Regensburg 2007 – scientific programme

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O: Fachverband Oberflächenphysik

O 8: Methods: Scanning Probe Techniques I

O 8.1: Talk

Monday, March 26, 2007, 11:15–11:30, H41

Tip-Sample Distance-Dependant Tunneling Spectroscopy of Ultra-Thin Layer of d8 Metal-Phthalocyanines — •Thiruvancheril Gopakumar, Jan Meiß, and Michael Hietschold — Chemnitz University of Technology, Institute of Physics, Solid Surfaces Analysis Group, D-09107 Chemnitz, Germany.

Tip-sample distance-dependant tunneling spectroscopy (TD-TS) on the thin layers of naphthalocyanine and tin-naphthalocyanine show a strong tip-sample distance-dependant HOMO-LUMO gap shrinking, which was assigned to the electronic nature of molecule-substrate interface.[a] For the clear understanding of this scenario and the factors which influence the HOMO-LUMO gap shrinking we have extended the TD-TS to ultra-thin film of d8 metal-phthalocyanine on HOPG (0001). A similar HOMO-LUMO gap shrinking is observed and the rate of change in HOMO-LUMO gap with respect to the distance is found to be decreasing/dependant on the molecular electronic nature, which is further understood in terms of molecular polarisabilty. Theoretical calculations were performed to correlate the molecular polarisability and the electronic nature (electron density) of frontier orbitals.

[a]. T. G. Gopakumar, F. Muller, M. Hietschold, J. Phys. Chem. B. 2006, 110(12), 6060-6065.