Ion beam induced luminescence in amorphous silica: Role of the silanol group content and the ion stopping power

Abstract Comparative in situ ionoluminescence (IL) experiments using light (H, He) and heavy ions (C, Si, Br) at MeV energies have been performed on three types of silica with different silanol group content (negligible, medium and high). In all cases the IL spectra consist of two predominant features: a blue band peaked at 460 nm (2.7 eV) and a red band peaked at 650 nm (1.9 eV). The relative yields of these two emissions and their kinetics as a function of fluence are strongly sensitive to the ion stopping power and are, also, moderately dependent on the OH content. The IL kinetic behavior is discussed in relation to previous results of the silica network compaction obtained from infrared spectroscopy. We confirm that the structural disordering induced by irradiation plays a crucial role on the migration of self-trapped excitons up to the recombination in color centers. The main effect of an increasing OH content is to greatly enhance the ratio of the red versus the blue emission yield. This can be explained by an additional non-bridging oxygen hole center generation channel produced by the scission of extrinsic Si–O–H bonds by electronic excitation that competes with the scission of strained intrinsic bonds.