Phase transformations of the Pt/Ru(0001) interface studied by photoemission

Mixing and magnetic properties of surface alloys: The role of the substrate

“…Also note that the preference for the hcp site for M/Ru(0 0 0 1) is more pronounced than for M/ Rh(1 1 1). There have been a few experimental studies of monolayers of metals deposited on Ru(0 0 0 1) [28][29][30][31]; in general, it is found that the first layer goes down pseudomorphically, except for the cases of Ag [14] and Au [15] which are found to reconstruct with a pattern of misfit dislocations. For the case where the substrate is Rh(1 1 1), we are aware of studies only with overlayers of Pt and Co.…”

CO Adsorption on PtRu/Ru(0001) Near Surface Alloys from Ultrahigh Vacuum to Millitorr Pressures

“…Previous studies of bimetallic surfaces have shown that upon formation of heteronuclear metal–metal bonds, large perturbations in the electronic (and therefore chemical) properties of the atoms in the surface are possible. − ,,, Specifically, these perturbations may manifest themselves as changes in core and valence level binding energies observed in photoemission experiments ,, as well as CO-adsorption energies. ,,,− Studies have shown that increases in metal core-level binding energies often correlate with a decrease in the thermal desorption temperature of CO. ,, To the extent that desorption temperatures correlate with adsorption energies, this decrease may be indicative of a decrease in adsorption energy of CO to the surface. These correlations are rationalized by electron redistribution, arising from both charge transfer and hybridization upon alloy formation of two metals.…”

“…Recently, researchers have exploited near surface alloys (NSAs) as model alloy catalysts to gain molecular and atomic level information using ultrahigh vacuum (UHV) surface science experiments. − ,− PtRu NSAs can be prepared by depositing submonolayer amounts of Pt on Ru(0001) and subsequent annealing. ,,, The annealing temperature determines the surface structure: annealing to temperatures of ∼800 K leads to large, hexagonally shaped, pseudomorphic Pt islands of monolayer thickness [Pt/Ru(0001)], , while annealing at ∼1273 K causes the Pt to intermix with Ru. ,, For submonolayer amounts of deposited Pt, the intermixed Pt is located exclusively in the topmost surface layer [PtRu/Ru(0001)] , and is randomly and homogeneously distributed throughout the topmost layer. , The surface of the PtRu NSA following annealing to ∼1273 K is composed of extended terraces with a small amount of mixed PtRu islands. , STM images reveal that the concentration of defects such as step edges and kinks appears similar to those found on single crystal surfaces of Pt and Ru . Infrared studies comparing low temperature adsorption of CO on Pt/Ru(0001) annealed at 700 K to PtRu/Ru(0001) NSAs annealed at 1300 K have been conducted previously.…”

“…4−8,11−19 PtRu NSAs can be prepared by depositing submonolayer amounts of Pt on Ru(0001) and subsequent annealing. 4,12,14,20 The annealing temperature determines the surface structure: annealing to temperatures of ∼800 K leads to large, hexagonally shaped, pseudomorphic Pt islands of monolayer thickness [Pt/Ru(0001)], 4,14 while annealing at ∼1273 K causes the Pt to intermix with Ru. 4,12,20 For submonolayer amounts of deposited Pt, the intermixed Pt is located exclusively in the topmost surface layer [PtRu/Ru(0001)] 4,12 and is randomly and homogeneously distributed throughout the topmost layer.…”

CO-Induced Photoemission Structures of the CO/Pt/Ru(0001) Interface

“…Platinum deposited on Ru(0001) at room temperature (RT) in submonolayer amount forms small, homogeneously distributed, two-dimensional islands with a relaxed, dendritic shape [6,7]. The condensate structure is compatible with the Pt(111) face and contains a big fraction of edge sites.…”