Aluminum oxide films were produced by reactive dc magnetron sputtering of Al in Ar+O2. The composition of the films was characterized by Rutherford backscattering measurements. Stoichiometric films possessed excellent optical properties with a refractive index of ∼1.6 for visible and near-infrared light. It was possible to produce stoichiometric films while keeping the target in the metallic mode of operation; the resulting deposition rate was 23 nm min-1, as compared to 0.95 nm min-1 for films grown from an oxidized target. An O/Al arrival rate ratio exceeding ∼17 was required for stoichiometric films to be grown at room temperature. The success of the present high-rate deposition strategy hinges on the use of a suitable deposition system geometry — including a large target-to-substrate distance and a small target size — and on the use of sufficient Ar pressure. Monte Carlo simulations are presented; they can be reconciled with our empirical data. © 1998 American Vacuum Society.