Structure of monolayer tin oxide films on Pt(111) formed usingNO2as an efficient oxidant

Abstract

Submonolayer Sn deposits on Pt͑111͒ and Sn incorporated in a ()ϫ))R30°Sn/Pt͑111͒ surface alloy were oxidized by NO 2 under ultrahigh-vacuum conditions. The oxide films formed were characterized by Augerelectron spectroscopy, low-energy electron diffraction ͑LEED͒, and scanning tunneling microscopy ͑STM͒. Four different surface morphologies were identified, depending on the preparation conditions, each of them exhibiting a distinct LEED pattern. STM revealed two ordered epitaxial overlayers. One is interpreted as the adsorption of SnO pseudomolecules at preferential sites to form a (4ϫ4) coincidence lattice with the substrate. The other structure forms an incommensurate tin oxide overlayer, exhibiting a long-range Moiré pattern. The remaining LEED patterns are associated with the formation of a regular stress-relief pattern that can transform into an ordered array of tin oxide islands upon repeated oxidation. This ordered island array exhibited a (5 ϫ5) superlattice with respect to the Pt͑111͒ substrate. The variety of SnO x overlayer morphologies is attributed to subtle differences in the oxide stoichiometry and alterations in the oxide/metal interface, in particular Pt-Sn alloying.

Structure of epitaxial graphene on Ir(111)

“…It is not always clear whether the meshes are to be considered incommensurate or commensurate [11], whether a mismatch in lattice parameter is accommodated by strain relief [12,13] or whether strain only plays a negligible role. Such superstructures have relevancy for nanopatterning, as in some cases they enable templated growth of clusters [14]- [16].…”

Adsorption of oxygen onPt3Sn(111)studied by scanning tunneling microscopy and x-ray photoelectron diffraction

“…5,6 Very recently, Batzill and co-workers investigated by means of Auger electron spectroscopy ͑AES͒, low-energy electron diffraction ͑LEED͒ and scanning tunneling microscopy ͑STM͒ the oxidation of Sn-Pt͑111͒ sur-face alloys. [7][8][9] Such surface alloys were prepared by deposition of tin on Pt͑111͒ and subsequent annealing. Several phases formed upon oxidation in various conditions of these surface alloys.…”

Techniques for the Study of the Structural Properties

“…128,129 Although it may not be easy to obtain structural parameters from STM images, this microscopy can be used in a straightforward way to study the shape or morphology of oxide nanostructures as a function of temperature and under reaction conditions. 130,131,132,133,134,135 Figure 8 illustrates how useful this technique can be. 136 Initially, Mo nanoparticles are present on a Au(111) substrate.…”