Field emission from undoped and nitrogen-doped tetrahedral amorphous carbon film prepared by filtered cathodic vacuum arc technique

The field emission results from undoped and nitrogen doped tetrahedral amorphous carbon (ta-C and ta-C:N) prepared by the filtered cathodic vacuum arc (FCVA) technique, deposited on both n⁺ and p⁺ -type Si are reported. The effect of different types of Si substrate and the film thickness on the onset electric field has been investigated. Three sets of ta-C samples with differing doping concentrations were used in the study: undoped p-type ta-C (p-ta-C), nitrogen weakly doped intrinsic ta-C (i-ta-C) and nitrogen heavily doped n⁺-type ta-C (n⁺-ta-C). The heterojunction-based field emission model gives a reasonable explanation for the behavior of the onset electric field measured. The heavily doped hetero-junction, n⁺-ta-C/p⁺-Si, demonstrated the lowest onset field of 10 V μm^-1 with current densities of 0.1 mA mm^-2 at 50 V μm^-1 due to the Zener tunneling arising from the severe band bending. A film thickness of 30-40 nm is more favorable for field emission due to the ease with which the film can be fully depleted. At some locations of i-ta-C films, various types of craters were formed after an electrical discharge at a high field (∼58 V μm^-1) followed by a subsequent reduction in the onset field to about 15 V μm^-1.