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 A, calculating the band gaps and optical matrix elements. Comparison with effective-mass theory shows that the latter is valid for wires wider than 23 A. 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