Migration behavior of single tungsten atoms and tungsten diatomic clusters on the tungsten (110) plane

Abstract

Detailed atomic jumps in the single W atom and W diatomic-cluster migration on the W{110} plane have been studied using the field ion microscope. From the two-dimensional displacement distributions measured at 299 and 309 K, it is concluded that single W atoms migrate by discrete nearest-neighbor random atomic jumps along the $〈111〉$ surface channels. From 1265 observations, the diatomic clusters are found to migrate mainly through three elementary displacement steps. The steps can be produced by two atomic jumps of any of the two atoms along the $〈111〉$ surface channels with intermediate bonds in the [$1\overline{1}0$] and [001] directions. These two atomic jumps are found to be slightly correlated with a correlation factor of 0.10 at 299 K and of 0.23 at 309 K. An anisotropy factor of the two-dimensional migrations is defined and measured. The pair interaction of two W atoms on the W{110} plane is also derived from the rate of single atom jumps and the rates of occurrence of diatomic-cluster elementary displacement steps. The interaction energy at the equilibrium separation is -(0.285±0.018) eV, while at the saddle point of the atomic jumps it is -(0.270±0.018) eV.