Open-system density matrix description of an STM-driven atomic switch: H on Si(100)

Zenichowski, Karl; Klamroth, Tillmann; Saalfrank, Peter

doi:10.1007/s00339-008-4833-3

Cited by 10 publications

(18 citation statements)

References 22 publications

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“…11,19 The resonance condition for |m → |n is met when = f − ( a + (n − m)¯ω) = eV, where ω is the harmonic frequency of the mode, Q. As in the "dipole" case, the molecular dissociation rate due to resonance-induced IET was approximated by Eq.…”

Section: The "Resonance" Mechanismmentioning

confidence: 99%

“…6,[10][11][12][13][14][15][16][17][18][19][20][21][22] The primary goal of these theoretical models and computational approaches is to describe the underlying process: inelastic electron tunneling (IET). While most of the tunneling current passing from the STM tip to a molecule-surface sample, or vice versa, is elastic, a few electrons can tunnel inelastically, particularly under certain system-specific conditions of voltage and current.…”

Section: Introductionmentioning

confidence: 99%

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Chemistry at molecular junctions: Rotation and dissociation of O2 on the Ag(110) surface induced by a scanning tunneling microscope

Roy

Mújica

Ratner

2013

The Journal of Chemical Physics

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The scanning tunneling microscope (STM) is a fascinating tool used to perform chemical processes at the single-molecule level, including bond formation, bond breaking, and even chemical reactions. Hahn and Ho [J. Chem. Phys. 123, 214702 (2005)] performed controlled rotations and dissociations of single O2 molecules chemisorbed on the Ag(110) surface at precise bias voltages using STM. These threshold voltages were dependent on the direction of the bias voltage and the initial orientation of the chemisorbed molecule. They also observed an interesting voltage-direction-dependent and orientation-dependent pathway selectivity suggestive of mode-selective chemistry at molecular junctions, such that in one case the molecule underwent direct dissociation, whereas in the other case it underwent rotation-mediated dissociation. We present a detailed, first-principles-based theoretical study to investigate the mechanism of the tunneling-induced O2 dynamics, including the origin of the observed threshold voltages, the pathway dependence, and the rate of O2 dissociation. Results show a direct correspondence between the observed threshold voltage for a process and the activation energy for that process. The pathway selectivity arises from a competition between the voltage-modified barrier heights for rotation and dissociation, and the coupling strength of the tunneling electrons to the rotational and vibrational modes of the adsorbed molecule. Finally, we explore the "dipole" and "resonance" mechanisms of inelastic electron tunneling to elucidate the energy transfer between the tunneling electrons and chemisorbed O2.

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Section: The "Resonance" Mechanismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Chemistry at molecular junctions: Rotation and dissociation of O2 on the Ag(110) surface induced by a scanning tunneling microscope

Roy

Mújica

Ratner

2013

The Journal of Chemical Physics

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“…This result was computed within a cluster model for the silicon surface and the adsorbate, applying first-principles quantum chemistry methods. Although a cluster moldel is only applicable to surfaces of semiconductors and insulators, the required quantities for the calculation of inelastic electron tunneling (IET) rates , are easily accessible (see, e.g., refs and ). For the current system we also want to use our results to simulate the highly local process of STM experiments as a second step.…”

Section: Introductionmentioning

confidence: 99%

Quantum Chemical Cluster Models for Chemi- and Physisorption of Chlorobenzene on Si(111)-7×7

et al. 2014

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Motivated by recent atomic manipulation experiments, we report quantum chemical calculations for chemi- and physisorption minima of chlorobenzene on the Si(111)-7×7 surface. A density functional theory cluster approach is applied, using the B3LYP hybrid functional alongside Grimme's empirical dispersion corrections (D3). We were able to identify chemisorption sites of binding energies of 1.6 eV and physisorption energies of 0.6 eV, both in encouraging agreement with the trend of experimental data. The cluster approach opens up the possibility of a first-principles based dynamical description of STM manipulation experiments on this system, the interpretation of which involves both the chemi- and physisorbed states. However, we found that special care has to be taken regarding the choice of clusters, basis sets, and the evaluation of the dispersion corrections.

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“…In the spirit of first order perturbation theory, the dipole contribution to the total rate could be simply added to the present model. 44,58,59 Because of the small magnitude of the STM-induced field at the surface and the efficient screening of the field by the electrons inside the metal, the former contribution is neglected altogether. 52 In the present work, the focus is on the non-adiabatic effects in metallic environments and vibration-phonon coupling is neglected as well.…”

Section: Electron-hole Pair Coupling Modelmentioning

confidence: 99%

A unifying model for non-adiabatic coupling at metallic surfaces beyond the local harmonic approximation: From vibrational relaxation to scanning tunneling microscopy

Tremblay

2013

The Journal of Chemical Physics

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A model for treating excitation and relaxation of adsorbates at metallic surfaces induced by non-adiabatic coupling is developed. The derivation is based on the concept of resonant electron transfer, where the adsorbate serves as a molecular bridge for the inelastic transition between an electron source and a sink. In this picture, energy relaxation and scanning tunneling microscopy (STM) at metallic surfaces are treated on an equal footing as a quasi-thermal process. The model goes beyond the local harmonic approximation and allows for an unbiased description of floppy systems with multiple potential wells. Further, the limitation of the product ansatz for the vibronic wave function to include the position-dependence of the non-adiabatic couplings is avoided by explicitly enforcing detailed balance. The theory is applied to the excitation of hydrogen on palladium, which has multiple local potential minima connected by low energy barriers. The main aspects investigated are the lifetimes of adsorbate vibrations in different adsorption sites, as well as the dependence of the excitation, response, and transfer rates on an applied potential bias. The excitation and relaxation simulations reveal intricate population dynamics that depart significantly from the simplistic tunneling model in a truncated harmonic potential. In particular, the population decay from an initially occupied local minimum induced by the contact with an STM tip is found to be better described by a double exponential. The two rates are interpreted as a response to the system perturbation and a transfer rate following the perturbation. The transfer rate is found to obey a power law, as was the case in previous experimental and theoretical work.

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Open-system density matrix description of an STM-driven atomic switch: H on Si(100)

Cited by 10 publications

References 22 publications

Chemistry at molecular junctions: Rotation and dissociation of O2 on the Ag(110) surface induced by a scanning tunneling microscope

Chemistry at molecular junctions: Rotation and dissociation of O2 on the Ag(110) surface induced by a scanning tunneling microscope

Quantum Chemical Cluster Models for Chemi- and Physisorption of Chlorobenzene on Si(111)-7×7

A unifying model for non-adiabatic coupling at metallic surfaces beyond the local harmonic approximation: From vibrational relaxation to scanning tunneling microscopy

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