Electrical resistivity of graphitized ultra-disperse diamond and onion-like carbon

Here we present the result of measurements of electrical resistivity of ultra-disperse diamonds (UDD) with different graphitization degrees and onion-like carbon (OLC) prepared by vacuum annealing of UDD samples at various fixed temperatures. Intermediate samples contain particles with a diamond core covered by closed curved graphitic shells. The temperature dependence of electrical resistivity rho (T) of these structures is characteristic for the systems with localized electrons and variable hopping-length hopping conductivity (VHLHC). The data on sample resistance are discussed in terms of the variation of dimensionality of conductivity and changing the number of defects in the system. (C) 2001 Published by Elsevier Science B.V.