First Principles Calculations of the Structural, Electronic and Optical Properties of Silicon Nanowires

First principles electronic structure calculations are used to investigate the electronic, structural and optical properties~of pure and germanium doped silicon nanowires. The effects of varying the wire diameter, growth direction and dopant concentration are investigated.~ Wires with diameters ranging from one to three nanometers and [001], [011] and [111] growth directions are studied. All the surfaces of the wires are hydrogen passivated and we investigate structures with dihydride, canted dihydride and 2x1 reconstructed structures. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.