Lateral manipulation with combined atomic force and scanning tunneling microscopy using CO-terminated tips

TL;DR

This study demonstrates the use of CO-terminated tips in combined atomic force and scanning tunneling microscopy to manipulate and assemble individual atoms and clusters on surfaces with high precision, revealing effects of tip asymmetry and tilt.

Contribution

It introduces the capability of CO-terminated tips to perform precise lateral manipulation and atom-by-atom assembly, highlighting the influence of tip asymmetry and tilt on force fields.

Findings

CO tips enable high-resolution manipulation of atoms and clusters.

Tip asymmetry causes distortion in lateral force fields.

Atom-by-atom assembly of iron clusters demonstrated.

Abstract

CO-terminated tips currently provide the best spatial resolution obtainable in atomic force microscopy. Due to their chemical inertness, they allow to probe interactions dominated by Pauli repulsion. The small size and inertness of the oxygen front atom yields unprecedented resolution of organic molecules, metal clusters and surfaces. We study the capability of CO-terminated tips to laterally manipulate single iron adatoms on the Cu(111) surface with combined atomic force and scanning tunneling microscopy at 7\,K. Furthermore, we find that even a slight asymmetry of the tip results in a distortion of the lateral force field. In addition, the influence of the tilt of the CO tip on the lateral force field is inverted compared to the use of a monoatomic metal tip which we can attribute to the inverted dipole moment of a CO tip with respect to a metal tip. Moreover, we demonstrate atom-by-atom assembly of iron clusters with CO tips while using the high-resolution capability of the CO tips in between to determine the arrangement of the individual iron atoms within the cluster. Additionally, we were able to laterally manipulate single copper and silicon adatoms without changing or losing the CO from the tip's apex.