Nucleation and evolution of zinc phthalocyanine thin films on the deactivated Si(111)-B √3 x √3 R30° surface

We report the growth evolution of thermally evaporated zinc phthalocyanine (ZnPc) on the deactivated Si(111) surface using scanning tunneling microscopy (STM). We find that the Ehrlich-Schwoebel barrier (ESB) associated with the ZnPc step edges is negligible, while the formation of molecular domain boundaries provides an activation barrier and additional nucleation sites which increases the film roughness and interrupts the anisotropic step-flow growth. By increasing the substrate temperature, the grain boundary density is significantly reduced, resulting in a well-controlled surface morphology. This study provides insight into the influence of the ESB and the grain boundary crossing barrier on the growth dynamics of organic thin films. (C) 2014 Elsevier B.V. All rights reserved.