Nanorubbing of Polythiophene Surfaces

摘要

Conjugated polymers have been attracting much attention due to their use in semiconducting devices such as organic thin film transistors.As a typical example,poly(3-hexylthiophene) (P3HT) is intensively studied for field-effect transistor (FET) applications because of its high charge mobility (up to 0.18 cm~2/Vcentre dots).The charge transport properties and the device performances are intimately related to the long-range order in the polymer films.It is therefore essential to control the degree of structural order,in particular the chain orientation,in conjugated polymer thin films.Various methods exist to align the chains in thin films such as stretching,Langmuir-Blodgett deposition,or "friction-transfer" technique.High degree of ordering can be achieved,leading to homogeneously organized films.In this communication,we describe a new orientation method suitable for conjugated polymers such as P3HT,which provides efficient orientation with precise control of the spatial localization of the oriented regions with a nanometric resolution,a feature that cannot be easily achieved with the "classical" techniques.This method combines in an original way two previously reported concepts:template growth and nanorub-bing.We have recently shown that a crystallization process can be used to align the chains in semicrystalline rigid polymers.Upon rubbing amorphous polymer surfaces (e.g.,poly(ethylenetereph-thalate),PET),we observed on the surface the formation of crystalline aggregates,perfectly aligned along the sliding direction.These aggregates then act as a template to propagate the chain orientation to the whole film when the polymer is heated to the crystallization temperature.This kind of template growth is clearly reminiscent of epitaxial growth.