It was predicted that the activation energies for S diffusion on the (100), (110) and (111) planes were 0.73, 0.41 and 0.29eV, respectively. The S exhibited a high mobility on the (111) plane. An adsorbed Ni atom on the latter plane was a trap, whereas a vacancy presented a high potential barrier to the diffusion of S atoms. The activation energy was expected to increase with increasing numbers of Ni adatoms and vacancies. The activation energies for the self-diffusion of S across an atomic step on the (111) plane were 1.55eV (upwards) and 0.98eV (downwards). They had a marked effect upon self-diffusion over this plane.

P.L.Cao, Z.G.Zhang: Physical Review B, 1989, 39[14], 9963-6