Structural changes in amorphous silicon layers have been investigated as a process route to obtain light emitting silicon nanostructures. The optical emission of the layers was studied by cathodoluminescence (CL). Under 1013 -1014 boron ions/cm2 implantation, nanosized crystalline structures grow in the amorphous matrix. A dominant emission band, centered at 400 nm, appears in the catodoluminescence spectrum of the low dose implanted film, while spectra with a 400 nm intense band and 480–500 nm and 650 weak bands are characteristic of higher dose implanted and anodized layers. The structural changes are correlated with the emission properties in the 400–650 nm range.