Ni(111) surface state observed with scanning tunneling microscopy

A high-resolution spectroscopy study of the electronic structure of the Ni(111) surface by scanning tunneling microscopy is presented. From the standing-wave pattern the electron dispersion of the surface state is determined using Fourier transform methods and compared with previous photoemission data. The dispersion parameters are found to change over a length scale of 30 nm whereas two dispersions with different binding energies but the same effective mass are found. The shifted dispersions could be resolved simultaneously at certain regions of the open terrace showing a splitting of the surface state by Delta E=60 +/- 15 meV.