Research: General Overview     

What are the atomic-scale origins of friction? How do structural modifications affect the effectiveness of catalysts? How do we produce the smallest, non-volatile computer memories? How do we observe best the structure of soft, biological matter? The mentioned topics might seem very far apart on the first sight. On the second sight, however, it becomes evident that the answers to these questions are all strongly related to one single, fundamental question: How are the (macroscopic) properties of materials determined by atomic-scale interactions and structural arrangements? Driven by questions as outlined above, my interest focuses on the mechanical, physical, and chemical properties of surfaces and interfaces at the nanometer scale applying an approach based on nanomechanical investigations.

Nanomechanics is a comparatively new branch of scientific research since mechanical experiments could not be realized on this scale in a controlled manner before the invention of the scanning force microscope in 1986. Today, after more than two decades of development, stable experimental set-ups equipped with ultra-sharp tips and highly resolving detectors for the measurement of the cantilever deflection are available. The versatility of these instruments is convincingly demonstrated by the long and continuously growing list of parameters, quantities, and effects that can be explored. Interactions that can be detected spatially resolved and with high resolution (often down to the atomic scale) include frictional, elastical, adhesional, and van der Waals interactions as well as Pauli repulsion etc. Electronical interactions, for example, open a new way to nanoelectronics, while "chemical" interaction forces such as chemical binding forces are bridging to physical chemistry and catalysis.

In our group, we probe these interactions with specialized, mostly home-built scanning force microscopes, which are operated under ambient conditions as well as at low temperatures, in ultrahigh vacuum, or in liquids, depending on the specific topic to be investigated. Additionally, most of the techniques we are applying differ from the usual standard of commercially available instruments and operation modes. The recently developed "noncontact" mode might serve as an example. One of its benefits is that it enables the atomic-scale imaging of surfaces with a resolution comparable to the one achieved by scanning tunneling microscopes, but without their intrinsic limitation to conducting surfaces. Other examples are so-called "dynamic" force spectroscopy modes or methods for the quantitative measurements of atomic-scale friction.

Specifically, my work is concentrated on four different topics. The first topic represents the high-resolution investigation of atomic-scale interactions by means of scanning force microscopy. For this purpose, a home-made scanning force microscope operated in ultrahigh vacuum and at low temperatures that should meet the highest standards regarding resolution and stability has been developed. The second project deals with the exploration of the fundamentals of friction (nanotribology) and, closely related, the nanomechanics of tip-sample contacts. Third, we pursue the application of new imaging modes to better study the structure of soft, biological matter. In addition, a new force microscope for investigating magnetic forces on the nanometer scale at various temperatures is in its final stage of testing. Examples for all directions can be found in the image gallery section; further information can either be downloaded from the publication section, or requested by mail.