AVS 50th International Symposium
    Nanometer Structures Monday Sessions
       Session NS-MoM

Paper NS-MoM1
Conductance and Stability of Atom-sized Al Contacts under High Biases

Monday, November 3, 2003, 8:20 am, Room 316

Session: Quantum Dots and Nanoscale Devices
Presenter: A. Sakai, Kyoto University, Japan
Authors: J. Mizobata, Toshiba Corp., Japan
A. Fujii, Kyoto University, Japan
S. Kurokawa, Kyoto University, Japan
A. Sakai, Kyoto University, Japan
Correspondent: Click to Email
Single-atom contacts (SACs) of metals are known to exhibit various unique properties and considered to be a candidate of interconnects in nanoelectronics. In our previous experiments, we studied high-bias conductance of Au and Au-alloy SACs and showed that they can be observed up to 2 V. In order to know the maximum rating of other metal SACs, we carried out conductance measurements of Al SACs for biases from 0.1 to 0.8 V and investigated the formation and the lifetime of Al SACs as a function of the bias voltage. All measurements were made in UHV at room temperature on breaking Al pin-plate contacts, where SACs were observed just before their complete breakage. We found that the formation probability p@sub Al@ of Al SACs decreases with increasing the bias and leads to the suppression of the first peak in the conductance histogram. Both p@sub Al@ and the first peak vanish at around 0.8 V. On the other hand, the average lifetime of Al SACs, <@tau@@sub Al@>, decreases almost linearly with increasing the bias but remains finite at 0.8 V. For comparison, we re-measured the high-bias conductance of Au SACs and found that p@sub Au@ and <@tau@@sub Au@> show similar bias dependence to that of p@sub Al@ and <@tau@@sub Al@>, respectively, though the relevant bias range is much higher for Au SAC: p@sub Au@, for example, survives up to 2.4 V. We consider that the reduction of p@sub Au@ and p@sub Al@ is due to a contact instability induced by electromigration, which fractures contacts in the middle of their deformation and hence reduces the chance of forming SACs. On the other hand, we found it difficult to explain the observed linear bias dependence of <@tau@@sub Al@> and <@tau@@sub Au@> by a simple rate theory since we know little about the effective contact temperature under high biases.