Influence of MgO surface conditions on the in-plane crystal orientation and critical current density of epitaxial YBCO films

✍ Scribed by J. Du; S. Gnanarajan; A. Bendavid

• Publisher: Elsevier Science
• Year: 2004
• Tongue: English
• Weight: 319 KB
• Volume: 400
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/j.physc.2003.07.005

✦ Synopsis

The effect of magnesium oxide (MgO) surface conditions on in-plane grain orientation and critical current density of epitaxial YBa 2 Cu 3 O 7 (YBCO) films was systematically investigated. The MgO substrates were either ''as received'' or stored for some time, cleaned using different methods and lithographically prepared for our step-edge junction devices. The YBCO films were grown via reactive thermal co-evaporation by Theva, GmbH. The surface characterisation of MgO substrates was studied using X-ray photoelectron spectroscopy (XPS). The in-plane grain orientation of the YBCO films was studied by means of X-ray diffraction (XRD) /-scan and the critical current density was measured for the XRD scanned samples. The surface condition of the MgO substrates was found to have a strong influence on the inplane grain orientation and the critical current density of the YBCO films. The MgO substrates with a degraded or contaminated surface gave rise to 45°grain misorientation in YBCO films and reduced the critical current density. A final process step using a low energy Ar ion beam etching (IBE) of the MgO substrates prior to the YBCO film deposition was found effective in removing the in-plane grain misorientation and promoting the growth of perfectly aligned c-axis YBCO films.