Highly Ordered Organic Molecular Thin Films on Silicon Studied by STM and LEED

Achieving growth of long-range ordered organic molecular thin films on inorganic substrates continues to be a significant challenge for organic electronics applications. Here, we report the growth of highly ordered zinc phthalocyanine (ZnPc) thin films both in-plane and out-of-plane on the deactivated Si(111) surface by scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). By adjusting the substrate temperature during deposition, the anisotropic step-flow growth mode can be accessed causing a reduction in the substrate symmetry which allows for the long-range in-plane ordering as well as the decrease of grain boundary density [1] [2]. Additionally, the ZnPc molecules are able to maintain a highly ordered configuration in multi-layers despite a gradual decrease in the molecule-substrate interaction, which is attributed to the strong interlayer $\pi$-$\pi$ interaction [2]. \newline \newline [1] S. R. Wagner, R. R. Lunt, and P. P. Zhang, \textit{Phys. Rev. Lett.} \textbf{110}, 086107 (2013).\newline [2] S. R. Wagner and P. P. Zhang, (Submitted).