Theory of the scanning tunneling microscope: Xe on Ni and Al

Mingo, Natalio; Jurczyszyn, L.; García‐Vidal, F. J.; Saiz-Pardo, R.; Andrés, Pedro; Flóres, F.; Wu, Shiyu; More, W.

doi:10.1103/physrevb.54.2225

Cited by 103 publications

(95 citation statements)

References 35 publications

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“…From both physical 1 and chemical 2 points of view, computational techniques have emerged, capable of predicting stable atomic structures of systems in their ground state. Quantitative calculation of tunneling currents at nanoscale contacts is also evolving towards enhanced accuracy, by combining methods from quantum chemistry and solid state physics 3,4 . One important issue concerns the combination of the previous two, namely the effect of the tunneling currents on the stable structures of these atom sized systems.…”

Section: I-introductionmentioning

confidence: 99%

Current-Induced Forces upon Atoms Adsorbed on Conducting Carbon Nanotubes

2001

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We calculate the forces acting upon species adsorbed on a single wall carbon nanotube, in the presence of electric currents. We present a self consistent real space Green function method, which enables us to calculate the current induced forces from an ab-initio Hamiltonian. The method is applied to calculate the force on an adsorbed O atom on a (5,5) carbon nanotube, for different bias voltages and adsorption sites. For good contact regimes and biases of the order of Volts, the presence of a current can affect the potential energy surfaces considerably. Implications of these effects for the induced diffusion of the species are analyzed. The dependence of the force with the nanotube radius is studied. In addition, the magnitude of inelastic electron scattering, inducing vibrational heating, and its influence on the adsorbates' drift, is commented.

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Section: I-introductionmentioning

confidence: 99%

Current-Induced Forces upon Atoms Adsorbed on Conducting Carbon Nanotubes

2001

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“…A second alternative is to resort to local orbital MD-DFT methods, specially those devised with the aim of computational efficiency, that allow first-principles studies of much more complex systems. The formulation in terms of local orbitals has an added value, as the transport properties can be easily calculated from the resulting (tight-binding or LCAO) electronic hamiltonian using non-equilibrium Green's function techniques [14]. Thus, efficient local-orbital MD-DFT methods are probably the best available tools for a first-principles analysis of complex nanowires.…”

mentioning

confidence: 99%

“…Typically, we use the thinnest part of the nanowire to define the interface between these two subsystems. Then, the differential conductance [14] is given by:…”

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confidence: 99%

First-principles simulations of the stretching and final breaking of Al nanowires: Mechanical properties and electrical conductance

et al. 2003

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The evolution of the structure and conductance of an Al nanowire subject to a tensile stress has been studied by first-principles total-energy simulations. Our calculations show the correlation between discontinuous changes in the force (associated to changes in the bonding structure of the nanowire) and abrupt modifications of the conductance as the nanowire develops a thinner neck, in agreement with the experiments. We reproduce the characteristic increase of the conductance in the last plateau, reaching a value close to the conductance quantum G0 = 2e 2 /h before the breaking of the nanowire. A dimer defines the contact geometry at these last stages, with three channels (one dominant) contributing to the conductance. PACS numbers: 73.63.b, 62.25.+g, 73.63.Rt, The electrical and mechanical properties of metallic nanowires have received a lot of attention [1]. Although point contacts have been studied for many years, only recently the gentle control of the distance between two metals using an STM-AFM [2] or a mechanically controlled breaking junction (MCBJ) [3] has allowed the experimental characterization of atomic contacts and the observation of quantum effects in both the conductance and the forces [2]. In a pioneering work, Scheer et al. [4] have shown, analyzing the superconducting properties of an atomic contact, how the transport properties of the system just before the breaking point depend on a few channels that they related to the atomic orbitals of the contact.The formation of necks and atomic contacts in stretched metallic nanowires has been analyzed theoretically using different approaches. The nanowire deformation can be studied by molecular dynamics simulations using either classical [5,6] or effective-medium theory potentials [7,8]. First principles calculations based on Density Functional theory (DFT) [9,10] provide a more accurate description of the mechanical properties and the electronic structure needed for the calculation of the conductance, but the large computational demand restricts most of the applications to the analysis of model geometries for the contact (e.g. monoatomic chains). Up to our knowledge, the most complete calculation of the deformation of a metallic nanowire has been presented by Nakamura et al [11], who analyzed, using DFT calculations, a Na nanowire with 39 atoms. In this simulation, the wire is elongated in steps of 0.2 or 0.4Å until it reaches the breaking point. The conductance is determined using the Landauer-Buttiker formula, where the transmission matrix is calculated from the self-consistent electrostatic potential using scattering techniques [12]. This calculation showed how the nanowire deformation was accompanied by a rearrangement of the atomic configuration, that introduces also jumps in the forces and the conductance of the system. Addressing this complex problem with a fullyconverged first-principles description would be still too computationally demanding. One possibility is to stick to accurate plane-wave (PW) DFT methods, carefully relaxing the condit...

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“…For bulk germanium, the pw method gives the lattice constant of 5.646 Å, bulk modulus of 70 GPa, and main energy gap of 0.52 eV. Simulations of STM images have been based on the non-equilibrium Green-function formalism [24][25][26], using density of states projected on separate orbitals (results of electronic structure calculation in framework of localorbital minimal-basis formalism). The tunneling current between the sample (denoted by S) and the tip (denoted by T) is given by…”

Section: Methods Of Calculationmentioning

confidence: 99%

Bromine adsorption on Ge(001) surface: comparative study for coverages of 0.25, 0.5, 0.75 and 1 monolayer

MikoÅ‚ajczyk¹,

Stankiewicz²

2009

Open Physics

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We present theoretical analysis of bromine adsorption on the Ge(001)-p(1Ã—2) surface. Bromine adsorbs dissociatively at the Ge(001) surface and the adlayer of bromine develops ordered structures of adatoms bound to substrate dimers. We analyse atomic configurations of the Ge(001) surface covered by 0.25, 0.5, 0.75 and 1 monolayer of bromine. Various stable surface structures, found in calculations, are presented and their energies are compared. Simulated STM images are also discussed for the considered configurations.

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Theory of the scanning tunneling microscope: Xe on Ni and Al

Cited by 103 publications

References 35 publications

Current-Induced Forces upon Atoms Adsorbed on Conducting Carbon Nanotubes

Current-Induced Forces upon Atoms Adsorbed on Conducting Carbon Nanotubes

First-principles simulations of the stretching and final breaking of Al nanowires: Mechanical properties and electrical conductance

Bromine adsorption on Ge(001) surface: comparative study for coverages of 0.25, 0.5, 0.75 and 1 monolayer

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