Artificial chessboard like textured YBCO films

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Abstract

A chessboard like structure of in-plane textured superconducting film with 4 × 4 μm2 elementary area has been fabricated by means of the homo-biepitaxial growing of YBCO film on yttria stabilized zirconia substrate. Regular arranged grain boundaries with fixed mismatch angle of 45° were realized. Each elemental square was connected to the four neighboring regions by π-Josephson junctions. Electro-physical properties of YBCO films with and without the chessboard like texture were measured. The magnetic field penetration into the chessboard like YBCO sample has been investigated by magneto-optical imaging at T = 4.2 K at different values of the applied magnetic field. The magneto-optical images have demonstrated the contribution of the grain-boundary superconducting transport to the formation of the magnetic field distribution inside the chessboard like sample.

Introduction

The study of artificial thin film high Tc texture structures is important in order to understand the transport properties of natural granular high Tc films [1] and to carry out the experimental confirmation of d-wave pairing symmetry in cuprate superconducting materials [2]. In addition, artificial texture influences on the optical properties of high Tc thin films with potential implication in the field of terahertz application [3]. In the present paper, we report on results of experimental investigation of electro-physical and magnetic properties of chessboard like structure YBCO film realized by the homo-biepitaxial technique.

Section snippets

Sample fabrication

The homo-biepitaxial growing is based on a 45° in-plane rotation of the grown YBCO films with respect to the substrate orientation realized by using a thin YBCO buffer layer deposited at a temperature (∼600 °C) out of the superconducting phase condition and lower than the optimal value (800 °C) [4]. Yttria-stabilized ZrO2 (YSZ) single crystal of (1 0 0) orientation was used as a substrate. YBCO films were deposited by dc magnetron sputtering with time modulated power as described in details in Ref.

Electro-physical measurements

Four electrodes (one to each corner) were connected to the square shape samples of 2 × 2 mm2 with and without chessboard like texture. Voltage–current ratio for opposite pairs of electrodes was measured as a function of temperature (T) in order to evaluate both the temperature associated with a full superconducting transition (Tcf) and the resistivity at T = 200 K (ρ(200 K)) calculated by Montgomery method [6]. For each sample the measurements were done for two orthogonal sides. The chessboard like

Acknowledgements

This work is partially supported by MIUR under the project “Sviluppo di componentistica avanzata e sua applicazione a strumentazione biomedica” and under the project FIRB-RBAU01PYB3.

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