Trapping levels in nanocrystalline porous silicon

Trapping levels in fresh (one month) and naturally aged (one year) nanocrys talline porous silicon have been investigated using the optical charging sp ectroscopy method. Four significant maxima and/or shoulders were observed f or fresh samples and five for aged ones. They have been attributed to five and six trapping levels, respectively. The trapping centers corresponding t o the most shallow four levels are situated at or nearby the internal surfa ce of the porous silicon films. (C) 2000 American Institute of Physics. [S0 003-6951(00)01621-1].