Diffusion of implanted 57Co in ZnO was determined at 660 to 950C using the modified radiotracer technique. The diffusion data (table 2) were found to obey an Arrhenius-type relationship:

D(m2/s) = 3 x 10-4exp[-2.9(eV)/kT]

Supported by diffusion data and conclusions provided in the literature, it was proposed that cobalt diffused substitutionally in ZnO.

Diffusion of Cobalt in Ion-Implanted ZnO. Koskelo, O., Räisänen, J., Tuomisto, F., Eversheim, D., Grasza, K., Mycielski, A.: Thin Solid Films, 2010, 518[14], 3894-7