AVS 51st International Symposium
    Surface Science Thursday Sessions
       Session SS3-ThA

Paper SS3-ThA4
Diffusion of Ir and W Atoms on W(110) @super *@

Thursday, November 18, 2004, 3:00 pm, Room 213B

Session: Surface Diffusion and Transport
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
Correspondent: Click to Email
Using field ion microscopy we have carried out extensive measurements of the migration of Ir and W atoms on the W(110) plane at temperatures from 300 to 370 K. In addition to nearest-neighbor jumps in the <111> direction, we recognized three types of long jumps, which may contribute to diffusion: double jumps along <111>, vertical jumps in the <110> direction and the horizontal jumps in the <100> direction. From analysis of the distribution of displacements, constructed from at least 1200 observations, we have found that long jumps play a significant role in diffusion at temperature higher than 340 K. The temperature dependence of all types of jumps was measured to derive activation energies and prefactors for diffusivities. Long jumps proceed with a higher activation energy and a higher prefactor than do single jumps for tungsten as well as for iridium atoms. The rate of single jumps is diminished by contributions from long jumps. However, contrary to expectation, the presence of long jumps does not raise the prefactor for diffusivity above the usual value. Comparisons are made of Ir with W and simple models accounting for our finding are proposed. @super *@Supported by the Department of Energy under Grant No. DEFG02-96ER45439 to the Materials Research Lab., and by the Petroleum Research Fund, under Grant ACS PRF No. 36919-AC5.