Organic transistors realized by an environmental friendly microcontact printing approach Amare Benor a , Benedikt Gburek b , Veit Wagner b , Dietmar Knipp a, * a Electronic Devices and Nanophotonics Laboratory, Jacobs University Bremen, Germany b Molecular and Nanoelectronics Laboratory, Jacobs University Bremen, Germany article info Article history: Received 8 December 2009 Received in revised form 24 January 2010 Accepted 25 January 2010 Available online 4 February 2010 Keywords: Microcontact printing Thin-film transistors Self-assembled monolayer abstract 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 con- ventional 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/ferro- cyanide 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. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction Patterning of micro- and nanostructures is central to modern science and technology, and it is particularly and widely recognized as one of the enabling methods and cor- nerstones for the revolution of microelectronics. Of the many methods, photolithography is by far the most com- mon and standard patterning method used in electronics industry [1]. However, photolithography is an expensive technology, and it is not necessarily the most suitable tech- nique for all electronic and photonic applications, where micro- and nanostructuring is required. For example, stan- dard photolithography is not compatible with organic semiconducting materials, since the exposure to ultraviolet light (UV) and the use of organic solvents may degrade the functional property of organic materials. Furthermore, photolithography is not applicable to curved or flexible substrates [2]. Due to these drawbacks a number of alter- native micro- and nano-patterning methods, like printing, stamping or embossing have been developed. Of these methods, printing processes have received particular attention, since printing processes allow for patterning of large area and flexible substrates at low cost. Microcontact printing (lCP), one of the printing meth- ods, has become an important technique in patterning mi- cro- and nanostructures. The approach was introduced by Whitesides and coworkers [3]. The method was success- fully applied to print monolayer of thiol on gold substrates or silane monolayers on glass or silicon substrates [3]. Gold films can be patterned by a ferri/ferrocyanide etching solu- tion after microcontact printing a hexadecanethiol (HDT, CH 4 (CH 2 ) 15 SH) self-assembled monolayers (SAMs) onto the metal film. Following this study, the HDT SAMs were 1566-1199/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.orgel.2010.01.025 * Corresponding author. E-mail address: d.knipp@jacobs-university.de (D. Knipp). Organic Electronics 11 (2010) 831–835 Contents lists available at ScienceDirect Organic Electronics journal homepage: www.elsevier.com/locate/orgel