Mobility of Ag adatoms on Ag(100)

Langelaar, M.H.; Breeman, M.; Boerma, D.O.

doi:10.1016/0039-6028(95)01208-7

Cited by 56 publications

(20 citation statements)

References 13 publications

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“…This value of E d (Ag ad ) is in agreement with the range of previous theoretical and experimental determinations, 0.37 to 0.45 eV. 29,[31][32][33][34][35] For the case with 30 L O 2,g , if Ag ad diffusion were to play a significant role in island nucleation, such a high E d would be inconsistent with the similar low value of E but much larger ͓assuming that E is determined by some formula such as Eq. ͑2͒, even in this more complex case͔.…”

Section: Discussionsupporting

confidence: 75%

The effect of common gases on nucleation of metal islands: The role of oxygen in Ag(100) homoepitaxy

Layson

Evans

Fournée

et al. 2003

The Journal of Chemical Physics

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Preexposure to molecular oxygen gas, O 2,g , can have a strong effect on the nucleation and growth of Ag islands on Ag(100) at 250 K. At this temperature, molecular oxygen dissociates efficiently at kink sites on steps. Subsequent deposition of Ag produces a far lower density of Ag ad islands than without oxygen. There is an associated increase in the Ag flux-scaling exponent, from 0.28 for the oxygen-free surface to 0.9 for the preexposed surface. Two-step deposition experiments show that species containing atomic oxygen diffuse freely across terraces and steps at this temperature and on the time scale of deposition.We hypothesize that the nucleating species contains both Ag and O, and that nucleation of islands is highly reversible ~critical size i>>1). The diffusion of small islands, if it occurs, is not sufficient to explain the data. Preexposure to molecular oxygen gas, O 2,g , can have a strong effect on the nucleation and growth of Ag islands on Ag͑100͒ at 250 K. At this temperature, molecular oxygen dissociates efficiently at kink sites on steps. Subsequent deposition of Ag produces a far lower density of Ag ad islands than without oxygen. There is an associated increase in the Ag flux-scaling exponent, from 0.28 for the oxygen-free surface to 0.9 for the preexposed surface. Two-step deposition experiments show that species containing atomic oxygen diffuse freely across terraces and steps at this temperature and on the time scale of deposition. We hypothesize that the nucleating species contains both Ag and O, and that nucleation of islands is highly reversible ͑critical size iӷ1). The diffusion of small islands, if it occurs, is not sufficient to explain the data.

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Section: Discussionsupporting

confidence: 75%

The effect of common gases on nucleation of metal islands: The role of oxygen in Ag(100) homoepitaxy

Layson

Evans

Fournée

et al. 2003

The Journal of Chemical Physics

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“…Recent STM studies of homoepitaxy on Ag(100) 38 , combined with Monte-Carlo simulations of an appropriate model for fcc (100) homoepitaxy, determined the diffusion barrier to be 0.33 eV. Low-energy ion scattering measurements of Langelaar et al 39 obtain a value of 0.40 eV. At this point we note that the experimental analyses of the diffusion barriers are not without problem.…”

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confidence: 79%

Ab initio study of step formation and self-diffusion on Ag(100)

Scheffler

1997

Phys. Rev. B

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Using the plane wave pseudopotential method we performed density functional theory calculations on the stability of steps and self-diffusion processes on Ag(100). Our calculated step formation energies show that the {111}-faceted step is more stable than the {110}-faceted step. In accordance with experimental observations we find that the equilibrium island shape should be octagonal very close to a square with predominately {111}-faceted steps. For the (100) surface of fcc metals atomic migration proceeds by a hopping or an exchange process. For Ag(100) we find that adatoms diffuse across flat surfaces preferentially by hopping. Adatoms approaching the close-packed {111}-faceted step edges descend from the upper terrace to the lower level by an atomic exchange with an energy barrier almost identical to the diffusion barrier on flat surface regions. Thus, within our numerical accuracy (≈ ±0.05 eV) there is no additional step-edge barrier to descent. This provides a natural explanation for the experimental observations of the smooth two-dimensional growth in homoepitaxy of Ag(100). Inspection of experimental results of other fcc crystal surfaces indicates that our result holds quite generally.

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“…Analysis of the temperature dependence of L c , together with an estimate of the room-temperature mobility from our STM study, leads to an estimate of E d ϭ0.40Ϯ0.04 eV for the activation barrier for terrace diffusion of Ag on Ag͑100͒, and Ϸ3ϫ10 13 s Ϫ1 for the prefactor. This should be compared with another experimental estimate of 0.4 eV using low-energy ion scattering, which assessed only the onset of diffusion, 23 and recent estimates from sophisticated ab initio electronic structure calculations of 0.52 eV ͑local-density approximation͒ and 0.45 eV ͑generalized gradient approximation͒, 24 and 0.50 eV ͑full-potential linear muffintin orbital͒. 25 …”

Section: Discussionmentioning

confidence: 99%

High-resolution LEED profile analysis and diffusion barrier estimation for submonolayer homoepitaxy of Ag/Ag(100)

et al. 1998

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We present a high-resolution low-energy electron diffraction study of two-dimensional island distributions formed by depositing 0.3 ML of Ag on Ag(100). The substrate temperature ranged between 170 and 295 K. From the ring structure or "splitting" of the diffraction profiles, we determine the behavior of the spatial correlation length characterizing the island distribution. The precise relationship between this correlation length and the mean island separation is also determined via an analysis of kinematic diffraction from island distributions in a realistic model of nucleation and growth. Resulting estimates of this separation are consistent with those based on results from a previous scanning tunneling microscopy study at 295 K. From the Arrhenius behavior of the correlation length, we estimate a terrace diffusion barrier for Ag on Ag (100) We present a high-resolution low-energy electron diffraction study of two-dimensional island distributions formed by depositing 0.3 ML of Ag on Ag͑100͒. The substrate temperature ranged between 170 and 295 K. From the ring structure or ''splitting'' of the diffraction profiles, we determine the behavior of the spatial correlation length characterizing the island distribution. The precise relationship between this correlation length and the mean island separation is also determined via an analysis of kinematic diffraction from island distributions in a realistic model of nucleation and growth. Resulting estimates of this separation are consistent with those based on results from a previous scanning tunneling microscopy study at 295 K. From the Arrhenius behavior of the correlation length, we estimate a terrace diffusion barrier for Ag on Ag͑100͒ of 0.40 Ϯ0.04 eV, with a vibrational prefactor of about 3ϫ10 13 s Ϫ1 . ͓S0163-1829͑98͒08819-5͔

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Mobility of Ag adatoms on Ag(100)

Cited by 56 publications

References 13 publications

The effect of common gases on nucleation of metal islands: The role of oxygen in Ag(100) homoepitaxy

The effect of common gases on nucleation of metal islands: The role of oxygen in Ag(100) homoepitaxy

Ab initio study of step formation and self-diffusion on Ag(100)

High-resolution LEED profile analysis and diffusion barrier estimation for submonolayer homoepitaxy of Ag/Ag(100)

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