Ultraviolet Raman spectra of single uncoated and SiO2-coated silicon-on-insulator nanowires: Phonon boundary scattering, wave-vector relaxation and stress

We study Raman spectra of single straight Si-on-insulator (SOI) nanowires (NWs) at the 364 nm excitation wavelength. Uncoated SOI NW Raman band downshift and asymmetric broadening appeared to be smaller than those reported for NW ensembles, where these effects are enhanced due to additional wave-vector relaxation associated with NW imperfections. We observe NW-diameter-inversely proportional symmetric Raman band broadening associated with the phonon boundary scattering (PBS). NW longitudinal optical phonon lifetime and mean free path are determined from the PBS band broadening. SiO2-coated NWs display stress transforming from tensile to compressive with a decrease in the NW width. (C) 2013 AIP Publishing LLC.