Orientation Control of Organic Conductor Thin Films by Magnetic Field

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Although well-oriented thin films of organic conductors are demanded for progress in molecular electronic devices, the orientation control of thin films of organic conductors have not been accomplished. The difficulty in the structural analysis of organic thin films is one of the bottlenecks to obtain the well-oriented organic conducting thin films. In this study, we have precisely determined the in-plane orientations of the epitaxial thin films of BEDT-TTF, perylene and p-sexiphenyl formed on the KCl (001) NaCl, and KBr (001) by using X-ray diffraction. In-plane crystal orientations of eptaxial organic thin films were investigated using a newly developed X-ray diffractometer. Organic materials was deposited onto KCl, NaCl and KBr substrates in vacuum. The obtained thin films were analyzed by using the X-ray difrractometer. The theta/2thata symmetry scan suggested that BEDT-TTF crystals in the thin films oriented in the relation of (10-2) BEDT-TTF // (001) KCl. Using this information, 03-2 asymmetry reflections that include the information of the in-plane orientations were searched as a function of rotation angle (φ) of a normal vector to the substrate surface (Fig.1). Consequently, the 03-2 reflections were successfully measured. From the measured directions of the diffraction vectors, it was determined that the in-plane epitaxial relationship of BEDT-TTF and KCl substrate is <211>_<BEDT-TTF> // <110>_<KCl>. The effects of magnetic filed on in-plane orientation of organic films were also examined.