Porous silicon (PS) was prepared by common electrochemical etching in HF-based electrolytes

and then annealed in plasma of hydrogen at different temperature(250～420℃)in this article. Atomic Force Microscope (AFM) was employed for imaging surface structure at an atomic level. Afterwards

photoluminescence (PL) measurement was applied. Different annealing temperature leads to great change of surface morphology and photoluminescence spectrum of porous silicon. Besides the band caused by quantum size effect

there also exists the efficient blue and violet band in PL spectra of PS. An asymmetric emission band appeared in PL spectrum of PS annealed at 250℃. It could be separated to three components by curve fitting. If these components can be attributed to the recombination of non-equilibrium carriers via three impurity centers in suboxide layer

the PL spectrum could be (explained). The surface composition of PS

which was subjected to the annealing treatment at 420～450℃

is considered to be SiO

x

:Si(H

O). In its PL spectrum

a new violet emission band not reported in literature before appeared. Its mechanism is still in study.