Low-energy Fe(+) ion implantation into silicon nanostructures

Si nanowhiskers, up to ~10 mn in height, were formed on Si at a high areal density of ~10(9) cm(-2) by electron-beam annealing prior to ion-implantation with 7 keV Fe(+). Fluences ranged from 3.7 x 10(13) to 4 x 10(15) Fe(+) cm(-2). The nanostructures were characterised using AFM and the retained Fe doses were determined with RBS. The dose was found to increase with fluence with a quadratic dependence. Implantation caused the nanowhiskers to grow in height and become sharper. The growth is attributed to the acquisition of Si and/or Fe atoms from damage-induced processes; the sharpening is explained by differential sputtering. These results are a significant step towards fabricating Fe doped Si nanostructures for enhancing the field emission.