X-ray induced luminescence of high-purity, amorphous silicon dioxide

Abstract

A comprehensive study of x-ray stimulated luminescence has been carried out on four types of high-purity, amorphous silica (a-SiO2). Both high OH and low OH as well as oxygen-excess and oxygen-deficient materials were studied. The room-temperature, visible x-radio luminescence (XRL) was measured continuously as a function of x-ray dose from zero to 400 Mrad volume average dose. In addition to the XRL measurements, electron paramagnetic resonance (EPR) was used to determine the concentrations of the two key radiation-induced defects, the E′ center and the nonbridging oxygen hole center (NBOHC). The XRL spectra were deconvolved into four Gaussian components with centers at 1.9, 2.2, 2.6, and 2.75 eV. The same centers and widths could be used to describe the spectra in all four types of a-SiO2, only the intensities varied. The 2.6 and 2.75 eV lines are strongly dose dependent, rising from near zero intensity at zero dose in all four materials. These two lines are strongly correlated with each other; they have essentially the same dependence on dose and sample type. This correlation suggests that these two lines are due to the same radiation-induced defect, or to closely related defects. The dose dependence and sample-to-sample variation of these two lines bear some similarities to the E′ concentrations. In contrast to the 2.6 and 2.75 eV lines, the 1.9 eV line has a high intensity at the lowest doses measurable. A simple phenomenological model is proposed to describe the 1.9 eV XRL line. This model involves two populations of defects; one population is present at zero dose and is assumed to be dose independent, while the second population is dose dependent. Evidence is presented that the dose-dependent defect is the NBOHC. The XRL due to the dose-independent population may be associated with a transient response to the x rays, or to a metastable defect; this population may not be observable in post-irradiation experiments such as EPR and conventional photoluminescence. Similar to the 1.9 eV line, the 2.2 eV line also has relatively high intensity at the lowest measurable x-ray dose. The behavior of this line is in general agreement with the self-trapped exciton model.

Luminescence properties of rare-earth ions in SiO2 glasses prepared by the sol–gel method

“…Our results are in general agreement with recent studies on radio-luminescence of pure silica [17,18]. In the present work, three bands were clearly identified at low T, at 1.9, 2.4, and 2.7 eV, respectively.…”

Low-temperature radio- and thermo-stimulated luminescence of SnO2-doped silica

“…1) with the same spectral parameters and temperature dependence of intensity. The 2.3 eV emission is indeed a known silica feature, probably related to self-trapped exciton [13]. Also the structures at 80 K and 200 K in TL glow curves are common to glassy and glass-ceramics samples and were already observed in other silica-based materials [12].…”

“…First, spectral components in RL and TL spectra of SnO 2 :SiO 2 glass-ceramics and Sn-doped silica are the same (Fig. 1), and correspond to those encountered in other silica-based materials [12] and in pure silica too [13], and this holds for TL glow curves as well (Fig. 4).…”

Gd3+-doped sol-gel silica glass for remote ionizing radiation dosimetry

“…It shows narrow and intense RL emission band centered at 314.4 nm (3.94 eV), with a FWHM of about 4.1 nm (0.051 eV). No other RL emission, related to defect centers [36], at lower energy could be detected. Moreover, no continuous background signal due to the stem effects has been observed [5].…”