Potential energy surface of alkali atoms adsorbed on Cu(001)

Fratesi, Guido

doi:10.1103/physrevb.80.045422

Cited by 17 publications

(24 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The same scenario is qualitatively obtained for all the investigated coverages, with smaller (larger) substrate distortions for thinner (thicker) layers [e.g., ∥ΔR∥ ¼ 0.62ð1.46Þ Å for 2 (4) ML]. Noteworthily, this deformation of the surface lattice is not associated with a quadratic increase in the elastic energy, as expected from harmonic theory and found, for example, for alkali atoms on metals [34]. On the contrary, the elastic energy that has to be spent to deform the ideal Co film to the optimized coordinates assumed when an adatom is accommodated in a bridge position was found to decrease at higher coverages, indicating a softening of the Co film [30].…”

Section: H Y S I C a L R E V I E W L E T T E R Ssupporting

confidence: 82%

Enhanced Atom Mobility on the Surface of a Metastable Film

et al. 2014

View full text Add to dashboard Cite

A remarkable enhancement of atomic diffusion is highlighted by scanning tunneling microscopy performed on ultrathin metastable body-centered tetragonal Co films grown on Fe(001). The films follow a nearly perfect layer-by-layer growth mode with a saturation island density strongly dependent on the layer on which the nucleation occurs, indicating a lowering of the diffusion barrier. Density functional theory calculations reveal that this phenomenon is driven by the increasing capability of the film to accommodate large deformations as the thickness approaches the limit at which a structural transition occurs. These results disclose the possibility of tuning surface diffusion dynamics and controlling cluster nucleation and self-organization. DOI: 10.1103/PhysRevLett.113.046102 PACS numbers: 68.43.Jk, 68.55.J-, 81.15.Aa Atomic diffusion on solid surfaces is a ubiquitous phenomenon that plays a fundamental role in determining a large variety of physical and chemical processes. An example is represented by the self-assembly of metallic nanosized clusters stabilized on either oxide or metallic substrates, which is exploited to produce nanopatterned materials in fast and parallel bottom-up approaches [1,2]. In this frame, adatom diffusion is of paramount importance, since the kinetic constraints typically determine the final morphology of the self-assembled nanostructures. In the field of heterogeneous catalysis, adatom diffusion is particularly relevant in cases where spill-over effects intervene and the reaction proceeds through different steps mediated by spatially separated active sites [3][4][5]: an enhanced atomic diffusivity can therefore boost the rate of the chemical reactions. On the other hand, in oxide supported metal clusters, catalysis, sintering due to Ostwald ripening, induced by atoms detaching from smaller clusters and diffusing to larger ones, often leads to catalyst deactivation [6].Various factors have been recognized to influence the diffusivity of atomic species on solid surfaces, for instance, (i) isotropic two-dimensional strain in heteroepitaxial systems, with an in-plane lattice mismatch between the film and the substrate [7,8]; (ii) mesoscopic strain, where the relaxations induced by the already nucleated islands significantly affect atomic motion [9]; (iii) availability of small amounts of foreign atoms (surfactants) that, being adsorbed on the substrate prior to the film deposition, can affect the intra-and/or interlayer mass transport [10-13]; (iv) presence of molecular species (chemisorbed or in the gas phase), such as, for instance, water [3] or CO [14]; and (v) long-range adatom-adatom interactions [15][16][17]. More recently, the enhancement of surface diffusion with acoustic standing waves has been proposed as a method for surface nanostructuring by driving atomic motion [18].In this Letter, we report on a remarkable increase of atomic diffusion with the thickness of an ultrathin metastable film, namely, tetragonally distorted body-centered (bct) Co grown on Fe(001). Previous qu...

show abstract

Section: H Y S I C a L R E V I E W L E T T E R Ssupporting

confidence: 82%

Enhanced Atom Mobility on the Surface of a Metastable Film

et al. 2014

View full text Add to dashboard Cite

show abstract

“…2 (a) (see the inset). The Na ions are adsorbed at the hollow site which was identified as the most favorable one for alkali adsorbates 40,46 . Regarding the magnetic coupling, adsorption of Na ions on the magnetic surface brought an intriguing change to the interlayer exchange coupling.…”

Section: Alkali-metal-induced Switching Of the Interlayer Magnetimentioning

confidence: 99%

“…Recently it was shown that incorporating a net charge in nanostructure can be achieved by electrolyte [35][36][37] , or by adding dopants 38 , whereas using scanning tunneling microscope or electron force microscope tip is also indispensable option 39 . Doping of magnetic entities with alkali metals or halogens can lead to a significant variation of the electrochemical properties 40,41 as well as their spin properties 42,43 . Moreover, alkali metals are illustrative free-electron systems and have relatively small ionization energies.…”

Section: Alkali-metal-induced Switching Of the Interlayer Magnetimentioning

confidence: 99%

Direct surface charging and alkali-metal doping for tuning the interlayer magnetic order in planar nanostructures

