Seminars Archive

Surface electronic structure determined by scanning tunnelling microscopy

Abstract
Scanning Tunnelling Microscopy (STM) can be used to probe the electronic properties of a surface in two ways: either in the direct spectroscopy mode or, indirectly, by observing the energy-resolved two dimensional Friedel oscillations caused by surface steps and defects. In the latter mode the electronic structure can be inferred from the energy and directional dependence of the screening wavelength. This may be applied successfully even for samples which can not be grown in high-quality since only a very small sample area is required and the real space crystal quality is monitored simultaneously with the electronic properties. The technique is best suited for probing the electronic structure close to the Fermi-level with high energy resolution both for the occupied and unoccupied states. An ideal application would therefore be the investigation of systems where many-body effects are expected to distort the one particle electronic structure close to the Fermi-level. In this talk the principles of electronic structure determination by STM will be explained and its capabilities will be illustrated using several examples. Furthermore a detailed comparison with angle-resolved photoemission will be made.