RADIATION-INDUCED RECRYSTALLIZATION AND ENHANCEMENT IN PHOTOLUMINESCENCE FROM POROUS SILICON

Porous Silicon (PS) samples were irradiated with different ionizing ra diations 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 i rradiated PS samples. Improvement in the luminescent properties was be st for samples irradiated with 10 MeV silicon ions. Partial restructur ing 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 recrystalli sation occurs in the irradiated region. The virgin PS sample exhibited only the (1 1 1) peak in the XRD pattern; whereas the irradiated PS s ample showed a (3 1 1) peak along with the (1 1 1) peak. The average s ize of the microcrystallites was calculated from the diffraction peak broadening, using Scherrer's formula. Depth profile studies, correspon ding to the average sizes of the microcrystallites confirmed the exist ence of (3 1 1) planes, and revealed that the degree of recrystallisat ion is maximum at the end of the trajectories of silicon ions. (C) 199 7 Elsevier Science B.V.