Nanostructured heterogeneous HfNxOy films comprising of nanoscale conductive hafnium nitride grains embedded in a matrix of dielectric oxide or oxynitride were deposited on silicon substrate by magnetron sputtering at room temperature. Electron emission with low threshold field 25 V/μm and good current stability were reported. The field emission characteristics depend on the concentration of hafnium nitride phase, revealing the nature of heterogeneous structure. Field enhancement in HfNxOy film was explained in terms of the interaction between the conductive grains separated by dielectric layers under external electric field. The experiment is expected to open a group of nanostructured heterogeneous material consisting of stable conductive nitride and insulating oxide for field emitter, and also provide an insight into the emission mechanism of carbon films. © 2003 American Institute of Physics.