Patterned growth of organic small-molecule layers
- PDF / 216,020 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 44 Downloads / 251 Views
I12.6.1
Patterned growth of organic small-molecule layers Soeren Steudel1, Dimitri Janssen2, Stijn Verlaak1 and Paul Heremans Polymer and Molecular Electronics group, IMEC, Kapeldreef 75, B-3001 Leuven, Belgium. 1 Department of Electrical Engineering, Katholieke Universiteit Leuven, Belgium 2 Department of Chemistry, Katholieke Universiteit Leuven, Belgium ABSTRACT We will demonstrate a novel approach to the problem of patterning organic small molecule layers, which is compatible with printing techniques. By locally changing the chemistry of the dielectric surface by means of Self-Assembly Monolayers (SAM), we predefine active and passive areas of the circuit. The subsequent growth of the organic film by sublimation takes place under growth conditions which cause the formation of a high-mobility, wellconnected two-dimensional (2D) grains in the predefined active area contrasting with illconnected, low-mobility 3D-grains in the passive area. We will explain this patterned growth in terms of a microscopic theory of nucleation of organic semiconductor on inert substrates and present experimental results.
INTRODUCTION With ongoing improvements in the performance of organic thin film transistors (OTFT) and the first demonstrations of inverters and oscillators the route towards circuits based on organic semiconducting materials is open. Organic thin film transistors are promising for cheap, flexible, large area applications. There are two groups of organic semiconducting materials – polymers and small molecules. The advantage of polymers lays in the simple solution process ability that allows the use of cheap printing technologies whereas evaporated small molecules show superior mobility comparable with amorphous silicon. Depending on the application, both approaches are potentially interesting. To prevent cross-talk between transistors in close proximity and to achieve a low off-current it is necessary to pattern the organic semiconductor layer. Several ways to pattern small molecules are already published – evaporation of the small molecules through a shadowmask [1], deposition of a water-soluble resist on top of the organic semiconductor followed by lithographic patterning [2] as well as using an integrated shadow-mask whereby a resist is lithographic patterned to achieve step edges around the intended active area [3]. The subsequently evaporated small molecule layer is discontinued by the step edges of the resist around the active area. Those ways of patterning small molecule layer have all in common that they require a mask – either shadow-mask or lithographic mask – to be aligned. The use of a hard mask reduces the flexibility of the design. There are further drawbacks connected with the abovementioned ways of patterning. For instance, the patterning with water-soluble resist results in some degradation of the characteristics of the transistors. We propose a new way of patterning films of small molecules that is compatible with printing techniques. In our new technique, we predefine active and passive parts on the
Data Loading...
