Formation and characteristics of undoped and doped tetrahedral amorphous carbon films

摘要

Synthesis of undoped and doped tetrahedral amorphous carbon (ta-C) films has been achieved using magnetic field filtered plasma stream system in an ambient gas of pure Ar and Ar with N{sub}2, respectively. The optical and electrical properties ofthese films as a function of the substrate bias voltages (V{sub}b) or nitrogen partial pressures (P{sub}N) have been studied using UV-visible optical absorption spectroscopy, Fourier-transform infra-red spectroscopy (FTIR) and measurements of electricalconductivity. The results show that ta-C films with a high sp3 fraction were formed when the V{sub}b was in the range of -10 to -50 V. The optical band gap of such ta-C films was found to be larger than 3 eV. The incorporation of nitrogen into the ta-Cfilms deposited at low P{sub}N (P{sub}N <25%), results in a slight drop in activation energy, which indicates that there is evidently some doping effect of nitrogen. The configurations of N atoms in ta-C network are identified and discussed.