Grain boundary effects in nanocrystalline diamond

Thin films of heavily boron doped plasma-enhanced chemical vapour deposition grown nanocrystalline diamond were experimentally investigated by means of low temperature transport methods and noise analysis as well. The influence of grain boundaries on superconductivity and other related quantum phenomena observed in this system was treated using phenomenological model according to which the superconducting diamond grains in the film are interconnected by a single or a few weak links having a characteristic dimension in the nanometre range. Comparing then the experimental values of critical current and current-induced Josephson's noise in the superconductivity transition region with the figures predicted by our model, its relevance for the description of boron-doped nanocrystalline diamond has been proved. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.