The photoluminescence (PL) of as prepared porous silicon (PS) etched in different time were studied. The variation of PS blue emission was similar with that of Si complexes vibration mode on PS surface so blue emission may be related to the defect states of surface Si complexes and hydrogen atoms on PS surface can remove irradiative centers and result in increasing PL intensity. The peak centered at 570 nm may be associated to the emission of porous polycrystalline silicon in PS surface, which can be proved by X-ray powder diffraction (XRD) and electron diffraction (ED) methods. (c) 2007 Elsevier Ltd. All rights reserved.