Phthalocyanines are a group of molecules interesting for application in both optical and electronic devices 1,2. Doping of molecular films alters the electronic structure resulting in films of different characteristics and functionality. This strongly motivates comprehensive and detailed studies for the development of new Pc-based molecular materials.
Investigation of Potassium (K) doped multilayer metal-free phthalocynines (H2Pc's) on Al(110) have been studied by Photoelectron Spectroscopy (PES) and X-ray Absorption Spectroscopy (XAS). The data have shown modification of the molecular electronic structure and (of the molecular) geometrical orientation depending on the alkali coverage.
K on multilayer H2Pc Al(110) have been characterized for increasing alkali coverages, from very low up to stechiometric ratio of 1 K atom per molecule. The alkali doses resulted in binding energy shifts of the N1s and C1s core level spectra indicating a strong interaction/charge transfer between the molecules and the alkali. Valence photoemission results have shown the appearance of a structure whose intensity increased with K doses confirming results reported in previous studies dedicated to metal Pc's 3. This feature has been attributed to the filling, by the alkali, of the former molecular LUMO as also confirmed by our XAS measurements. Furthermore, a very interesting result has been evidenced by our XAS measurements showing (for the first time) a progressive change in the orientation of the molecular plane with respect to the surface, depending on the alkali concentration.
1 G. Gu, G. Parthasarathy, and S. R. Forrest, Appl. Phys. Lett. 74, 305 (1999)
2 S. Riad, Thin Solid Films 370, 253 (2000)
3 O.V. Molodtsova, J. Appl. Physics, 98, 93702 (2005)
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