Island growth kinetics during the vapor deposition of gold onto TiO2(110)

Vapor deposition of Au on the TiO2(110) surface at 150-300 K has been examined using X-ray photon spectroscopy and low energy ion scattering. Two-dimensional islands are initially formed up to a certain average critical coverage (theta(cr)). At coverages above theta(cr), added Au mainly goes on top of these, forming three-dimensional islands. Even though thermodynamically the islands would prefer to form three-dimensional islands from the onset of growth, kinetic limitations constrain the growth initially to two-dimensional islands. The critical coverage is found to decrease with temperature, showing an apparent activation energy of -2.2 kJ mol(-1), but is independent of Au vapor flux. The critical coverage was also seen to increase with the defect density of the TiO2 surface. This behavior is explored using a kinetic model which includes surface energetic parameters for Au atom migration. (C) 1999 Elsevier Science B.V. All rights reserved.