Ordered assembly of alpha-quinquethiophene on a copper oxide nanotemplate

The organic semiconductor alpha-quinquethiophene (T5) is used as the active layer in organic field-effect transistors. We have investigated the adsorption of T5 on the (110) surface of copper and on the CuO nanotemplate formed by the high-temperature exposure of Cu(110) to molecular oxygen. The results were obtained with high-resolution scanning tunneling microscopy (STM) under ultra-high-vacuum (UHV) conditions. The adsorption of T5 on copper is an important model system because it mimics the active-layer-electrode interface in organic devices. The molecules were observed to adsorb onto both the pristine Cu(110) surface and the CuO nanotemplate, showing a greater affinity for the pristine copper surface. Surprisingly, however, the T5 molecules assembled with a much higher degree of long-range order on the oxygen-passivated portion of the surface.