Effect of oxidation on the electrical properties of granular copper nanostructures

Abstract

The structural and electrical properties of thin granular metal films obtained by laser electrodispersion were studied. Such structures, which consist of amorphous copper grains 5 nm in size, were established to be extremely stable against oxidation. For instance, when oxidized in air, copper grains were covered by Cu2O oxide shells about 1 nm thick after a period of a few days, after which further growth of the oxide in thickness stopped. The oxidized close-packed structures conduct current through intergrain tunneling electron transitions, whereas in partially oxidized structures the conduction involves tunneling electron hopping between conducting ensembles made up of several nanoparticles. It was shown that the size of the nanoparticles and of the conducting ensembles can be found by analyzing the temperature dependence of the conductivity and, independently, from the I–V characteristics of the films.