Morphology of InN nanorods using spectroscopic Raman imaging

We report the vibrational properties of vertical and oblique InN nanorods (NRs) grown by molecular beam epitaxy (MBE). Surface optical (SO) Raman mode at 561 cm1, belonging to E1 symmetry [SO(E1)], is identified along with symmetry allowed Raman modes of E2(low), E2(high), and E1(LO) at 87, 489, and 589 cm1, respectively, corresponding to wurtzite InN phase. Usually, SO phonon modes arise due to breakdown of translational symmetry of surface potential at surface defects, which are attributed by the surface roughness. Intensity distribution of E1(LO) and SO(E1) phonon modes over a specified area have been analysed using Raman area mapping with an optical resolution of 400 nm. Imaging with E1(LO) phonon mode, originating from the bulk of the sample, distinguishes the vertical NRs alone. We are able to resolve NR morphologies in both vertical and oblique cases with additional Raman mapping analysis of SO(E1) phonon mode, emerging from the surface irregularities, which are confined to the tip of MBE grown NRs. Copyright (c) 2013 John Wiley & Sons, Ltd.