Photoelectron diffraction structure determination of Cu(100)c(2 x 2)-N

Using scanned-energy mode photoelectron diffraction of the N 1s photoemissi on, combined with multiple scattering modelling calculations, the structure of the Cu(1 0 0)c(2 x 2)-N has been investigated. While the results are br oadly consistent with N adsorption in a fourfold coordinated hollow site, a lmost coplanar with the outermost layer, this model can only be fitted to t he data with unphysically large vibrational amplitudes, strongly suggesting that some static adsorbate-induced substrate distortion is involved. The b est-fit structure involves an unusual symmetry-lowering large amplitude (0. 34 Angstrom) rumpling of the outermost Cu layer. This result is entirely co nsistent with the results of a recent scanning tunnelling microscopy study of this surface. (C) 2001 Elsevier Science B.V. All rights reserved.