Organic transistors realized by an environmental friendly microcontact printing approach

A patterning method was developed that allows for combining the advantages of a low cost microcontact printing process on rigid and flexible substrates with the advantages of conventional semiconductor processing. The patterning approach combines printing of self-assembled monolayers with selective dewetting while being compatible with conventional semiconductor processes. Alkyl thiol self-assembled monolayers were printed on gold and silver films on rigid and flexible substrates. The printed regions turn hydrophobic while the bare regions remain hydrophilic. The hydrophilic regions of the surface were selectively wetted by a polymer like poly-methyl methacrylate. The selectively patterned poly-methyl methacrylate is used as etch resist while the bare regions of the gold film were patterned by a potassium iodide/iodine solution. The potassium iodide/iodine etchant is compatible with conventional semiconductor processing in contrast to the commonly used ferri/ferrocyanide etching solutions. The method allows for patterning of gold and silver films with submicron dimension on flexible and rigid substrates. Organic thin-film transistors were realized with drain and source fabricated by the proposed approach. The performance of the organic transistor is comparable to devices fabricated by photolithography.