Combined scanning tunneling microscopy and kinetic Monte Carlo study on kinetics of Cu-coordinated pyridyl-porphyrin supramolecular self-assembly on a Au(111) surface

We have studied the kinetics of Cu-coordinated pyridyl-porphyrin supramolecular self-assembly on Au(111) using scanning tunneling microscopy (STM) through evaluating the island density variation as a function of substrate temperature and molecular deposition rate. We analyzed the experimental data using the classical nucleation theory and derived a molecular diffusion barrier of 0.68 +/- 0.06 eV, a pyridyl-Cu bonding energy of 0.20 +/- 0.09 eV, and a critical nucleus size of three. These results are confirmed by kinetic Monte Carlo (KMC) simulations. We also studied the postnucleation phenomena and revealed that below 373 K unstable islands (with sizes equal or smaller than the critical nucleus size) were formed upon the deposition and dissolved subsequently.