Nanoscale modification of silicon and germanium surfaces exposed to low-energy helium plasma

Abstract

Complex surface nanostructures were observed in germanium and silicon samples exposed to low energy (24 or 36eV ion kinetic energy) helium plasma. Pyramidal growth is observed in germanium across the temperature range studied (185°C to 336°C), while signifcant modifcation in silicon was only observed at 630°C. Nano-wire growth was observed in both germanium and silicon, and appears to be linked to the strength of the electric feld, which in turn determines the implantation energy of the helium ions. Nanostructure formation is proposed to be driven by surface adatom migration which is strongly infuenced by an Ehrlich-Schwoebel-type surface instability. The role of helium in this model is to drive germanium interstitial formation by ejecting germanium atoms from lattice sites, leading to germanium interstitial difusion towards the sample surface and subsequent adatom and surface nanostructure formation. Show more