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HL: Halbleiterphysik

HL 19: Organische Halbleiter I

HL 19.10: Vortrag

Dienstag, 25. März 2003, 13:15–13:30, BEY/81

Nature of the interface formation between a perylene derivative and passivated semiconductor substrates: Raman spectroscopy studies — •G. Salvan, B. Paez, S. Silaghi, T.U. Kampen, and D.R.T. Zahn — Institut für Physik, Technische Universität Chemnitz,D-09107 Chemnitz,Germany

Molecules of 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) were deposited by thermal evaporation onto highly doped S-passivated GaAs(100):2x1 substrates in ultra high vacuum. Raman spectra were recorded under resonant conditions allowing the detection of the most intense internal molecular modes even for sub-monolayer coverages. The first molecules arriving on the chalcogen passivated GaAs surfaces adsorb at defects due to dopant atoms [1,2]. Annealing at 620 K induces desorption of all molecules except those interacting with these defects. The Raman spectra reveal that these molecules preserve their chemical structure, the interaction taking place via fractional charge transfer. The molecules adsorbed on the passivated surface are involved in weaker interactions, comparable to those in molecular crystals. The relative intensities of GaAs LO and PLP features show that the adsorption process leaves the band bending within the substrate unchanged.

[1] C. Kendrick, A. Kahn, Appl. Surf. Sci. 123-124 (1998) 405. [2] S. Park, T.U. Kampen, D.R.T. Zahn, W. Braun, Appl. Phys. Lett. 76 (2000) 3200.