Research efforts in the Department of Prof. Kern at the Max-Planck-Institute for Solid State Research are centered on nanometer-scale science and technology, primarily focussing on solid state phenomena that are determined by small dimensions and interfaces. Materials with controlled size, shape and dimension ranging from clusters of a few atoms to nanostructures with several hundred or thousand atoms to ultra thin films with nanometer thickness are studied. A central scientific goal is the detailed understanding of interactions and processes on the atomic and molecular scale. Novel methods for the characterization and control of processes on the nanometer scale as well as tools to manipulate and assemble nanoobjects are developed. Of particular interest are: fundamentals of epitaxial growth and self-organization phenomena, atomic scale fabrication and characterization of metal, semiconductor and molecular nanostructures, quantum electronic transport in nanostructures, atomic scale electron spectroscopy and optics on the nanometer scale. As surface phenomena play a key role in the understanding of nanosystems the structure, dynamics and reactivity of surfaces in contact with gaseous or liquid phases are also in the focus of interest. The research portfolio is illustrated in figure 1.
The capability to control and manipulate individual atoms and molecules at surfaces with sub-Angstrom precision allows to engineer nanoscale structures where the physical and chemical properties are unique functions of size and shape. Magnetic nanostructures can be made out of traditional non magnetic elements, new electronic quantum devices can be built and specific functionality can be modeled in single molecules. Additionally, molecular functionality can be tuned controlling the chemical structure, the geometrical environment or using external excitation sources as light, magnetic or electrical fields. Our goal is to probe the physical properties of nanostructured systems focusing on the local electronic properties of atomic-scale structures at surfaces. Our main research tools are Scanning Tunneling Microscopy and Spectroscopy which are used in an ultra-high-vacuum (UHV) environment at temperatures below 10K and in magnetic fields up to 14 Tesla. These allow us to manipulate and probe materials down to the atomic scale. Electronic and vibrational properties are probed with elastic and inelastic tunneling spectroscopy. These local spectroscopies have been used on clean metals, alloys, in the vicinity of, or on adsorbed atoms and molecules or intrinsic defects. The Kondo effect in correlated electron systems has been studied on different metallic substrates and tuned through ligand field effects. Structures enabling spin engineering are specifically addressed in novel materials like surface alloys.
Molecular nanostructuring at surfaces bears unique potential, particularly when designed molecular species are employed, whose structure can be adapted to specific needs. The central objective of our research is the development of novel and efficient approaches for combining molecular building blocks into desired functional architectures at well defined substrates. Noncovalent interactions as hydrogen bonding, ionic bonding and metal-ligand interactions are applied for the rational design of molecular nanostructures. The envisaged functionalities comprise molecular magnetism, novel heterogenous catalysis, selective host-guest interactions and new concepts of molecular motion and conformational changes. Scanning tunneling microscopy not only allows us to image molecules adsorbed at surfaces with unprecedented resolution but also to follow supramolecular self-assembly and chemical complex formation in real space and time. In the frame of the present priority program we bring together our molecular nanostructuring expertise with the ability to measure transport on a local scale with the tip of a scanning tunneling microscope. To this end we use tunneling- as well as point contact spectroscopy.
For further information please refer to our web page: www.fkf.mpg.de/kern/