering. The SrTi03 was deposited onto AI2O3 by flash evaporation. The as‐deposited films on both substrates had an (001) orientation and were superconductors. Annealing the films in O2 improved their crystal 1inity and raised their critical temperatures (Tc). A detailed X‐ray diffraction study of the YBaCuO films was carried out. Values for the particle sizes and nonuniform strains along the c axis were obtained from broadened diffraction lines by using an integral breadth method. It was found that the broadening was mainly caused by nonuniform strain. It was also observed that nonuniform strain decreased as the films were annealed at various temperatures. The Tc's of the films were very sensitive to changes in nonuniform strain.

Superconducting Bi system thin films have been formed on MgO(100) substrates by RF magnetron sputtering from three Pb‐doped targets: Bi2.4 Pb0.6 Sr2 Ca2 CU3 O x ,Bi 1.6 Pb0.4 Sr3 Ca3 CU3 O x and Bi 1.6 Pb 0.4 Sr2 Ca2 CU4.5 O x. The as‐grown films formed at substrate temperatures above 600 °C showed superconductivity, though, they did not contain Pb.The film, formed at 660°C and kept at the same substrate temperature and gas pressure as the sputtering conditions for 5 h after deposition, showed a resistivity drop at 115 K and zero resistivity at 83 K. The Jc value of the film was 4x105 A/cm2 at 77 K and 3x107 A/cm 2 at 20 K.

The annealing steps have been shown to be a crucial determinant of the quality of Tl‐based superconducting films. In this study, we discuss the formation of the superconducting Tl2Ba2CaCu2O8 and Tl2Ba2Ca2Cu3O10 phases with varied post‐annealing temperature and fixed annealing time. A x‐ray, electron micro‐probe, and scanning electron microscopy were carried out to evaluate the structure of superconducting phases formed for each annealing condition. For films deposited on SrTiO3 substrates and heat‐treated at 870°C for 15 min, the lower Tc phase Tl2Ba2CaCu2O8 becomes a major phase. The films consist of nearly pure Tl2Ba2Ca2Cu3O10 phase with Tc (R=0) in the range of 100K to 118K and c‐axis perpendicular to the film plane were obtained after annealing 880‐890°C for 15 min. These films were epitaxy growth on SrTi03 substrates.

Thin films of the Tl‐based superconductors often have relatively poor properties because of film/substrate interdiffusion which occurs during the anneal. We have therefore investigated the use of BaF2 as a diffusion barrier. TICaBaCuO thin films were deposited by dc magnetron sputtering onto MgO <100> substrates, both with and without an evaporation‐deposited BaF2 buffer layer, and post‐annealed in a Tl over‐pressure. Electrical properties of the films were determined by four‐point probe analysis, and compositions were measured by ion‐backscattering spectroscopy. Structural analysis was performed by X‐ray diffraction and scanning electron microscopy. The BaF2 buffer layers were found to significantly improve the properties of the TICaBaCuO thin films.

Highly oriented YBCO films were produced on MgO(100) single crystal substrates. The direction of c axis was perpendicular to the film plane, whereas those of a and b axes were at random directions. The critical current density of the films was significantly high ca. 7x105 A/cm2. The critical transition temperature (Tc) of the YBCO film formed on a metal substrate, predeposited with YSZ as a buffer layer, was similar to those of the YBCO on MgO substrate. The possibility for the formation of superconductor films on metal substrates is suggested from these results.

Epitaxial thin films of YBaCuO were prepared by multilayer deposition from Y, Cu, and BaF2 sources with: (1) the a‐axis perpendicular to (100)SrTiO3; (2) the c‐axis perpendicular to (100)SrTiO3; and (3) the [110] axis perpendicular to (110)SrTiO3. XRD patterns as well as SEM and HREM images confirm that the films are highly oriented, essentially epitaxial. Both the a‐axis oriented and the c‐axis oriented films exhibit zero resistance at 91K. The [110] oriented film shows the sharpest transiton with a transition width of IK and zero resistance at 85K. The zero field critical current density, Jc, determined magnetically, is in excess of 107A/cm2 at 4.4K and 1.04 x 106A/cm2 at 77K for the c‐axis oriented film; for the a‐axis oriented film we obtained 6.7 x 106A/cm2 at 4.4K and 1.2 x 105A/cm2 at 77K. The orientation dependence of the critical current density in the basal plane of the a‐axis oriented film was studied. The largest Jc's occur along the in‐plane <100> axes of the substrate.

Thin films of YBa2Cu3O7‐δ have been deposited on samples of LaGaO3 substrates by multilayer E‐beam evaporation. Alternating layers of Cu, Y2O3, and BaF2 were deposited on polished (001) substrates. An annealing study was performed to thoroughly blend the layers and minimize substrate interdiffusion. Films were prepared by annealing in wet oxygen at temperatures between 800 °C and 1000 °C. Four point resistance versus temperature curves were obtained to determine the superconducting transition temperature and transition width. Auger depth profiling was performed as a function of annealing cycle to determine the amount of blending of the layers and quantify any substrate diffusion..

The annealing behavior of Ba2YCu3+xO7+y films grown by coevaporation of BaF2, Y and Cu on SrTiO3 has been studied as a function of temperature. Upon annealing at temperatures below 800°C, the phase forming first is Ba2YCu4O8, independent of the starting stoichiometry. Higher temperatures, above approximately 825 ° C are needed for Ba2YCu3O7 to crystallize.

The properties of thin films prepared by coevaporation of Y, Cu and Ba.F2, followed by post anneals in O2/H2O, are described. In particular, we emphasize what is known about. the relationship between the processing variables and the physical and chemical structure of the resulting films.