The growth of InN on Si (1 1 1) substrates, by nitrogen rf plasma source molecular beam epitaxy (RF-MBE), has been investigated. Compact InN films and nanopillar heterostructures were grown depending on the used buffer layer, V/III flux ratio and substrate temperature. The epitaxial structures were characterized by high-resolution X-ray diffraction (HR-XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence (PL) spectroscopy and Hall-effect measurements. The structural quality of the InN films improved with the use of a thin low-temperature (LT) InN or a GaN/AlN buffer layer and this also resulted to a reduction of the background electron concentration and increase of electron mobility. The InN film grown on a GaN/AlN buffer layer exhibited a HR-XRD rocking curve for the (0002) reflection with full-width at half-maximum (FWHM) of 0.44 degrees, an electron concentration of 1.35 x 10(19) cm(-3) and electron mobility of 1210 cm(2)/Vs. The effect of N/In flux ratio on the nanopillars' dimensions was in qualitative agreement with the self-regulated growth mechanism that has been identified in the growth of InN on GaN (0 0 0 1) surfaces. (C) 2008 Elsevier B.V. All rights reserved.