Observation of molecular orientation at nano-meter scale using polarized synchrotron radiation

Sekiguchi, Tetsuhiro  ; Baba, Yuji  ; Shimoyama, Iwao   ; Hirao, Norie; Narita, Ayumi; Mannan, M. A.*; Koswattage, K.

We report on a new analytical system we are recently developing in order to clarify creation and growth mechanisms of orientation of organic semiconductors in nano-meter scale. Using the instrument, it is possible to measure polarization angle dependence of X-ray absorption fine structure (XAFS) spectra at nano-meter level using photoelectron emission microscopy; thus, it probes direction of chemical -bonds in nanometer scale. We report on fundamental studies of silicon phthalocyanine thin films, which we first try to clarify orientation mechanism of the organic semiconductor. Samples were prepared by wet-based methods followed by annealing. XAFS spectra and their angle dependent data are well understood by core-excited electronic states calculated under Z+1 approximation model. We have found that one-dimensional polymers are synthesized on the substrate, where phthalocyanine planes are stacked face-to-face, and that the chain axis is perpendicular to the substrate.