Transmission electron microscopy of defect cascades in YBa2Cu3O7−δ produced by ion irradiation

Abstract YBa2Cu3O7-δ single crystals were irradiated with 50 and 85 keV Kr+ and Xe+ ions to low doses, producing spatially isolated defect cascades. One irradiation was performed at low temperature. The resulting defects were investigated by conventional and high-resolution transmission electron microscopy. They were found to have primarily an amorphous-like structure with an inwardly directed (vacancy) strain field. Evidence for lattice melting, with coherent or incoherent recrystallization at some defect cascade sites, is presented for the first time.