Polycrystalline AlN films were deposited on Si(100) and Si(111) substrates by sputtering in an N-2 + Ar gas mixture at a substrate temperature in the range 200-500 degrees C. The effect of the preparation conditions-substrate temperature. sputtering pressure, r.f. power and gas mixture-on the physical and chemical properties of the films were investigated by means of X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy. The polycrystalline oriented AlN films were obtained at deposition rates in the range 0.20-0.56 mu m h(-1) with an N-2/Ar gas flow ratio of 100%. The film average grain size was estimated to be 60-80 nm. The good agreement between the measured Auger parameter (alpha = 1463.0 +/- 0.1 eV) and the tabulated value (alpha = 1462.9 eV) with a binding energy standard deviation of 0.05 eV indicated the formation of the AlN compound.