X-Ray Reflectivity Study of Interdiffusion at YBa2Cu3O7-x and Metal Interfaces

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We present a study of interdiffusion at interfaces of YBa2Cu3O7-x (YBCO) and metals, Au, Ag, and Pb by using X-ray reflectivity. YBCO thin films were epitaxially grown by off-axis sputter deposition and coevaporation, with the $c$-axis perpendicular to the SrTiO3 substrate surfaces. The capping layers were subsequently deposited on the YBCO film in situ and ex situ near room temperature. Glancing incident X-ray reflectivity was employed to investigate the surfaces and their buried interfaces. We find that interdiffusion at the interfaces of Au/YBCO and Ag/YBCO is negligible. However, a large interdiffusion zone, ${\sim} 60$ Å, is present at the Pb/YBCO interface and the lead films grown, both in situ and ex situ, were entirely oxidized. We do not observe any diffraction peaks from the Pb/YBCO films. The diffraction peaks are found up to (007) from the YBCO films of the Au/YBCO and Ag/YBCO films. This implies that the loss of crystalline structure in a ${\sim} 300$-Å-thick YBCO film underneath Pb is caused by interdiffusion.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2003-03-15