The observation of visible photoluminescence (PL) from porous silicon (PS) at room-temperature has stimulated many studies for potential applications in silicon-based optoelectronics.And the PL characteristics of PS is one of the most concentric problems.But the PL mechanism is still a controversial issue.In order to have a further study on the PL characteristics of PS luminescence and discuss the PL mechanism

this letter reported the optical properties of transition-metal (copper) doped porous silicon by immersion plating in metal ion solutions (CuSO

4

).Immersion or electroless plating refers to the plating of soluble metal ions onto a base material without applying a bias.In order to research the influence on photoluminescence of PS by copper-doping

the photoluminescence spectrum and the Fourier transform infrared (FTIR) spectroscopy were measured.Comparing the PL spectrum of the as-deposited porous silicon with the Cu-doped PS

the PL intensity of the Cu-doped PS decreased dramatically and the PL peak locations had a blue shift obviously.That is to say

there was a photoluminescence quenching of porous silicon by immersion plating in copper sulfate solution.And the PL intensity decayed more dramatically with the increasing concentration of the copper sulfate aqueous solution and the immersion time.Fourier transform infrared spectroscopy indicated that:(1) the intensity of the SiH

x

stretching absorption peaks (2 090～2 050 cm

-1

) and the Si-H stretching absorption peaks (620 cm

-1

) decreased after immersion plating;(2) There was a strong absorption at 1 109 cm

-1

due to Si-O-Si in the Cu-doped samples.Studies revealed that the quenching effect of Cu-doped PS may be related to the decrease of Si-H bonding and the nonradiative recombination center played by Cu induced surface electronic states.But the blue shift of the PL peak locations may results from the existence of oxidation on the surface of Cu-doped porous silicon.All of above experiments indicated that

the PL of porous silicon was quenched by copper-doping;and metal deposition occurred simultaneously with the oxidation of silicon to silicon dioxide (SiO

2

).