Atomic-scale smooth Ir films have been deposited on MgO buffered Si(1 0 0) by the pulsed laser deposition (PLD) technique. The whole growth process of the bilayer films was in situ monitored by using reflection high-energy electron diffraction (RHEED) apparatus. The Ir/MgO/Si(1 0 0) hetero structures were also characterized by X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The RHEED observations show that the growth mode of the hetero structures is 2D layer-by-layer growth. The crystalline quality of epitaxial Ir films is comparable to that of single crystals. The achievement of the single-crystal-like epitaxial Ir films with atomic-scale smooth surfaces (Ra = 0.47 nm) is ascribed to the improved crystalline quality of the MgO buffer layer. (C) 2004 Elsevier B.V. All rights reserved.