Ion-beam-induced modification of Ni silicides investigated by Auger-electron spectroscopy

Surface modifications induced by Ar bombardment on Ni silicides have been investigated with the use of Auger-electron spectroscopy. The compounds considered are all the six predicted in the Ni-Si equilibrium phase diagram. The relative Si to Ni concentration varies between the surface and at a depth of a few tens of angstroms; the surface region is richer in Si than the near-surface region. Changes in the ion-beam energy in the range 0.5-5 keV also significantly affect the compositional and electronic properties of the surface and near-surface regions. By changing the ion-beam energies, the silicide surface can be modified in a controlled and reversible way, leading in some cases to the formation of a surface layer with composition and chemical properties characteristic of higher-Si-content Si-rich silicides. Surface segregation seems the dominant mechanism in the observed Si enrichment, and in the final product the chemical bonding plays an important role.