Further evidence for quantum confinement in porous silicon

The origin of the photoluminescence (PL) of porous silicon is being extensively investigated. In this letter, we offer detailed analyses of the PL spectra, of which about 3%–5% show small extrema that superimpose the larger main peak. Spacing between these smaller maxima is reproducible and independent of the main peak energy and sample history, while energy steps between them correlate with differences in the exciton energies due to changing the sizes of the quantum wires by complete monolayers of atoms.