Karl Franzens University Graz
Graz University of Technology
|
|
| |
Karl Franzens University Graz | Graz University of Technology | |
Single-molecule manipulation and molecular assembly on surfaces Functional molecules are of general interest for a fundamental understanding of physical and chemical processes, but also for applications in nanotechnology from novel materials over molecular machines to molecular electronics. Two kinds of functional molecules will be discussed in this presentation, all studied by scanning tunneling microscopy at low temperatures, thus imaging and manipulating at the single-molecule level: First, so-called molecular switches with at least two stable states that can be reached reversibly will be discussed [1]. It is found that not only the chemical structure of the molecules, but also their atomic-scale environment plays an important role in the switching process, leading to periodic switching patterns [2]. Second, the controlled assembly of functional molecules by “on-surface-synthesis” [3] will be presented. Such a bottom-up construction of stable molecular networks with pre-defined topology and shape represents a key challenge in the field of molecular nanotechnology. Polymerization on stepped surfaces allows to align the molecular chains and to determine the catalytically active sites for the activation process[4]. The shape of the molecular nanostructures can be precisely tuned via the chemical structure of the initial building blocks, even enabling a hierarchical growth mode by the sequential creation of reactive sites within the molecules [5]. This method allows the formation of homogeneous conjugated polymers, which are then pulled off the surface with the STM tip to measure their conductance as a continuous function of the electrode-electrode distance (Fig.1), thus characterizing the charge transport regime [6]. Finally, the adsorption and growth of such organic nanostructures on inorganic crystallites, thus creating a hybrid system [7], will be discussed. |