Low-dose radiation effects in thin films of high-temperature superconducting YBa{sub}2Cu{sub}3O{sub}(7-x) irradiated by 1-MeV electrons

摘要

Radiation effects are investigated in thin epitaxial films of the high-T{sub}c superconductor (HTSC) YBa{sub}2Cu{sub}3O{sub}(7-x) irradiated by low doses of 1-MeV electrons. The maximum radiation dose (4 × 10{sup}16 electrons/cm{sup}2) is chosen from the condition that the defects formed as a result of electron-nucleus collisions cause a negligible lowering of the critical temperature of YBa{sub}2Cu{sub}3O{sub}(7-x). Under this condition the main source of radiation effects in HTSC films can be processes involving excitation of the electronic subsystem of YBa{sub}2Cu{sub}3O{sub}(7-x). When YBa{sub}2Cu{sub}3O{sub}(7-x) films are irradiated by doses of (1-4) × 10{sup}16 electrons/cm{sup}2 their critical temperature T{sub}c is observed to increase (in contrast to published reports of a decrease in T{sub}c at irradiation doses greater than 10{sup}18 electrons/cm{sup}2) and then, after the irradiation has stopped, to relax over time to its original value. These effects are similar to those observed in the photoexcitation of the electronic subsystem of YBa{sub}2Cu{sub}3O{sub}(7-x) (photostimulated superconductivity). A decrease of the critical current density in the irradiated YBa{sub}2Cu{sub}3O{sub}(7-x) films is also observed, which is due to radiation-stimulated changes of the transmissivity to supercurrent of the dislocation walls in low-angle interblock boundaries.