MgO films were deposited by pulsed mid-frequency magnetron sputtering from metallic targets in the mixture of Ar and O-2 gas. The surface morphology, crystalline structure, and optical properties were characterized by using atomic force microscopy (AFM), X-ray diffraction (XRD), and spectroscopic ellipsometry, respectively. The secondary electron emission coefficients of MgO films were measured by using a self-made apparatus in He gas. A pronounced hysteresis phenomenon of target voltage, current, and deposition rate with increasing and decreasing O-2 flow rate was observed. The structure of films deposited at a metallic mode changes from Mg phase to the mixed Mg and MgO phase, and the films have a very rough surface. All the films deposited at oxide mode have high transparency and smooth surface, and show (2 2 0) preferred orientation growth. The refractive index and extinction coefficient at a wavelength of 670 nm for MgO films deposited at oxide mode with a O-2 flow rate of 3 sccm are 1.698 and 1.16 x 10(-4), respectively. The secondary emission coefficient at a Elp of 57.8 V/(cm Torr) for MgO films deposited at a O-2 flow rate of 3 sccm is 0.16, which is higher than that of MgO films deposited by e-beam evaporation. (C) 2002 Elsevier Science B.V. All rights reserved.