Showing papers by "Wolfgang Eberhardt published in 2004"
TL;DR: This work demonstrates a versatile technique for imaging nanostructures, based on the use of resonantly tuned soft X-rays for scattering contrast and the direct Fourier inversion of a holographically formed interference pattern, which is a form of Fourier transform holography and appears scalable to diffraction-limited resolution.
Abstract: Our knowledge of the structure of matter is largely based on X-ray diffraction studies of periodic structures and the successful transformation (inversion) of the diffraction patterns into real-space atomic maps. But the determination of non-periodic nanoscale structures by X-rays is much more difficult. Inversion of the measured diffuse X-ray intensity patterns suffers from the intrinsic loss of phase information, and direct imaging methods are limited in resolution by the available X-ray optics. Here we demonstrate a versatile technique for imaging nanostructures, based on the use of resonantly tuned soft X-rays for scattering contrast and the direct Fourier inversion of a holographically formed interference pattern. Our implementation places the sample behind a lithographically manufactured mask with a micrometre-sized sample aperture and a nanometre-sized hole that defines a reference beam. As an example, we have used the resonant X-ray magnetic circular dichroism effect to image the random magnetic domain structure in a Co/Pt multilayer film with a spatial resolution of 50 nm. Our technique, which is a form of Fourier transform holography, is transferable to a wide variety of specimens, appears scalable to diffraction-limited resolution, and is well suited for ultrafast single-shot imaging with coherent X-ray free-electron laser sources.
626 citations
TL;DR: One-dimensional Co atomic wires grown on Pt(997) have been investigated by x-ray magnetic circular dichroism and the easy axis of magnetization, the magnetic anisotropy energy, and the coercive field oscillate as a function of the transverse width of the wires, in agreement with theoretical predictions for 1D metal systems.
Abstract: One-dimensional Co atomic wires grown on Pt(997) have been investigated by x-ray magnetic circular dichroism. Strong changes of the magnetic properties are observed as the system evolves from 1D- to 2D-like. The easy axis of magnetization, the magnetic anisotropy energy, and the coercive field oscillate as a function of the transverse width of the wires, in agreement with theoretical predictions for 1D metal systems.
129 citations
TL;DR: In this article, angle-resolved photoemission spectra of the γ phase of manganese were analyzed using a recently developed approach that combines density functional and dynamical mean field methods (LDA + DMFT).
Abstract: We present angle-resolved photoemission spectra of the γ phase of manganese as well as a theoretical analysis using a recently developed approach that combines density functional and dynamical mean-field methods (LDA + DMFT). The comparison of experimental data and theoretical predictions allows us to identify effects of the Coulomb correlations, namely, the presence of broad and nondispersive Hubbard bands in this system.
26 citations
TL;DR: In this article, the local electronic structure in sub-nanometer diameter MoS2−Ix nanotubes is investigated by soft X-ray absorption and Xray fluorescence spectroscopies.
Abstract: The local electronic structure in subnanometer diameter MoS2−Ix nanotubes is investigated by soft X-ray absorption and X-ray fluorescence spectroscopies. The nanotubes are found to be semiconducting, with a band gap of 0.4 ± 0.2 eV. The density of electronic states is altered in both the conduction and the valence band as compared to 2H−MoS2. Electronic structure calculations based on simple model structures suggest that the changes can be mainly attributed to the effect of Mo−S−Mo bond angle distortion imposed by the small diameter of the nanotubes.
13 citations