Anisotropic empty electron-band states at the pseudo-5×5 Si(111)/Cu interface

The partial (s-d) density of empty states at the Cu site in the pseudo-5×5 Si(111)/Cu interface has been investigated by polarization-dependent x-ray absorption spectroscopy at the Cu ${\mathit{L}}_{2,3}$ edges. The absorption spectra are strongly dichroic showing a metallic edge in the interface plane and a quasigap in the perpendicular direction. The two-dimensional nature of the electron-band states at the pseudo-5×5 interface layer is therefore directly probed.