Stable and metastable structures of Co on Cu(001): An<i>ab initio</i>study

Pentcheva, Rossitza; Scheffler, Matthias

doi:10.1103/physrevb.61.2211

Cited by 72 publications

(53 citation statements)

References 34 publications

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“…These include sandwichlike growth where atoms from a low surface-energy substrate climb on top of the overlayer. [2][3][4] Other possibilities of more relevance in this study include the development of bilayer islands on single-element metal substrates [4][5][6][7][8] and on alloy substrates. [9][10][11] The development of flat-topped or mesalike multilayer islands has also been observed on single-element metal substrates [12][13][14][15][16] and on alloys.…”

Section: Introductionmentioning

confidence: 99%

Formation and coarsening of Ag(110) bilayer islands on NiAl(110): STM analysis and atomistic lattice-gas modeling

et al. 2010

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Scanning tunneling microscopy analysis of the initial stages of film growth during deposition of Ag on NiAl(110) reveals facile formation of bilayer Ag(110) islands at temperatures of 130 K and above. Annealing subsequent to deposition at 130 K induces coarsening of the bilayer island distribution. The thermodynamic driving force for bilayer island formation reflects a lower relative surface energy for films of even layer thicknesses. This feature derives from quantum size effects due to electron confinement in the Ag film. The kinetics of island formation and relaxation is controlled by terrace and edge-diffusion barriers, detachment barriers, interlayer diffusion barriers, and layer-dependent adsorption and interaction energies. These key energies are determined from density-functional theory analysis and incorporated into an atomistic lattice-gas model for homogeneous island formation, where specification of the adatom hop rates is consistent with detailed balance. Model analysis via kinetic Monte Carlo simulation elucidates the role of strongly anisotropic interactions in development during deposition of elongated island growth shapes and also in facilitating upward mass transport needed for bilayer island formation. The model succeeds in recovering island densities at lower temperatures but experimental densities exceed model predictions at higher temperatures plausibly due to heterogeneous nucleation at surface defects. The same model successfully describes postdeposition coarsening of small islands grown at 130 K. Scanning tunneling microscopy analysis of the initial stages of film growth during deposition of Ag on NiAl͑110͒ reveals facile formation of bilayer Ag͑110͒ islands at temperatures of 130 K and above. Annealing subsequent to deposition at 130 K induces coarsening of the bilayer island distribution. The thermodynamic driving force for bilayer island formation reflects a lower relative surface energy for films of even layer thicknesses. This feature derives from quantum size effects due to electron confinement in the Ag film. The kinetics of island formation and relaxation is controlled by terrace and edge-diffusion barriers, detachment barriers, interlayer diffusion barriers, and layer-dependent adsorption and interaction energies. These key energies are determined from density-functional theory analysis and incorporated into an atomistic lattice-gas model for homogeneous island formation, where specification of the adatom hop rates is consistent with detailed balance. Model analysis via kinetic Monte Carlo simulation elucidates the role of strongly anisotropic interactions in development during deposition of elongated island growth shapes and also in facilitating upward mass transport needed for bilayer island formation. The model succeeds in recovering island densities at lower temperatures but experimental densities exceed model predictions at higher temperatures plausibly due to heterogeneous nucleation at surface defects. The same model successfully describes postdeposition coarsenin...

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Section: Introductionmentioning

confidence: 99%

Formation and coarsening of Ag(110) bilayer islands on NiAl(110): STM analysis and atomistic lattice-gas modeling

et al. 2010

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“…Results are obtained in a p 3 3 unit cell with 16 k k points in the Brillouin zone. The energy cutoff of the basis set is 13.8 Ry, which provides a numerical accuracy of 0.02 eV in the surface energy of a 5 ML-thick Co(001) slab [19]. The structural optimization along the diffusion path is performed with damped Newton dynamics [20].…”

