Characteristic regularities in condensation of nickel layers on the surface of a tungsten single crystal

Condensation and adsorption of Ni with a thickness from several tenths of a monoatomic layer to several hundred layers on the surface of a single-crystal W tip has been studied by field emission microscopy in a wide range of surface temperature $T$. In contrast to adsorption of Si on W, adsorption of Ni on W does not induce any W surface reconstruction in the entire range of substrate temperatures $T$. Phenomena of bulk diffusion and field reconstruction of the surface are not observed as well. At multilayer Ni coatings, Ni crystallites with peculiar structure and faceting grow on the W surface (on close-packed and loose W faces at small and large $T$ values, respectively). The presence of a strong external electric field makes it possible to retain crystallites on the W surface at temperatures much higher than their dissolution temperature in the absence of an external field.