Small 17, 2101637 (2021)
Mechanical and Chemical Interactions in Atomically Defined Contacts
Damla Yesilpinar1,2, Bertram Schulze Lammers1,2, Alexander Timmer2, Zhixin Hu3, Wei Ji4, Saeed Amirjalayer1,2,5, Harald Fuchs1,2 and Harry Mönig1,2,*
1 Physikalisches InstitutWestfälische Wilhelms-Universität
2 Center for Nanotechnology Heisenbergstraße, 11, 48149 Münster, Germany
3 Center for Joint Quantum Studies and Department of Physics Tianjin University Tianjin 300350, China
4 Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials and Micro-Nano Devices Renmin University of China Beijing 100872, China
5 Center for Multiscale Theory and Computation 48149 Münster, Germany
* harry.moenig@uni-muenster.de
Abstract
Providing fundamental insights in atomic interactions, dedicated methods in atomic force microscopy allow measuring the threshold forces needed to move single adsorbed atoms or molecules. However, the chemical and structural properties of the probe-tip can drastically influence the results. Establishing atomically defined contacts in such experiments, the tips in the present study are functionalized with various chemically and structurally different terminations. Xenon atoms are moved along an atomically defined metal/metal-oxide boundary where all tips show a pulling mechanism and slight force variations, which are assigned to polarization effects within the tip-sample junction. Detaching Xe atoms from the boundary involves a significantly higher energy barrier where chemical reactive Cu-tips cause Xe pickup before any lateral manipulation. Passivating the tip by inert probe particles (Xe or CO) allows further approaching the surface Xe atom. Yet, the small vertical attraction and pronounced tip relaxations prevent reaching sufficient threshold forces inducing manipulation. In contrast, the high structural rigidity of oxygen-terminated Cu-tips allows manipulations even beyond the threshold where they evolve from initial pulling, via sliding to pushing mode. The detailed quantitative analysis of the processes in the atomically defined junctions emphasizes the mechanical and chemical interactions for highly controlled experiments with piconewton sensitivity.
