Structural characterization of α,ω-DH6T monolayer films grown at the liquid-liquid interface

The molecular self-organization of alkyl-functionalized hexathiophene monolayers prepared at the solvent-water interface is investigated by complementary microscopy techniques. Our study focuses on the influence of solvents and initial droplet volume on the resulting film morphology. Long-range extended domains in the monolayer regime are detected by visible light microscopy only for toluene. Small-area electron diffraction (SAED) proofs the formation of single-crystalline monolayers with structural parameters identical to the organic bulk crystals. A deviant molecular orientation derived from near-edge-x-ray absorption fine structure (NEXAFS) linear dichroism as well as a strong film degradation of time provide an indication for incorporated solvent molecules into the organic layer. The comparison with conventional vacuum-sublimated films shows significantly larger crystalline domains for the solvent-prepared monolayer films thus reducing the morphology influence on the transport properties in organic semiconductor films.