Diffusion in diamond-like carbon

The diffusion of carbon and five other elements in amorphous carbon (a-C) films was studied. One set of samples were sp(2) dominated a-C and the other set of samples were sp(3) dominated tetrahedral amorphous carbon (ta-C). The films were deposited using mass separated ion beam deposition under UHV conditions. The diffusion of C-13 as well as that of hydrogen and deuterium was studied using high resolution elastic recoil detection analysis. No apparent self-diffusion could be detected using this technique. The diffusion of hydrogen was found to start at temperatures between 600 and 800 degreesC. For deuterium, activation energies of 3.34(5) and 3.39(5) eV were found for diffusion in ta-C and a-C, respectively. Tungsten, copper and silver were used to study the diffusion of metals in ta-C. Up to annealing temperatures of 1000 degreesC no diffusion took place in the samples. During annealing at 1200 degreesC the ta-C is converted into graphite, making diffusion into the carbon matrix possible. The fact that there is no diffusion of copper in ta-C at temperatures below 1200 degreesC shows that ta-C is a possible diffusion barrier between copper and silicon. (C) 2003 Elsevier Science B.V. All rights reserved.