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Both, the top-down as well as the bottom-up assembly of light-emitting organic aggregates has led to promising nanophotonic devices such as waveguides and nanolaser [1,2]. The top-down approach is more flexible in generation of arbitrary morphologies, whereas the bottom-up assembly still allows the easy fabrication of nanoscopic aggregates such as needle-like crystallites . Here, results of a systematic study of the growth of green light-emitting 2,5-di-4-biphenyl-thiophene (PPTPP) molecules on the \hkl(001) faces of muscovite and phlogopite mica are reported. Atomic force microscopy provides information about the crystallites' morphology. An epitaxial relationship and the orientation of the molecules on the surface is deduced from low energy electron diffraction (LEED) and from fluorescence microscopy. On muscovite initially a commensurate wetting layer of lying molecules is formed with subsequent formation of clusters. For higher coverages these clusters assemble into mutually parallel nanowires. On phlogopite mica no wetting layer is observed, but diffraction from islands of upright molecules. Fibers grow along three different directions, until they start bending. It is found that overall PPTPP has a growth behavior more similar to that of the phenylenes as compared to that of the thiophenes.
 F. Quochi, F. Cordella, A. Mura, G. Bongiovanni, F. Balzer, and H.-G. Rubahn, Appl. Phys. Lett. 88 (2006) 041106.  S. Fujiwara, K. Bando, Y. Masumoto, F. Sasaki, S. Kobayashi, S. Haraichi, S. Hotta, Appl. Phys. Lett. 91 (2007) 021104.  M. Schiek, F. Balzer, K. Al-Shamery, J.R. Brewer, A. Lützen, and H.-G. Rubahn, Small 4 (2008) 176.
16. jun. 2009
Scanning Probe Microscopies and Organic Materials XVII