Arrangement of molecules at lattice defect in an organic crystal

Abstract

Many important properties of organic crystals are known to be controlled by a small amount of impurities and lattice imperfections. We have reported the molecular arrangements at defects in some metal complxes which are composed of elements such as N,O and metal in addition to C and H. The lattice energy or defect energy calculation of these materials could not be carried out with sufficient accuracy, because of the existence of such hetero atoms. In this paper we show defect structures found in epitaxial films of a simple hydrocarbon, quarterylene(Fig.1), which contains no hetero atoms and their structure was partly studied. Quarterylene purified by sublimation in a stream of nitorogen gas was deposited on a cleaved (001) surface of several kinds of alkali-halides in a vacuum of 5x10-5 Pa. The substrates cleaved in air were preheated for two hours in the vacuum and were colled at a desined temperature. The film thickness was controlled to be about lOnm.At the substrate temperatures lower than 170°C, the quarterylene film is composed of long fibrous crystals, whose long axes are parallel to two perpendicular directions in the substrate surfaces. At higher temperatures than 170°C, planar continuous crystals grow together with some fibrous ones as shown in Fig.2.