Formation of a metallic contact: jump to contact revisited

The transition from tunneling to metallic contact between two surfaces does not always involve a jump, but can be smooth. We have observed that the configuration and material composition of the electrodes before contact largely determine the presence or absence of a jump. Moreover, when jumps are found preferential values of conductance have been identified. Through a combination of experiments, molecular dynamics, and first-principles transport calculations these conductance values are identified with atomic contacts of either monomers, dimers, or double-bond contacts.

This work is part of the research program of the “Stichting FOM.” Financial support through Grants No. FIS2004-02356 and No. MAT2005-07369-C03-1 of the Spanish MEC, and No. ACOMP06/138 of the Generalitat Valenciana is acknowledged. C. U. and M. J. C. acknowledge a Ramón y Cajal grant of the Spanish MCyT.