Luminescence of high-temperature yttrium-based superconductors

Luminescense spectra of thin films and single crystals of YBa2Cu3O7−x high-temperature superconductors were measured under optical excitation by synchrotron radiation (E = 10.2 eV) and by electrons (cathodoluminescence) with an energy of 6 keV. It has been shown that in all the spectra the main contribution is made by a blue band with an energy of ≈2.9 eV, which is, apparently, the luminescence inherent to the crystal. The time characteristics of luminescence were measured. It turned out that 80% of all the luminescence requires a very long time (τ > 10−6 s) to reach its final level.A model of luminescence appearance is proposed, which is based on luminescence of oxygen quasi-molecules formed by the decay of electronic excitations (luminescence of self-localized and defect-localized excitons)