STM study of a self-assembly behavior of phthalocyanine and 1-bromohexadecane on highly oriented pyrolytic graphite

In this paper, we present the results of using alkane derivatives to assist in the adsorption of planar molecules by employing 1-bromohexadecane(C16Br) and phthalocyanine (Pc) as examples. Their assembly behaviors have been well resolved on the observed STM images. The observations presented in this work demonstrate that single molecular arrays of Pc can be obtained with a template of C16Br on highly oriented pyrolytic graphite (HOPG) substrate surface to allow high-resolution STM studies. Binary mixtures of different molar ratios were also observed. By adjusting the molar ratio of Pc to C16Br to about 1:3-1:4, uniform assembly can become dominative on the surface. The resulting high stability and the well ordered assembly are attributed to the increased adsorption barrier of alkanes. This approach could be adapted to the studies of other molecules to observe molecular features and could be helpful in obtaining two-dimensional assemblies of monodispersed molecules, especially planar molecules.