In the light of recent experimental as well theoretical studies, we summarize our present understanding polar oxide surfaces and examine fundamental issues regarding their stability. The focus is on surface atomic configurations (relaxations, reconstructions, non-stoichiometry, etc) obtained under specific preparation conditions associated electronic structure. We discuss several mechanisms at work surfaces, such relaxation effects, change covalency in layers, partial filling states,...

Whenever a compound crystal is cut normal to randomly chosen direction, there an overwhelming probability that the resulting surface corresponds polar termination and highly unstable. Indeed, oxide surfaces are subject complex stabilization processes ultimately determine their physical chemical properties. However, owing recent advances in preparation under controlled conditions improvements experimental techniques for characterization, impressive variety of structures have been investigated...

Thickness matters: Ultrathin oxide films on metals can greatly enhance catalytic activity, for example, in CO oxidation an FeO(111) film grown a Pt(111) substrate. Under the reaction conditions, bilayer FeO restructures to form trilayer OFeO (see picture). Experimental evidence structure/morphology of and theoretical modeling mechanism its formation surface are presented.

The oxides of copper have attracted the attention scientists already for more than hundred years. This fascination is fueled by many outstanding properties material, example, a semiconducting behavior that led to first diode fabricated in electronics, pronounced excitonic response stimulated an intense search Bose-Einstein condensation, and pivotal role unconventional superconductivity. Despite this central position past present research activities, aspects are not sufficiently understood...

The electronic and atomic structures of several $(1\ifmmode\times\else\texttimes\fi{}1)$ terminations the (110) polar orientation ${\mathrm{SrTiO}}_{3}$ surface are systematically studied by first-principles calculations. structure two stoichiometric SrTiO ${\mathrm{O}}_{2}$ characterized marked differences with respect to bulk, as a consequence polarity compensation. In former, Fermi level is located at bottom conduction band, while in latter formation peroxo bond between oxygens results...

2014 Nous présentons une étude par diffusion des rayons X de la transition Peierls du bronze bleu K0,3MoO3 incluant variation thermique l'intensité réflexions satellites 1er et 2e ordre en dessous Tc, complète caractérisation fluctuations structurales (dépendance température anisotropie) au- dessus Tc mesure précise vecteur d'onde ondes densité charge au-dessus en-dessous Tc.L'analyse phase dans le cadre d'une théorie champ moyen est justifiée.Elle conduit à valeurs raisonnables couplage...

Relying on first principles simulations of stoichiometric MgO, ZnO, and NaCl ($1\ifmmode\times\else\texttimes\fi{}1$) ultrathin (111) films, we demonstrate the existence a critical thickness below which polarity is uncompensated: surface charges are bulklike, total dipole moment formation energy grow linearly with thickness. This study reveals novel facets problematics akin to nanoscopic size objects opens stimulating perspectives polar nanostructures properties reactivity unaffected by...

The structural stability of an FeO(111) film supported on Pt(111) was studied by density functional theory (DFT) as a function oxygen pressure. results showed formation O-rich phases at elevated O2 pressures and revealed site specificity the oxidation process within coincidence (Moiré) structure between Pt(111), ultimately resulting in ordered pattern O−Fe−O trilayer islands, observed scanning tunneling microscopy (STM). In addition, high resolution STM images (√3 × √3)R30° superstructure...

Using an ab initio total energy approach, we study the stability of free and Ag(111)-supported MgO(111) ultrathin films. We unravel a novel microscopic mechanism stabilization polar oxide orientations, based on strong modification MgO structural phase diagram with respect to bulk material. predict that, at low thickness, films which are either unsupported or deposited Ag(111) display graphitelike ${B}_{k}$ structure rather than expected rocksalt one. Our results provide consistent...

The electronic structure of stoichiometric ${\mathrm{Y}}_{2}$${\mathrm{O}}_{3}$ is studied both theoretically and experimentally. X-ray absorption, performed through total-yield measurements at the K ${\mathit{L}}_{\mathrm{II}}$ edges yttrium atoms edge oxygen atoms, has given access to empty states various orbital characters in conduction band. shape valence band was obtained by means photoemission spectroscopy. These results are compared with self-consistent, semiempirical tight-binding...

We present a first-principles study of the adsorption palladium monolayer on polar MgO (111) surface. On clean unreconstructed surface, our spin-polarized calculations confirm existence partially occupied states in gap both oxygen and magnesium terminations. The characteristics Pd are controlled by strong character surface thus differ substantially from those reported for (100) In particular, electron transfers and/or orbital hybridization between atoms substrate take place, inducing...

Relying on an ab initio approach to model MgO/metal interfaces, we unravel the specificity of polarization effects in oxide monolayer limit. We show that rumpling supported film is a structural response interfacial charge transfer. Surface characteristics such complex supports can thus be directly tuned by adequate choice metal and oxide. This mechanism equally affects films nonpolar polar orientations. Contrary thicker films, there no electrostatic signature distinguishing two types orientation.

Compact CeO 2 (111) films grown on Ru(0001) can be transformed into well‐shaped nanoparticles by annealing them in an oxygen‐poor environment. With increasing temperature, the particles undergo a distinct shape evolution that finally leads to crystallites exposing wide (100) facets. The atomic structure of termination is determined with combination high‐resolution scanning tunneling microscopy and density functional theory. Two surface reconstructions are identified compatible need...

Abstract We studied CO oxidation on FeO(1 1 1) films Pt(1 at submonolayer oxide coverages ultrahigh vacuum and near‐atmospheric pressure conditions. The bilayer islands are inert towards 2 formation. In contrast, the FeO 2− x trilayer structure shows substantial production that reaches a maximum ≈40 % coverage both results provide compelling evidence /Pt(1 interface is most active in oxidation. Although boundaries possesses weakly bound oxygen species, strong binding of to Pt favors reaction...

GGA overestimates the stability of polar and/or non-stoichiometric surfaces.

Stable polar oxide surfaces must be simultaneously electrostatically compensated and in thermodynamic equilibrium with the environment. As a paradigm, $\mathrm{MgO}(111)\mathrm{\text{\ensuremath{-}}}p(2\ifmmode\times\else\texttimes\fi{}2)$ reconstructed surface is shown to involve combinations of Mg-covered terminations peculiar insulating electronic structure, favored O-poor conditions, O-terminated octopole, stabler more O-rich environments. Such picture, which could not have been foreseen...

We present an analytical method for treating the tunneling current between a tip and sample in scanning microscopy (STM) that goes beyond independent-electrode (Bardeen) approximation is valid smaller tip-to-surface separations. The extremity of represented by single spherical potential well. This well strongly coupled to neighboring atoms, as electrode, both which we leave general form. wave function entire system obtained matching procedure, from total determined. If associated with...