Sexiphenyl thin films were grown by Hot Wall Epitaxy on air-cleaved mica (001) surfaces at substrate temperatures between 293 K and 440 K. For the entire temperature range, organic thin films show nano-needle like morphology. The nano-needles grown at low substrate temperature (293 K) are shortest, and their growth is accompanied by a simultaneous formation of flat islands which disturbs the growth of nano-needles. On the contrary, unusually long nano-needles with typical lengths up to the mm range evolve during the growth at a substrate temperature close to the material’s thermal desorption temperature at about 440 K. X-ray diffraction reveals two different crystalline orientations for nano-needles in the entire temperature range. At low substrate temperatures dominantly the (111) plane of the â-phase is formed parallel to the mica (001) surface. At elevated temperatures another strong texture becomes dominant which is close to the (11-2) crystal orientation. In contrast to this, crystallites with the preferred orientation (001) parallel to the surface of the substrate are formed at low substrate temperature (293 K). This crystal orientation can be associated with flat islands observed in the early growth stage.

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