Structural rearrangements during the initial growth stages of organic thin films of F16CuPc on SiO2

We present an experimental study on the first stages of the thin film growth of the organic molecule F16CuPc (hexadecafluoro-copper-phthalocyanines) on SiO2. By means of in situ X-ray reflectivity, in situ grazing incidence X-ray diffraction (GIXD), and ex situ atomic force microscopy (AFM), we provide a detailed picture of the film growth mode and its structural evolution at the nanometer scale. We discovered the formation of a low-density layer of molecular aggregates with heights between 5 and 10 angstrom at the interface with the SiO2 and show that, on top of this interfacial layer, the nucleation and two-dimensional growth of elongated islands of upright standing molecules take place. Structural changes are observed, pointing to significant relaxations of the lattice parameters within the first layers of standing molecules.