Controllable restructuring of a metal substrate: Tuning the surface morphology of gold

Organic thin films composed of naphtho[2,3-a]pyrene, a very promising multifunctional polyaromatic hydrocarbon for use in optoelectronic devices, are demonstrated to restructure the pristine Au(111) 22 x root 3 surface. The perturbation of the herringbone reconstruction was used to gauge the interaction strength of the organic molecule with the substrate through a series of controlled adsorption and annealing treatments. The overall behavior of the system is interpreted as an interplay between thermodynamic and kinetic factors, dictated by the temperature of the sample and the surface coverage of the molecules. The restructuring mechanism involves the exchange of Au atoms from the herringbone reconstruction to the step edges. Our results reveal that the molecular and substrate equilibrium structure is only achieved after annealing the system to >470 K. This infers that caution should be taken when organic-metal interfaces are constructed by low or room temperature deposition, as they may not correspond to the equilibrium structures, and therefore, may misrepresent the adlayer structure which exists at the realistic working conditions of devices. (C) 2011 Elsevier B.V. All rights reserved.