Cathodoluminescence and IR absorption of oxygen deficient silica - Influence of hydrogen treatment

Cathodoluminescence (CL) and infrared (IR) absorption of silica samples with normal stoichiometry as well as with an extremely high level of oxygen deficit were studied. Additionally, the samples have been treated or non-treated in hydrogen at 800 degrees C. Crystalline quartz was used as reference of the luminescence energetic yield determination and revealing of the glassy state role in defect production under electron beam. The luminescence spectra of silica show the red band at 1.85 eV due to non-bridging oxygen and the two bands at 2.7 and 4.4 eV due to twofold-coordinated silicon. The energetic yield for CL is about 0.1%, for X-ray excited luminescence (XL) it approaches to 0,15%. CL of quartz at low temperatures possesses the self-trapped exciton luminescence mainly. Under electron beam irradiation there occurs production and destruction of luminescence centers in glass, whereas X-ray excitation mainly leads to electron and hole recombination on existing centers. After hydrogen treatment the IR spectra show the appearance of Si-H and Si-O-H vibration bands, independent of the oxygen deficiency. The hydrogen treatment strongly affects the cathodoluminescence properties of oxygen deficient silica by modifying the luminescence centers themselves.