The conductivity of the graphene-like carbon films: Anomaly in the 80–120 K temperature range

The paper presents the results of conductivity studies in natural carbon films in the temperature range from 78 to 220 K. The data of structural studies using scanning electron microscopy and Raman spectroscopy are given. It has been found that the deposition of natural carbon on substrates with a conductive coating of indium oxide allows to obtain a new type of structure, that is, thin films, represented by homogeneous carbon nets, in the nodes of which there are globular nano-sized particles in the form of distorted graphene planes. The behavior of the current-voltage characteristics of carbon films containing graphene-like fragments was studied by nanosecond voltammetry. It was established that the sample resistance sharply increased and the sample diamagnetism exhibited (persisting for 50 thermal cycles) at the critical temperature.