Anomalous long-term degradation of photoluminescence in porous silicon layers

The main systematic features of degradation of photoluminescence of porous silicon layers during long-term storage in air are studied. A profound increase in the photoluminescence intensity and a shift of the photoluminescence peak to shorter wavelengths in the optical spectra are observed for all samples. It is found that the degree of degradation depends on the initial crystallographic orientation of the silicon substrate. The decrease in the average diameters of silicon nanoclusters in porous silicon samples is attributed to chemical processes that occur at the developed porous surface with participation of atmospheric oxygen.