Theory of long-range forces in AFM and current versus distance curves in STM on Au(111)

Drakova, D.; Doyen, G.

doi:10.1016/j.susc.2004.05.020

Cited by 2 publications

(9 citation statements)

References 15 publications

(46 reference statements)

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“…Within the same theory in a recent study of the tunnelling currents in the STM on Au(111) [5] we showed that the image potential influences the tunnelling current ( ) J z at large tip-sample separations z. Significant deviation from the exponential decay of the tunnelling current as a function of z was observed both in the theoretical and the experimental data at large z.…”

supporting

confidence: 80%

“…[5], the interaction energy and force between the tip and the sample surface. Their variation with the tip-sample distance is plotted in Fig.…”

Section: Force On Au(111): Results and Discussionmentioning

confidence: 99%

“…No absolute tip-sample distances can be extracted from the AFM experiments, therefore the calibration of the distances in Fig. 1 was done by reminding that in our recent study of the tunnelling currents on Au(111) [5] we obtained tunnelling resistance of 8 10 W at eight Å from the point of zero force, as measured by Cross et al 8 Å away from their point of zero force. Hence, the absolute tip-sample distances in our theory and in the AFM experiments of Cross et al are identical, the point of zero force being approximately 4 Å from the Au(111) surface in our theory.…”

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confidence: 99%

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QND theory of long range forces in AFM on Au(111)

Drakova

Doyen

2005

Physica Status Solidi (b)

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The nature of the long range forces in atomic force microscopy (AFM) between a tungsten tip and the Au(111) surface is studied within Quantum Nano Dynamics (QND), treating many‐particle interactions and long range screening effects. A new mechanism of long range forces between a neutral tip and a metal surface is suggested due to the interaction with the image potential in the tip and the sample of a single electron localized on the Au(111) surface in front of the tip, in the presence of the AFM tip, and the image screening it provides. Force between a W‐tip and Au(111) – measured in AFM (circles and crosses, left‐hand axis, Ref. [1]) and calcu‐lated within QND theory (full curve, right‐hand axis). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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supporting

confidence: 80%

“…[5], the interaction energy and force between the tip and the sample surface. Their variation with the tip-sample distance is plotted in Fig.…”

Section: Force On Au(111): Results and Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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QND theory of long range forces in AFM on Au(111)

Drakova

Doyen

2005

Physica Status Solidi (b)

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“…The physics generating the atomic contrast is the physics of excited states created in the tunneling process. Many‐particle interactions, long‐range image screening of the short‐living excited states provided the explanation of numerous “strange” observations in STM and STS: the anomalously high corrugation amplitude on clean flat metal surfaces 4, unexpected spectral features in the STS 9, remote projection of spectral signals 9, special features in the current vs. distance curves, and long‐range interactions in the atomic force microscopy 28, to mention a few. This gives us confidence about the plausibility of the quantum dynamic theory and the physical relevance of its results.…”

Section: Resultsmentioning

confidence: 74%

“…The process of local electron injection and the relaxation of the transiently living ions due to local interactions within the nanocomplex and the long‐range screening effects via coupling to the polarizable environment lead to phenemena observed in the STM and STS: large corrugation amplitude on clean metal surfaces, imaging of adsorbates as indentations, the observation of quantum mirages, and of features in the STS, which are not compatible and cannot be explained with the ground‐state properties of the sample. The QND theory provides the understanding of all these seemingly unrelated observations within the same theory and model, as was reported earlier 4, 9–11, 28.…”

Section: Discussionmentioning

confidence: 99%

Theory of tip‐dependent imaging of adsorbates in the STM: CO on Cu(111)

Drakova

Nedjalkova

Doyen

2005

Int J of Quantum Chemistry

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ABSTRACT:The processes of local electron injection or extraction in the scanning tunneling microscopy (STM) and spectroscopy (STS) lead to the creation of short-lived excited states localized at the electrode surfaces. The dynamic relaxation of the transient negative or positive ion resonances, due to both local and long-range interactions, is the clue to the understanding of numerous phenomena in STM/STS ranging from the "anomalously" large tip height corrugation amplitudes on clean metal surfaces to the observation of quantum mirages and features in the STS, which are not observed with the help of other surface spectroscopies. Quantum nanodynamics theory (QND) has been applied to calculate the interaction potential of a single CO molecule with the Cu(111) surface, with a transient negative ion resonance formed when an electron is injected from the tip, and the tunneling conductance on the clean and CO covered Cu(111) surface using a clean metal tip Al/Al(111) and a Pt(111) tip with an adsorbed CO molecule at the apex. Within QND and three-dimensional scattering theory, regarding the tunneling as an excited-state problem, we provide the explanation of the tip-dependent STM image of a single CO molecule on Cu(111). The appearance of the CO molecule as an indentation, using a clean metal tip and as a protrusion with a tip terminated by a CO molecule, is understood as a result of tunneling through two competing channels. Tunneling via adsorbate-induced ion resonances enhances the tunneling conductance. In contrast, tunneling via metal ion resonances only leads to attenuation of the conductance in the presence of the adsorbate. The current in the vicinity of the adsorbed CO molecule is reduced when a clean metal tip is used; i.e., CO appears dark in the STM image, because metal ion resonances on Cu(111) derive from the surface states with image state components coupling to plasmons and are therefore very diffuse. With a CO-terminated tip, the major current channel is, for symmetry reasons, from the 2π-derived orbital of the tip CO molecule, via the diffuse 2π-derived orbital of the CO molecule on the sample, hence adsorbed CO appears bright.

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Theory of long-range forces in AFM and current versus distance curves in STM on Au(111)

Cited by 2 publications

References 15 publications

QND theory of long range forces in AFM on Au(111)

QND theory of long range forces in AFM on Au(111)

Theory of tip‐dependent imaging of adsorbates in the STM: CO on Cu(111)

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