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CPP: Chemische Physik und Polymerphysik

CPP 15: Poster: Dünne Filme, Monolagen und Oberfl
ächen

CPP 15.1: Poster

Mittwoch, 13. März 2002, 16:30–18:00, B

Distance dependent excited-state relaxation of MePTCDI on semiconductor substrates in the isolated molecule limit — •Eugenio Lunedei, Eugenio Lunedei, Helmut Port, Hans Christoph Wolf, Helmut Port, and Hans Christoph Wolf — 3. Physikalisches Institut, Universitaet Stuttgart

The distance dependence of the interaction between organic isolated molecules and semiconductor substrates were measured in–situ at T = 10 K by picosecond time-resolved fluorescence techniques, using inert Argon layers as spacer. Ultrathin organic layers (0.01 MonoLayer, ML) of MePTCDI (N,N’-dimethylperylene-3,4:9,10-bis(dicarboximide)) were UHV-deposited on He-cooled MoS₂ (Molybdenum Disulfide) and Si(111):H (H–terminated Silicon) semiconductor substrates after the evaporation of variable thickness (0-200Å) spacer Argon layers. At this level of coverage the molecules are

non interacting, isolated from each other, and the fluorescence spectra result definitively monomeric. By reducing the spacer thickness a strong shortening in molecular fluorescence lifetime (more than two orders of magnitude) is observed on MoS₂, whereas a weaker shortening is observed on Si(111):H. The quantitative description of the different results will be discussed.