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Growth, structure and physical properties of YBa2Cu3Ox (YBCO) thin films and YBCO/CeO2 heterostructures on tilted-axes NdGaO3 (NGO) substrates with an inclination of normal of the substrate from the [1 1 0] axis were investigated. It was shown that the orientation of epitaxial YBCO thin films is influenced by the deposition rate and the presence of symmetrical-equivalent directions [1 1 0] and [1 1 0] in the substrate and [1 0 0], [0 1 0] and [0 0 1] in the CeO2 layer. Domain structure and morphology of the YBCO thin film surface change with an increase of the inclination angle. The YBCO thin films on the tilted-axes substrates are twinned of the same way as on (1 1 0) NGO substrates. However, formation of one or both twinning complexes is suppressed with an increase of the inclination angle. [Copyright &y& Elsevier]

The current–phase relation (CPR) of a YBa2Cu3Ox Josephson junction (JJ) on a bicrystal sapphire substrate was determined using the dependences of the amplitudes of the harmonic and subharmonic Shapiro steps and the critical current dependences of the DC-SQUIDs on external magnetic field. The deviations of CPR from sinusoidal one, caused by asymmetric dc biasing, result in an appearance of subharmonic Shapiro steps and in asymmetric shape of the SQUID modulation of the Ic(H) dependence. Precise measurements suppose sinusoidal CPR for symmetrical bicrystal junctions, while for asymmetric current flow in JJ the contribution of second harmonic in CPR increases monotonously. [Copyright &y& Elsevier]

Ramp-type Josephson junctions with YBCO superconducting electrodes and PrBa2 Cu2.6 Ga0.4 O6+δ (PBGCO) barriers were fabricated and characterized. The YBCO ramp junctions with 25 nm-thick barriers of PBGCO showed typical resistively- shunted-junction (RSJ)-like I-V behavior and 1σ spread of less than 13% in critical current density. Differential conductance-voltage characteristics registered using a lock-in technique indicate that the resonant tunneling via localized states in the barriers plays a dominant role in the conduction process of the ramp junctions. [ABSTRACT FROM AUTHOR]

Abstract: Structure, orientational features, and twinning of epitaxial superconductive YBa2Cu3O x (YBCO) thin films and YBCO/CeO2 heterostructures on (110) NdGaO3 (NGO) and tilted-axes NdGaO3 substrates with an inclination of normal of the substrate from the [110] axis were investigated by X-ray diffraction methods. Orthorhombic structure of NdGaO3 results in an increase of the angle between (110) and (1 1 0) twinning planes in YBCO films to 90.20° and in a difference in volume of two twin domain systems. The orientation of epitaxial YBCO thin films was shown to be influenced by the deposition rate and the presence of symmetrical-equivalent directions [110] and [1 1 0] in the substrate and [100], [010], and [001] in the CeO2 layer. Domain structure of the YBCO thin film changes with an increase in the inclination angle. The YBCO thin films on the tilted-axes substrates are twinned in the same way as on (110) NGO substrates. However, formation of one or both twinning complexes is suppressed with an increase of the inclination angle. [Copyright &y& Elsevier]

Experimental results for DC interferometers of asymmetric topology with high-Tc bicrystal Josephson junctions are reported. Model of the tilted bicrystal junctions is discussed. As a model, parallel array of alternating `0'' and `π'' contacts was studied numerically. It has been shown that the array can act as either 0- or π-junction. Both the array characteristics and the critical current dependence on applied magnetic field for the array and DC interferometer are discussed. [Copyright &y& Elsevier]

Abstract: Thin YBa2Cu3O7 films were fabricated by 2-opposed DC magnetron sputtering onto NdGaO3 substrates, tilted from standard (110) orientation by 0–26°, and their surface morphology and electrical characteristics were investigated. Normal state resistivity (at 295K) and microwave surface resistance (at 77K and ∼8GHz) of the films demonstrated anisotropy, introduced by the tilted substrate, and some improvement of the superconducting parameters of the films was observed at small tilt angles (θ ∼1.5–3°). The increase of the microwave surface resistance at high tilt angles for the current tracks, perpendicular to the steps of the substrate, was described in the framework of a simple model, which takes into account the complex conductivity of the film and the weak links between the film terraces. [Copyright &y& Elsevier]

Abstract: The results of the study (at 77K) of electrical parameters of YBCO thin films deposited on tilted NdGaO3 substrates using a 2-opposed-magnetron sputtering technique are reported. The films prepared on the substrates with tilt angle ∼3° demonstrated less surface roughness and higher critical current density. The minimum of the surface resistance (measured at 8GHz) was observed at a smaller tilt angle of ∼1.5°. The surface resistance demonstrated some anisotropy in the film plane, induced, possibly, by the tilted substrate. [Copyright &y& Elsevier]