Step edge fluctuations on clean Ni(111) were investigated using low-energy electron microscopy. When interpreted as capillary waves the fluctuations yield values of the Step edge fluctuations on clean Ni(111) were investigated using low-energy electron microscopy. When interpreted as capillary waves the fluctuations yield values of the

Ni Defects and Diffusion in Metals - IX Ni

surface mass diffusion coefficient Ds and the step edge stiffness β̃ at 1050 to 1340K. β̃(θ,T) was of magnitude ∼300meV∕nm at 1200K, almost independent of step orientation θ, and decreased with increasing temperature T. At the lower temperatures, the decay of capillary modes depended on wave vector q as q3, as expected for surface diffusion over terraces next to the step. Also, the deduced surface diffusion coefficient, described by:

Ds (cm2/s) = 1.0 x 10-4 exp[-0.65(eV)/kT]

was consistent with that on similar surfaces when scaled to homologous temperatures by the melting temperature Tm, in keeping with a recently suggested universality. A component of step relaxation driven by bulk diffusion above 0.65Tm was reasonably consistent with bulk diffusion results obtained much earlier using radio tracer methods. This result was contrasted with earlier discussions that postulate a regime of high-temperature surface diffusion with a large activation energy and very large pre-factor. Sublimation detected here by step edge flow near 0.75Tm was consistent with the known cohesive energy.

Step Fluctuation Studies of Surface Diffusion and Step Stiffness for the Ni(111) Surface. M.Ondrejcek, M.Rajappan, W.Swiech, C.P.Flynn: Physical Review B, 2006, 73[3], 035418 (8pp)