Research
The objective of our team is to study the physical and chemical properties of single adsorbates and adsorbate structures on the atomic length scale. The technique of choice is low-temperature scanning probe microscopy, primarily scanning tunneling microscopy (STM). The strength of the scanning probe techniques lies in their ability to analyze the structural environment of one particular defect or adsorbate on the atomic length scale and to probe the local properties of this individual, well-characterized structure.
In the last years we were mainly interested in STM experiments on individual adsorbates on ultrathin insulating films. Ultrathin insulating films on metal substrates facilitate the use of the scanning tunneling microscope to study the electronic properties of single atoms and molecules, which are electronically decoupled from the metallic substrate. Most importantly, many physical and chemical properties are not only quantitatively but also qualitatively different on an insulating surface from those on a (semi-)conducting surface. Hence, it becomes of supreme importance to the scope of science, as it advances to the atomic length scale, to include insulating materials. New experimental possibilities which are to be examined comprise (meta-)stable charging processes of individual adsorbates and STM-induced chemistry of single molecules on insulators. Furthermore, these investigations shall open new research avenues in molecular electronics, as they combine the following two elements: the electronic decoupling of an adsorbate provided by the insulator and the ability of STM to analyze the structural environment of an adsorbed molecule.
Our running scanning tunneling microscope works at a temperature of 5K under ultra-high vacuum conditions. A second machine is presently being built up that includes the possibility to measure forces on the atomic length scale. In the following years, a third apparatus is planned which will allow measurements in strong magnetic fields to additionally study magnetic properties.
The group was established in March 2007 by the hiring of Jascha Repp on a Lichtenberg-professorship, funded by the Volkswagenstiftung.