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Institute
We have studied the surface chemistry of 6H-SiC(0001) and 6H-SiC (000 (1) over bar) after wet-chemical treatment using photoelectron spectroscopy (PES) andlow-energy electron diffraction (LEED). The origin of chemically shifted components in the Si2p and C1s spectra is discussed in the light of previous studies onwet-chemically prepared surfaces and on silicate adlayer reconstructed surfaces. On 6H-SiC(0001) an ordered silicate adlayer was prepared by etching the surface withsulfuric acid based agents.
The interface region of friction-welded joints Al-Fe samples is investigated by scanning Auger Spectroscopy, Electron Probe Micro-analysis (EPMA), X-ray Photoelectron spectroscopy, and Photoemission Electron Microscopy, performed at the synchrotron light source (BESSY). We investigated polished samples cut to obtain a cross-section of the Al-Fe joints. At the Al-Fe interface there is a small number of Fe teeth protuding into the adjacent Al-matrix. Beside this mechanical interlock mechanism we identify an Fe-Al alloy which is formed in an almost homogeneous interface layer of approximately 80 micron thickness. We determine the valence band spectra within that layer and notice that the alloying formation is limited to the interface region. In addition, the profile of both, the Fe and O distribution within the Al next to that interface is determined. A model of the friction-welding mechanism is derived and discussed in terms of the ability of achieving low temperature Fe-Al joints.
This poster describes the beamline proposed for the BESSY II U49/2 Undulator by the Collaborating Research Group of BTU Cottbus, HMI Berlin and the TU Darmstadt. The beamline is designed with both high resolution electron spectroscopy, valence band measurements and PEEM in mind and utilises the wide energy range of the U49 Undulator 40−1500eV.
The design chosen is based on a Petersen PGM [1] but with the grating illuminated with parallel light [2]. This modification allows variation of the monochromator higher order content or resolution, spot size without changing the focus. The performance of the beamline was investigated using various programs available at BESSY. The Undulator character- istics were evaluated using both SMUT and WAVE, and the optical performance of the monochromator was checked using REFLEC and RAY.
The calculations show a resolving power of 2×104 with a flux of the order 1013 photons s−1 over the energy range covered by the mono- chromator. The maximum nominal second order contributions are ≈ 2% at 300 eV for the first Undulator harmonic and ≈ 9% for the third harmonic at 500 eV, both of which can be reduced by increasing the grating incidence angle and, or decreasing the Undulator Pinhole size.
N2O-Oxidation of Si(100)
(2001)
Electrochemically-induced oxidation and reduction reactions of UHV-cleaved GaAs(110) surfaces have been studied after emersion under potential control using highresolution synchrotron-induced photoelectron spectroscopy. High quality spectra of the As and Ga core 3d lines and the valence band region have been obtained. Thespectra of the anodic oxide show strong emission of bulk-like Ga2O3 and some As2O3 with the admixture of suboxides and hydroxides. Ga2O3 and As2O3 arecathodically reduced leaving the GaAs surface covered mostly with elemental As, some As-H and remnants of Ga-suboxides and -hydroxides.