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Strain effect on electronic and structural properties of metal nanoislands grown on reconstructed Au(111)

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The growth of various metal elements on the Au(111) surface is characterized by an initial ordered island nucleation at the elbows of the surface herringbone reconstruction, where shorter lattice constant affects the energetics and electronic properties of the adsorbates. Here we focus on Fe and Pd on Au(111), investigated by combining scanning tunneling microscopy and spectroscopy experiments (STM/STS) and density functional theory simulations (DFT).

A characteristic peak measured in the electron local density of states of Fe/Au(111) at Fermi level indicates the presence of a nondispersive minority Fe dz2 state, while less prominent contributions to the LDOS are predicted from the Au(111) surface state upon hybridization with the overlayer Fe states. The peak energy was measured to shift from occupied to unoccupied states as a function of position within Fe islands. We related this effect to the reconstruction-induced local Fe-Fe bond length variation [1].

The assignment of atom-size features, observed by STM close to herringbone elbows at low Pd coverage, to adsorbed, substituted, or subsurface Pd atoms is sometimes disputed in the literature, and here addressed by DFT simulations. The low activation barriers computed for the diffusion of adsorbed Pd, and bias-dependent contrast in simulated tunneling currents following attenuation of the Au(111) sp-surface state, support the interpretation of black spots observed in STM as subsurface Pd atoms, rather than on-surface ones [2].

[1] F. Donati, G. Fratesi, A. Mairov, M. Passoni, C.S. Casari, C.E. Bottani, M.I. Trioni, and A. Li Bassi, Phys. Rev. B (2011) in press

[2] G. Fratesi, J. Phys.: Condens. Matter 23, 015001 (2011)

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