Scanning probe microscope based nanolithography on conducting polymer films

We demonstrate successful nanolithography to pattern organic semiconductor films by using the oscillating tip of an atomic force microscope (AFM). The nano-indentation technique, which was previously used to create trenches on materials including thin photoresist and metal films, has now been systematically studied and applied to the most commonly used semiconducting polymer, regioregular poly(3-hexylthiophenc) (P3HT). We discover that the internal tensile strain in the films and the long P3HT molecules have actually enabled us to eliminate all major common problems of the nano-indentation method to date, namely the refilling of the trenches by debris, tip contamination by debris, and the short AFM tip life time, which have so far seriously hampered and limited the practical applications of the nano-indentation technique. The trenches that we have created are generally formed through the entire P3HT film, with a clean bottom Virtually free from debris. Successful pattern transfer to the underneath inorganic semiconductor has been achieved by a wet chemical etch with the created organic nanostructures as the etching mask. Furthermore, no obvious degradation of the AFM tip either by debris contamination or mechanical wearing is observed after many days of nanolithography. This allows nanostructures over tens of microns in length to be reproducibly fabricated in large numbers.