Reversible quenching of photoluminescence in stain etched porous silicon at HNO3 posttreatment and role of oxygen bonds

The effect of posttreatment in HNO3 at room temperature on the photoluminescence properties and surface chemical bonds of stain etched porous silicon were investigated. It was shown that, such posttreatment results in reversible quenching of photoluminescence. Investigation of the FTIR spectra showed that this posttreatment allows dividing usually occurring simultaneously processes of hydrogen desorption and surface oxidation in two separate processes. It is found that the photoluminescence quenching associated with significant desorption of hydrogen from the surface of porous silicon under the HNO3 action, and its subsequent recovery associated with surface oxidation in air. This recovery of luminescence is correlated with the appearance of absorption on the oxygen bonds at 1180 cm−1 and 1045 cm−1. Stability of photoluminescence peak position, despite of changing intensity, both in treated and untreated samples, during exposure to air, correlates with the absorption stability on the oxygen bonds at 1108 cm−1 and 882 cm−1. These oxygen bonds arise during the formation of stain etched porous silicon and are present in the luminescent and nonluminescent samples. Thus, these oxygen bonds can lead to the occurrence of local levels in the bandgap of silicon nanocrystallites, creating radiative recombination centers.