Fabrication of Thin Oriented Organic Layers and Micropatterns by Zone Casting

Abstract

AbstractZone casting—a special solution processing method for obtaining highly ordered continuous layers of soluble organic materials—can also be applied for fabricating patterned layers. In this method, solution is continuously supplied onto a substrate that is withdrawn at a controlled rate, and the solvent evaporates from the surface of a meniscus formed between a flat nozzle and the substrate. Due to the gradient of a solute concentration, its solidification proceeds within the narrow zone localized in the meniscus. In this way solute molecules can be self‐assembled at surfaces into different anisotropic nanostructures (columns, rods, lamellae, or microcrystals) uniaxially aligned parallel to the substrate. Under some conditions various phenomena like dewetting, fingering instability, stick‐slip motion, etc., come into play, leading to various periodic perturbations in the film deposition. Examples of continuous and patterned layers of different materials such as low molecular weight (semi)conductors, chromophores, discotic molecules, and block copolymers, which can successfully be processed using this technique, are shown. Typical layers obtained through this method are shown to have good properties as active layers in field effect transistors.