Rastertunnel- und Kraftmikroskopie in der Organischen Chemie

Single-molecule electronics: from chemical design to functional devices

The use of single molecules in electronics represents the next limit of miniaturisation of electronic devices, which would enable to continue the trend of aggressive downscaling of silicon-based electronic devices.

2D self-assembly of oligo(p-phenylene vinylene) derivatives: from dimers to chiral rosettes

Enantiomerically pure oligo(p-phenylene vinylene) diaminotriazine derivatives and a short structurally related achiral diaminotriazine derivative, all having a rigid backbone in common, are studied to self-assemble at the solution-graphite interface by scanning tunneling microscopy. As a function of the length of the backbone, different two-dimensional motifs are formed (dimers and rosettes) that are rationalized in terms of the balance between different intermolecular interactions, in this case, intermolecular hydrogen bonding and the packing requirements of the alkyl chains on a graphite surface. In addition, the effect of molecular chirality on monolayer chirality is investigated, revealing molecular size-dependent expressions of the monolayer chirality.

Classification of Scanning Probe Microscopies

In the last few years scanning probe microscopy techniques have gained significant importance in a variety of different research fields in science and technology. A rapid development, stimulated by the invention of the scanning tunneling microscope in 1981 and still proceeding at a high pace, has brought about a number of new techniques belonging to this group of surface analytical methods. The large potential of scanning probe microscopes is documented by over 1000 publications per year. Due to the fact that a number of different terms and acronyms exist, which are partially used for identical techniques and which are sometimes confusing, this article is aimed at classification and at an overview on the analytically most important techniques with clarification of common terms. Emphasis will be put on analytical evaluation of scanning tunneling and scanning force microscopy, as up to now these techniques have gained the highest importance for analytical applications.

Visualization of Surfactants on Nanostructured Palladium Clusters by a Combination of STM and High-Resolution TEM

Scanning tunneling microscopy (STM) and high-resolution transmission electron microscopy (TEM) have been used to determine the dimensions of a series of palladium clusters stabilized by tetraalkylammonium salts. Electrochemically prepared colloids were used in which the average diameter of the inner metal core was varied between 2 and 4 nanometers, and the size of the ammonium ions was adjusted in the series (+)N(n-C(4)H(9))(4) < (+)N(n-C(8)H(17))(4) < (+)N(n-C(18)H(37))(4). The difference between the mean diameter determined by STM and that measured by TEM allows the determination of the thickness of the protective surfactant layer. On the basis of these studies, a model of the geometric properties of ammonium-stabilized palladium clusters has been proposed. Suggestions for the mechanism of the STM imaging process are also made.