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Enhancement of surface self-diffusion of platinum atoms by adsorbed hydrogen

Abstract

Surface diffusion of atoms is an important phenomenon in areas of materials processing such as thin-film growth and sintering. Self-diffusion (that is, diffusion of the atoms of which the surface is comprised) has been much studied on clean metal and semiconductor surfaces1,2. But in most cases of practical interest the diffusion happens on surfaces partly covered by atoms and molecules adsorbed from the gas phase. Adsorbed hydrogen atoms are known to be capable of both promoting and inhibiting self-diffusion3,4,5,6,7, offering the prospect of using adsorbed gases to control growth or sintering processes8,9,10,11. Here we derive mechanistic insights into this effect from observations, using the scanning tunnelling microscope, of hydrogen-promoted self-diffusion of platinum on the Pt(110) surface. We see an activated Pt–H complex which has a diffusivity enhanced by a factor of 500 at room temperature, relative to the other Pt adatoms. Our density-functional calculations indicate that the Pt–H complex consists of a hydrogen atom trapped on top of a platinum atom, and that the bound hydrogen atom decreases the diffusion barrier.

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References

  1. 1

    Tringides, M. C. (ed.) Surface Diffusion (Proc. NATO Conf. ASI Ser. B 360, Plenum, New York, 1997).

  2. 2

    Ehrlich, G. Direct observations of the surface diffusion of atoms and clusters. Surf. Sci. 246, 1–12 (1991).

  3. 3

    Kellogg, G. L. Hydrogen inhibition of exchange diffusion on Pt(100). Phys. Rev. Lett. 79, 4417–4420 (1997).

  4. 4

    Kellogg, G. L. Hydrogen promotion of surface self-diffusion on Rh(100) and Rh(311). Phys. Rev. B 55, 7206–7212 (1997).

  5. 5

    Nara, J., Sasaki, T. & Ohno, T. Adsorption and diffusion of Si atoms on the H-terminated Si(001) surface: Si migration assisted by H mobility. Phys. Rev. Lett. 79, 4421–4424 (1997).

  6. 6

    Stumpf, R. H-enhanced mobility and defect formation at surfaces: H on Be(0001). Phys. Rev. B 53, R4253–R4256 (1996).

  7. 7

    Stumpf, R. H-induced reconstruction and facetting of Al surfaces. Phys. Rev. Lett. 78, 4454–4457 (1997).

  8. 8

    Esch, S., Hohage, M., Michely, T. & Comsa, G. Origin of oxygen induced layer-by-layer growth in homoepitaxy on Pt(111). Phys. Rev. Lett. 72, 518–521 (1994).

  9. 9

    Fiedorow, R. M. J. & Wanke, S. E. The sintering of supported metal catalysts. J. Catal. 43, 34–42 (1976).

  10. 10

    Wong, K., Johansson, S. & Kasemo, B. Nanofabricated model catalysts; manufacturing and model studies. Faraday Discuss. 105, 237–246 (1996).

  11. 11

    Alcock, C. B. & Hooper, G. W. Thermodynamics of the gaseous oxides of the platinum-group metals. Proc. R. Soc. Lond. A 254, 551–561 (1960).

  12. 12

    Anger, G. et al. Microfacets of the (2 × 1) reconstructed Pt(110) surface seen in the adsorption dynamics of H2. Surf. Sci. 219, L583–L589 (1989).

  13. 13

    Linderoth, T. R., Horch, S., Lægsgaard, E., Stensgaard, I. & Besenbacher, F. Surface diffusion of Pt on Pt(110): Arrhenius behavior of long jumps. Phys. Rev. Lett. 78, 4978–4981 (1997).

  14. 14

    Vanderbilt, D. Soft self-consistent pseudopotentials in a generalized eigenvalue formalism. Phys. Rev. B 41, R7892–R7895 (1990).

  15. 15

    Kresse, G. & Furthmüller, J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comput. Mater. Sci. 6, 15–50 (1996).

  16. 16

    Perdew, J. P. et al. Atoms, molecules, solids, and surfaces: Applications of the generalized gradient approximation for exchange and correlation. Phys. Rev. B 46, 6671–6687 (1992).

  17. 17

    Tersoff, J. & Hamann, D. R. Theory and application for the scanning tunneling microscope. Phys. Rev. Lett. 50, 1998–2001 (1983).

  18. 18

    Kalff, M., Comsa, G. & Michely, T. How sensitive is epitaxial growth to adsorbates? Phys. Rev. Lett. 81, 1255–1258 (1998).

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Acknowledgements

We thank P. R. Rasmussen, T. R. Linderoth and B. Kasemo for discussions. This work was supported by the Danish National Research Foundation through the Center for Atomic-scale Materials Physics (CAMP), and by the VELUX and the Knud Højgaard foundations.

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Correspondence to F. Besenbacher.

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Further reading

Figure 1: Illustration of the Pt(110)-(1 × 2) surface, consisting of one-dimensional troughs separated by ridges of close-packed Pt rows.
Figure 2: Six STM images (56 × 31 Å2) extracted from a typical STM movie.
Figure 3: Mean-square displacements 〈x 2〉 (in nearest-neighbour (nn) sites2 s−1) for different H background pressures.
Figure 4: The calculated energy along the two different diffusion paths shown in Fig. 1.

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