Boron nitride nanogranular films on n-type silicon substrates were prepared and their field-emission performance was tested. The films started their electron emission at a mean electric field of 4.0 V/mu m. The current density reached 1 mA/cm(2) at 6.2 V/mu m. The Fowler-Nordheim plot gave an enhancement factor beta of 360. The films were boron-rich. As measured by scanning electron microscopy and atomic force microscopy, the films contained the cone-shaped islands with the diameter of 20-40 nm, which were believed to enhance the local electric field. Their performance parameters were comparable to the values of the samples with micrometer roughness. (C) 2008 American Vacuum Society.