Adhesion and Diffusion of Zinc-Phthalocyanines on the ZnO (10(1)over-bar0) Surface

We study the adhesion and the diffusion of single zinc-phthalocyanine (ZnPc) molecules on a ZnO (10 (1) over bar0) surface by means of model potential molecular dynamics. We find that the molecule is easily adsorbed on the surface, and we identify the ZnPc adsorption sites. The diffusion at room temperature is studied by metadynamics. We find that the molecule is able to diffuse by hopping between the surface dimer rows along the [010] crystallographic direction with a free energy barrier as small as similar to 0.4 eV. At temperatures T > 700 K, a different mechanism is found with large diffusion paths along the surface trench grooves.