It is well-known that antimony (Sb) in silicon (Si) diffuses via vacancies.  Therefore, by combining the observation of diffusion enhancement of Sb in Si substrate during cobalt silicidation, Honeycutt et al.  concluded that cobalt silicidation generates Si vacancies in the adjacent Si region that is in contact with cobalt disilicide layer.
Figure 2794 shows the solid solubility of some impurities (including Sb) in silicon.
Figure 2794. Solid solubility of impurities in silicon.
 P. Fahey, G. Barbuschia, M. Moslehi, and R. W. Dutton, Appl. Phys. Lett.
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 J. W. Honeycutt and G. A. Rozgonyi, Appl. Phys. Lett. 58, 1302 (1991).