Tailoring of organic nanofiber growth for a new type of waveguides

It has been shown recently, that organic nanofibers grown from para-hexaphenyl and from α-sexithiophene molecules can be used as a new type of nanoscopic waveguides. Their growth is due to a self-assembly process, thus large quantities of aligned nanofibers can be fabricated simultaneously. Because of the growth mechanism of the nanofibers, their widths and heights are limited to a few 100 nm and a few 10 nm, respectively. In this paper we show how this kind of control has been obtained via modification of the bare muscovite surface before organic molecule deposition. Introducing e.g. a thin layer of Au islands before nanofiber growth results in an up to 15-fold increase in height, whereas the mean width and the optical properties of the fibers remain almost unchanged. Au films of varying thickness lead to tailor-made height profiles along the fiber. Using atomic force microscopy the details of these Au/organic heterostructures are examined and the growth is compared to growth on untreated mica. By scratching the fibers with an AFM tip grating structures have been written into the fibers.