Origin of emission from porous silicon: Temperature-dependence correlation with proton conductivity

The excitation, emission, and Fourier transform infrared (FTIR) spectra of freshly prepared and aged porous : silicon (PS) are examined. The effects of aging and temperature changing on the emission and excitation spectra of fresh and aged PS samples is also studied. Aging in air is found to result in a redshift in the emission spectrum, but a blueshift in the excitation spectrum. Increasing the temperatures leads to a general decrease in the emission intensities of both samples: however, the green emission of fresh sample shows an unusually large and sudden increase in its intensity at the same: temperature at which the proton conductivity in the silicon wafer increases. The temperature dependence of the O-H vibration intensity of silicon wafers shows a sudden decrease at that temperature. These results are consistent with a model in which the excitation leads to the formation of exciton in the confined nanostructure, and the formation of electron and hole that are trapped by surface traps, whose nature is dependent on the chemical composition of the surface land thus;its age). These conclusions are confirmed by the results of the FTIR spectra of the two samples, the temperature dependence of the emission, and its correlation with the proton conductivity in the fresh PS.