Current-induced conditioning of hydrogenated amorphous carbon thin films for field emission

The field emission characteristics of hydrogenated amorphous carbon (a-C:H) thin films subjected to electrical current stressing have been examined. In these a-C:H films, deposited by radio frequency PECVD, an initially high, applied electric field (> 40 V mum(-1)) is sometimes required before the onset of electron emission. The threshold field in subsequent voltage cycles tend to converge after three or four cycles. By current stressing of the a-C:H films to different current levels it is shown that it is possible to remove the need for a conventional conditioning cycle. Measurements performed on unstressed films sometimes show that conditioning is required even after initial testing when samples are retested. In films, which have been current-stressed, the films remain fully conditioned even after 87 h after the original tests have been performed. The surface morphology of the current-stressed films is examined using atomic force microscopy and shows that the surface of the stressed area has been altered with three distinct regions present. The prime novelty of this work shows that conditioning of a-C:H films can be achieved through the use of current stressing. (C) 2001 Elsevier Science B.V. All rights reserved.