Site-dependent evolution of electrical conductance from tunneling to atomic point contact

TL;DR

This study uses atomic-scale STM to explore how electrical conductance varies at different atomic sites on Pb surfaces, revealing site-dependent behaviors during the transition from tunneling to contact regimes.

Contribution

It provides detailed insights into site-specific conductance evolution and highlights the role of atomic configuration and chemical interactions in atomic-scale electron transport.

Findings

Conductance varies with contact site during transition from tunneling to contact.

Hollow sites exhibit higher conductance than on-top or bridge sites in contact regime.

Atomic configuration significantly influences electron transport in atomic junctions.

Abstract

Using scanning tunneling microscopy (STM), we investigated the evolution of electrical conductance between a Pb tip and Pb(111) surface from tunneling to atomic point contact at a site that was defined with atomic precision. We found that the conductance evolution depended on the contact site, for instance, on-top, bridge, or hollow (hcp and fcc) sites in the Pb lattice. In the transition from tunneling to contact regimes, the conductance measured at the on-top site was enhanced. In the point contact regime, the hollow sites had conductances larger than those of the other sites, and between the hollow sites, the hcp site had a conductance larger than that of the fcc site. We also observed the enhancement and reversal of the apparent height in atomically resolved high-current STM images, consistent with the results of the conductance traces. Our results indicate the importance of atomic configuration in the conductance of atomic junctions and suggest that attractive chemical interactions have a significant role in electron transport between contacting atoms.