Direct observation of atomic processes: silicon adatoms on tungsten surfaces

A wide variety of the behaviors of single silicon adatoms on tungsten surfaces have been studied in the field ion microscope (FIM). Existing works are summarized, and some new results are presented. Diffusion parameters for single silicon atoms on the W[110] plane were found to be Esub(d) = 0.70 +- 0.07 eV and D0 = 3.1 x 10-4 x 10sup(+-1.28) cm2 s-1, where Esub(d) is the activation energy of diffusion and D0 the diffusivity. Although chain-form atomic clusters were often formed when more than one adatom was present on a plane, the clusters were not stable during diffusion. Silicon atom transport on the W[110] plane is thus achieved dominantly by migration of single silicon atoms. The desorption field as a function of radial distance from the W[110] plane center was measured, and the data were related to the field distribution on the plane at a given applied voltage. The binding energy of silicon adatoms on the W[110] plane was estimated from the desorption field. Relative pair energies for the Si-Si interaction on the W[110] plane for several bond lengths were obtained from the relative frequencies of observing these bonds in the FIM. (Auth.)