Cation disorder in superconducting HgBa2CaCu2O6+delta films prepared on SrTiO3 substrates

Hg-Ba-Ca-Cu-O thin films prepared on SrTiO3 (100) substrates generally exhi bit shorter c-axis unit cell lengths and lower zero-resistance superconduct ing transition temperatures as compared to bulk. Microstructural studies of HgBa2CaCu2O6+delta films based on X-ray diffraction (XRD) and extended X-r ay absorption fine structure (EXAFS) revealed shorter BaO-CuO2 interplanar distances and longer CuO2-CuO2 average distances as compared to those repor ted for bulk compounds. It is suggested that the observed cationic disorder causes smaller c-axis lattice parameter and is probably induced by the lat tice mismatch between film and substrate. The observed atomic rearrangement s are expected to influence superconducting properties of the Hg-based film s. (C) 1999 Elsevier Science B.V. All rights reserved.