On the origin of Ru bilayer island growth on Pt(111)

From Adlayer Islands to Surface Alloy: Structural and Chemical Changes on Bimetallic PtRu/Ru(0001) Surfaces

“…The same preferences were shown to be responsible for the higher stability of the Ru bilayer compared to monolayer islands on Pt(111) surfaces. [28,29] On Ru(0001), blocking of island or step-edge growth by locally alloyed regions lying in front of the step edge might also play a role in the surface morphology after annealing to T > 850 K. This would be analogous to Pd on Ru(0001), where the growth of strongly irregularly shaped islands at T = 840 K was attributed to exchange processes in combination with preferred overgrowth of Pd-free areas. [30] Therefore, the transition from smooth and round islands and decorations after annealing to 750 K to more kinked and irregularly shaped ones after annealing to 850 K could be promoted by the onset of surface alloying, in addition to the quenching effects mentioned above.…”

Anomalous temperature dependence of antistripe width in the annealing of submonolayer Fe on Ru(0001)

“…The temperature evolution of the double-layer to a monolayer structure has recently been discussed in the Ru/Pt(111) system. 19 We find that the triangular vacancy islands on the same terrace have the same orientation while vacancy islands at nearest-neighbor terraces always have opposite orientations. The edges of the triangular vacancy islands align along one type of the close-packing crystalline directions.…”

Segregation and Stability in Surface Alloys: PdxRu1−x/Ru(0001) and PtxRu1−x/Ru(0001)

“…First, during Pt deposition on Ru(0001) at elevated temperatures (500-600 K), Pt atoms prefer to adsorb on the Ru substrate rather than on the pseudomorphic Pt islands grown thereon. [36] Furthermore, Ru was observed to grow in bilayer islands upon deposition on Pt(111) at 400-500 K [71] or upon deposition on pseudomorphically grown Pt islands on Ru(0001) at 500-600 K. [72] These observations show that both, Pt and Ru deposits prefer adsorption on Ru 3 sites rather than on Pt 3 sites. This is supported also by the present findings, by the growth behavior of Ru on the Pt 0.…”

“…A recent STM study of the processes occurring during PtRu/ Ru(0001) surface alloy formation at 850-900 K had provided convincing evidence that at these low temperatures surface alloy formation starts by detachment of Pt atoms from the edges of the Pt islands and step decorations, which were formed during preceding Pt deposition (deposition at room temperature), and the reversible exchange of the diffusing Pt adatoms with terrace Ru atoms. [36] Because both, Ru and Pt adatoms prefer to adsorb on Ru 3 sites rather than on sites containing Pt, [36,72] only Pt-free areas are overgrown under these conditions. Lateral exchange at the interface between Pt step decorations and former Ru steps was excluded at this temperature.…”