High-temperature induced nano-crystal formation in ion beam-induced amorphous silicon ripples

Abstract

We report on in-situ investigations of a recrystallization process of amorphous and damaged crystalline parts generated during ion-beam induced rippling on a Si(100) surface. The ripple structure was created by 60 keV ⁴⁰Ar⁺ irradiation with a dose of ~5×10¹⁷ ions/cm² at ion incident angle of 60° with respect to the surface normal. At this dose the ripples have an average spatial periodicity of about 715 nm and surface undulations with an amplitude of about 40 nm. Structure and morphology of ripples were studied by two types of X-ray scattering (grazing incidence diffraction and amorphous scattering) methods, transmission electron microscopy and atomic force microscopy. X-ray grazing-incidence amorphous scattering pattern were recorded in-situ for a temperature range from 250 to 750°C. Up to about 500°C mainly we found a single broad scattering maximum corresponding to the Si(111) inter-planar distances. At higher temperature these peaks become sharp and intense indicating the onset of a re-crystallization process in the amorphous top layer. Two processes were found, a formation of crystalline islands on top of the former amorphous surface ripples and a growth of polycrystalline twins close to the former amorphous-crystalline interface.