Existence of a Pb1-like defect center in porous silicon

We performed a detailed study of electron spin resonance (ESR) spectra of porous silicon (PS) samples at different stages of treatment and with different porosities. In addition to the commonly observed Pb0-like dangling bond, results of curve fitting to our ESR spectra show that a Pb1-like center, similar to the Pb1 center observed at the (100) crystalline-Si/SiO2 interface, appears in the PS nanostructure. The ratio of the number of Pb1-like centers to that of Pb0-like centers is related to the PS porosity. Remote hydrogen plasma processing of the annealed PS does not change the ratio significantly, although the total numbers of Pb0-like and Pb1-like centers are reduced and photoluminescence efficiency is improved.