Porous silicon (PS) samples were prepared by common electrochemical etching in HF-based electrolytes. Significantly increased current density (150 mA/cm(2)) during anodization led to the accumulation of oxygen on the internal surface of the pores in the PS. Annealing of the samples was achieved in plasma of hydrogen for 15-30 min. During annealing at higher temperature (420-450degreesC) for 15 min or at lower temperature (250degreesC) for a longer time (30 min),. the: hydride coverage of the internal surface of the pores was replaced by a high-quality suboxide partially oxidized hydride layer or suboxide layer, as was shown by the evolution of infra-red absorption spectra due to annealing. Efficient violet and blue emissions were observed in these samples, which could be the result of the recombination of non-equilibrium carriers via an impurity center in the suboxide layer. In the sample that has a suboxide partially oxidized hydride layer, the luminescence mechanism needs a further investigation. (C) 2002 Elsevier Science B.V. All rights reserved.