Dresden 2003 – scientific programme
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DS: Dünne Schichten
DS 24: Poster
DS 24.46: Poster
Tuesday, March 25, 2003, 14:30–17:00, P2a
Influence of structural properties on electronic transport in ITO/α-NPD/Ag films — •Jens Pflaum1, Norwin von Malm2, Stephan Hirschmann1, Heinz von Seggern2, and Jörg Wrachtrup1 — 13. Phys. Inst., Universität Stuttgart, 70550 Stuttgart — 2Fachbereich Materialwissenschaften, TU-Darmstadt, 64287 Darmstadt
We present charge carrier time-of-flight (TOF), X-ray and AFM studies on α -NPD layers ( 1 µ m) sandwiched between electrodes of ITO and Ag. Although the NPD film is of rather amorphous structure, as revealed by X-ray diffraction, defined TOF transient pulses for hole carriers were observed. In contrast, for electrons the TOF signals indicate only dispersive transport and strong limitation by trapping. At room temperature the hole mobility amounts to (5.6±0.1) × 10−4 cm2 /Vs showing an almost linear increase with temperature up to (2.1±0.1) × 10−3 cm2 /Vs at 373K. Just above this temperature, which coincides with the glass transition temperature of NPD, a remarkable increase of the hole mobility was observed. In addition, by X-ray diffraction an increase of the crystalline fraction in the NPD film above the glass transition together with a roughening of the NPD/Ag interface was measured. From this observation we conclude on the dependence of the electronic transport in these films on their structural characteristics. Supported by the DFG (OFET-Schwerpunktprogramm).