A study of the effects of nitrogen incorporation and annealing on the properties of hydrogenated amorphous carbon films

The electronic properties of hydrogenated amorphous carbon films deposited using a Plasma Technology DP800 radio frequency plasma-enhanced chemical vapour deposition system are investigated. Films deposited on the driven electrode have a Tauc optical band-gap of 0.9-1.2 eV, a refractive index of 1.8-2.3, and are hard and diamond-like. However, films deposited on the earthed electrode are softer and polymer-like with a Tauc optical band-gap of 2-3 eV and a refractive index of 1.5-1.7. Both types of film have been grown with varying amounts of nitrogen in an attempt to dope them and measure their characteristics. Films grown on the driven electrode showed current versus voltage (I/V) characteristics indicative of Poole-Frenkel type conduction. However, the I/V characteristics of the films grown on the earthed electrode exhibited high resistivity (typically 10(14)-10(15) Omega cm). Thermal annealing of the films grown on the earthed electrode has also been investigated. The films containing nitrogen were found to be more sensitive to annealing. (C) 1999 Elsevier Science Ltd. All rights reserved.