title: The growth and thermal properties of Au deposited on Rh(111): formation of an ordered surface alloy.
abstract: Scanning tunnelling microscopy (STM), low energy ion scattering spectroscopy (LEIS), X-ray photoelectron spectroscopy (XPS) and high resolution electron energy loss spectroscopy (HREELS) were applied for studying Au deposited on the Rh(111) surface. Both the deposition of Au at different substrate temperatures (400-800 K) and the effect of annealing Au deposited at 500 K were investigated. Gold deposition at 500 K, investigated by STM and LEIS methods, revealed that up to half monolayer Au the system exhibits clearly layer-by layer growth; however, above this coverage a slight deviation was identified, mainly due to kinetic and morphological effects. A continuous cover layer of Au was formed only above ∼2.5 monolayers (ML). Below this coverage, the pseudomorphic character of the Au overlayer was clearly proven by STM, but this feature disappears at 4 ML coverage. A moderate (5-10%) surface mixing of the two metals was observed only above 600 K, for both annealing the Au layer formed at lower temperatures and performing the deposition at elevated temperatures. Above 600 K a clear step-flow growth mechanism was verified. Depending on the Au coverage, a more extended mixing of the top layer and the sublayer was observed at even higher temperatures. In this case, nano-range ordering of the alloyed layer was detected by STM, where the lateral extension of the uniform commensurate (2 × 1) domains was around 4 × 4 nm2. In this case, the local intralayer mixing of Rh and Au can locally reach a value of 50%. The proposed structural model for the (2 × 1) alloy phase was also corroborated by HREELS investigations on CO adsorption.
authors.affiliation: MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, Rerrich B. tér 1., H-6720 Szeged, Hungary. aberko@chem.u-szeged.hu ovari@chem.u-szeged.hu.
authors.forename: László
authors.initials: L
authors.lastname: Óvári
authors.affiliation: MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, Rerrich B. tér 1., H-6720 Szeged, Hungary. aberko@chem.u-szeged.hu ovari@chem.u-szeged.hu.
authors.forename: András
authors.initials: A
authors.lastname: Berkó
authors.affiliation: Department of Applied and Environmental Chemistry, University of Szeged, Rerrich B. tér 1., H-6720 Szeged, Hungary.
authors.forename: Gábor
authors.initials: G
authors.lastname: Vári
authors.affiliation: Department of Applied and Environmental Chemistry, University of Szeged, Rerrich B. tér 1., H-6720 Szeged, Hungary.
authors.forename: Richárd
authors.initials: R
authors.lastname: Gubó
authors.affiliation: Department of Physical Chemistry and Materials Science, University of Szeged, Rerrich B. tér 1., H-6720 Szeged, Hungary.
authors.forename: Arnold Péter
authors.initials: AP
authors.lastname: Farkas
authors.affiliation: MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, Rerrich B. tér 1., H-6720 Szeged, Hungary. aberko@chem.u-szeged.hu ovari@chem.u-szeged.hu and Department of Applied and Environmental Chemistry, University of Szeged, Rerrich B. tér 1., H-6720 Szeged, Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Kónya