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 G 0 (2 e 2 / h ) peak was observed in the conductance histogram of H 2 /Cu contacts, whereas a low conductance tail (<1 G 0 ) was observed with H 2 /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 H 2 /Cu and H 2 /Au contacts was further investigated using differential conductance (d I /d V ) 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 G 0 peak in the conductance histogram of the H 2 /Cu contacts.