Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 50: [CPP] Organic Electronics and Photovoltaics III (Joint Session DS/CPP/HL/O)

O 50.2: Talk

Wednesday, March 24, 2010, 09:45–10:00, H37

Investigations on thickness dependence of electrical characteristics and stability of self-assembled monolayers — •Dana Habich — FAU Erlangen-Nürnberg, Institute of Polymer Materials

We investigated the influence of the molecular chain length (n) of aliphatic Cn-phosphonic acids on the electrical characteristics of self-assembled monolayers (SAMs) based on these molecules. SAMs prepared on aluminium/aluminium oxide (Al/AlOx) and conductive indium tin oxide (ITO) substrates behave as molecular dielectric layer. In integrated devices (e.g. capacitors) with activated Al-bottom electrode, the dielectric layer is created from a double-layer AlOx/SAM. Capacitance and breakdown voltage correlates monotonically with the SAM thickness, the current density at low voltage does not follow the expected correlations in detail. We address this behavior to morphological changes of the SAMs on AlOx, from an amorphous structure for short chains to a crystalline state for longer alkyl chains. To decouple the relative contributions of the AlOx and the SAM to the insulation, an independent analytical approach to characterize the SAM was chosen: cyclic voltammetry on SAM decorated ITO. The faradic current of a redox active compound in solution is indirect proportional to the molecular chain length. Qualitatively, this observation proofs the conclusions from the capacitor measurements. The system ITO/SAM, further provide an approach for functional coatings on ITO with the possibility to tune addressability and stability of the electrodes. Stability was investigated by static contact angle and STM measurements before and after electrical stress. Ref.: Org. Electron. 10 (2009) 1442.