Optical emission of YBa2Cu3O7–<i>δ</i> and copper samples irradiated by slow electrons under laser-induced evaporation
Abstract
A comparative analysis of emission spectra of laser-induced plasma and cathodoluminescence of YBa2Cu3O7–δ and copper samples is carried out. The identification of plasma luminescence reveals the presence of Y, Y+, Ba, Ba+, and Cu emission lines and continual emission of molecular and cluster fragments Cu–O with a peak at 2.7 eV. The bands of intrinsic electron–photon radiation emitted by copper irradiated by slow electrons are detected at 2.0 and 4.5 eV. It is shown that the main contribution to the wide-band luminescence of Y–Ba–Cu–O at 2.7 and 3.7 eV is made by radiative transitions at the defect centers on oxygen vacancies of the type F and F+. The narrow-band radiation at 3.36 and 2.95 eV, which is sensitive to the superconducting transition, is found to belong to charge-sensitive centers of oxygen chemisorption appearing at the surface due to free charge carriers.