AVS 52nd International Symposium
    Surface Science Thursday Sessions
       Session SS1-ThA

Paper SS1-ThA7
Atom Transport in One-Dimensional Surface Diffusion

Thursday, November 3, 2005, 4:00 pm, Room 202

Session: Transport and Structural Stabilization of Surfaces
Presenter: G. Antczak, University of Illinois at Urbana-Champaign
Authors: G. Antczak, University of Illinois at Urbana-Champaign
G. Ehrlich, University of Illinois at Urbana-Champaign
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We present an investigation of self-diffusion on the W(211) plane, done using atomic resolution field ion microscopy, which gives insight into the mechanism of migration of atoms in a one-dimensional system. We distinguish two temperature regions in diffusion over this surface. A low temperature region, where diffusion proceeds by the standard, well-known mechanism - jumps to nearest-neighbor sites, and a slightly higher temperature region, where double transitions start to play a significant role. The transition between these two regions is gradual. The existence of double jumps starts to be non-negligible at a temperature T = 310 K and the ratio of double to single transitions reaches 0.66 at a temperature T = 325 K. The importance of transitions occurring during the transient time is also examined. To get information about ratios of long jumps, the distributions of displacements consisting of 1200 observations for each temperature, is analyzed for regular measurement as well as for transient time measurements. In the lower temperature range, 300 measurements for each temperature are used to establish an Arrhenius plot for the diffusivity. For the first time it is shown that long transitions raise the prefactor for the diffusivity above the usual values. However, this increase is smaller than expected from a model of independent jumps. Activation energies and prefactors for double as well as single transitions are derived. A mechanism of long transitions on W(211) is proposed and compared to the mechanism for two-dimensional diffusion on W(110). Research supported by the Department of Energy under Grant No. DEFG02-91ER45439 to the Materials Research Lab.