Binding energy of image-potential states: Dependence on crystal structure and material

Giesen, K.; Hage, F.; Himpsel, F. J.; Riess, H. J.; Steinmann, W.

doi:10.1103/physrevb.35.971

Cited by 127 publications

(29 citation statements)

References 21 publications

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“…2(b)). The energy of IPS obtained from photoemission is approximately 0.6 eV below vacuum energy (E V ) for Ag(111) [22] and 0.5 eV for Ag(100) [23]. Our values are therefore larger than those expected for both surfaces, as the work functions are 4.64 eV (Ag(100)) and 4.75 eV (Ag(111)) [24,25].…”

Section: Resultscontrasting

confidence: 38%

Weak competing interactions control assembly of strongly bonded TCNQ ionic acceptor molecules on silver surfaces

et al. 2014

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The energy scale of interactions that control molecular adsorption and assembly on surfaces can vary by several orders of magnitude, yet the importance of each contributing interaction is not apparent a-priori.Tetracyanoquinodimethane (TCNQ) is an archetypal electron acceptor molecule and it is a key component of organic metals. On metal surfaces, this molecule also acts as an electron acceptor, producing negatively charged adsorbates. It is therefore rather intriguing to observe attractive molecular interactions in this system that was reported previously for copper and silver surfaces. Our experiments compared TCNQ adsorption on noble metal surfaces of Ag(100) and Ag(111). In both cases we found net attractive interactions down to the lowest coverage. However, the morphology of the assemblies was strikingly different, with 2D islands on Ag(100) and 1D chains on Ag(111) surfaces. This observation suggests that the registry effect governed by the molecular interaction with the underlying lattice potential is critical in determining the dimensionality of the molecular assembly. Using first-principles 2 density functional calculations with van der Waals correction scheme, we revealed that the strengths of major interactions (i.e., lattice potential corrugation, intermolecular attraction, and charge transferinduced repulsion) are all similar in energy. Van der Waals interactions, in particular, almost double the strength of attractive interactions, making the intermolecular potential comparable in strength to the diffusion potential and promoting self-assembly. However, it is the anisotropy of local intermolecular interactions that is primarily responsible for the difference in the topology of the molecular islands on Ag(100) and Ag(111) surfaces. We anticipate that the intermolecular potential will become more attractive and dominant over the diffusion potential with increasing molecular size, providing new design strategies for the structure and charge-transfer within molecular layers.

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Section: Resultscontrasting

confidence: 38%

Weak competing interactions control assembly of strongly bonded TCNQ ionic acceptor molecules on silver surfaces

et al. 2014

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“…42 For this relaxed surface, we obtain a work function ͑⌽ = V vac − E F ͒ of 4.25 eV, which is slightly below the measured value of around 4.4 eV. 15,18,43 By applying the embedding Green-function method, a slightly larger work function of 4.58 eV is obtained. In order to investigate the image potential states, we take the electrostatic image plane position given by Ishida and Liebsch 44 of 2.86 a.u.…”

Section: Image Potential States Of Ag(100)mentioning

confidence: 99%

Image potential and field states at Ag(100) and Fe(110) surfaces

2007

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By combining the first-principles concept based on the density functional theory with a model vacuum potential, we calculate image potential states and analogous ones in the presence of an electric field applied on a nonmagnetic Ag͑100͒ surface and a magnetic Fe͑110͒ surface. Our investigations are based on the Greenfunction embedding technique, which allows us to treat a truly semi-infinite surface and whence yields a continuum of bulk states. This turns out to be of crucial importance in order to investigate the qualitative difference between localized image or field states located in a band gap of the substrate and states in resonance with bulk states present at the same energies. This difference leads to remarkable changes in the binding energy versus field dispersion of the states. Furthermore, we show that in the case of the Fe͑110͒ surface, the calculated magnetic exchange splitting increases with the electric field and is also modified by the transition from field states to surface resonance states.

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“…6(a)]. 16,47,48 Then, increasing both the vacuum gap and the bias voltage, i.e., using the (13.2Å, 6.7 V) set point, we are able to identify both n = 1 and 2 FERs. As seen from Fig.…”

Section: A Field Emission Resonance Statesmentioning

confidence: 99%

Plane-wave based electron tunneling through field emission resonance states

et al. 2013

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Field emission resonances (FERs) on Cu(100) surface are investigated by means of tunneling regime simulations performed with a plane-wave based transport calculation method. FERs are located near the surface and decay into the vacuum, and their accurate simulation requires a faithful description of vacuum states. This type of simulations is thus not possible using the popular transport methods based on atom-centered localized basis sets and the use of plane waves becomes important. We introduce a procedure to treat self-consistently (SC) the finite bias nonequilibrium problem in tunneling regime. Image potential effects are included in a semiempirical way within the SC calculation. Tunneling through FERs is studied following a practical strategy to approximate the inelastic transmission for states lying in the band gap of the surface. As our approach permits the use of any tip geometry, tip effects on the energy and wave functions of FERs are explored. The method reported here provides an ideal tool for the simulation of FERs aimed at the understanding of experimental STS (scanning tunneling spectroscopy) observations.

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Binding energy of image-potential states: Dependence on crystal structure and material

Cited by 127 publications

References 21 publications

Weak competing interactions control assembly of strongly bonded TCNQ ionic acceptor molecules on silver surfaces

Weak competing interactions control assembly of strongly bonded TCNQ ionic acceptor molecules on silver surfaces

Image potential and field states at Ag(100) and Fe(110) surfaces

Plane-wave based electron tunneling through field emission resonance states

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