Magnetism of Nanostructures
The project investigates the possibility to synthetize via self-organized growth the smallest surface supported ferromagnetic nanostructure which retains its magnetic orientation at room temperature and possibly provides the bit unit in future high density magnetic storage applications. A second aim of the present project is to demonstrate individual reading and writing of ferromagnetic units for densities of 10 T dots/in² and beyond by means of spin-polarized STM.
Magnetism at the Atomic Level
The magnetism of transition metal particles and dilute surface alloys is investigated from an atomistic point of view by using spin-polarized scanning tunneling microscopy and synchrotron radiation spectroscopy. The aim is to expand our fundamental understanding and control over the magnetic properties of nanosized materials of current interest.
Nanocatalysis inspired by Enzymatic Cofactors
This project aims to understand catalytic processes on the atomic scale. The first goal is to find suitable model systems to study catalytic reactions. These can be created by the growth of small metal clusters on ultrathin superstructured oxide films. In a further step the reaction pathway is to be investigated by means of inelastic tunnelling spectroscopy and thermal desorption spectroscopy.
Nucleation, Aggregation, Self-organization, Epitaxial Growth
Epitaxial growth of thin films and single crystals has long been regarded as an art rather than a science. For the thin film part, a detailed atomic scale understanding of equilibrium and kinetic issues has been achieved through a combined effort of experiment and theory. We are using kinetic Monte Carlo simulations and the non-linear coupled differential equations from nucleation theory to model nucleation, growth, and coarsening. These models are compared to experiment in order to identify the key parameters, such as adatom diffusion and binding energies. Our nano-mechanical experiments are equally backed up by theoretical modeling using empirical potentials. For ab-initio calculations of experimentally determined material properties we entertain collaborations with theory groups.
Nanotribology and Mechanical Properties of Nanostructures
Nanotribology is a relatively young research field which still bears many undiscovered and unexplained phenomena. Despite the fact that friction of nano-meter sized mechanical contacts behaves in general quite differently from macroscopic friction, the motivation for us to have an activity in nano-tribology is that part of the discoveries may well be transferred to the more relevant mesoscopic length scales, and that nano-tribology gives access to mechanical and electronic properties at the nanometer lengthscale. For instance the kinetics of water capillary condensation from background humidity was found to be at the origin of the variation of friction force with sliding speed, and friction forces could be related to an effective atomic interaction potential. We are currently investigating friction and deformation of surface adsorbed objects carbon nanotubes in order to derive estimates of their mechanical properties, such as radial Young moduli and shear strength.
Adressable Cold Cathode for Flat Panel Screens and e-beam Projection Lithography
This project studies the feasability of a cold cathode electron emitter. The emitter is based on the tunnel effect. Potential applications include flat panel displays with high pixel density and low energy consumption as well as programmable electron beam projection lithography.
Supramolecular Architecture at Surfaces
This project intends to explore the potential of supra-molecular chemistry at surfaces. The project is a collaboration with Prof. J.V. Barth and Prof. K. Kern.
Electron Spin Flip with the STM, Ferromagnetic Resonance with XMCD
When an electron is placed into a magnetic field oriented along the z-axis,the spin up and down states split up by the Zeemann energy. Recent work suggests that the noise spectrum of the tunnel current recorded with an STM above unpaired spins contains a peak at the according frequency. However, the experiments are challenging, since this signal is weak and situated in the RF region, requiring high frequency detection of the tunnel current. In a collaboration with Dr. G. Boero of the group of Prof. R. Popovic in micro-technical engineering at EPFL, we are currently attempting to record the peak as a function of DC field and tip-sample distance above surface adsorbed molecules with radicals. If this approach is feasible, one of the ideas is to use molecules with known g-factor of their radical as probe for the local magnetic field, for instance created by a magnetic nanostructure. In the literature this technique has been called electron spin resonance (ESR) STM, we prefer to call it electron spin flip STM (ESF-STM) since at present we do not intend to apply additional AC-fields as in ESR.