Surface structure characterization of ultra-thin films of Au deposited on Pd(111)

Ultra-thin films of Au were deposited on the Pd(111) surface and then characterized by X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and X-ray photoelectron diffraction (XPD) generated by synchrotron radiation. The Au films were deposited at room temperature (300 K) and subsequently annealed at 400 degrees C (673 K) and 610 degrees C (883 K). XPD analyses indicated that the gold films were 7 and 6 ML thick, for the annealing temperatures of 400 degrees C and 610 degrees C, respectively. The film interlayer distances exhibited an oscillatory behavior, with a 5% contraction between the top and the second layers, a 3% expansion between the second and the third layers, for the film annealed at 400 degrees C, and a 2% expansion in the interlayer distance between the top and the second layers and a 4% contraction between the second and the third layers, for the film annealed at 610 degrees C For both annealing temperatures, the interlayer distances between the third and the fourth layers and between the fourth and the fifth layers exhibited a 1% expansion and a 2% contraction. For the film annealed at 610 degrees C, XPD results revealed that the Pd(111) surface was covered by Au islands, with some bare patches exposed. (C) 2015 Elsevier B.V. All rights reserved.