Low-Defect Nanodiamonds and Graphene Nanoribbons Enhanced Electron Field Emission Properties in Ultrananocrystalline Diamond Films

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 °C annealed films exhibit superior EFE properties such as turn-on fields of 1.3 and 0.8 V/μm and corresponding EFE current densities of 7180 and 3180 μA/cm2, respectively. These EFE current densities are improved by ∼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.