We have attempted to grow a-axis-oriented gamma '-Fe4N epitaxial films with smooth surfaces at around 400 degrees C on LaAlO3(LAO)(1 0 0), SrTiO3(STO)(1 0 0) and MgO(1 0 0) substrates by molecular beam epitaxy using solid Fe and a radio-frequency NH3 plasma as the Fe and N sources, respectively. The lattice mismatch of these substrates to gamma '-Fe4N is 0%, 3% and 11%, respectively. Epitaxial growth of gamma '-Fe4N films was successfully achieved on the STO(1 0 0) and LAO(1 0 0) substrates. It was found from reflection high-energy electron diffraction and X-ray diffraction that the a-axis orientation of gamma '-Fe4N was degraded with increasing lattice mismatch. High-angle annular dark-field scanning transmission electron microscopy and electron energy-loss spectroscopy measurements showed that amorphous Al-O layers were present at the gamma'-Fe4N/LAO interface. (C) 2011 Elsevier B.V. All rights reserved.