a-Axis-oriented undoped n-BaSi2 epitaxial films were grown on Si(111) substrates by molecular beam epitaxy, and the crystalline quality and grain boundaries were investigated by means of reflection high-energy electron diffraction, X-ray diffraction, and transmission electron microscopy (TEM). The grain size of the BaSi2 films was estimated to be approximately 0.1-0.3 mu m, and straight grain boundaries (GBs) were observed in the plan-view TEM images. Dark-field TEM images under a two-beam diffraction condition showed that these GBs consist mostly of BaSi2 {011} planes. The diffusion length of minority carriers in n-BaSi2 was found to be approximately 10 mu m by an electron-beam-induced current technique. (C) 2012 Elsevier B.V. All rights reserved.