A novel high-current, high-resolution, low-kinetic-energy electron source for inverse photoemission spectroscopy.

A high-current electron source for inverse photoemission spectroscopy is described. The source comprises a thermal cathode electron emission system, an electrostatic deflector-monochromator, and a lens system for variable kinetic energy (1.6-20 eV) at the target.

Electron energy loss spectroscopy with parallel readout of energy and momentum.

We introduce a high energy resolution electron source that matches the requirements for parallel readout of energy and momentum of modern hemispherical electron energy analyzers. The system is designed as an add-on device to typical photoemission chambers. Due to the multiplex gain, a complete phonon dispersion of a Cu(111) surface was measured in 7 min with 4 meV energy resolution.

Standing spin waves in ultrathin magnetic films: a method to test for layer-dependent exchange coupling.

We introduce a method to test theoretical models for the layer dependence of exchange coupling constants in ultrathin magnetic films. The method is based on the observation of high-energy and high-momentum standing spin wave modes using high-resolution electron energy loss spectroscopy. Experimental data are presented for 5-8 layers of fcc cobalt deposited on Cu(100).

Chlorine-enhanced surface mobility of Au(100).

Motivated by experimental studies of two-dimensional Ostwald ripening on Au(100) electrodes in chlorine-containing electrolytes, we have studied diffusion processes using density functional theory. We find that chlorine has a propensity to temporary form AuCl complexes, which diffuse significantly faster than gold adatoms. With and without chlorine, the lowest activation energy is found for the exchange mechanism.

An electron energy loss spectrometer designed for studies of electronic energy losses and spin waves in the large momentum regime.

Based on 143° electrostatic deflectors we have realized a new spectrometer for electron energy loss spectroscopy which is particularly suitable for studies on surface spin waves and other low energy electronic energy losses. Contrary to previous designs high resolution is maintained even for diffuse inelastic scattering due to a specific management of the angular aberrations in combination with an angle aperture. The performance of the instrument is demonstrated with high resolution energy loss spectra of surface spin waves on a cobalt film deposited on the Cu(100) surface.

Spin-polarized electron energy loss spectroscopy of high energy, large wave vector spin waves in ultrathin fcc Co films on Cu(001).

The realm of high energy, large wave vector spin waves in ultrathin films and at surfaces is unexplored because a suitable method was not available up to now. We present experimental data for an 8 ML thick Co film deposited on Cu(001) which show that spin-polarized electron energy loss spectroscopy can be used to measure spin-wave dispersion curves of ultrathin ferromagnetic films up to the surface Brillouin zone boundary.

Step line tension on a metal electrode.

The step line tension in electrochemical systems differs conceptually from the line tension on metals in the vacuum because it refers to different boundary conditions. A procedure is established for calculating the electrochemical line tension and is applied to a novel model of the interface comprising both a stepped metal electrode and an electrolyte solution. To first order, the potential dependence of the line tension is governed by the energy of the step dipole in the electric field of the space charge in the solution.

Potential dependence of step and kink energies on Au(100) electrodes in sulfuric acid.

Using electrochemical STM we studied monolayer high Au islands on Au(100) electrodes in sulfuric acid as a function of the electrode potential. We made use of theoretical and experimental methods recently developed for UHV experiments on metal islands. It is demonstrated that these models are likewise applicable to islands on metal electrodes in a liquid environment.