Adsorption of EP-PTCDI on Si(111) 7x7 Surfaces

E.A. SÁNCHEZ, V.A. ESAULOV, J.E. GAYONE, O. GRIZZI, AND L.N. SERKOVIC

San Carlos de Bariloche, Argentina

Conferencia; 13th International Conference on Solid Films and Surfaces; 2006

The interest on the study of highly organized materials assembled from organic semiconductor molecules has increased in the last decades because of their applications to optoelectronic devices such as thin film transistors, photovoltaic, liquid crystal, light emitting diodes and very recently, to fabrication of single-molecule devices like fluorescence switches and sensors [1]. It has been shown that the electrical and optical properties of the self-assembled materials are strongly dependent on the intermolecular interactions and thus the dimensional structures. The particular interest of molecules derivative of perylene tetracarboxylic diimide (PTCDI) comes from their unique class of n-type semiconductor, in comparison to more common p-type counter part in organic semiconductors [1]. In this work the adsorption of (2,9-Di(pent-3-yl)-anthra[,1,9-def:6,5,10-d´e´f´] diisoquinoline -1,3,8,10- tetrone (EthylPropyl - PTCDI) on the reconstructed Si(111) 7x7 surface is studied by scanning tunneling microscopy (STM). The molecules were deposited from a Knudsen cell under ultra high vacuum conditions onto the Si single crystal held at room temperature. At very low doses, less than a monolayer, no cluster formation but the adsorption of isolate single molecules has been observed. Besides, we have not observed preferential absorption on defects like vacancies or linear faults present on the Si substrate. This low molecule mobility can be due to the high reactivity of the clean Si surface with unsaturated dangling bonds, like it happens with similar perylene molecules (PTCDA) [2]. STM images with molecular resolution show different electronic corrugation for different tip-tosample bias potentials. Further studies are in progress in order to get information about the adsorption site and the interaction of a single molecule with the Si substrate, and about the growth mechanism for coverages above the monolayer (thin film formation). [1] K.Balakrishnan, A. Datar, Tammene Naddo, J. Huang, R. Oitker, M. Yen, J. Zhao and L. Zang, J. Am. Chem. Soc. 128 (2006) 7390; and references therein. [2] T. Soubiron, F. Vaurette, J.P. Nys, B. Grandidier, X. Wallart and D. Stiévenard, Surf. Sci. 582 (2005) 178. Further studies are in progress in order to get information about the adsorption site and the interaction of a single molecule with the Si substrate, and about the growth mechanism for coverages above the monolayer (thin film formation). [1] K.Balakrishnan, A. Datar, Tammene Naddo, J. Huang, R. Oitker, M. Yen, J. Zhao and L. Zang, J. Am. Chem. Soc. 128 (2006) 7390; and references therein. [2] T. Soubiron, F. Vaurette, J.P. Nys, B. Grandidier, X. Wallart and D. Stiévenard, Surf. Sci. 582 (2005) 178.