Radiation induced recrystallisation and enhancement in photoluminescence from porous silicon

Porous Silicon (PS) samples were irradiated with different ionizing radiations which included 1 and 6 MeV electrons, Co-60 gamma rays and 10 MeV silicon ions. Improvement in the efficiency of photoluminescence (PL) and its stability with time were invariably observed in all the irradiated PS samples. Improvement in the luminescent properties was best for samples irradiated with 10 MeV silicon ions. Partial restructuring of Si-O-Si and Si-H type species into Si-OH was confirmed from the infrared spectra of pre-and post-irradiated samples, Grazing, angle X-ray diffraction (XRD) analysis revealed that preferential recrystallisation occurs in the irradiated region. The virgin PS sample exhibited only the (1 1 1) peak in the XRD pattern; whereas the irradiated PS sample showed a (3 1 1) peak along with the (1 1 1) peak. The average size of the microcrystallites was calculated from the diffraction peak broadening, using Scherrer's formula. Depth profile studies, corresponding to the average sizes of the microcrystallites confirmed the existence of (3 1 1) planes, and revealed that the degree of recrystallisation is maximum at the end of the trajectories of silicon ions. (C) 1997 Elsevier Science B.V.