The surface migration of sub-monolayers of K on the (112) plane of W was studied by using a field emission fluctuation method. The activation energies were deduced from the temperature dependence of the diffusion coefficient at temperatures of between 395 and 490K. A marked anisotropy of the surface diffusion coefficient was found at lower temperatures. This decreased with increasing temperature. Thus, the [111]/[110] ratio of the diffusion coefficients was equal to about 10 at 400K, but was equal to only 1.5 at 490K. Surface diffusion along the [111] direction was much more rapid than that along the [110] direction. This was attributed to the anisotropy of the atomic structure of the substrate.

J.Beben, C.Kleint, R.Meclewski: Journal de Physique - Colloque C6, 1987, 48[11], 545-50