Regensburg 2007 – scientific programme

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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices

SYOE 8: Poster Session SYOE

SYOE 8.38: Poster

Tuesday, March 27, 2007, 18:00–20:00, Poster B

Structure and unusual thermal behaviour of a prototype organic semiconductor (Diindenoperylene) — •Bernd Maier, Jörg Ihringer, and Frank Schreiber — Institut für Angewandte Physik, Auf der Morgenstelle 10, 72076 Tübingen

A recently suggested model for the bulk structure is compared with X-ray powder data collected at 18<T<298 K in steps of Δ T=10 K with a modified image plate Camera (Huber) and at room temperature with an automated X-ray powder diffractometer, both in Guinier-geometry. The unit cell agrees well with the suggested model. Refinement of lattice constants (program SIMPRO) yield b=13.08 (0.016), c=15.09 (0.008) at 298 K and b=12.97 (0.020), c=14.94 (0.009) at 18 K. The thermal dependence at 18<T<298 K will be given. Due to pseudo symmetry the lattice constants (space group P1) correlate strongly with atomic coordinates. A profile refinement with the Rietveld Method would solve the problem, however, there is some more work needed to evaluate a first set of approximate atomic coordinates.

In addition, a highly irreversible phase transition to high temperature phase occurs. Upon heating with a rate of 0.2 K/min the high temperature phase appears at around 370 K. The high temperature phase remains stable when cooling to 50 K. However, only part of material undergoes this transition, as both phases coexist in the whole temperature range.