Landolt-Börnstein - Group III Condensed Matter

13.2 Mechanisms of surface diffusion


This chapter discusses mechanism of surface diffusion on metals. Evidence for different surface diffusion mechanisms comes from experiment (e.g. field-emission microscopy) and theory. In the cases of self-diffusion and atomic hetero-diffusion on the metals the fundamental diffusion step is the jump of adsorbed atoms from one equilibrium adsorption site to the next, with the jump distance equal to the separation between sites. An equivalent mechanism has been postulated for surface vacancies (terrace vacancies). Another surface diffusion mechanism prevalent at low temperature and on surfaces of some atomic roughness, e.g. fcc (110) orientation, involves an exchange between adatom and surface atom. A specific low-temperature mechanism is tunneling. This has been observed for adsorbed hydrogen atoms on W (110). At high temperatures, several mechanisms have been proposed. The first mechanism concerns the non-local surface diffusion of adsorbed atoms or complexes. The second mechanism is based on order-disorder transitions at a surface which causes a non-exponential increase in the number of diffusable species.

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13.2 Mechanisms of surface diffusion
Book Title
Diffusion in Solid Metals and Alloys
13 Surface diffusion on metals
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Landolt-Börnstein - Group III Condensed Matter
  • H. Mehrer
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  • H. P. Bonzel
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