Effect of Pressing on Luminescence Spectra of Fumed Silica

We study the effect of pressing at a pressure of 1.6 MPa on the photoluminescence (PL) and pulsed cathodoluminescence (PCL) spectra of high-purity fumed silica powder at room temperature and in ambient air. PL is excited by laser radiation at 193 nm, and PCL is excited by electron beam with particle energies of 100–300 keV. Luminescence spectra of fumed silica are changed substantially after pressing. The relative intensity with respect to the luminescence intensity at 300 nm of both PL and PCL in the range 300–450 nm increase after pressing, while the relative intensity of both PL and PCL in the range 260–290 nm decrease. The pressing-sensitive luminescence band in the range 300–450 nm may be related to the defect composed of two facing surface sylilenes. The band in the range 260–290 nm is related to the other surface-related emitting center.