Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 58: Poster Session III (Solid/liquid interfaces; Metals; Semiconductors; Oxides and insulators)
O 58.11: Poster
Mittwoch, 28. März 2012, 18:15–21:45, Poster B
Removal of carbon impurities in tungsten by extended annealing — •Sven Kalka, Sara Wanjelik, and Mathias Getzlaff — Heinrich Heine Universität, Düsseldorf
In order to carry out experiments in the field of surface science, atomically clean surfaces have to be prepared. A clean surface on the atomic scale is also important when used as a substrate for further experiments, like deposition of thin films. In the case of W(110) surfaces, most of the adsorbates can easily be removed by heating the crystal to about 2000K. Tungsten carbides however are stable even at high temperature and need to be removed separately. Carbon is an impurity within the bulk and diffuses to the surface again, so the cleaning procedure needs to be repeated. Thus, the removal of the carbon impurities within the bulk or at least the near surface region is desirable. We exposed the crystal to an oxygen atmosphere of 10−6mbar, while heating it for several days. With this approach, we reduce the carbon content within the crystal and the subsequent diffusion of carbon to the surface. By STM imaging and LEED, we can evaluate the remaining impurities on the surface directly. Comparison of STM images at different stages of the annealing process indicates a reduction of carbon within the bulk.