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 sp ² and sp ³ 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 sp ² and sp ³ 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.