Spontaneous growth and luminescence of Si/SiO_x core-shell nanowires

Silicon nanowires were prepared by a thermal evaporation of MoSi ₂ heating rods under controlled temperature and atmosphere. Transmission electron microscopy and selected area electron diffraction show that the nanowire consists of a crystalline Si core and an amorphous SiO _x shell. There exist two major forms of nanowires possessing different morphologies and growth directions, which may indicate that different mechanisms predominate in the growth process. The photoluminescence of the Si/SiO_x core-shell nanowires presents two emission bands, around 550 and 600 nm, respectively.