Dresden 2017 – wissenschaftliches Programm
CPP 9.2: Vortrag
Montag, 20. März 2017, 15:30–15:45, ZEU 260
Inter-facial charge transfer studied in organic hetero-structure field-effect transistors. — •Eduard Meister, Stefan Schmidt, and Wolfgang Brütting — Institut für Physik, Universität Augsburg, Germany
In this work we studied inter-facial morphology dependent charge transfer (CT) happening in hetero-structure FETs based on vapour deposited small molecules. Therefore we used alpha-sexithiophene (α-6T) as donor and hexafluorotetracyanonaphthoquinodimethane (F6TCNNQ) as acceptor. The lowest unoccupied molecular orbital of F6TCNNQ is placed below of the highest occupied molecular orbital of α-6T, so that from an energetic point of view CT from α-6T to F6TCNNQ molecules should occur. As evidence of CT we observed strong reduction of the switch-on voltage.
In order to get more information about morphology dependent CT and charge transport we produced devices with different gate insulator surfaces acting as template: blank SiO2, as well as additional PMMA and thermally smoothed tetratetracontane  passivation layers. The morphology of α-6T layers was studied by atomic force microscopy and X-ray diffraction measurements. We employed also morphology dependent contact doping by application of tetrathiafulvalene tetracyanoquinodimethane salt contacts in contrast to mostly used gold electrodes. For the study of the transport mechanisms we performed temperature dependent measurements and calculated an upper limit of the activation energy for all the used configurations.
 L. Pithan et al., J. Chem. Phys. 143 (2015) 164707.