Surface alloying at the SnPt(111) interface: a study by x-ray photoelectron diffraction

Surface alloys and alloy surfaces: the platinum-tin system

“…It is an interesting notion that the height of the pyramids corresponds to approximately 10 atomic layers or the tin depletion range found by XPD in case of the Pt(111)-Sn surface [37]. At any rate, the pyramidal form of the stress relief is the most "aesthetic" of all three surfaces under study here.…”

“…The observation of a well defined periodicity in LEED for the Sn/Pt(111) system and the parallel indications of the presence of tin in the subsurface in amount corresponding to approximately 25 at% indicates that we have a true ordered compound which extends for several atomic layers [37]. This behavior appears to be similar to that of the Co-Pt system [94], although in the case of Sn-Pt it was not possible to evidence the same kind of sharp alloy/substrate interface reported for Co/Pt(111).…”

“…The formation of multilayer surface alloys has also been investigated in the Sn-Pt(111) system, where Galeotti et al [37] reported the formation of ordered, epitaxial alloyed Pt-Sn phases. The deposition of amounts of Sn up to 5 monolayers (ML) at room temperature led to disordered or anyway non-epitaxial tin films.…”

“…ICISS has also provided evidence that diffusion in the Fe/Cu(100) system occurs only in a very small fraction of the area of the surface [106]. Although the diffusion coefficient of Sn in Pt is not known, considering the bulk diffusion coefficient of other metals in platinum Sn diffusion into the Pt substrate should be negligible in a such temperature range [37], so that the mechanism of alloying appears to be dominated here, too, by surface diffusion of Pt atoms through defects of the Sn film. However, the mechanisms of diffusion in these systems, as well as in the Pt-Sn one is something that still needs to be studied in detail.…”

“…The right row shows the LEED results corresponding to the structural models described in the text. From [37]. shift of the Sn core level peaks 0.3 eV with respect to the "as deposited" Sn film.…”