On-Demand Final State Control of a Surface-Bound Bistable Single Molecule Switch

A quinone based single-molecule switch as building block for molecular electronics

Using a model molecule, we show that it is possible to create molecules that show the required properties for use as elements in a molecular circuit or computer: two conformations with similar energy but different electric conductivity, and the possibility to switch between those by applying an external electric field.

Single hydrogen atom manipulation for reversible deprotonation of water on a rutile TiO2 (110) surface

The discovery of hydrogen atoms on the TiO₂ surface is crucial for many practical applications, including photocatalytic water splitting. Electronically activating interfacial hydrogen atoms on the TiO₂ surface is a common way to control their reactivity. Modulating the potential landscape is another way, but dedicated studies for such an activation are limited. Here we show the single hydrogen atom manipulation, and on-surface facilitated water deprotonation process on a rutile TiO₂ (110) surface using low temperature atomic force microscopy and Kelvin probe force spectroscopy. The configuration of the hydrogen atom is manipulated on this surface step by step using the local field. Furthermore, we quantify the force needed to relocate the hydrogen atom on this surface using force spectroscopy and density functional theory. Reliable control of hydrogen atoms provides a new mechanistic insight of the water molecules on a metal oxide surface.

Tip-Induced Inversion of the Chirality of a Molecule's Adsorption Potential Probed by the Switching Directionality

The switching behavior of surface-supported molecular units excited by current, light, or mechanical forces is determined by the shape of the adsorption potential. The ability to tailor the energy landscape in which a molecule resides at a surface gives the possibility of imposing a desired response, which is of paramount importance for the realization of molecular electronic units. Here, by means of scanning tunneling microscopy, a triazatruxene (TAT) molecule on Ag(111) is studied, which shows a switching behavior characterized by transitions of the molecule between three states, and which is attributed to three energetically degenerate bonding configurations. Upon tunneling current injection, the system can be excited and continuously driven, showing a switching directionality close to 100%. Two surface enantiomers of TAT show opposite switching directions pointing at the chirality of the energy landscape of the adsorption potential as a key ingredient for directional switching. Further, it is shown that by tuning the tunneling parameters, the symmetry of the adsorption potential can be controllably adjusted, leading to a suppression of the directionality or an inversion of the switching direction. The findings represent a molecule-surface model system exhibiting unprecedented control of the shape of its adsorption potential.

How to control single-molecule rotation

The orientation of molecules is crucial in many chemical processes. Here, we report how single dipolar molecules can be oriented with maximum precision using the electric field of a scanning tunneling microscope. Rotation is found to occur around a fixed pivot point that is caused by the specific interaction of an oxygen atom in the molecule with the Ag(111) surface. Both directions of rotation are realized at will with 100% directionality. Consequently, the internal dipole moment of an individual molecule can be spatially mapped via its behavior in an applied electric field. The importance of the oxygen-surface interaction is demonstrated by the addition of a silver atom between a single molecule and the surface and the consequent loss of the pivot point.

Edge, size, and shape effects on WS2, WSe2, and WTe2 nanoflake stability: design principles from an ab initio investigation

The magic nanoflakes, obtained by the evaluation of the relative stability function, are n = 9 and 14 for all chemical compositions, whereas n = 12 is a magic number for WS₂ and WSe₂.