Microstructure and current transport properties of single-layer YBa2Cu3O7-x and multiple-layer YBa2Cu3O7-x/(Ba0.05, Sr095)TiO3 superconductor films

• Published in: Thin solid films 2005-09, Vol.488 (1-2), p.217-222
• Main Authors: LUO, Y, HUGHES, R. A, PRESTON, J. S, BOTTON, G. A
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Cuprates superconductors (high tc and insulating parent compounds); Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Superconductivity; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2005.04.003

YBa2Cu3O7-x (YBCO) films grown by pulsed laser deposition on (100) LaAlO3 substrates show a strong thickness dependence on the electrical properties. Films in excess of 0DDT3 D*mm show a critical current density that decreases with increasing thickness. In contrast, nano-composite films, consisting of a stack of alternative YBCO and (Ba0DDT05, Sr0DDT95)TiO3 (BSTO) layers with a total thickness of up to 5 D*mm, show improved electrical properties. In order to understand this phenomenon, a detailed microstructural characterization has been undertaken. Transmission electron microscopy observations show that cracks, stacking faults and grain boundary are present on the single-layer films, while a high-quality microstructure is observed for the nano-composite multiple-layer films although defects at YBCO /BSTO interfaces are still present. In addition, nano-composite films have a reduced surface roughness. In this complex microstructure, the digital Moire technique reveals that the YBCO /BSTO interfaces play a crucial role in controlling the propagation of defects in YBCO.