Annealing effects on field emission properties of tetrahedral amorphous carbon films

Field emission properties of annealed tetrahedral amorphous carbon (ta-C) films deposited by a filtered cathodic vacuum arc technique on silicon, were investigated. With the increasing annealing temperatures, the ratio of sp2 and sp3 of the annealed ta-C films increased and some nano-structures were formed too. Necessary conditioning steps, with which threshold fields of most ta-C films decrease, could be avoided with the samples annealed above 700°C in a furnace with a flow of nitrogen gas. Moreover, with the first round ramping of applied voltage, a relatively low threshold field of 8 V/μm was obtained from the sample annealed at 800°C. To modify the surface microstructure of the ta-C films further, both nitrogen and acetylene gases were introduced into furnace while annealing. As a result, a relatively low threshold field of 5 V/μm could be achieved at the first ramping round from the annealed ta-C film. This indicates that both the modified ratio of sp2 and sp3 as well as the thin overgrown carbon layer from the decomposition of acetylene contributed to the improvement in field emission properties of the carbon films.