The profile distribution and lattice location of Zn atoms after laser irradiation of ion implanted Si and Ge substrates have been determined by ion beam analysis techniques. In Si the implanted Zn is completely zone refined to the surface whilst in Ge considerable trapping and supersaturation are obtained. Zn is a fast interstitial diffuser in Si and a slow substitutional diffuser in Ge. This result confirms the kinetic trapping model in which the solid phase diffusivity of the considered dopant plays an important role in determining the velocity at which the interfacial segregation coefficient deviates from the equilibrium value.