Self diffusion studies on cobalt thin films

Abstract

The study of lateral diffusion in thin metallic films is important from the application point of view, especially in electromigration reliability studies. Lateral self diffusion in cobalt thin films is studied using a non-destructive tracer scanning method. Neutron irradiation is employed to make a well-defined radioactive (6°Co) region in the middle of a continuous cobalt thin film stripe of width 3 mm. The experimental data are fitted to the appropriate solution of the diffusion equations by means of a non-linear least square fitting procedure using a computer. The diffusion experiments are conducted in the temperature range 30(0600°C in argon atmosphere. This thin film data are compared with the diffusion data available on bulk cobalt. The activation energy for surface diffusion obtained (0-14 eV) is very much smaller than the reported activation energy for grain boundary diffusion in cobalt.

Singular behaviour of atomic ordering in Pt–Co nanocubes starting from core–shell configurations

“…The ordering may be enhanced by the surface segregation of Pt atoms and/or pronounced atomic diffusion at the surface. 28 We believe that the temperature-dependent ordering behaviour can be explained by the degree of atom replacements via diffusion. The diffusion length L ˉ[m] of atoms during the annealing time τ [s] at an increased temperature T [K] is described by the following equation S1 †).…”

“…The ordering may be enhanced by the surface segregation of Pt atoms and/or pronounced atomic diffusion at the surface. 28…”

Nanostructural Analysis of Co‐Re/γ‐Al2O3 Fischer‐Tropsch Catalyst by TEM and XRD

“…The formation of the hcp structure from fcc by diffusion is not considered to be significant in the catalysts due to the low process temperatures and small cobalt self‐diffusion coefficients. For instance, the self‐diffusion coefficient of cobalt based on the reported diffusion coefficients is 3.75×10 −22 cm 2 /s at 400 °C, considering the temperature dependency of the diffusion coefficient [35,36,37] . This indicates that the phase transformation of cobalt from fcc to hcp by atomic diffusion and re‐ordering of the atomic planes is slow.…”

“…For instance, the self-diffusion coefficient of cobalt based on the reported diffusion coefficients is 3.75 × 10 À 22 cm 2 /s at 400 °C, considering the temperature dependency of the diffusion coefficient. [35,36,37] This indicates that the phase transformation of cobalt from fcc to hcp by atomic diffusion and reordering of the atomic planes is slow.…”