Münster 1999 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 12: Poster I
HL 12.92: Poster
Montag, 22. März 1999, 14:00–18:00, Z
Optical characterisation of PTCDA films grown on Si substrates — •G. Salvan1, A.Yu. Kobitzky2, M. Friedrich3, M. Schumann3, T.U. Kampen3, and D.R.T. Zahn3 — 1Babes-Bolyai University, Cluj-Napoca, Romania — 2Novosibirsk State University, Russia — 3Institut f"ur Physik, Technische Universit"at, D-09107 Chemnitz
3,4,9,10-Perylenetetracarboxylic dianhydride (PTCDA) was deposited using organic molecular beam deposition (OMBD) onto hydrogen passivated Si(111). The growth of the PTCDA films was monitored in situ and online by means of Raman and photoluminescence spectroscopy in spectral ranges of 1200-1700 cm−1 and 500-1000 nm, respectively. In addition, IR reflectance and transmittance spectra were recorded in order to observe the non-Raman active modes. Raman and IR spectra reveal molecular vibrational modes, allowing us to characterise the quality of the PTCDA films and the interaction with the substrate. The experimentally determined frequencies are in excellent agreement with values calculated using tight-binding density functional theory. The peak splitting in the C=O modes around 1770 cm−1 is due to a dipole-dipole interaction between neighbouring PTCDA molecules. This may be attributed to two different orientations of PTCDA molecules, perpendicular to each other. A broad photoluminescence band below the LUMO-HOMO gap at around 710 nm was observed.