Deposition order controls the first stages of a metal-organic coordination network on an insulator surface

We report on first stages toward the formation of a surface-confined metal-organic coordination network (MOCN) by sequential deposition of biphenyl-4,4′-dicarboxylic acid and iron atoms on the surface of a bulk insulator, calcite (10.4). The influence of the deposition order on the structure formation is studied by noncontact atomic force microscopy operated in ultrahigh vacuum at room temperature. It is found that sequential deposition facilitates MOCN formation when the organic linker molecules are first adsorbed on the surface, followed by iron deposition. This observation is explained by first-principles computations, indicating that the metal-molecule interaction dominates over the molecule-molecule interaction on the surface. The observed MOCN islands are elongated in the [010] substrate direction, demonstrating a templating effect of the underlying substrate. This experimental finding is confirmed by calculations suggesting that the MOCN network matches the calcite lattice periodicity in the [010] direction but not in the [421] direction. This work, thus, demonstrates the decisive influence of both deposition order and lattice matching on the formation of an extended MOCN on a bulk insulator surface.