Transient photoluminescence decay in porous silicon and siloxene

The photoluminescence decay after laser pulse excitation is studied in porous silicon and siloxene as a function of sample temperature, detection wavelength, laser intensity, and pulse length. The time dependence in all samples is characterized by a nonexponential decay directly after the laser excitation and a single exponential decay for long times after the laser pulse. The exponential decay is identical for the porous silicon samples and annealed siloxene and depends only on detection wavelength and sample temperature. As prepared siloxene exhibits the same decay characteristics. However, the nonexponential decay is more pronounced and the single exponential decay is a factor of 2-5 faster compared with annealed siloxene. The decay of the photoluminescence is another indication of the identical origin of the strong visible luminescence in porous Si and in annealed siloxene.