Doping silicon with erbium by recoil implantation

In attempt to achieve strong surface doping of silicon with erbium, silicon was implanted with 250-keV argon ions through a thin erbium film deposited on the target surface. As a result, erbium recoil atoms were knocked out of the film and incorporated into the silicon substrate. In this way, silicon was doped with erbium atoms to a concentration of 5 $\cdot$ 10$^{20}$ cm$^{-3}$ within a depth slightly above 10 nm. For the formation of stable optically active ErO$_n$ complexes, oxygen recoil atoms were also incorporated into silicon. During the subsequent heat treatment, about half of the implanted erbium atoms segregated in the surface SiO$_2$ layer. The main fraction of erbium retained in silicon after heat treatments is optically inactive.