Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 15: Organic Electronics and Photovoltaics II (Joint Session with DS/CPP/O)

HL 15.2: Talk

Monday, March 22, 2010, 14:15–14:30, H8

Can X-ray microspectroscopy probe inhomogeneities in the electron structure of organic devices? — •Christian Hub, Martin Burkhardt, Marcus Halik, and Rainer Fink — Interdisciplinary Center for Molecular Materials (ICMM), Universität Erlangen, Egerlandstraße 3, 91058 Erlangen, Germany

The degree of homogeneity in the morphology of organic thin film devices has a major impact on the charge transport properties. Real devices usually strongly deviate from the ideal device structure since epitaxial growth with low defect concentrations cannot be achieved. We have recently started to investigate pentacene-based OFETs, which were prepared using commercial silicon nitride membranes as dielectric showing excellent transport characteristics. The overall device thickness is sufficiently small to perform scanning transmission X-ray microspectroscopy (SXTM) experiments at the PolLux microspectroscope. Grains with varying preferential orientation in the polycrystalline pentacene films are detected using the significant local NEXAFS dichroism. The local NEXAFS contrast is utilized to investigate differences in the electronic structure within these films while the devices are operated. Using the standard photomultiplier tube of the PolLux as detector no pronounced changes were observed when current is driven through the organic films. Therefore electron detection was implemented to further enhance the sensitivity of the microscope to ultrathin films. We will discuss the related problems and opportunities to use local NEXAFS with lateral resolution below 30 nm. The work is funded by the BMBF under contract 05 KS7WE1.