Karl-Heinz Rieder’s research while affiliated with Swiss Federal Laboratories for Materials Science and Technology and other places

This article reviews the manipulation of single molecules by scanning tunneling microscopes, in particular, vertical manipulation, lateral manipulation, and inelastic electron tunneling manipulation. For a better understanding of these processes, we shortly review imaging by scanning tunneling microscopy as a prerequisite to detect the manipulated species and verify the result of the manipulation and scanning tunneling spectroscopy and inelastic electron tunneling spectroscopy, which is used to chemically identify the molecules before and after the manipulation that employs the tunneling current.

This article reviews manipulation of single molecules by scanning tunnelling microscopes, in particular vertical manipulation, lateral manipulation, and inelastic electron tunnelling (IET) manipulation. For a better understanding of these processes, we shortly review imaging by scanning tunnelling microscopy – as a prerequisite to detect the manipulated species and to verify the result of the manipulation – as well as scanning tunnelling spectroscopy and IET spectroscopy which are used to chemically identify the molecules before and after the manipulation that employs the tunnelling current.

The scanning tunneling microscope, invented and developed in the 1980s in the IBM research laboratory in Rüschlikon, has become the dominent scientific tool in surface science and together with its younger brother the atomic force microscope, is widely used also in many other modern research areas. This account contains very personal anecdotal memories from a colleague who worked in a neighboring lab in Rüschlikon describing some events at the periphery of the development of this ingenious instrument.

A single propene molecule, located in the junction between the tip of a scanning tunneling microscope (STM) and a Cu(211) surface can be dehydrogenated by inelastic electron tunneling. This reaction requires excitation of the asymmetric C-H stretching vibration of the ═CH(2) group. The product is then identified by inelastic electron tunneling action spectroscopy (IETAS).

Manipulation experiments have been performed with single molecules of the hydrocarbon propene on a copper(211) surface at 7 K. Depending on the location of the methyl group, propene forms two enantiomorphous pairs of different adsorbate states. Beyond repositioning of the molecules via vertical and lateral manipulations with the STM tip, conversions between the different adsorbate geometries were observed. The role of inelastically tunneled electrons and the electric field in the junction between tip and surface are discussed as origins of adsorbate mode conversion. Copyright © 2010 John Wiley & Sons, Ltd.

Falsche Händigkeit? Kein Problem! K.-H. Ernst et al. beschreiben in ihrer Zuschrift auf S. 4125 ff. eine Prozedur zur Konfigurationsumkehr einzelner chiraler Adsorbate. Durch inelastisch tunnelnde Elektronen aus einer Rastertunnelmikroskopspitze werden Molekülschwingungen angeregt, die dann Aktionen wie Rotation, Translation oder die Inversion der absoluten Konfiguration bewirken.

Wrong handedness? No problem! K.-H. Ernst et al. describe in their Communication on page 4065 ff. how the chirality of single adsorbates can be switched into the opposite enantiomeric state. By using inelastically tunneling electrons from the tip of a scanning tunneling microscope in an ultra-high vacuum, certain molecular vibrations are excited that, in turn, cause different actions such as hopping, rotation, and chirality conversion at the surface.

Chiralitätsumkehr durch Elektronen: Propenmoleküle bilden chirale Komplexe bei Adsorption auf einer Kupferoberfläche. Inelastisch gestreute Tunnelelektronen aus der Spitze eines Rastertunnelmikroskops regen molekulare Schwingungen an, die zur Rotation oder Diffusion des Adsorbats auf der Oberfläche führen. Bei höheren Tunnelströmen wird auch die Umwandlung in die entgegengesetzte Konfiguration beobachtet.

Pumped up: Propene molecules form chiral complexes when adsorbed on a copper surface. Inelastically scattered tunneling electrons from the tip of a scanning tunneling microscope induce rotation or diffusion of the adsorbate on the surface. Higher tunneling currents can lead to conversion of the adsorbate into the opposite enantiomer.

The adsorption and switching behavior of 3,3′,5,5′-tetra-tert-butylazobenzene (meta-TBA) are investigated by low-temperature scanning tunneling microscopy on three different metal substrates: Au(111), Cu(111), and Au(100). The trans state is the most stable configuration after adsorption, displaying similar appearances in the STM images, independent of the substrate. However, the self-assembly and switching behavior is highly dependent on the chemistry and corrugation of the surface. On the Au(111) surface, the tip-induced isomerization is probed successfully and different driving mechanisms are characterized. The experimental images are in good agreement with calculated ones. However, the switching effect is completely suppressed on Cu(111) and Au(100).