Field emission from as grown and nitrogen incorporated tetrahedral amorphous carbon/silicon heterojunctions grown using a pulsed filtered cathodic vacuum arc technique

Abstract

This article reports the field emission measurements on as grown tetrahedral amorphous carbon (ta-C) and nitrogen incorporated tetrahedral amorphous carbon (ta-C: N) films grown using a pulsed filtered cathodic vacuum arc technique. The effect of varying thickness on field emission in the as grown ta-C films and the effect of varying nitrogen content in ta-C: N films have also been studied. The values of threshold field of emission (Eturnon) increase with decrease of thickness in the as grown ta-C films. Nitrogen incorporation up to 5.2at.% in ta-C films decreases the value of Eturnon from 9.9to5.1V∕μm and thereafter it starts increasing again. To understand the mechanism of electron emission, a realistic energy band diagram of ta-C:N∕n++Si heterojunction has been proposed from the experimentally measured valence and conduction band offsets, using in situ x-ray photoelectron spectroscopy and optical spectroscopy data already published in DRM 9 (2000) 1148. The data are explained using the Fowler and Nordheim theory. The field emission results obtained reveal that there exists a barrier to emission and the main barrier is at the front surface and this is related to the conduction band offset of the ta-C:N∕n++Si heterojunction.