Adsorption of metal adatoms on FeO(111) and MgO(111) monolayers: Effects of charge state of adsorbate on rumpling of supported oxide film

Abstract

International audienceWe present a theoretical density-functional theory study on the deposition of metal atoms (Ir, Pd, Pt, Ag, and Au) on FeO(111) and MgO(111) monolayers supported on Pt(111). We show the existence of a strong coupling between the charge state of the adsorbed adatom and the local polaroniclike distortion of the oxide film, and we identify two qualitatively different adsorption modes in which the distortion either reinforces the rumpling of the supported oxide film (positively charged adsorbates) or reduces or even reverses the cation-anion stacking (negatively charged adsorbates). Thus, the adsorption mode is a response to the charge state of the adsorbate and is driven mainly by the capacity of adatoms to exchange electrons with the support

Controlling the charge state of supported nanoparticles in catalysis: lessons from model systems

“…20a, for electrostatic reasons. 240 Of course, the opposite is also true. A substrate with low electronegativity (small work function) favors electron flow towards the oxide, and in this case it is the oxide cations that are displaced outwards, Fig.…”

Electron trapping in misfit dislocations of MgO thin films

“…According to density-functional theory ͑DFT͒ and Kelvin probe studies, the MgO film reduces by ϳ1.5 eV. 24,25 The effect is caused by an electron transfer out of the film that creates a positive interface dipole and the suppressed electron spillout at the metal surface. Surface defects may alter this trend due to their influence on the local charge distribution.…”

Charge-State-Dependent Diffusion of Individual Gold Adatoms on Ionic Thin NaCl Films

“…Hence, the charging does not only affect the barrier height, but even the qualitative diffusion behavior is completely different. The selective interaction of Au − adatoms with the moiré pattern can be rationalized when considering that the charging of Au is accompanied by a strong relaxation pattern of the surrounding NaCl ions [1,12]. Apparently, this relaxation pattern interacts with the buckling of NaCl ions resulting from the interfacial moiré pattern.…”

“…We further observe that Au anions on a bilayer of NaCl on Cu(111) show a diffusion pattern corresponding to the moiré pattern of the interface of NaCl to the underlying metal substrate. Apparently, the ionic relaxations in the polar insulating film that are present around negatively charged Au − anions [1,12] interact with the bucklings of ions in bilayer NaCl films that arise from the incommensurate interface with the substrate.The experiments were carried out with two homebuilt low-temperature STM apparatuses with a base temperature of 5 K. NaCl was evaporated thermally onto a clean Cu(111) single-crystal surface such that defect-free (100)-terminated NaCl bilayer islands were formed [13] with smaller patches of a third NaCl(100) layer on top of them. Gold atoms were deposited with the sample inside the STM at T < 10 K. All voltages refer to the sample bias with respect to the tip.…”

“…We further observe that Au anions on a bilayer of NaCl on Cu(111) show a diffusion pattern corresponding to the moiré pattern of the interface of NaCl to the underlying metal substrate. Apparently, the ionic relaxations in the polar insulating film that are present around negatively charged Au − anions [1,12] interact with the bucklings of ions in bilayer NaCl films that arise from the incommensurate interface with the substrate.…”