The effect of epitaxial strain on RBa2Cu3O7 thin films and the perovskite substrate

Originating from the lattice mismatch and the difference in the thermal exp ansion coefficients between substrate crystal and the epitaxial film, a str ain field is formed at the interface. The superconducting transition temper ature of epitaxial layer of high-temperature superconductors (HTS) can be t uned by the strain field. In our study, the HTS films were deposited by pul sed laser ablation on SrTiO3 (STO) and NdCaO3 (001) substrates with thickne ss below and above the critical thickness for pseudomorphic growth. Results of X-ray structural investigations will be shown. Our observations fit wit hin the frame of the available data on the effect of high pressure on HTS m aterials. We will present evidence that the strain field is affecting the s ubstrate, namely the cubic to tetragonal transition of STO, too. (C) 2000 E lsevier Science B.V. All rights reserved.