X-ray-induced luminescence in crystalline SiO2

Abstract

The x-ray-induced ‘‘blue’’ emission from commercially available, high-quality synthetic quartz has been studied between 80 and 300 K. Three overlapping bands, each having a different quenching temperature, have been experimentally resolved in the as-grown crystals. These bands peak at 440, 425, and 380 nm; their half-widths are 0.64, 0.75, and 0.92 eV; and they thermally quench in the 120–160, 170–210, and 220–270 K regions, respectively. An intense electron irradiation at room temperature or an electrodiffusion (sweep) in a hydrogen atmosphere eliminates the band at 380 nm. Our results suggest that the 380-nm band arises from recombination of an electron with a hole trapped adjacent to an alkali-compensated aluminum ion (i.e., an Al–M+ center). The origins of the bands at 440 and 425 nm remain unknown. As an application of these results, a screening test is described which could assist quality control during selection of quartz bars for use in precision frequency control devices.