The migration of oxygen in ion-beam-amorphized c-SiO2 (α-quartz) was investigated by means of nuclear reaction analysis using the resonant reaction 18O(p, α) 15N for oxygen depth profiling. Only very small amounts of oxygen were observed to diffuse in crystalline or in Xe+-ion beam-amorphized α-quartz after high-temperature annealing. However, a dramatic migration of oxygen occurs in Cs+-implanted α-quartz in the same temperature range (600-900°C), where Cs diffuses out of the amorphized layer and epitaxial recrystallization occurs. These results point out to a strong correlation of all these processes. A mechanism to explain the observed indiffusion of 18O is proposed and is related to the Cs migration and the topological modification to achieve epitaxial regrowth of the SiO2 matrix. © 2000 American Institute of Physics.