Modelling of non-contact atomic force microscopy imaging of individual molecules on oxide surfaces

Abstract

We have modelled NC-AFM imaging of organic molecules adsorbed on the MgO(100) and TiO2(110) surfaces, to study whether molecules adsorbed at well determined surface sites could serve as markers for chemical resolution of surface species and possible mechanisms of adsorption and manipulation of such molecules with NC-AFM tips. We calculated images of perfect MgO and TiO2 surfaces and considered the adsorption of the formate ion and 3-{4-[Tris-(3,5-di-tert-butyl-phenyl)-methyl]-phenoxy}-propionic acid (C52H72O3) at the MgO(100) and TiO2(110) surfaces, respectively, using several types of oxide tip models. The results demonstrate that using adsorption of even small molecules, such as formate, for identifying surface chemical species in NC-AFM images may not be practical. The interaction of hydrocarbon molecules with perfect oxide surfaces is weak and their adsorption should be aided by attaching special anchoring groups. Flat molecules can be identified by their shape, but simultaneous atomic resolution inside the molecule and on the substrate under the same imaging conditions is not feasible.

Cooperative mechanism for anchoring highly polar molecules at an ionic surface

“…The underlying CaF 2 ͑111͒ lattice cannot be simultaneously resolved together with the molecules, for similar reasons as those explained previously for formate on MgO͑100͒. 38 We can, however, unambiguously assign the crystal directions by comparison to atomically resolved images of bare CaF 2 ͑111͒ taken before molecule deposition.…”

TEM-assisted dynamic scanning force microscope imaging of (001) antigorite: Surfaces and steps on a modulated silicate

“…If the tip images the surface with atomic resolution, the tip-surface distance is roughly between 0.3 and 0.4 nm (Hofer et al 2003), which are distances close to interatomic distances. As is shown, e.g., for molecules on insulating surfaces (Sushko et al 2006), the tip can lower reaction potentials and therefore can trigger chemical reactions on the surface. One possible and very simple mechanism could be that the moving tip may induce jumps of H atoms, which jump from one O atom to another O atom that is not terminated by H. Such processes and much more complicated ones could explain the observations we have made during atomic resolution imaging.…”

Modeling of NC‐AFM Imaging of Alkanethiols on the Au (111) Surface

“…The structure of SiO 2 tips and the potential model for their interaction with all-atom organic molecules have been described in detail elsewhere. 18,19 The SiO 2 tips and the united atom CH 2 and CH 3 beads were interacting via Lennard-Jones potential developed for silicalites and alkanes. 20 In this paper we focus on calculating the tip/SAM interactions and predicting NC-AFM images using the approach developed previously.…”