Dasa

Stepanyuk

2015

Phys. Rev. B

View full text Add to dashboard Cite

The continuous reduction of magnetic units to ultra small length scales inspires efforts to look for a suitable means of controlling magnetic states. In this study we show two surface charge alteration techniques for tuning the interlayer exchange coupling (IEC) of ferromagnetic layers separated by paramagnetic spacers. Our ab − initio study reveals that already a modest amount of extra charge can switch the mutual alignment of the magnetization from anti-ferromagnetic to ferromagnetic or vice verse. We also propose adsorption of alkali metals as an alternative way of varying the electronic and chemical properties of magnetic surfaces. Clear evidence is found that the interlayer magnetic order can be reversed by adsorbing alkali metals on the magnetic layer. Moreover, alkali metal overlayers strongly enhance the perpendicular magnetic anisotropy in FePt thin films. These findings combined with atomistic spin model calculations suggest that electronic or ionic way of surface charging can have a crucial role for magnetic hardening and spin state control.

show abstract

“…Convergence criteria were equivalent to those of our recently calculated alkali-metal potential-energy surfaces. 28 Structures were determined by allowing adatoms to relax from initial fourfold hollow sites for both the L 7 and L 5 overlayers, finding equivalent results in the two cases. A number of trial 0.6 ML structures, similar to those outlined elsewhere, 29 were also modeled but were found to be unstable by at least 30 meV per Li atom.…”

mentioning

confidence: 99%

Charge redistribution in the formation of one-dimensional lithium wires on Cu(001)

et al. 2010

View full text Add to dashboard Cite

We describe the formation of one-dimensional lithium wires on a Cu͑001͒ substrate, providing an atomicscale description of the onset of metallization in this prototypical adsorption system. A combination of helium atom scattering and density-functional theory reveals pronounced changes in the electronic charge distribution on the formation of the c͑5 ͱ 2 ϫ ͱ 2͒R45°Li/Cu͑001͒ structure, as in-plane bonds are created. Charge donation from Li-substrate bonds is found to facilitate the formation of stable, bonded, and depolarized chains of Li adatoms that coexist with an interleaved phase of independent adatoms. The resultant overlayer has a commensurate charge distribution and lattice modulations but differs fundamentally from structurally similar charge-density wave systems. Self-organized, nanometric wires are ideal prototypes for exploring the electronic changes that occur during the process of bond formation at a surface. Epitaxial deposition onto intrinsically anisotropic substrates-such as ͑110͒ oriented, 1 stepped, 2-6 or reconstructed 7 single crystals-has been particularly useful in this regard. The approach can yield long, robust wires that are easier to study than freestanding structures.8 It is also of interest for the study of lowdimensional phenomena, including charge-density waves ͑CDWs͒, 9,10 which have been identified in a variety of lowdimensional p-block 11 and d-block 3,9 epitaxial systems. In contrast, one-dimensional ͑1D͒ s-block systems have not previously been identified but could offer nonlocal, freeelectronlike properties that would contrast with the local nature of d-band systems. In the case of alkali metals on lowindex surfaces, a difficulty in forming 1D surface structures is the nature of interadsorbate interactions.12,13 Heavy alkali metal adatoms are highly polarized and tend toward isotropic, hex-type overlayers. As we demonstrate in the present work, light alkali metals behave differently, a fact that can be attributed to stronger and more localized adatom-substrate interactions. The resulting atomic chains of Li have a 1D structural character and they offer a unique opportunity for the observation of the charge redistribution as metallic bonds form in the surface plane. We use a combination of helium atom scattering ͑HAS͒ and density-functional theory ͑DFT͒ to probe directly the electronic structure of these anisotropic Li films, which we show to be characterized by inhomogeneous electronic-charge distributions and the coexistence of two distinct Li adatom states.Previous electron 14,15 and atom 16 diffraction studies have shown that a series of well-ordered submonolayer Li adatom structures forms on Cu͑001͒ at low temperature. Upon deposition, Li adatoms condense from a dilute lattice gas into an ordered c͑2 ϫ 2͒ structure at 0.5 monolayers ͑ML͒ with adatoms occupying fourfold hollow sites, 17,18 as sketched in Fig. 1͑a͒. Adatoms in the c͑2 ϫ 2͒ structure have a large separation and Ne scattering indicates that they act as independent Einstein oscillators: 16,19 both factors po...

show abstract

Potential energy surface of alkali atoms adsorbed on Cu(001)

Cited by 17 publications

References 46 publications

Enhanced Atom Mobility on the Surface of a Metastable Film

Enhanced Atom Mobility on the Surface of a Metastable Film

Direct surface charging and alkali-metal doping for tuning the interlayer magnetic order in planar nanostructures

Charge redistribution in the formation of one-dimensional lithium wires on Cu(001)

Contact Info

Product

Resources

About