Redistribution of erbium and oxygen recoil atoms and the structure of silicon thin surface layers formed by high-dose argon implantation through Er and SiO$_{2}$ surface films

Using analytical high-resolution electron microscopy, the Si structure and the redistribution of Er and O recoil atoms embedded in thin ($\sim$10 nm) surface layers by Ar$^+$ implantation with an energy of 250–290 keV and a dose of 1 $\times$ 10$^{16}$ cm$^{-2}$ through Er and SiO$_2$ films, respectively, and subsequent annealing are studied. It is established that Si recrystallization fails at a distance of $\sim$20 nm from the surface, where the erbium concentration of 5 $\times$ 10$^{19}$ cm$^{-3}$ critical for failure is achieved at $T$ = 950$^{\circ}$C. It disproves the generally accepted model of Er-atom transfer by the recrystallization front into SiO$_2$ on the surface. Instead, it is shown that the redistribution of O recoil atoms to the initial oxide during annealing for immobile Er atoms provides the formation of surface-inhomogeneous erbium phases in such a way that the oxygen-enriched Er–Si–O phase turns out to be concentrated in the oxide, while the depleted Er–Si phase remains in Si. It explains the partial loss of implanted Er after removal of the oxide together with the Er–Si–O phase. It was shown that the formation of a high density of microtwins (locally up to 10$^{13}$ cm$^{-2}$) is associated with the formation of Ar bubbles and clusters, which is atypical for (100)–Si recrystallization.