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The solid-phase epitaxial regrowth of 175 keV Rb ϩ -implanted ␣-quartz during thermal annealing in air or 18 O 2 was studied as a function of the temperature ͑р1170 K͒ and the implanted Rb fluence ͓(0.1-6)ϫ10 16 ions/cm 2 ͔. Rutherford backscattering channeling spectrometry was used to characterize the damage profiles. The role of the oxygen exchange between the annealing gas and the SiO 2 matrix was highlighted by measuring the 16 O and 18 O profiles by means of time-of-flight elastic recoil detection analysis. Complete epitaxial recrystallization of the amorphized layers was observed after a 1 h annealing in air ͑at 1170 K͒ or in 18 O 2 ͑at 1130 K͒. The recrystallization rate in air follows a two-step Arrhenius process, with activation energies of 2.7Ϯ0.4 and 0.6Ϯ0.2 eV above and below an annealing temperature of 1070 K. The three processes, namely, planar recrystallization of the amorphized a-SiO 2 layer, alkali ion out-diffusion, and 16 O⇔ 18 O exchange, are highly correlated. This correlation is discussed with the help of the concept of the SiO 2 network topology. Finally, the surface topography was measured using an atomic force microscope, which gave evidence of swelling of the SiO 2 matrix during implantation and recompaction during epitaxy.

Light-emitting centers in alkali-ion-implanted α 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 2.5×1016 50keV Na ions/cm2 or 175keV Rb ions/cm2, in O218 atmosphere in the temperature range of 673–1173K. In addition to the known intrinsic subbands at 2.40, 2.79, and 4.30eV, which previously were associated with specific defects in the silica matrix, a strong violet band at 3.65eV and a band at 3.25eV have been identified. Both are intimately correlated with the presence of the implanted alkali atoms and recrystallization process. With respect to the 3.25eV 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.

The luminescence properties of ion-beam doped silica and quartz depend sensitively on the ion species and fluence and the thermal processing during and after ion implantation. In an attempt to achieve high luminescence intensity and full planar recrystallization of α-quartz, we studied double Ge∕Rb-ion implantation, where the Rb ions serve as a catalyst only. Synthetic α-quartz samples were irradiated with 175 keV Rb ions and subsequently with 120 keV Ge ions with fluences of 1×1014–1×1016ions∕cm2 and postannealed at 1170 K in air. A comparative analysis of the epitaxy, migration of the implanted ions, and cathodoluminescence (CL) were carried out. The CL spectra exhibit three strong emission bands in the blue/violet range at 2.95, 3.25, and 3.53 eV, which were assigned to Rb- and/or Ge-related defect centers. For up to 1015 implanted Geions∕cm2, large fraction (75%) of the Ge atoms reach substitutional Si sites after the epitaxy.

The luminescent properties of quartz and silica doped with photoactive ions depend on the structural and chemical properties of the matrix and doping elements. The dynamic solid phase epitaxy of ␣-quartz during Ba + -ion implantation at 300-1170 K and its relationship to cathodoluminescence emission are investigated in this work. Rutherford backscattering channeling analysis revealed that the amorphous layer created by 1 ϫ 10 15 175 keV Ba ions/ cm 2 at 300 K almost disappeared when the implantation temperature was raised to 1120 K. Between 770 and 1100 K the cathodoluminescence spectra taken at room temperature exhibit dramatic changes with the implantation temperature and allow to distinguish between color centers related to quartz, ion-irradiated silica, and implanted Ba ions. After achieving almost complete epitaxial recovery, only a violet band at 3.4 eV remained, which we attribute to Ba-related luminescence centers. Samples first implanted with Ba ions and then postannealed in air or 18 O 2 atmosphere up to 1320 K did not show full epitaxy of the amorphized layer.