Thin film of MgO is widely used as a protecting layer of plasma display panel (PDP). We prepared the MgO thin films using ion beam-assisted deposition (IBAD) technique with the aim of controlling the crystal orientation, density and composition of the films. Oxygen ion beam was utilized to irradiate the growing films. The ion beam irradiation was performed by electron cyclotron resonance (ECR) type ion source. The flux of evaporated MgO was produced using an electron gun. Energy and current density of the ion beam as well as deposition rate were taken as the parameters to control the deposition. Crystallinity, density and composition of the films were measured using X-ray diffraction (XRD) and Rutherford backscattering spectroscopy (RBS). Experimental results suggest that the ion beam irradiation during film growth strongly influences the crystal properties of the films to have the best orientation for high efficiency secondary electron emission. It is also confirmed that the oxygen ion irradiation makes the MgO films oxygen-rich. (C) 2003 Elsevier B.V. All rights reserved.