Raman spectroscopy and transmission electron microscopy were employed to study the vibrational properties and the microstructure of epitaxially grown InN films on GaN/Al2O3 templates. The variations of the InN lattice constants, as deduced by electron diffraction analysis, along with the red-shifted E22 mode frequency reveal that InN films exhibited residual tensile stress, strongly dependent on the epilayer growth temperature. Threading dislocations were the dominant structural defects in the films, having a density in the order of 109 to 1010/cm2. Profile analysis of the E22 Raman peak by means of the spatial correlation model provided useful information concerning the effective mean length for free phonon propagation (L), which was a measure of the structural quality of the samples. In all the studied samples, L monotonically increases with decreasing threading dislocation density of pure screw and mixed type character. Raman and Transmission Electron Microscopy Characterization of InN Samples Grown on GaN/Al2O3 by Molecular Beam Epitaxy. J.Arvanitidis, M.Katsikini, S.Ves, A.Delimitis, T.Kehagias, P.Komninou, E.Dimakis, E.Iliopoulos, A.Georgakilas: Physica Status Solidi B, 2006, 243[7], 1588-93