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confidence: 99%

Non-Arrhenius Behavior of the Island Density in Metal Heteroepitaxy: Co on Cu(001)

et al. 2003

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We present a combined theoretical and experimental study of island nucleation and growth in the deposition of Co on Cu(001) -a prototype for understanding heteroepitaxial growth involving intermixing. Experimentally, ion scattering is employed. Using density-functional theory, we obtain energy barriers for the various elementary processes and incorporate these into a kinetic Monte Carlo program to simulate the heteroepitaxial growth. Both the simulations and the experiments show a unique N-shape dependence of the island density on temperature that stems from the interplay and competition of the different processes involved. DOI: 10.1103/PhysRevLett.90.076101 PACS numbers: 68.55.-a, 61.43.Hv, 68.35.Fx, 82.40.Bj Heteroepitaxial metallic structures, such as Co=Cu multilayers represent a new material that has high potential for the development of magnetoelectronic devices. In order to control the interfacial properties it is important to achieve a quantitative understanding of the morphology that develops during growth and its dependence on the growth conditions. A standard model for the initial stages of growth is given by nucleation theory [1], where the island density n x is expressed in terms of the deposition rate F, the adatom hopping rate D D 0 exp ÿE d =k B T , and the binding energy E b of the critical nucleus of size i,The linear dependence of lnn x on 1=T is widely used to deduce quantities such as activation barriers from islanddensity measurements, when adatoms form islands on top of the substrate [2]. However, in heteroepitaxial systems, deposited atoms may incorporate into the substrate displacing substrate atoms into the growing layer [3][4][5][6][7][8][9]. The effect of site exchange is not considered in Eq. (1). A prototypical system where intermixing takes place is Co on Cu(001). A broad [5,6] and bimodal [6] island-size distribution was observed in submonolayer growth studies using scanning-tunnelling microscopy (STM) -in contrast to a Poisson-like distribution anticipated in standard nucleation theory [1]. In addition Nouvertné et al. reported that the island density at 415 K is slightly higher than at 295 K [6], which is at variance with the predictions of Eq. (1). The island composition was found to depend on the growth conditions and to vary from mostly Co to mostly Cu. Moreover, a correlation has been observed between island composition and island size [5,6].From a fundamental standpoint, it is important to extend nucleation theories to account for intermixing. However, to date, only a few studies have attempted this [4,10 -13]. Chambliss and Johnson proposed that substitutional Fe atoms constitute stable nuclei for the growth of Fe on Cu(001) [4]. By accounting for monomer stability [i 0 in Eq. (1)] at substitutional Fe pinning sites, they found that the island density is independent of F=D. Meyer and Behm assumed irreversible pinning of adatoms at substitutional nucleation centers and found that the island density goes through a minimum with increasing temperature -consistent with that...

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“…Strong relaxation for two monolayers of Co and Mn on Cu͑001͒ substrate (Ϫ17.0% and Ϫ30.86%, respectively͒ were also obtained in Refs. 23 25 where the values of ⌬d 12 /d 0 ϭϪ20.7% and ⌬d 23 /d 0 ϭ9.5% were found using the FLAPW method with the generalized gradient approximation ͑GGA͒ ͑Ref. 41͒ for the exchange-correlation potential.…”

Section: Resultsmentioning

confidence: 99%

“…Basically surface ES for different transition metals ͑TM's͒ or a monolayer of TM on an inert substrate was investigated. [19][20][21][22][23][24] There exist a few papers where the transition metal alloy surfaces were investigated. 24 -29 The ͑001͒ and ͑110͒ surfaces were studied very intensively for B2 NiAl alloy.…”

Section: Introductionmentioning

confidence: 99%

Surface electronic structure of Ti-based transition metal alloys

et al. 2002

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The electronic structure of the ͑001͒ and ͑110͒ surfaces for B2 Ti-based transition metal alloys were investigated using the full-potential linearized augmented plane-wave method in the local-density approximation. The evolution of the electronic structure of alloys at the different surfaces in comparison with the bulk ground states is analyzed. The ferromagnetic order is displayed in the case of Fe or Co top layer for the ͑001͒ surface. The surface magnetic moment of Fe and Co (2.27 B and 0.87 B ) reduces drastically inside the film. The influence of a surface on the electron properties of alloys is discussed.

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Stable and metastable structures of Co on Cu(001): Anab initiostudy

Cited by 72 publications

References 34 publications

Formation and coarsening of Ag(110) bilayer islands on NiAl(110): STM analysis and atomistic lattice-gas modeling

Formation and coarsening of Ag(110) bilayer islands on NiAl(110): STM analysis and atomistic lattice-gas modeling

Non-Arrhenius Behavior of the Island Density in Metal Heteroepitaxy: Co on Cu(001)

Surface electronic structure of Ti-based transition metal alloys

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