Site determination and thermally assisted tunneling in homogenous nucleation

TL;DR

This study combines microscopy and theoretical calculations to investigate how copper atoms and small clusters adsorb, move, and tunnel on a copper surface at low temperatures, revealing site preferences and tunneling behavior.

Contribution

It provides new insights into the site preferences and thermally assisted tunneling mechanisms of copper monomers, dimers, and trimers on Cu(111).

Findings

Atoms in trimers occupy only fcc sites.

Monomers and dimers can occupy both fcc and hcp sites.

Dimer configurations enable thermally assisted tunneling below 5 K.

Abstract

A combined low-temperature scanning tunneling microscopy and density functional theory study on the binding and diffusion of copper monomers, dimers, and trimers adsorbed on Cu(111) is presented. Whereas atoms in trimers are found in fcc sites only, monomers as well as atoms in dimers can occupy the stable fcc as well as the metastable hcp site. In fact the dimer fcc-hcp configuration was found to be only 1.3 meV less favorable with respect to the fcc-fcc configuration. This enables a confined intra-cell dimer motion, which at temperatures below 5 K is dominated by thermally assisted tunneling.