Diffusion of adsorbates on metal surfaces

Gomer, R.

doi:10.1088/0034-4885/53/7/002

Cited by 1,063 publications

(703 citation statements)

References 138 publications

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“…2,3 The diffusion coefficient related to recovery from a small perturbation of some equilibrium condition is considered. This requirement of a small perturbation justifies a linear regime where the flux is proportional to the thermodynamic force.…”

Section: Introductionmentioning

confidence: 99%

Chemical Diffusion Coefficient of Electrons in Nanostructured Semiconductor Electrodes and Dye-Sensitized Solar Cells

2004

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The properties and physical interpretation of the electron diffusion coefficient, D n , observed in nanostructured semiconductors and dye-sensitized solar cells by small perturbation electrical and electrooptical techniques are investigated. The chemical diffusion coefficient is defined as the product of a thermodynamic factor (that accounts for the effect of nonideal statistics in a gradient of chemical potential) and a jump diffusion coefficient (that depends on average hopping distances and rates). The thermodynamic and kinetic similarities, as well as the differences, between interacting ions in the lattice and electrons in nanostructured semiconductors are discussed. From these considerations, the chemical diffusion coefficient of electrons for multiple trapping transport in nanoporous dye solar cells can be calculated indirectly, and the results are in agreement with the reduction of the kinetic-transport equations in the quasistatic approximation. The chemical diffusion coefficient in several models for electrons is discussed: for a wide but stationary distribution of sites energies, giving the Fermi-level dependent D n [Fisher et al. J. Phys. Chem. B 2000, 104, 949] and for the enhancement of the diffusivity by effect of electrostatic shift of energy levels [Vanmaekelbergh et al. J. Phys. Chem. B 1999, 103, 747]. This last model is shown to correspond to the mean-field approximation to interaction in a lattice gas. A general expression containing all of these cases is provided, and several important consequences of the distinction between macroscopic diffusion and single particle random walk are pointed out.

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Section: Introductionmentioning

confidence: 99%

Chemical Diffusion Coefficient of Electrons in Nanostructured Semiconductor Electrodes and Dye-Sensitized Solar Cells

2004

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“…In the present experiment it was not possible to study the diffusion of water by the shadowing method [6,17] because of difficulties in the one-side covering of the emitter with an H2 O layer. (The tip assembly was not thermally screened.)…”

Section: Surface Diffusion Experimentsmentioning

confidence: 92%

“…5 and 6 show that the motion of the diffusion front does not obey well the diffusion relation (x 2 )/t = cD [17], where D is the chemical diffusion coefficient and c is a constant. Apparently a strong interaction between molecules is responsible for this.…”

Section: Surface Diffusionmentioning

confidence: 99%

“…Typical dependences of the square displacement of the sharp boundary (or the diffusion distance) x 2 on the annealing time [17] When the temperature range used for the obServation of the sharp-boundary diffusion of water (contracting bright spot) was close to the thermal desorption temperature, the diffusion could be accompanied by the thermal desorption of water at slightly higher temperatures. At 137 K the desorption of water was explicitly seen (Fig.…”

Section: Surface Diffusion Experimentsmentioning

confidence: 99%

“…Information on the magnitude of the diffusion barrier for adsorbed 12O is derived from the theoretical prediction: (i) the height of the diffusion barrier is approximately 10% to 40% of the value for the desorption barrier [3,17]; (ii) the differences in binding energy between various types of sites should correspond rather closely to the diffusion barrier. This consideration leads to the conclusion that the energy barrier for the surface diffusion of I12O molecules on metals should range from 3 to 27 kJ/mol [1].…”

Section: Surface Diffusionmentioning

confidence: 99%

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Adsorption of H₂O on Pt Field Emitter: Surface Diffusion and Field-Induced Effects

1995

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Adsorption of an Η2 O layer onto a Pt field emitter tip under the influence of an electric field and the surface dichusioii of water were studied by using the field electron microscopy method. The presence of a negative field (field electron microscopy mode of operation), examined in the range of 33-44 MV/cm, significantly reduced the water coverage on the emitter at temperatures above 120 K. The reduction could also occur upon drawing a high density field emission current when the emitter was kept at 78 K. Surface dichusion of water, which was observed in the temperature range 120-132 K, corresponded to the "unrolling the carpet" mechanism and started from a water multilayer to a surface region water-and/or hydrogeri-submonolayer covered. This was accompanied by the transitioii process from the state of the current-and field-induced redistribution of Η2O to the state of thermal equilibrium. The activatioii energy of the dichusioii was found to be 19 and 25 kJ/mol depending oii the crystallographic direction. A positive electric field of 44 MV/cm, which was applied at temperatures of the substrate in excess of 121 K, decreased the field emission of the system and raised the desorptioii temperature of the layer over 720 K. It is assumed that the negative electric field causes reorientation of Η2 O molecules at the surface of platinum tip. The positive as well as negative electric fields promote the field desorption of water, which is in accordance with the results reported before.

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Diffusion in Porous Media

Kärger

Valiullin

2011

Encyclopedia of Magnetic Resonance

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Diffusion of adsorbates on metal surfaces

Cited by 1,063 publications

References 138 publications

Chemical Diffusion Coefficient of Electrons in Nanostructured Semiconductor Electrodes and Dye-Sensitized Solar Cells

Chemical Diffusion Coefficient of Electrons in Nanostructured Semiconductor Electrodes and Dye-Sensitized Solar Cells

Adsorption of H₂O on Pt Field Emitter: Surface Diffusion and Field-Induced Effects

Diffusion in Porous Media

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Diffusion of adsorbates on metal surfaces

Cited by 1,063 publications

References 138 publications

Chemical Diffusion Coefficient of Electrons in Nanostructured Semiconductor Electrodes and Dye-Sensitized Solar Cells

Chemical Diffusion Coefficient of Electrons in Nanostructured Semiconductor Electrodes and Dye-Sensitized Solar Cells

Adsorption of H2O on Pt Field Emitter: Surface Diffusion and Field-Induced Effects

Diffusion in Porous Media

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Adsorption of H₂O on Pt Field Emitter: Surface Diffusion and Field-Induced Effects