Noncontact Atomic Force Microscopy - Yale School of Engineering ...

P.II-08
Towards a molecule-based Ferroelectric-OFET: surface modification of
PZT mediated through functionalized thiophene derivates
Peter Milde 1 , Kinga Haubner 2 , Evelyn Jaehne 2 , Denny Köhler 1 , Ulrich Zerweck 1 , and
Lukas M. Eng 1
1 Department of Applied Photophysics, TU Dresden, Dresden, Germany
2 Institute of Macromolecular Chemistry and Textile Chemistry, TU Dresden, Dresden, Germany
Organic field effect transistors (OFETs) and their application have become a field of
intense research due to significant advances in molecular design and integration [1]. For
an OFET-design whith a gate “electrode” that is made out of a ferroelectric (FE), we may
expect even more functionality due to the strong and remanent electric field arising from
bound surface charges at the FE/molecule interface [2]. In order to achieve excellent
electric transport properties, a high degree of intermolecular ordering is inevitable [3].
In our approach, lead zirconate titanate (PZT) is used as material of choice for designing
an ultrathin ferroelectric gate electrode in a Ferroelectric-OFET. The focus of the present
work is on the film formation process of the molecularly thin organic conduction layer
based on α,ω-dicyano-β,β*-dibutylquaterthiophene (DCNDBQT). Film formation is
effectively promoted through specifically designed, bifunctional self-assembling
molecules (CNBTPA: 5-cyano-2-(butyl-4-phosphonic acid)-3butylthiophene) which act
as template layer (see Fig. 1). We report on nc-AFM and KPFM [4] investigation of the
template layer's structural and electronical properties.
D
Org.
DCNDBQT
Ferroelectric Gate
Conductive Gate
Figure 1: Schematic of the proposed molecular OFET design. The CNBTPA template layer
promotes both bonding of the organic semiconductor onto the PZT substrate and the self
assembling of the DCNDBQT layer.
[1] see for instance: phys. stat. solidi A 205(3) (2008)
[2] S. Gemming, R, Luschtinetz, W. Alsheimer, G. Seifert, Ch. Loppacher, and L.M. Eng, Journal of
Computer-Aided Materials Design 14(S1), 211 (2007)
[3] K. Haubner, E. Jähne, H.-J.P. Adler, D. Köhler, Ch. Loppacher, L.M. Eng, J. Grenzer, A.
Herasimovich, and S. Scheinert, phys. stat. solidi A 205(3), 430 (2008)
[4] U. Zerweck, Ch. Loppacher, T. Otto, S. Grafström, and L.M. Eng, Phys. Rev. B 71, 125424 (2005)
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