Photoemission and theoretical investigations on NO2 doping of copper phthalocyanine thin films

The doping effect by NO2 molecules of copper phthalocyanine (CuPc) thin films has been studied by means of X-ray photoemission spectroscopy (XPS). The core level spectra indicate that the NO2 molecules form a stable chemical bond with the copper central atom of the molecule, determining charge transfer effects also in the nitrogen spectra. Instead, no variation on the carbon chemical state is experimentally observed. Theoretical calculations, perfort-ned by means of Dmol(3) code, confirm that the most reactive part of the CuPc molecule is the copper atom, while the outer benzene rings are completely not affected by the NO2 molecule adsorption. The theoretical calculations, in terms of charge transfer and effects on the core levels, agree very well with the experimental data. (C) 2004 Elsevier B.V. All rights reserved.