Chemically guided epitaxy of Rb-irradiated α-quartz

Abstract

The solid-phase epitaxial regrowth of 175 keV Rb+-implanted α-quartz during thermal annealing in air or 18O2 was studied as a function of the temperature (⩽1170 K) and the implanted Rb fluence [(0.1–6)×1016 ions/cm2]. Rutherford backscattering channeling spectrometry was used to characterize the damage profiles. The role of the oxygen exchange between the annealing gas and the SiO2 matrix was highlighted by measuring the 16O and 18O 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 K) or in 18O2 (at 1130 K). The recrystallization rate in air follows a two-step Arrhenius process, with activation energies of 2.7±0.4 and 0.6±0.2 eV above and below an annealing temperature of 1070 K. The three processes, namely, planar recrystallization of the amorphized a-SiO2 layer, alkali ion out-diffusion, and 16O⇔18O exchange, are highly correlated. This correlation is discussed with the help of the concept of the SiO2 network topology. Finally, the surface topography was measured using an atomic force microscope, which gave evidence of swelling of the SiO2 matrix during implantation and recompaction during epitaxy.