ELECTRON DOSE DEPENDENCE AND OXYGEN IMPLANTATION EFFECT ON CATHODOLUMINESCENCE INTENSITY IN SYNTHETIC SILICA GLASS

A luminescence band at 2.75 eV in silica glass, Coming 7940, excited w ith 1 keV electron beam was measured as a function of beam current and dose. The initial luminescent intensities at 2.75 eV, taken within 1 s of the beginning of irradiation, were proportional to the beam curre nt in the range 0.8 to 12.7 mu A/mm(2). The luminescent intensities as a function of dose were observed at current densities of 3.0, 4.8, an d 12.7 mu A/mm(2). The intensities increased Linearly for doses < 0.1 C/cm(2) (the first stage) and the rate of growth decreased at that dos e (the second stage) until the maximum intensity (the third stage). Th e intensity then decreased with increasing electron dose and did not r ecover (the fourth stage). Although the luminescent intensities differ ed for each beam current, the four stages were identical for these thr ee current densities. We propose that these four stages are created by competition between generation and destruction of luminescent centers . We attribute the change in rate of increase, the subsequent maximum followed by the decrease to a loss of oxygen from the irradiated spot. Oxygen ion implantation was performed (dose of 3 X 10(16) ions/cm(2) at 50 keV) and the initial intensity of the 2.75 eV band on the first stage was enhanced by a factor of 8. The luminescence centers were cre ated by oxygen ion implantation, therefore, the centers are related to oxygen.