Photoluminescence and Raman scattering in axial Si/Ge nanowire heterojunctions

In crystalline, dislocation-free, Si/Ge nanowire axial heterojunctions grown using the vapor-liquid-solid technique, photoluminescence and Raman spectroscopy reveal a SiGe alloy transition layer with preferential chemical composition and strain. In addition to the lattice mismatch, strain in Si/Ge nanowires is observed from a temperature dependent study to be affected by the difference in Si and Ge thermal expansion. The conclusions are supported by analytical transmission electron microscopy measurements. (C) 2009 American Institute of Physics. [doi:10.1063/1.3240595]