Light-emitting defects and epitaxy in alkali-ion-implanted α quartz

Light-emitting centers in alkali-ion-implanted alpha quartz have been investigated with respect to the solid phase epitaxial growth of the ion irradiation induced amorphous zone. Cathodoluminescence was studied under the conditions of chemical epitaxy in annealing the samples, implanted with 2.5x10(16) 50 keV Na ions/cm(2) or 175 keV Rb ions/cm(2), in O-18(2) atmosphere in the temperature range of 673-1173 K. In addition to the known intrinsic subbands at 2.40, 2.79, and 4.30 eV, which previously were associated with specific defects in the silica matrix, a strong violet band at 3.65 eV and a band at 3.25 eV have been identified. Both are intimately correlated with the presence of the implanted alkali atoms and recrystallization process. With respect to the 3.25 eV band reported in the literature, they are discussed to be correlated with the presence of nanoclusters in Si-enriched, and Ge- and Sn-implanted SiO2 structures.