IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Wednesday Sessions
       Session SS1-WeA

Paper SS1-WeA7
Calculations of Elastic and Vibrational Inelastic Electron Tunneling Images

Wednesday, October 31, 2001, 4:00 pm, Room 120

Session: New Opportunities in Surface Microscopy
Presenter: M. Persson, Chalmers University, Sweden
Authors: M. Persson, Chalmers University, Sweden
F. Olsson, Chalmers University, Sweden
N. Lorente, IRSAMC, Univ. P. Sabatier Touluose, France
Correspondent: Click to Email
The inelastic electron tunneling spectroscopy (IETS) in the STM is capable of mapping the vibrational excitation of single molecules in real space with sub-Å spatial resolution and meV spectral resolution.@footnote 1@ Despite the obvious promise of a spectroscopy with these unique capabilities, STM-IETS raises several issues that we need to address by theory to fully exploit this spectroscopy. These issues include; (1) why are so few modes detected; (2) what can be learnt from IET images; (3) what is the nature of the coupling between the tunneling electron and the vibration; (4) what determines the vibrational lineshape ? To this end we have studied the excitation mechanism in STM-IETS using a generalization of Tersoff-Hamann theory to IET combined with density functional calculations.@footnote 2,3@ We have shown that this many-electron theory give quantitative agreement with experiments and have identified several general effects: (1) elastic and inelastic contributions to the IET tend to cancel; (2) a symmetry selection rule connecting the symmetries of the IET images, adsorbate-induced states at the Fermi level and the vibrational mode; (3) a Fano-like lineshape for the second derative of the tunneling current with bias. These effects will be illustrated from a comparison of results of calculated vibrational inelastic images from several systems with experiments, in particular, oxygen adsorbed on silver surface, which provides a typical example of inelastic coupling through a single resonance level.@footnote 4@ We will also illustrate the applicability of the Tersoff-Hamann approximation for the calculations of elastic STM images. @FootnoteText@ @footnote 1@ B.C. Stipe, M.A. Rezaei and W. Ho, Science 208, 1732 (1998); Phys. Rev. Lett. 82, 1724 (1999). @footnote 2@ N. Lorente and M. Persson, Phys. Rev. Lett. 85, 2997 (2000). @footnote 3@ N. Lorente, M. Persson, L. Lauhon, and W. Ho, Phys. Rev. Lett. 86, 2593 (2001). @footnote 4@ J.R. Hahn and W. Ho, Phys. Rev. Lett. 85, 1914 (2000).