Hafnium oxide thin films with a reactive dual-magnetron sputtering system were studied. They can be used for multilayer dielectric mirrors at wavelengths of 250 nm and longer. The regimes (and modes) at different electric powers and gas flows were studied and operational points were found. The power and oxygen-control (lambda-control) techniques were applied to optimize the optical quality of the hafnium oxide film. The dispersion curves of the refractive index and extinction coefficient for different regimes were obtained. The reflectivity and transmission of HfO2/ SiO2 stacks are demonstrated, with losses of <0.1% at the wavelength of 800 nm. (C) 2007 Elsevier B.V. All rights reserved.