▎ 摘　　要

It is known that the electron field emission (EFE) properties of ultrananocrystalline diamond (UNCD) films were usually produced by doping. Here, we performed a low-pressure annealing treatment without doping to promote the EFE properties of UNCD films. The results show that the 900-1000 degrees C annealed films exhibit superior EFE properties such as turn-on fields of 1.3 and 0.8 V/mu m and corresponding EFE current densities of 7180 and 3180 mu A/cm(2), respectively. These EFE current densities are improved by similar to 18 and 8 times compared to the unannealed UNCD films. The results show that larger diamond grains crack at subgrain boundaries into smaller ones with a low defect concentration, while trans-polyacetylene transforms to graphene nanoribbons to form a conductive network after high-temperature annealing, enhancing the EFE properties. We offer a low-cost and more convenient method to prepare UNCD films with superior EFE characteristics for applications in diamond-based cold cathode emission devices.