Orientation and temperature dependence of electron-induced crystallization in Si and Ge

Si and Ge samples of different substrate orientations were implanted with 50 keV Xe+ ions to a dose around 10(11) ions/cm(2) where the amorphous zones, created by individual ions, remained spatially isolated. The samples were subsequently irradiated at either 90 or 300 K with electrons having energies from 25 to 300 keV in a transmission electron microscope (TEM). At all electron energies and at both temperatures a significant fraction of amorphous zones crystallized, showing that this effect is not due to a temperature increase and occurs at energies below the threshold displacement energy. Preliminary results show that in Ge the crystallization rate depends on the substrate orientation, while in Si this effect was not observed. The results are discussed in terms of possible explanations for epitaxial growth.