CNx thin films were prepared using low pressure plasma enhanced chemical vapour deposition, and then bom-barded by low-energy N+2. The compositions before and after+2 bombardment were compared using x-ray photoelectron spectroscopy. The electron field emission characteristics of CNx thin films before and after N+2bombardment were studied under the pressure of 10-6 Pa. For the samples, the tu-on emission field decreased from 2.5 V/μm to 1.2 V/lμm while the stable current density increased from 0.5 mA/cm2 to a value larger than l mA/crm2 before and after the bombardment. Our results illustrate that the field emission characteristics were improved after the bombardment of N+2 .