CONDITIONS OF LUMINESCENCE DEGRADATION OR ENHANCEMENT IN POROUS SILICON

We report that the exposure of porous silicon(PS) to continuous laser light in air results in quenching the intensity of PL(photoluminescence) spectrum peaked at 800 nm, but enhancing that of PL spectrum peaked at 740 nm, which is not recovered by annealing the samples at 160 degrees C in vacuum for 1 hour. When the light exposure is done in vacuum, the intensity of the PL spectra is reduced over the entire range of wavelength and easily recovered at room temperature. From the FTIR (Fourier transform infrared spectroscopy) measurements, it has been shown that the light-induced change of PL in air occurs as a result of optically induced oxidation on the anodized surfaces of PS. These results suggest that whether the light soaking in air induces an enhancement or a degradation of PL depends on the degree of oxidation or hydride formation on the surface of as-prepared PS.