Berlin 2005 – scientific programme
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O: Oberflächenphysik
O 20: Organische Dünnschichten II
O 20.1: Talk
Saturday, March 5, 2005, 10:45–11:00, TU EB202
Interface Formation of Phthalocyanines with Hydrogen Passivated Si(111) — •Mihaela Gorgoi and Dietrich R.T. Zahn — Institut für Physik, Technische Universität Chemnitz, D-09107 Chemnitz, Deutschland
Hybrid devices such as organic light emitting diodes, solar cells or thin film transistors, based on phthalocyanine (Pcs) materials and silicon receive special attention nowadays. Therefore the knowledge of the Pc/Si interface electronic properties is required. This work studies the interface formation between the organic semiconductors, namely copper phthalocyanine (CuPc) and perfluorinated copper phthalocyanines (F4CuPc,F16CuPc), and hydrogen passivated Si(111) using photoemission and inverse photoemission spectroscopy. With these techniques the energy level alignment of the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) with the valence band maximum (VBM) and the conduction band minimum (CBM) of Si are determined. The HOMO and LUMO for the three materials reveal dissimilar trends in the direction of energy shifts as a function of Pcs thickness. While for CuPc the shift is towards higher binding energy with increasing film thickness, for F16CuPc both HOMO and LUMO are shifting towards lower binding energy. The energy shifts are proposed to originate from changes in molecular orientation and the direction of the shifts to arise from the degree of fluorination.