Dresden 2006 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 23: POSTER Functional Organic Thin Films
CPP 23.27: Poster
Thursday, March 30, 2006, 17:00–19:00, P2
The influence of SiO2 dielectric interface modification on ambipolar transport in Pentacene TFTs — •Niels Benson1, Marcus Ahles1, Thomas Mayer1, Eric Mankel1, Andrea Gassmann1, Roland Schmechel2, and Heinz v. Seggern1 — 1TU Darmstadt, Institute of Materials Science, Petersenstraße 23, D-64287 Darmstadt, Germany — 2Forschungszentrum Karlsruhe (FZK) Institut für Nanotechnologie, PF 3640, 76021 Karlsruhe, Germany
Recently an n-type Pentacene OFET, using traces of Calcium between SiO2 and Pentacene has been demonstrated. This OFET exhibits electron transport properties similar to those of holes observed in a corresponding p-type OFET. Results on XPS measurements unveiling the influence of Ca on the SiO2 surface are presented. According to these measurements, the first deposited Ca performs a chemical reaction with the SiO2 interface. Metallic Ca is found only at higher nominal thickness. Moreover, characteristics of OFETs are presented, where thin intermediate polymer dielectrics selected with respect to functional end groups and their polarity have been employed between SiO2 and Pentacene. A clear correlation between the occurrence of ambipolar transport and the molecular polarity has been revealed. From the present results, interface modifications with different polymer dielectrics as well as traces of Ca result in different interfacial electron trap densities, allowing a modification of the OFET threshold. This is a step toward to a better control of the device properties for organic integrated circuits and ambipolar OFETs.