IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Friday Sessions
       Session SS3-FrM

Paper SS3-FrM8
Cu(100)c(2x2)-N: a New Type of Adsorbate-Induced Surface Reconstruction

Friday, November 2, 2001, 10:40 am, Room 122

Session: Clean and Adsorbed Surfaces
Presenter: D.P. Woodruff, University of Warwick, UK
Authors: S.M. Driver, University of Warwick, UK
J.-T. Hoeft, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany
M. Polcik, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany
M. Kittel, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany
R. Terborg, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany
R.L. Toomes, University of Warwick, UK
J.-H. Kang, University of Warwick, UK
D.P. Woodruff, University of Warwick, UK
Correspondent: Click to Email
Using a combination of N 1s scanned-energy mode photoelectron diffraction and scanning tunnelling microscopy the Cu(100)c(2x2)-N surface is shown to undergo a symmetry-lowering reconstruction with a large amplitude (0.34 Å) periodic distortion of the outermost Cu layer perpendicular to the surface. This contrasts with the more usual surface layer density changes or parallel distortions which are the primary characteristic of other metal surface reconstructions. Atomic resolution imaging under varying tip conditions shows that in the c(2x2) phase STM appears to always image as asperities the Cu atoms, and not the N atoms, and that the N induces the unusual rumpling of the outermost Cu layer. This structural modification is quantified by the PhD data. Our STM images also provide a clear demonstration of the dangers of an over-simplistic interpretation of such data in terms of adsorbate atomic coordinates. The presence of the rumpling reconstruction, which we attribute to N-induced compressive surface stress, allows one to understand many detailed aspects of the mesoscopic c(2x2) island structures observed in this system (and reported in earlier STM investigations). Not only can the general self-organisation be attributed to the minimisation of the long-range elastic strain field energy, but similar elastic strain arguments arising from local rumpling can account for the N-N attraction needed for the island formation. In addition, the symmetry-lowering nature of the reconstruction provides a simple explanation for the systematic width variations of the inter-island boundaries.