DC CONDUCTION IN DIAMOND-LIKE CARBON-FILMS OBTAINED BY LOW-ENERGY CLUSTER BEAM DEPOSITION

Carbon films have been obtained by low-energy cluster beam deposition. Clusters of different size distributions centered around C-n = 900, 60, 20 have been selected because of their very different mean hybridization: high sp(2) content for C-900, highly sp(3) for C-20, C-60 being intermediate. Thus, three types of film have been grown and their de conductivity has been investigated in the temperature range 80-473 K. The temperature dependence of the conductivity is explained by carrier hopping and percolation theory. Hopping transport occurs through pi states randomly distributed in energy and in the solid. The pi state densities determined near the Fermi level show that the three types of film remember the hybridization of the different mean free cluster size. Conduction properties of the film are compared with those of a-C films prepared by other techniques.