Dynamically stable nanostructures in heavy-ion implanted silica glass

Abstract

Previously reported experimental data have been used for kinetic analysis of the dynamically stable structure formation under implantation of 60 keV Au– or Cu– ions into silica glass. The kinetics has been analyzed in the frame of the one-dimensional model of evolution of the implant depth distribution, with taking into account the surface recession due to sputtering, as is also, with considering the local implant production, drift and diffusion.The kinetic analysis has shown that the maximum number of implanted atoms retained in the irradiated substrate (maximum retained ion fluence) is independent of detailed ion-range distribution. The maximum retained ion fluence depends on ratios between the following quantities: the ion flux, the mean projectile range, the surface recession rate, the implant drift velocity and the implant diffusion coefficient. A method has been proposed for evaluation of the surface recession's role in the saturation kinetics. Estimations conducted for 60 keV Au– ion implantation of silica glass have shown that the surface recession predominates in the saturation kinetics.Surface recession does not dominate for 60 keV Cu– ion implantation of silica glass. Formation of dynamically stable structures during 60 keV Cu– ion implantation of silica glass cannot be explained if the drift of implants is excluded from considerations. Considerations have shown that the drift's contribution increases with increasing the ion flux. A mechanism of depleted region formation in the dynamically stable structures has been demonstrated. According to this mechanism, formation of a depleted region within the implanted layer is caused by expelling effect of electric field from the region where the electric field is zero. Necessary drift velocity is provided by Cu+ solutes. A method utilizing images of the dynamically stable structures has been proposed for evaluation of the implant drift's role in the saturation kinetics.