Research News
The images show a cross-section through the electron distribution within tungsten. Figure 1 (above) shows the measured values, Figure 2 (below) the computed values. Source: Research Centre Jülich/UC Davis/Lawrence Berkeley National Laboratory/Univ. Erlangen-Nürnberg/Nat. Inst. for Materials Science Hyogo/Univ. Mainz/LMU Munich
More information:
www.helmholtz.de/fzj-spektroskopie
The results can be looked up in the current issue of the professional journal "Nature Materials" (doi:10.1038/nmat3089). The commenting article "News & Views" predicts considerable potential with regard to material research for the method.
Looking at Deeper Layers
Physical properties of solid materials are based on electronic conditions inside the material. An international research team including the Research Centre Jülich now achieved investigation of these conditions in hitherto unfathomed depth. For their measurements the researchers from Germany, the USA and Japan used the well-established method of angle resolved photoemission spectroscopy. This method has been in use since the 1970s. Scientists subject samples with rays of light. This causes electrons to escape from the material. The distribution of angle and energy of the escaping electrons yields information regarding the electronic conditions of the sample, for instance, the position and movement of electrons or magnetic properties. Yet so far, this was possible only on surfaces to a depth of the upper five to ten atomic layers. Too few electrons from deeper layers escaped to be caught in the detectors of measuring devices. The scientists involved in the project now calibrated the light source of the synchrotron SPring-8 in Japan in such a way, that as many photons as possible hit the sample on the smallest surface area possible. Experimental physicists from Jülich, Erlangen, Mainz and Berkeley optimised the spectrometer used and investigated specimen materials with low lattice vibrations in order to obtain the highest possible degree of detail in the results. Theoretical physicists from Munich and Davis developed models with which the measurement results could be interpreted. By means of the particularly bright high energy light of up to six kiloelectronvolt, a specialised electron spectrometer and cleverly selected specimen material, the scientists then were able to look at the electrons inside of tungsten and gallium arsenide to a depth ten times deeper than before.
