Electron Transport Properties of Au, Ag, and Cu Atomic Contacts in a Hydrogen Environment

This study investigates the electron transport properties of Au, Ag and Cu atomic contacts in a hydrogen environment at 10 K, by using the mechanically controllable break junction (MCBJ) technique. A sharp 0.2 G0 (2e2/h) peak was observed in the conductance histogram of H2/Cu contacts, whereas a low conductance tail (<1 G0) was observed with H2/Au contacts. The conductance behavior of the Ag contacts was found not to change by the introduction of hydrogen, thus, indicating a weak interaction between hydrogen and Ag atomic contacts. The atomic configuration of the H2/Cu and H2/Au contacts was further investigated using differential conductance (dI/dV) spectra and statistical analysis of the length of the atomic contacts. This revealed that a single hydrogen molecule is bridged between the Au electrodes via hydrogen-decorated Au chains, while a single hydrogen molecule bridges the Cu electrodes directly. The atomic configuration of the contacts explained the appearance of a sharp 0.2 G0 peak in the conductance histogram of the H2/Cu contacts.