The amorphous to crystal transition temperature has been measured in capped () and uncapped (GST) films (thick) after irradiation with a in the range between and. In the capped samples the crystallization temperature increases with fluence (at). This effect is due to the doping of the GST layer with a few atom percent of recoiled O and Si atoms. The influence of the chemical species on the crystallization kinetics overcomes the effect of the ion-induced local rearrangement that instead decreases the transition temperature by a few degrees in the uncapped samples. Recoil implantation through the use of a thin capping layer may then be a viable alternative to the direct doping of chalcogenide thin films.