Zn-TPP electron transfer on Ag and Si surfaces

The importance of substrate and interfaces has been exploited in this experimental study of monolayers of Zn-tetraphenyl-porphyrin on Ag(110) and Si(111). XPS,NEXAFS, and RESPES were used to investigate the bonding nature, the adsorption geometry and the electron transfer dynamics between the molecule and the surfaces.
C. Castellarin-Cudia et al., ChemPhysChem 11, 2248–2255 (2010).
      

               

          
We report on the preparation of a conformationally controlled Zn-tetraphenyl-porphyrin (ZnTPP) single layer on two possible substrates, Ag(110) and Si(111).The ZnTPP molecule is characterized by four phenyl groups bonded to the macrocycle and a central Zn atom. As substrates we have chosen silver, normally used as contact in photovoltaic or transistor devices, and silicon, worldwide employed in semiconductor industry. The substrate can influence the thin film morphology, the distortion of the molecules and the electronic charge transfer as a consequence.

Depending on the substrate, the adsorption orientation is mainly mastered by the coupling of the phenyl legs or the macrocycle with the surface. The ResPES behavior indicates that for the phenyl rings the charge transfer into the substrate is less favorable than on the Ag(110) case and comparable to the multilayer case. Core level photoemission indicates that the molecule is interacting with the substrate using a macrocycle pyrrole ring, while the phenyl rings are rotated in such a way to minimize the interaction with the substrate.
The molecular orientation with respect to the substrate was monitored using angular dependent near edge x-ray absorption fine-structure spectroscopy (NEXAFS), while the electronic properties of the filled states were investigated using x-ray and ultraviolet photoemission (XPS and UPS).

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Substrate Influence for the Zn-tetraphenyl-porphyrin Adsorption Geometry and the Interface-Induced Electron Transfer

C. Castellarin-Cudia, P. Borghetti, G. Di Santo, M. Fanetti, R. Larciprete, C. Cepek, P. Vilmercati, L. Sangaletti, A. Verdini, A. Cossaro, L. Floreano, A. Morgante and A. Goldoni

ChemPhysChem Volume 11, Issue 10, pages 2248–2255, July 12, 2010
Article first published online: 10 JUN 2010
DOI: 10.1002/cphc.201000017
Last Updated on Wednesday, 18 January 2012 15:42