RESUMEN
We have deposited Au films in ultra-high vacuum onto a rhenium ([Formula: see text]) surface in submonolayer and multilayer concentrations and studied them by means of low- and medium-energy electron diffraction in the temperature range between 300 and 800 K. In the submonolayer range, Au forms several low-energy electron diffraction (LEED) phases, namely, a (1 × 3), a (1 × 4), a (1 × 5) and a (1 × 6) phase, consisting of one-dimensionally ordered Au chains in the [[Formula: see text]] direction, until the formation of a complete pseudomorphic monolayer is indicated by a (1 × 1) LEED phase. In the multilayer regime, a (1 × 8) LEED phase appears over a surprisingly wide coverage range from about two to at least eight monolayers, which we interpret as a hexagonal uniaxially compressed reconstructed Au overlayer on pseudomorphically grown hexagonal close-packed gold layers. In order to get access to absolute Au coverages, we have performed LEED (I,V) measurements and carried out a LEED structure determination for the (1 × 1) phase. We propose the formation of a full Au monolayer in which both the Re trough and top-row sites are being covered by Au atoms. The data are discussed and compared with those from previous studies on related systems.
RESUMEN
A novel H(2) molecular adsorption state on metal surfaces has been detected by temperature-programmed desorption and electron energy loss spectroscopy experiments of the H(2)/Pd(210) system. The molecular nature of this state has been verified by isotope exchange experiments. This molecular state leads to a decrease of the surface work function while atomic hydrogen on Pd(210) causes an increase. Ab initio total-energy calculations have confirmed all experimental findings. Through these calculations the microscopic nature of this novel molecular adsorption state could be identified; it turns out that this state is stabilized by the presence of atomic hydrogen on the Pd(210) surface.
RESUMEN
A low-temperature recording diode is described which allows the determination of adsorption-induced contact potential differences with an accuracy of better than 0.5 mV. Some experimental work function results of the hydrogen adsorption on platinum (111) and (997) single-crystal faces are presented which demonstrate the usefulness of the method.