Electron field emission from amorphous carbon thin films as a function of annealing

Abstract

The electron field emission properties of nitrogenated hydrogenated amorphous carbon (a-C:H:N) thin films were analysed, and the emission process modelled. The films were deposited on silicon substrates using a radio frequency plasma enhanced chemical vapour deposition system. The samples were subsequently annealed in a nitrogen atmosphere at a fixed temperature for times between 600 and 2400 s. The field emission current, I , was measured as a function of the macroscopic applied electric field, E , using a sphere-to-plane electrode configuration. Emission current at fields as low as 10 V/μm were measured. There is a marked improvement in the emission characteristics with annealing of the films. A classical Fowler–Nordheim analysis on the experimental data, assuming ` β ' factors equal to unity, yielded unrealistic values for the emission barrier and emission area. Therefore, an alternate emission model based on band bending in the film is proposed to explain the experimental results. In this model the substrate is the true cathode with the carbon film acting as a space charge interlayer.