Measurement of luminescence from silica glasses: an optical x-ray absorption fine structures study at Si K-edge

Soft x-ray excited optical luminescence (XEOL) of silica glasses was studied with respect to the excitation x-ray energy (near the Si K-edge) and irradiation time. The luminescence spectra showed emission bands at 3.1 eV and 2.7 eV, assigned to B_2β and B_2α oxygen deficient centers in silica glasses, and the luminescence yields of these bands changed drastically before and above the Si K-edge. Si K-edge photoluminescence yield (PLY) spectrum of the band at 3.1 eV was similar to Si K-edge XANES spectrum recorded in the photocurrent mode for the same silica sample, except for the negative edge jump in the PLY spectrum.

The time evolutions of the band intensity at 3.1 eV were also investigated under the excitation by soft x-ray below and above Si K-edge. The band intensity in both cases decreased slightly with the irradiation. These results indicate that a part of B_2β centers in the silica glass probably changed to other types of oxygen deficiencies by the electron excitation effect. In the early stage of the irradiation, a rapid increase in the intensity of the 3.1 eV band was also observed, indicating that soft x-ray irradiation produced luminescence sites such as B_2β centers.