Chemiluminescence of anodized and etched silicon: evidence for a luminescent siloxene-like layer on porous silicon.

Treatment of anodized or chemically etched silicon ("porous silicon") with dilute nitric acid or persulfate solution results in weak chemiluminescence in the visible region. Concentrated nitric acid reacts violently with porous Si produced by anodization with a bright flash of light. The fact that similar reactions occur with siloxene (Si 6 H 6 O 3 ) prepared from CaSi 2 suggests that the visible emission seen with porous Si can be attributed to this substance.