Electrical properties, texture, and microstructure of vicinal YBa[sub 2]Cu[sub 3]O[sub 7−δ] thin films (original) (raw)
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Applied Physics Letters
Vicinal YBa 2 Cu 3 O 7Ϫ␦ ͑YBCO͒ thin films of thickness hϭ20-480 nm are grown by pulsed-laser deposition on 10°miscut ͑001͒ SrTiO 3 substrates. The anisotropic resistivities, c-axis texture, and critical temperature drastically depend on the thickness of vicinal films. High-resolution electron microscopy reveals a defect microstructure with strong bending of the YBCO lattice near the SrTiO 3 interface and improved film microstructure at larger distances to the substrate. The required layer thickness for microstructure relaxation and increase of electrical conductivity are significantly larger than the critical thickness of c-axis oriented YBCO films.
Monocrystalline YBa[sub 2]Cu[sub 3]O[sub 7−x] thin films on vicinal SrTiO[sub 3] (001) substrates
Applied Physics Letters, 2003
The correlation between the vicinal properties of SrTiO 3 ͑001͒ substrates and the twinning in YBa 2 Cu 3 O 7Ϫx thin films grown by pulsed-laser deposition is studied using x-ray diffraction with reciprocal space mapping. The vicinal properties, i.e., angle and in-plane orientation, play a significant role in the anisotropic strain starting at the interface between substrate surface and film, and affect the twin behavior of YBa 2 Cu 3 O 7Ϫx . On substrates having an ͓110͔ in-plane orientation of the step edges, a completely preferred twin pair is observed if the vicinal angle is increased to 0.60°. Whereas on substrates having their step edges oriented along one of the crystallographic axis, the films exhibit a detwinning as the vicinal angle increases. For ␣ϭ1.10°a maximum detwinned, i.e., monocrystalline film is obtained. At this angle, the diffusion length of YBa 2 Cu 3 O 7Ϫx during the growth matches the terrace length of SrTiO 3 . Up to this specific angle, the films are grown perpendicular to the optical instead of the crystallographic surface.
IEEE Transactions on Appiled Superconductivity, 2001
The surface morphology, microstructure and transport properties of epitaxial YBa 2 Cu 3 O 7 and PrBa 2 Cu 3 O 7 thin films and heterostructures deposited on slightly vicinal substrates of SrTiO 3 by high pressure oxygen sputtering were studied. The vicinal angles of the substrates and bicrystals were less then 13 0 . Depending on the tilt angle of the substrate a transition from spiral or island to step-flow growth leading to an improvement of the surface roughness was observed. Atomic force and transmission electron microscopy were used for these investigations. Furthermore, electrical and structural properties of YBa 2 Cu 3 O 7 thin films on vicinal offcut SrTiO 3 bicrystals with different grain boundary types were studied. This included junctions with a 2x 12 0 tilt or twist of the YBa 2 Cu 3 O 7 c-axis across the grain boundary. In comparison to conventional [001]tilt grain boundaries bicrystal Josephson junctions [100]-tilt grain boundaries showed high I c R n -products of up to 1.2 meV at 77 K and up to 8 meV at 4.2 K. IV-curve instabilities, probably of magnetic origin due to flux flow in the electrodes, often could be observed for junctions biased with high current densities.
Improved J/sub c/ of bilayer YBa/sub 2/Cu/sub 3/O/sub 7-δ/ thin film structures
IEEE Transactions on Appiled Superconductivity, 1999
A bs t r actCritical-current (J,) measurements Io r GBCO) and TX-GBCOTYBCO bilayers were performed with transport measurements a t different applied magnetic fields. The f i l m samples were prepared by pulsed laser deposition and patterned as microbridges. The highest Jc ( 1 . 5 x l o 6 A/cmz) at 75 K in 5 Tesla (Hllab) was observed for TX-GBCONBCO bilayers, which showed a 40 % increase in J, over YBCO under the same conditions. The bilayer samples possess a T, at 90 K and display superconducting properties similar to YBCO. A possible mechanisms for the high Jc of bilayer YBCO films is discussed. Development of these bilayer and multilayer structures represents a promising new direction t o improve the superconducting properties of YBCO since the TX-GBCO layer provide both protection against corrosion and a significant improvement in J.. YBazC%O,.a (YBcO), G$.6C4.~Ba,.~L4.~C%O,.~ px-
Two-Dimensional Behavior of YBa 2 Cu 3 O x Films on SrTiO 3 Substrates
Acta Physica Polonica A, 1997
Long-term (up to 18 months) degradation of textured YBa2 C u3Ox films prepared by laser ablation and magnetron sputtering on single crystal SrΤiO 3 , MgO and Al2 O 3 substrates were investigated. All films at each stage of exposition displayed a clearly visible quasi-2D behavior. From the measurements of the Kosterlitz-Thouless temperature it could be concluded that tle oxygen content and density of charge carriers remained constant. It follows that the main consequence of degradation is the omission of some planes from the transport of supercurrent and tle samples could be described in the model of layered structure with variable number of conducting planes. Using this model we find that effective thickness of an isolated CuO2 plane in samples with greatest internal damage is d 2 Å.