Paramagnetic center in porous silicon: A dangling bond with C3v symmetry

Paramagnetic centers in self-supporting porous Si films formed by anodization of Si(100) and (111) wafers have been studied by X-band electron paramagnetic resonance (EPR) at room temperature. The EPR spectra indicate that this center has C3v symmetry, and the angular dependence of the line position is described by a g tensor axially symmetric about a 〈111〉 axis; g∥=2.0024, g⊥=2.0080 for the (100) film and g∥=2.0020, g⊥=2.0088 for the (111) film. The small g shift along the 〈111〉 axis indicates that the center is assigned to be a dangling bond localized on a single silicon atom. The results indicate that the surface of as-anodized porous Si maintains a crystallinity of silicon.