Dresden 2003 – scientific programme
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HL: Halbleiterphysik
HL 25: Organische Halbleiter II
HL 25.8: Talk
Tuesday, March 25, 2003, 17:00–17:15, BEY/81
Electronic properties and chemical stability of dimethyl-3,4,9,10-perylene tetracarboxylic diimide surfaces — •G.N. Gavrila1, H. Mendez1, J. Wells2, D. Vyalikh3, T.U. Kampen1, and D.R.T. Zahn1 — 1Institut für Physik, Technische Universität Chemnitz, D-09107 Chemnitz, Germany — 2Trinity College, Dublin, Ireland — 3Russian-German Laboratory at BESSY II, D-12489 Berlin-Adlershof, Germany
Thin films of DiMePTCDI can be used to decrease the barrier heights of Ag/S-GaAs(100) from 0.55eV to 0.45eV by changing the thickness of the organic interlayer between 0 ÷60 nm. In the transport properties, the highest occupied molecular orbital (HOMO) position and its offset with valence band maximum (VBM) are important when the holes are the transport carriers, while for electrons the barrier is determined by the LUMO and CBM offset. Ultraviolet photoemission spectroscopy measurements were employed to determine the HOMO and VBM offset for the DiMe-PTCDI/S-GaAs(100) case to be (0.86 ±0.10) eV and the HOMO position with respect to Fermi level it is found at (2.04 ±0.10) eV. Photon energy dependent spectra shows a energy dispersion for the HOMO band of 0.1eV. Beside the electronic properties, the chemical stability of such organic modified Schottky diodes are also studied. Oxygen exposure to DiMePTCDI grown on S-GaAs(100) induces a shift of the Fermi level from its original position of 2.04 eV above the HOMO towards the middle of the band gap of the organic layer. This shift is affecting the transport properties.