Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 36: Poster III

HL 36.3: Poster

Wednesday, February 27, 2008, 16:30–19:00, Poster D

Charge carrier injection studies into wide band gap organic semiconductors — •Maximilian Nothaft, Fedor Jelezko, Jens Pflaum, and Jörg Wrachtrup — 3. Phys. Ins., Univ. Stuttgart, 70550 Stuttgart, Germany

Charge carrier injection into the LUMO of wide band-gap organic single crystals of small molecules, like naphthalene or anthracene, is difficult to realize because of the request for air-stable contact materials providing low work functions in the range of 2.0eV. E.g. to explore the transport in these molecular semiconductors by FET or SCLC measurements, a stable carrier injection at the respective contact interfaces has to be guaranteed. In this contribution we will present two different approaches on the injection of charge carriers into crystals of the organic semiconductors p-terphenyl and anthracene. At first, free electron injection was performed via a scanning electron microscope at voltages between 5kV to 30kV and, at second, by use of evaporated Al/Au contacts. From space charge limited current measurements up to 200V, we conclude on the transport parameters in these materials. Furthermore, it will be shown that simultaneous injection of holes and electrons yields to recombination electroluminescence from the wide band-gap host crystals, which resembles that of the optically excited fluorescence spectra. As an outlook, the effect of intentional doping of these organic crystals by certain guest molecules such as pentacene and dibenzoterrylene will be discussed.