Time-resolved photoluminescence study of stabilised iron-porous silicon nanocomposites

Porous silicon (PS) passivated by iron (PS/Fe) shows an intense, board and stable photoluminescence (PL) band centred at 1.77 eV. The time-resolved photoluminescence (TRPL) of PS and PS/Fe, in the range of some tenth of μs, were investigated at room temperature. Contrary to PS, the TRPL spectrum of PS/Fe exhibits a multi-band profile, attributed to the presence of iron in porous silicon matrix. Hence, the passivation of PS by iron provides the formation of two states located in the PS band gap. The PL decay line shape, in PS and PS/Fe, is well described by stretched exponential. The decay time (τ) in PS has been found lower than that of PS/Fe which is due to the reduction of the non-radiative transitions. Such paths occur when excited carriers escape by tunnelling from less passivated nanocrystallites silicon. The analyses of the TRPL spectra as well as the decay times approve the passivation of Si nanocrystallites by iron.