Direct observation of irradiation-induced nanocavity shrinkage in Si

Nanocavities in Si substrates, formed by conventional H implantation and th ermal annealing, are shown to evolve in size during subsequent Si irradiati on. Both ex situ and in situ analytical techniques were used to demonstrate that the mean nanocavity diameter decreases as a function of Si irradiatio n dose in both the crystalline and amorphous phases. Potential mechanisms f or this irradiation-induced nanocavity evolution are discussed. In the crys talline phase, the observed decrease in diameter is attributed to the gette ring of interstitials. When the matrix surrounding the cavities is amorphiz ed, cavity shrinkage may be mediated by one of two processes: nanocavities can supply vacancies into the amorphous phase and/or the amorphous phase ma y flow plastically into the nanocavities. Both processes yield the necessar y decrease in density of the amorphous phase relative to crystalline materi al. (C) 2001 American Institute of Physics.