Enhancing the field emission properties of amorphous carbon films by thermal annealing

Polymer-like hydrogenated and nitrogenated amorphous carbon films (a-C:H:N) have been deposited on silicon and glass substrates using a Plasma Technology DP800 radio frequency plasma enhanced chemical vapour deposition system. This equipment was configured with an earthed water-cooled substrate table, allowing the carbon films to grow under low bias conditions yielding films with refractive indices of similar to 1.5 - 1.7, and E-04 optical band-gaps of similar to 3 - 4 eV. The field emission properties of these films have been studied using a sphere-to-plane anode-cathode configuration, and the dependence on annealing treatment investigated. A significant lowering of the emission threshold field has been measured after treating the films for 1800 s at 400 degrees C. This has been correlated with a simultaneous study of the change in the films' microstructural properties. We conclude that the changes commensurate with the onset of graphitization are beneficial for field emission, and that the associated improvements in the films' mechanical stability will aid incorporation into large-area displays. (C) 1999 Elsevier Science S.A. All rights reserved.