Breaking down and reconstruction of islands during the film growth of CuPc on HOPG

We have observed breaking down and reconstruction of islands in the film growth of a copper phthalocyanine (CuPc) film on highly ordered pyrolytic graphite using photoelectron spectroscopy (PES) and atomic force microscopy (AFM). At the initial deposition of CuPc, the film adopts the Stranski-Krastanov mode and the islands increase normally with the nominate film thickness. At a critical thickness around 6nm, the islands break down suddenly into small clusters. Further deposition drives the reunion of clusters to form large islands again and makes the film coverage smaller at a nominate thickness of 13nm. The nonmonotonic PES data and AFM morphology confirmed the re-exposure of the substrate and the first layer CuPc during the island reconstruction process. This nonmonotonic growth behavior may exist widely in many anisotropic molecular film growth processes where the thin film phases are confined or restricted by the symmetry of the substrate and different from their bulk phases.