As a coating material for silicon field emitters, amorphous carbon nitride (a-C:N) by helical resonator plasma enhanced chemical vapor deposition has been proposed. Thermal annealing in nitrogen ambient up to 600 °C was carried out to investigate the effects of heat treatment on the field emission. The structural and compositional modifications induced by the annealing were followed by several analytical techniques: Fourier transformation infrared (FTIR) spectroscopy, elastic recoil detection analysis (ERDA), and x-ray photoelectron spectroscopy. FTIR and ERDA analyses indicate that hydrogen loss occurs for annealing temperatures higher than 300 °C. Amorphous-C:N films significantly lowered the turn-on voltage and increased the emission current of the silicon emitters. After annealing at 600 °C, the field emission property was further enhanced presumably due to the efficient conduction through the a-C:N films induced by an increase of the number and/or the size of the graphitic domains. © 1998 American Vacuum Society.