AVS 49th International Symposium
    Nanometer Structures Thursday Sessions
       Session NS-ThM

Paper NS-ThM11
High-bias Conductance in Single-atom Contacts of Au Alloys

Thursday, November 7, 2002, 11:40 am, Room C-207

Session: Single Molecule Devices
Presenter: A. Sakai, Kyoto University, Japan
Authors: J. Mizobata, Kyoto University, Japan
A. Fujii, Kyoto University, Japan
S. Kurokawa, Kyoto University, Japan
A. Sakai, Kyoto University, Japan
Correspondent: Click to Email
Single-atom contacts of Au have a strong tendency to exhibit a conductance quite close to 1G0, one quantum unit of conductance, as long as a bias voltage is less than 1 V. They show a well-defined peak at 1G0 when their conductance data are plotted in a histogram. With increasing the bias, however, the 1G0 peak decreases in height and disappears at 1.9 V at room temperature. This result suggests that a single-atom 1G0 contact of Au becomes unstable under high biases, perhaps due to an extremely high current density in the contact, which may cause electromigration or current-induced bond weakening. In an effort to improve the stability of single-atom contacts of Au, we have recently carried out experiments on Au alloy contacts, containing Ag and Pt as solute atoms, and compared their high-bias conductance with that of pure Au. All measurements were performed at room temperature with varying the bias from 0.2 V to 2.0 V. In the case of an Au20wt%Ag alloy, we found that the 1G0 peak is systematically higher than that of pure Au for 0.2-1.2 V. The Ag alloying is thus effective for improving the stability of Au single-atom contacts against high contact current. However, the 1G0 peak height difference between AuAg and pure Au disappears for higher biases, and the positive effect of Ag alloying is somehow limited for biases lower than 1.4 V. On the other hand, an alloying with 20wt%Pt yields no enhancement in the 1G0 peak height, and the peak disappears at 1.0 V. Therefore the effect of alloying on the high-bias 1G0 conductance of Au depends on an alloying element.