0000000000030843
AUTHOR
Ch. Ziethen
showing 10 related works from this author
Element-Selective Magnetic Imaging in Exchange-Coupled Systems by Magnetic Photoemission Microscopy
1998
We have used a photoemission microscope to obtain element-resolved magnetic contrast in stacked magnetic thin film systems. Magnetic information is thereby provided by X-ray magnetic circular dichroism. Elemental sensitivity, which is crucial for studying magnetic coupling phenomena in systems with several different layers, is achieved by tuning the energy of the illuminating photons to atomic absorption edges. We present measurements of a Ni-coated Co micropattern on Cu(001), and a wedged Co/Cr/Fe(001) sample. In the former sample the Ni magnetization is seen to follow the magnetization of the Co pattern, thereby changing from an out-of-plane easy axis in areas without underlying Co to in…
Soft X-ray photoelectron microscopy used for the characterization of diamond, a-C and CN , thin films
2002
Abstract This article gives an overview about the application of X-ray photoemission electron microscopy (X-PEEM) used for the analysis of carbon thin films. We present the results of an X-ray absorption near edge structure (XANES) study of CVD diamond, a-C and CNx films on Si (100) as well as a defect analysis of a hard disc scratch test. The sp2/sp3 ratio of the carbon films was determined and mapped in the electron micrographs, which show localized defects in the surface.
Investigations of the corrosion protection of ultrathin a-C and a-C:N overcoats for magnetic storage devices
2004
Abstract The thickness-dependent corrosion protection of carbon overcoats for magnetic hard disks can be analyzed by collecting X-ray absorption near edge structure (XANES) spectra at the Co L3-edge. Co is the main constituent of the protected magnetic media underneath. The spectra of the Co absorption edge display a strong peak for pure metallic, non-oxidized Co. This peak splits up into several sub-structures for oxidized Co. Therefore, XANES spectra provide a straightforward method to determine the overcoat thickness, leading to closed coverage and corrosion protection of the underlying material. A similar approach was carried out by X-ray photoelectron spectroscopy (XPS). Standard a-C:N…
Recent progress in photoemission microscopy with emphasis on chemical and magnetic sensitivity
1997
Abstract With the improved access to synchrotron radiation sources photoemission electron microscopy is developing into a versatile analytical tool in surface and materials science. The broad spectral range and the well-defined polarization characteristics of synchrotron light permit a unique combination of topographic, chemical, and even magnetic investigations down to a mesoscopic scale. The potentiality of photoemission electron microscopy is demonstrated by several experiments on surfaces and microstructured thin film systems, which have been carried out with a newly designed instrument. We discuss its different modes of operation with respect to both microscopy and spectroscopy. A comb…
IMAGING OF DICHROISM IN PHOTOEMISSION ELECTRON MICROSCOPY AT NONMAGNETIC MATERIALS USING CIRCULARLY POLARIZED SOFT X-RAYS
2002
A new approach for investigations of circular dichroism in the angular distribution of photoelectrons (CDAD) is presented. The image contrast using a photoemission line of a certain material is combined with imaging of the angular distribution pattern using a photoemission electron microscope (PEEM). CDAD can be used to investigate pure scattering information by means of the same instrument in microscopically selected regions on a surface. The experiment combines angle-resolved XPS imaging with the indirect mapping of the local environment of atoms by means of CDAD holography. In a conventional photoelectron diffraction or photoelectron holography experiment, it is necessary to move the sa…
NanoESCA: imaging UPS and XPS with high energy resolution
2005
Abstract A novel imaging electron spectrometer has been used for laterally resolved ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) in the soft X-ray range. The instrument is based on a high-resolution emission microscope optics using a cathode lens and an imaging dispersive analyser. The analyser is corrected for the leading aberration term ( α 2 -term) by means of two hemispherical analysers in antisymmetric configuration with an appropriate transfer lens. Small-area spectra as well as energy-filtered images have been taken in the soft X-ray range for a meteorite sample and in the range of the d-band of a Cu polycrystal. An energy resolution of 106 …
Fast elemental mapping and magnetic imaging with high lateral resolution using a novel photoemission microscope
1998
Abstract Using tunable soft X-ray synchrotron radiation and a new-generation photoemission electron microscope with integral sample stage and microarea selector, elemental images and local XANES spectra have been measured. Given the present conditions (PM3 at BESSY), the lateral resolution was in the range of 130 nm with the potential of considerable improvement with high-brilliance sources (a base resolution of 25 nm was obtained in threshold photoemission). Measurements at the oxygen K-edge demonstrate that differences in the local chemical environment of the emitter atom are clearly revealed and can thus be used as a fingerprint technique for its chemical state and geometrical surroundin…
Microspectroscopy and spectromicroscopy with photoemission electron microscopy using a new kind of imaging energy filter
2001
The use of an imaging retarding field analyser attached to the FOCUS IS-PEEM is described. This kind of energy filter is a simple, powerful tool to obtain microspectra from areas of down to about 1 μm using (V)UV and X-ray excitation sources. First results of microspectroscopy measured by excitation with a laboratory as well as a synchrotron X-ray source are presented.
Peculiarities of imaging one- and two-dimensional structures in an emission electron microscope. 1. theory
2000
Local changes in work function cause deviations of the electrical microfield near a sample surface as a result of the uniform accelerating field distribution between the sample (cathode) and the extractor electrode (anode). This results in a change in the electron trajectories. As a consequence, the microscope image shows remarkable changes in position, size, intensity and lateral resolution of distinct details, which can be quantitatively described by the calculations presented here. Analysing these effects in the image gives an opportunity to determine the real lateral size of the observed structures and the distribution of local contact potentials.
Size dependence of magnetic domain patterns in exchange-biased Permalloy/NiO microstructures
2002
The magnetic domain structure in Permalloy (Ni81Fe19) micropatterns (10?100??m) on NiO has been investigated by means of soft x-ray photoemission electron microscopy. The exchange anisotropy between the Ni81Fe19 patterns and the NiO layer results in the formation of complex domain structures which markedly differ from the simple Landau?Lifshitz configurations. The domain structures reflect the competition between the exchange anisotropy and the dipole?dipole interaction in a weakly coupled system. The observed domain structures change with the feature size, as the domain patterns lose complexity in the smaller structures.