Effect of applied electric field on the molecular orientation of epitaxially grown organic films

In order to control and obtain desired molecular orientations, we investigated the effects of applying an electric field during the epitaxial growth of organic crystals in this study. We deposited interdigitated gold electrodes on polished KCl (001) substrates, and then grew copper phthalocyanine (CuPc) thin films, applying the voltages during evaporation process. Using an energy dispersive grazing incidence x-ray diffraction system, we evaluated the orientations of α-CuPc crystals relative to the KCl substrates. The CuPc crystals with applied electric fields were found to orient in different directions from those of the usual epitaxially grown films without applied electric fields. These facts suggest that the combination of applying an electric field and epitaxial growth provide us a new method to control the molecular orientation in the organic thin films.