Fourier Transform-STM: determining the surface Fermi contour

Surface states that cross the Fermi level give rise to a surface Fermi contour, in complete analogy with the notion of a bulk Fermi surface for metals. The shape of the Fermi contour is important when discussing the screening at the surface, Fermi surface nesting, Kohn anomalies, etc. To determine the Fermi contour, the usual technique of choice has been angleresolved photoemission. Recently, we have introduced a new and simple method for determining surface Fermi contours. It is based on a Fourier Transform of STM images obtained at low bias voltage and low temperature. Here we review the results obtained so far, and discuss the method in comparison to photoemission. Finally, we suggest that Fourier Transform-STM can be a valuable tool for studying periodicities in the electronic structure of materials, e.g. charge density waves and charge ordering.