On the preparation and electronic properties of clean W(1 1 0) surfaces |
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Authors: | M. Bode S. Heinze R. Wiesendanger |
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Affiliation: | Institute of Applied Physics and Microstructure Research Center, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany |
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Abstract: | We have studied the influence of oxygen pressure during the cyclic annealing used for the cleaning of W(1 1 0) surfaces. For this purpose the surface morphology and electronic properties are measured by means of scanning tunneling microscopy (STM) and spectroscopy (STS), respectively. It is found that the surfaces with impurity atom densities as low as 2 × 10−3 can be obtained by gradually reducing the oxygen pressure between subsequent annealing cycles down to about 2 × 10−8 mbar in the final cycle. Only on the clean surface a bias-dependent spatial modulation of the local density of states (LDOS) is observed at step edges and around impurity sites by STS. In addition, we find a pronounced peak in the occupied states. In combination with density functional theory calculations these features can be traced back to a dispersive pz-dxz-type surface resonance band and the lower band edge of a surface state, respectively. |
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Keywords: | Scanning tunneling microscopy Scanning tunneling spectroscopies Tungsten Tungsten oxide Single crystal surfaces Surface segregation Surface electronic phenomena |
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