axis but coalesced laterally with respect to each other implies defects associated with the positioning boundaries between the individual grains. Hence, inhomogeneous strain distribution within the film is expected, which leads to inhomogeneous broadening of the Raman peaks. In addition, the selection rules could be relaxed by the deformation potential originating from small displacement of atoms from their equilibrium positions. Such phenomenon has been observed in nano-crystals or GaN films with anisotropic strain. Finally, a band centered around 380 cm -1 is also observed. In a previous study the appearance of this band has been associated with localized gap mode due to In vacancies. This suggestion is somewhat in line with the In-deficient nature observed in our TEM image, A clear shift of approximately 5 cm -1 toward higher wavenumber for A1(LO) is observed from the 4.2 nm InN film. Such shift can be due to the presence of compressive strain within the film and/or the coupled longitudinal optical phonon-plasmon mode (LPP+). It should be mentioned that all Raman signals we observed are much broader than that typical line width from bulk counterparts. The pronounced asymmetric broadening can be due to the combined effects of disorder-activated scattering caused by various grain sizes in ultra-thin InN layer, surface optical modes of InN and Fano interference caused by discrete phonon modes and background continuum electron transitions in the system. Despite the fact that our XRD results support the presence of compressive strain, the contribution of LPP+ cannot be ruled out due to the surface accumulation effect especially for InN nanostructures. Further studies are currently underway to unveil the thickness-dependent optical and electrical properties of InN.