  Growth of mono-dispersed AlGaN nanowires of ternary wurtzite phase is
reported using chemical vapour deposition technique in the vapour-liquid-solid
process. The role of distribution of Au catalyst nanoparticles on the size and
the shape of AlGaN nanowires are discussed. These variations in the morphology
of the nanowires are understood invoking Ostwald ripening of Au catalyst
nanoparticles at high temperature followed by the effect of single and
multi-prong growth mechanism. Energy-filtered transmission electron microscopy
is used as an evidence for the presence of Al in the as-prepared samples. A
significant blue shift of the band gap, in the absence of quantum confinement
effect in the nanowires with diameter about 100 nm, is used as a supportive
evidence for the AlGaN alloy formation. Polarized resonance Raman spectroscopy
with strong electron-phonon coupling along with optical confinement due to the
dielectric contrast of nanowire with respect to that of surrounding media are
adopted to understand the crystalline orientation of a single nanowire in the
sub-diffraction limit of about 100 nm using 325 nm wavelength, for the first
time. The results are compared with the structural analysis using high
resolution transmission microscopic study.
