Quantifying the evolution of atomic interaction of a complex surface with a functionalized atomic force microscopy tip

Abstract

terminating the tip of an atomic force microscope with a co molecule allows data to be acquired with a well-known and inert apex. Previous studies have shown conflicting results regarding the electrostatic interaction, indicating in some cases that the negative charge at the apex of the co dominates, whereas in other cases the positive charge at the end of the metal tip dominates. to clarify this, we investigated CaF 2 (111). CaF 2 is an ionic crystal and the (111) surface does not possess charge inversion symmetry. far from the surface, the interaction is dominated by electrostatics via the negative charge at the apex. closer to the surface, pauli repulsion and co bending dominate, which leads to an unexpected appearance of the complex 3-atom unit cell. We compare simulated data in which the electrostatics are modeled by point particles versus a charge density calculated by Dft. We also compare modeling pauli repulsion via individual Lennard-Jones potentials versus a total charge density overlap. In doing so, we determine forcefield parameters useful for future investigations of biochemical processes.

Probing the Nature of Chemical Bonds by Atomic Force Microscopy

“…Hydrogen bonds are caused by electrostatic interaction between a positively charged H atom and a negatively charged ligand. Probing such a bond with a CO terminated tip could cause a lateral force if one assumes that the CO terminated tip has a negative charge at its very end as evident from its interaction with a Cu N surface [ 72 ], Cl vacancies [ 73 ] and a CaF surface [ 74 ]. If the hydrogen bond leads to an increased charge density between the ligands, a weak signature of repulsion might emerge.…”

Advances in dynamic AFM: From nanoscale energy dissipation to material properties in the nanoscale

“…Still, while the advantage of continuous models should be acknowledged and admitted, it is probably the destiny of the atomic microscope to teach and describe materials by providing a deeper insight of nanometer and atomic processes. After all, friction is not a fundamental force and atomic processes should explain forces and the phenomena that is classically observed [89,90]. dAFM methods are further advancing in terms of throughput [91], the imaging of cells [92] and sophisticated control and data processing methods [93] implying that the scope of the community is increasing together with an understanding of the nanoscale.…”

Revealing buckling of an apparently flat monolayer of NaCl on Pt(111)

“…Again in the STM data all Cl anions can be observed, whereas in the AFM images only approximately one-third of them appear, but this time as higher f features. This reverse behavior of the AFM images for this functionalized tip compared to a metal tip is understood from AFM images of ionic surfaces with CO-terminated tips to be mainly due to the electrostatics of a negatively charged front atom of the tip, whereas a metal tip is positively charged [20,27,29].…”