Using photoelectron emission microscopy with hard-X-rays

We present several successful test cases of using photoelectron emission microscopy (PEEM) for photon energy up to 25 keV. First, the full extended X-ray absorption fine structure analysis was implemented in areas as small as 100 mum(2) for transition-metal K edge absorption spectra and, therefore, demonstrated the feasibility of combining structural and chemical analysis with hard-X-ray absorption spectroscopy with high lateral resolution. We also show that PEEM can be used in a transmission (radiography) mode as an imaging detector for hard-X-ray, This approach again leads to the unprecedented 0.3 mum lateral resolution, particularly critical for the use of coherence-based phase contrast techniques in real time X-ray radiology. (C) 2001 Elsevier Science B.V. All rights reserved.X1114sciescopu

Photoemission microscopy with microspot-XPS by use of undulator radiation and a high-throughput multilayer monochromator at BESSY

Kleineberg U, Menke D, Hamelmann F, et al. Photoemission microscopy with microspot-XPS by use of undulator radiation and a high-throughput multilayer monochromator at BESSY. In: Journal of Electron Spectroscopy and Related Phenomena. JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA. Vol 103. ELSEVIER SCIENCE BV; 1999: 931-936.We present a new experiment for photoelectron microspectroscopy by use of undulator radiation, which has been set up at the beamline U2 at the Berlin electron storage ring BESSY 1. This approach employs a non-imaging simulated hemispherical electron energy analyser attached to an imaging photoemission electron microscope (FOCUS IS-PEEM) with integrated microarea selector. The photoemission microscope exhibits a lateral resolution of 25 nm (with 4.9 eV UV-excitation), while the resolution with incident synchrotron radiation in the soft X-ray range is about 100-120 nm (mainly due to chromatic aberrations). Photoemission microscopy as well as photoelectron microspectroscopy of selected areas on the sample surface were performed by using the third harmonic of the direct undulator beam which was monochromatized and refocused by a two-element multilayer optic in the 70-95 eV energy range. The multilayer monochromator operating at near-normal incidence consists of a concave spherical multilayer mirror (r=650 mm) and a plane multilayer grating (blazed grating 1221 L/mm, blaze angle 0.8 deg). Both elements were coated with a Mo/Si multilayer of equal d-spacing (20 doublelayers, d = 10.5 nm) to enhance the reflectivity for EUV radiation at near-normal incidence angles. The characterization of the individual optical components by EUV reflectometry shows a peak reflectance of about 47% at a photon energy of 95 eV in the case of the focusing multilayer mirror while the first order diffraction efficiency of the multilayer blaze grating was measured to be up to 32%. The evaluation of the photoelectron spectra measured with this set-up displays that the spectral resolution of the incident radiation is better than 0.7 eV, while it is about 2-4 eV in the case of a two-multilayer-mirror configuration. Analysis of the surface topography and the chemical composition of inhomogeneities of thin evaporated layers on a mesoscopic scale are the main applications of this experiment. (C) 1999 Elsevier Science B.V. All rights reserved

Chemical microanalysis by selected-area ESCA using an electron energy filter in a photoemission microscope

Schmidt O, Ziethen C, Fecher GH, et al. Chemical microanalysis by selected-area ESCA using an electron energy filter in a photoemission microscope. In: Journal of Electron Spectroscopy and Related Phenomena. JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA. Vol 88. ELSEVIER SCIENCE BV; 1998: 1009-1014.We present a new and simple device for microspectroscopy being independent of the mode of electron-excitation. Micro-Xray photoelectron spectroscopy, electron-induced Anger-spectroscopy, as well as local energy-loss spectroscopy were used to investigate metal-adsorption on silicon. This new approach employs a non-imaging electron energy analyser attached to a new-generation photoemission electron microscope with integral microarea selector. Photoelectron microspectroscopy was performed using the direct beam of an undulator (U2 at BESSY) being monochromatised and focused by means of multilayer optics at hv = 95 eV. Similarly, local Auger-electron and EELS spectra have been taken using a simple electron gun for the excitation. The chemical compositions of inhomogenities in thin layers of indium on silicon and the local state of oxidation of a structured Pt-Co multilayer have been determined. (C) 1998 Elsevier Science B.V

The development and application of imaging EXAFS spectromicroscopy

The capability to perform absorption spectroscopy with hard x-rays was added to the synchrotron imaging spectromicroscopy technique. We present several successful test cases. First, the EXAFS (extended x-ray absorption fine structure) analysis was implemented in areas as small as few mu m(2) for transition-metal K edge absorption spectra. The corresponding structural information was complemented by chemical information from the near-edge region. Specifically, in the case of a cross-sectional cut steel different Fe oxidation states were found at different depths. Tests on a PVD grown TiN film revealed areas with oxidized Ti. Overall, these tests demonstrate the feasibility of combining structural and chemicals analysis with hard x ray absorption and high lateral resolution.X115sciescopu

Heusler compounds as ternary intermetallic nanoparticles: Co2FeGa

This work describes the preparation of ternary nanoparticles based on the Heusler compound Co2FeGa. Nanoparticles with sizes of about 20 nm were synthesized by reducing a methanol impregnated mixture of CoCl2 center dot 6H(2)O, Fe(NO3)(3) center dot 9H(2)O and Ga(NO3)(3) center dot xH(2)O after loading on fumed silica. The dried samples were heated under pure H-2 gas at 900 degrees C. The obtained nanoparticles-embedded in silica-were investigated by means of x-ray diffraction (XRD), transmission electron microscopy, temperature dependent magnetometry and Mossbauer spectroscopy. All methods clearly revealed the Heusler-type L2(1) structure of the nanoparticles. In particular, anomalous XRD data demonstrate the correct composition in addition to the occurrence of the L2(1) structure. The magnetic moment of the particles is about 5 mu(B) at low temperature in good agreement with the value of bulk material. This suggests that the half-metallic properties are conserved even in particles on the 10 nm scale. RI Balke, Benjamin/A-5958-2009; Felser, Claudia/A-5779-2009; Kolb, Ute/A-2642-2011; Mugnaioli, Enrico/E-6237-2011; Fecher, Gerhard/H-2470-2011; Jenkins, Catherine/A-7740-201

Heusler compounds as ternary intermetallic nanoparticles: Co2FeGa

This work describes the preparation of ternary nanoparticles based on the Heusler compound Co2FeGa. Nanoparticles with sizes of about 20 nm were synthesized by reducing a methanol impregnated mixture of CoCl2 center dot 6H(2)O, Fe(NO3)(3) center dot 9H(2)O and Ga(NO3)(3) center dot xH(2)O after loading on fumed silica. The dried samples were heated under pure H-2 gas at 900 degrees C. The obtained nanoparticles-embedded in silica-were investigated by means of x-ray diffraction (XRD), transmission electron microscopy, temperature dependent magnetometry and Mossbauer spectroscopy. All methods clearly revealed the Heusler-type L2(1) structure of the nanoparticles. In particular, anomalous XRD data demonstrate the correct composition in addition to the occurrence of the L2(1) structure. The magnetic moment of the particles is about 5 mu(B) at low temperature in good agreement with the value of bulk material. This suggests that the half-metallic properties are conserved even in particles on the 10 nm scale