The Role of Charge Localization in Current‐Driven Dynamics

Jorn, Ryan; Livshits, Ester; Baer, Roi; Seideman, Tamar

doi:10.1560/ijc.47.1.99

Cited by 4 publications

(5 citation statements)

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“…This indicates that the ionic state additional charge compared to the neutral state is delocalized among carbon atoms that are far from the adsorbed hydrogen atom. Charge localization was shown in previous work to be the origin of the equilibrium difference between the neutral and charged states as the nuclei respond to the new charge localized in their vicinity. Conversely, systems where the added charge in the transient ionic state is strongly delocalized are expected to show at most minimal if any equilibrium change upon charging.…”

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confidence: 85%

Current-Driven Hydrogen Desorption from Graphene: Experiment and Theory

Gao

Pal

Seideman

et al. 2016

J. Phys. Chem. Lett.

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Electron-stimulated desorption of hydrogen from the graphene/SiC(0001) surface at room temperature was investigated with ultrahigh vacuum scanning tunneling microscopy and ab initio calculations in order to elucidate the desorption mechanisms and pathways. Two different desorption processes were observed. In the high electron energy regime (4-8 eV), the desorption yield is independent of both voltage and current, which is attributed to the direct electronic excitation of the C-H bond. In the low electron energy regime (2-4 eV), however, the desorption yield exhibits a threshold dependence on voltage, which is explained by the vibrational excitation of the C-H bond via transient ionization induced by inelastic tunneling electrons. The observed current independence of the desorption yield suggests that the vibrational excitation is a single-electron process. We also observed that the curvature of graphene dramatically affects hydrogen desorption. Desorption from concave regions was measured to be much more probable than desorption from convex regions in the low electron energy regime (∼2 eV), as would be expected from the identified desorption mechanism.

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confidence: 85%

Current-Driven Hydrogen Desorption from Graphene: Experiment and Theory

Gao

Pal

Seideman

et al. 2016

J. Phys. Chem. Lett.

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“…One of the interesting potential applications of current-driven dynamics in junctions is individually driven molecular machines. ,, A molecular machine is defined as a molecule or an assembly of molecular components that is designed to perform mechanical motion in response to an external stimulus . To date efforts to construct systems that respond to stimuli by directed motion have focused largely on using electrochemical charging, photochemical excitation, or chemical reactions to produce dynamic events. , Although traditional molecular machines have been driven in the solution phase, there has been growing effort to constructs such devices in the dry state on a solid support.…”

Section: Introductionmentioning

confidence: 99%

“…In addition to a dry environment, the molecular junction introduces the possibility of driving molecular machines individually (or coherently), on a single device level, rather than as an ensemble. It promises also the possibility to design machines that perform sustained unidirectional motion rather than stepwise evolution. ,, Finally, the dissipative nature of the environment in a molecular scale device could provide adequate relaxation such that additional chemical and light-driven stimuli would be unnecessary to reset the machine to its initial state.…”

Section: Introductionmentioning

confidence: 99%

“…The extent of the induced dynamics is correlated with the degree of charge localization across the molecule-plus-contacts system. 6 When the additional charge is highly delocalized, the equilibrium displacements in Figure 1 are small, resulting typically in weak coupling between the electronic and nuclear motions. An example is the classic junction where a highly conjugated molecule is contacted to gold electrodes via sulfur atoms.…”

Section: Introductionmentioning

confidence: 99%

“…It promises also the possibility to design machines that perform sustained unidirectional motion rather than stepwise evolution. 3,6,9 Finally, the dissipative nature of the environment in a molecular scale device could provide adequate relaxation such that additional chemical and light-driven stimuli would be unnecessary to reset the machine to its initial state.…”

Section: Introductionmentioning

confidence: 99%

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Implications and Applications of Current-Induced Dynamics in Molecular Junctions

Jorn

Seideman

2010

Acc. Chem. Res.

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Instances of strongly nonadiabatic electronic-vibrational energy transfer have been studied since the early days of quantum mechanics and remain a topic of fundamental interest. Often such transfers are associated with electronic resonances, temporary states where transient localization of charge on the molecule provides a mechanism for channeling electronic energy into vibrational excitation. Extensively studied in the gas phase, electron resonance scattering also occurs with surface adsorbed molecules, where it manifests itself in broadened cross sections and desorption of adsorbates from metal surfaces. In this Account, we focus on a related topic: the implications of nonadiabatic, resonance-mediated scattering to the exciting field of molecular electronics. In this context, researchers can induce directed nuclear dynamics and control these processes in single molecules in contact with metallic and semiconducting electrodes. We discuss a variety of consequences and applications of current-driven nuclear excitation in molecular devices, ranging from the design of new forms of molecular machines to surface chemistry at the single-molecule level and atom-resolved lithography. We highlight two specific examples of molecular nanomachines. In the first, a Au-C(60)-Au transistor, the current induces the oscillatory motion of the center-of-mass coordinate of the C(60). The second, a zwitterion-based rattle, demonstrates excitation of intramolecular motion as the positively charged moiety is threaded back and forth through the negatively charged carbon ring. Finally, we discuss the current-induced desorption of organic molecules from Si(100) both to suggest the potential for controlled surface nanochemistry and to develop guidelines for the design of stable molecular junctions. Modeling the exchange of energy between tunneling electrons and the vibrational degrees of freedom of a target molecule subject to bias voltage, open boundary conditions in the electronic subspace, and the dissipative effects of the electrodes poses a fascinating challenge to contemporary theories of inelastic electron transport. A scattering theory of density matrices is motivated by the need to address large amplitude, chemically relevant dynamics in tandem with an appropriate treatment of the electronic scattering problem. We provide a qualitative discussion of the theory and note the limits in which it reduces to well-known approaches.

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