Unique Determination of “Subatomic” Contrast by Imaging Covalent Backbonding

The origin of so-called “subatomic” resolution in dynamic force microscopy has remained controversial since its first observation in 2000. A number of detailed experimental and theoretical studies have identified different possible physicochemical mechanisms potentially giving rise to subatomic contrast. In this study, for the first time we are able to assign the origin of a specific instance of subatomic contrast as being due to the back bonding of a surface atom in the tip–sample junction

Consecutive Charging of a Molecule-on-Insulator Ensemble Using Single Electron Tunnelling Methods

We present the local charge state modification at room temperature of small insulator-supported molecular ensembles formed by 1,1′-ferrocenedicarboxylic acid on calcite. Single electron tunnelling between the conducting tip of a noncontact atomic force microscope (NC-AFM) and the molecular islands is observed. By joining NC-AFM with Kelvin probe force microscopy, successive charge build-up in the sample is observed from consecutive experiments. Charge transfer within the islands and structural relaxation of the adsorbate/surface system is suggested by the experimental data

Controlling Molecular Self-Assembly on an Insulating Surface by Rationally Designing an Efficient Anchor Functionality That Maintains Structural Flexibility

Molecular self-assembly on surfaces is dictated by the delicate balance between intermolecular and molecule–surface interactions. For many insulating surfaces, however, the molecule–surface interactions are weak and rather unspecific. Enhancing these interactions, on the other hand, often puts a severe limit on the achievable structural variety. To grasp the full potential of molecular self-assembly on these application-relevant substrates, therefore, requires strategies for anchoring the molecular building blocks toward the surface in a way that maintains flexibility in terms of intermolecular interaction and relative molecule orientation. Here, we report the design of a site-specific anchor functionality that provides strong anchoring toward the surface, resulting in a well-defined adsorption position. At the same time, the anchor does not significantly interfere with the intermolecular interaction, ensuring structural flexibility. We demonstrate the success of this approach with three molecules from the class of shape-persistent oligo(<i>p</i>-benzamide)s adsorbed onto the calcite(10.4) surface. These molecules have the same aromatic backbone with iodine substituents, providing the same basic adsorption mechanism to the surface calcium cations. The backbone is equipped with different functional groups. These have a negligible influence on the molecular adsorption on the surface but significantly change the intermolecular interaction. We show that distinctly different molecular structures are obtained that wet the surface due to the strong linker while maintaining variability in the relative molecular orientation. With this study, we thus provide a versatile strategy for increasing the structural richness in molecular self-assembly on insulating substrates