X-ray Microscopy Imaging of the Grain Orientation in a Pentacene Field-Effect Transistor

We demonstrate the application of scanning transmission X-ray microscopy (STXM) to image the angular distribution of grains in organic semiconductor thin film devices on the example of pentacene field-effect transistors. The in-plane orientation of the molecules in the channel region and underneath the top conducting electrodes was derived from polarization dependent STXM investigations. The method allows the determination of the actual grain size and the correlation of the electronic transport and structural properties on the nanometer length scale.