HfNxOy films are deposited by ion beam-assisted deposition on (1 0 0) silicon substrates at room temperature. According to X-ray diffraction analysis, at least two phases exist in HfNxOy film, and X-ray photoelectron spectroscopy results are in good agreement with these analysis. Both annealing and increasing assisting ion beam current increase the concentration of the beta-Hf7O8N4 phase in HfNxOy films. Field emission with low turn on field is reported. Field emission results suggest that the concentration of beta-Hf7O8N4 plays an important role in field emission properties. Hydrogen plasma treatment also enhances field emission properties. These results indicate that the HfNxOy film is an excellent material for field emitter. (c) 2004 Elsevier B.V. All rights reserved.