Raman and photoluminescence study of ion beam irradiated porous silicon: a case for the astrophysical extended red emission?

Abstract We have measured photoluminescence (PL) and Raman spectra of porous silicon (PS) thin films subjected to irradiation with 30 keV He + ion beams. Fluence has been changed between 10 14 and 10 16 ions/cm 2 . The results show a decrease of the photoluminescence intensity by increasing the ion fluence, probably due to the formation of induced non-radiative recombination centres. The increase of defects density and the partial amorphization of the samples have been studied through Raman spectroscopy and a comparison with the induced damage in single-crystalline silicon has been considered. The characteristic PL wavelength (600–800 nm) supports the hypothesis that silicon nanostructures are an attractive carrier for the so called “Extended Red Emission” (ERE) observed in many astronomical objects. However, the possibility to tune the PL quantum efficiency by ion irradiation indicates that silicon nanostructures in space could loss their photoluminescence capability in those environments where cosmic ion bombardment plays a relevant role.