Abstract:
To study the heteroepitaxial growth of apolar organic compounds on apolar inorganic substrates, the n-alkanes dotriacontane (C32H66) and tritriacontane (C33H68), dissolved in n-heptane, were deposited onto the (0001) face of highly oriented pyrolytic graphite (HOPG). It was found that both n-alkanes display epitaxial crystal growth. The hexagonal symmetry of the substrate surface is reflected by the three preferred orientations of the platelike crystals. The orientation of the alkane crystals was determined using polarization microscopy and atomic force microscopy. A Stranski-Krastanov mechanism for three-dimensional epitaxial growth is proposed, in which the first layer of n-alkane molecules on the graphite surface is assumed to be one of the well-known monolayer structures. Three-dimensional nucleation of the n-alkane crystals occurs on this layer, in such a way that the hydrocarbon chains of the crystal are parallel to those in the monolayer. From the point group symmetry of the n-alkane contact plane and the substrate surface, it was deduced that the epitaxial nuclei Of C32H66 and C33H68 can be deposited in six and three orientations, respectively, which is in agreement with the experimental results.