Strain induced photoluminescence from silicon and germanium nanowire arrays

The optical properties of silicon and germanium nanowires grown within the pores of hexagonal mesoporous silica matrices have been characterised by ultraviolet absorption and photoluminescence (PL) spectroscopy. A clear blue-shift in the PL of the semiconductor composite materials was observed as the diameter of the nanowires decreased from 85 to 22 angstrom. Powder X-ray diffraction revealed that, as the diameter of the confined nanowires decreased, the strain on the crystallographic structure of the nanowires increased, due to escalating lattice expansion, resulting in a shift in the PL maximum to higher energies. The ability to manipulate the optical properties in templated semiconductor nanowires, through strain engineering, has important implications for the design of future optical devices.