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 are (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 Irm-l with current densities of 0.1 mA mm(-2) at 50 V mu m(-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 (similar to 58 V mu m(-1)) followed by a subsequent reduction in the onset field to about 15 V mu m(-1). (C) 1998 Elsevier Science S.A.