Electrical properties of self-assembled carbon networks

In the past years, the interest in the physics of mesoscopic device structu res has increased as the patterning of such systems became more and more ap plicable. Mesoscopic structures uncover new physics since size effects play an important role. For patterning, self-organizing processes are promising , but they can also bear difficulties. Self-organization phenomena are, how ever, interesting from a physical point of view and offer cheap possibiliti es for production purposes. But they are not totally regular, and one proce ss is restrained to a limited number of structures and materials. For the u nderstanding of the electrical behavior of these mesoscopic structures, the form and the slight variation of one from the other have to be taken into account as well as the material properties. In this paper, we present an el ectrical characterization of carbon networks produced by a self-organizing process. The net structure consists of hexagonal basis cells with a diamete r of about 1 mu m and the dimensions of the interconnections of about 100 n m. We find that in the temperature range from 4.2 to 150 K, the specific re sistivity rho depends on temperature T as rho(T) proportional to T-0.3 3 ex p([T-0/](1/p)) and the transport mechanism, therefore, is variable range ho pping. For 4.2 K < T < 26 K, it is p = 4 and the local activation energy sc ales as epsilon(alpha)(T) proportional to T-3/4. In the temperature range f rom 4.2 to 30 K, the current-voltage characteristics exhibit a temperature- dominated part in the low-voltage regime and a voltage-dominated part in th e high-voltage regime. The first can be described according to Mott's law, whereas the second scales as sigma(E) = sigma(1) exp(A*E-n), where A and si gma(1) depend on temperature. A change of the factor n from 1 to 0 takes pl ace with increasing electric field.