Highly efficient patterning of organic single-crystal transistors from the solution phase

A novel solution based technique for the fabrication of field-effect transistors (FET) arrays, in which the patterning of the organic crystals is achieved by self-aligned method to pattern droplets of an organic semiconductor solution. The surface of Si/SiO2 substrates containing arrays of gold electrode pads is chemically modified with octadecyltrimethoxy-silane (OT) in order to generate a hydrophobic substrate around the gold electrodes. The organic semiconductor solution used were oligothiophenes with solubilizing side-chain substituents dissolved in a halogenated aromatic solvent such as bromobenzene, 1,2-dichlorobenzene (DCB) or 1,2,4-trichlorobenzene (TCB). A very small amount of nearly saturated molecular solution was added to a beaker containing an immiscible host liquid for patterning of molecular solutions in halogenated solvents. The presence of the liquid vortex was found to significantly improve the selectivity of the molecular solution droplet formation.