Optical properties of free-standing silicon quantum wires

We present theoretical studies of the optical properties of free-standing Si quantum wires, using an empirical tight-binding model which includes d orbitals and second-neighbor interactions. The excitonic effects are included within the effective-mass approximation. The predicted exciton transition energy for a quantum wire with a width of 27 Å agrees with the observed luminescence for a sample of similar size. We found that the thermally averaged exciton oscillator strengths for quantum wires with widths around 8 Å can become comparable to that of bulk GaAs.