We measure the quantized conductance in Au-Pd and Au-Ag alloy nanocontacts for a wide range of Pd and Ag concentrations, and study how the ${1G}_0$ conductance of Au changes with alloying. In Au-Pd, the ${1G}_0$ peak in a conductance histogram decreases in height with increasing Pd concentration, and disappears at around 80-at.% Pd. The ${1G}_0$ peak shows no peak shift and forms no subpeaks upon Pd alloying. This result indicates that the ${1G}_0$ conductance in Au-Pd nanocontacts is due to an all-Au atomic link connecting electrodes. Assuming a simple contact geometry, we calculate the formation probability of a Au link as a function of the Pd concentration, and find good agreement with the concentration dependence of the ${1G}_0$ peak height. On the other hand, in Au-Ag, the ${1G}_0$ peak can be observed for an entire range of Ag concentration, and its peak height changes as a linear compositional average of those of pure Au and Ag.

• Received 16 August 2001

DOI:https://doi.org/10.1103/PhysRevB.65.125410