Comment on ‘‘Observation of two-dimensional Fermi contour of a reconstructed Au(111) surface using Fourier transform

In a recent paper, Fujita and co-workers report image can be interpreted as a picture of the LDOS on the observation of the two-dimensional (2D) at the Fermi level (EF) and, consequently, standing Fermi contour of the s–p derived surface state on waves with wave vector q=2kF are visible in such the reconstructed Au(111) surface [1]. This is images. A 2D Fourier transform of a standing done by Fourier transforming scanning tunneling wave image produces a map of the k-vectors microscopy (STM) constant-current images of contributing to the wave pattern. The wave vectors standing wave patterns obtained at low bias voltfor electrons with energy close to F are confined age and low temperature. to lie on the Fermi contour and, thus, the Fourier The s–p surface-state electrons on noble metal transform will display the Fermi contour scaled (111) surfaces constitute a quasi-2D free-electronby a factor of two, as we have previously pointed like gas. Standing waves in the electronic local out [2,3]. density of states (LDOS) are the result of scatterAn advantage of this method to determine ing of surface-state electrons from the potentials surface Fermi contours is that one obtains inforassociated with step edges and impurities. mation about the local electronic structure in the Electrons with energy E set up quantum interferarea scanned by STM [2,3]. This is in contrast to ence patterns with a wave vector q=2k E , where a photoemission experiment, for example, which k E is dictated by the dispersion relation E(k). averages over macroscopic areas of the surface. At low bias voltage, a constant-current STM Fujita et al. [1] have studied whether there is any local influence of a specific domain of the Au(111) herringbone reconstruction [4] on the Fermi con* Corresponding author. Fax: +45-86-12-07-40. E-mail address: [email protected] (F. Besenbacher) tour. They claim that the local Fermi contour has