Solid-phase epitaxy of amorphous silicon induced by electron irradiation at room temperature

Abstract

The technique of cross-sectional electron microscopy has been used to investigate the mechanism of electron-beam-induced solid-phase epitaxy of amorphous silicon at room temperature. Cross sections of samples with surface and buried amorphous layers were irradiated in a transmission electron microscope with electrons of energies higher than the threshold energy for atomic displacement and the induced recrystallization process was characterized. Evidence is given that the dominant mechanism of recrystallization is the diffusion to the amorphous-crystalline interface of the defects produced by elastic displacements both in the crystalline and in the amorphous region. The diffusion length of such defects results in the order of 25--30 nm and is approximatively the same in the crystalline and amorphous Si. Electron-beam irradiation is shown to induce room-temperature polycrystalline nucleation in the amorphous layer. Such a process becomes competitive with solid-phase epitaxy for a dose higher than 5\ifmmode\times\else\texttimes\fi{}${10}^{5}$ C/${\mathrm{cm}}^{2}$.