First-principles calculations of the electronic properties of silicon quantum wires

We have performed first-principles pseudopotential calculations for H-terminated Si wires with thicknesses from 12 to 23 \AA{}, calculating the band gaps and optical matrix elements. Comparison with effective-mass theory shows that the latter is valid for wires wider than 23 \AA{}. We have used our data to analyze the luminescent properties of highly porous Si fabricated by electrochemical etching of Si wafers in HF-based solutions.