Regensburg 2004 – wissenschaftliches Programm

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SYOH: Organic and Hybrid Systems for Future Electronics

SYOH 5: Poster

SYOH 5.67: Poster

Donnerstag, 11. März 2004, 18:00–21:00, B

Field Effect Transistor and Space Charge Limited Current Measurements on Tetracene and Perylene Single Crystals — •G. Ulbricht¹, J. H. Smet¹, J. Niemax², Ch. Herb², and K. von Klitzing¹ — ¹MPI-FKF, Stuttgart — ²3. Phys. Inst. Uni Stuttgart

The study of charge carrier transport in organic single crystals is an experimental challenge. Among other things, the intrinsic carrier concentration is very low and doping quite difficult. Increasing the amount of charge carriers using a field effect geometry instead offers improved access to the intrinsic charge transport properties of these materials. We are investigating single crystals of tetracene and perylene. In order to get a working FET, the gate isolation has to fulfil some stringent requirements. We have screened several materials suitable as gate dielectrics. With the polymer PPX (poly-para-xylylene or parylene), field effect transistors on tetracene single crystals can be prepared reliably without significant damage to the delicate crystal surface. The properties of these FET’s were examined down to liquid helium temperatures, and the influence of different sample preparation techniques will be discussed. To understand the pronounced influence of different metals for the source-electrode, we have measured space charge limited currents (SCLC) on tetracene and perylene. Trap concentrations as low as 1·10¹³ cm⁻³ in Bridgman-grown perylene attest the high quality of the crystals used. These SCLC measurements also show deficient charge carrier injection for many contact metals, especially in perylene. Therefore, carrier injection was systematically evaluated, both in the SCLC as well as in the FET geometry. Supported by the DFG (Sm64/4-1, Ka 427/8).