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

Originating from the lattice mismatch and the difference in the thermal expansion coefficients between substrate crystal and the epitaxial film, a strain field is formed at the interface. The superconducting transition temperature of epitaxial layer of high-temperature superconductors (HTS) can be tuned by the strain field. In our study, the HTS films were deposited by pulsed laser ablation on SrTiO3 (STO) and NdCaO3 (001) substrates with thickness below and above the critical thickness for pseudomorphic growth. Results of X-ray structural investigations will be shown. Our observations fit within the frame of the available data on the effect of high pressure on HTS materials. We will present evidence that the strain field is affecting the substrate, namely the cubic to tetragonal transition of STO, too. (C) 2000 Elsevier Science B.V. All rights reserved.