Kinetics of radiation-induced segregation in electron-irradiated dilute NiSi and NiGe alloys

The efficiency and the kinetics of the radiation-induced segregation during 3 MeV electron irradiation has been investigated in dilute NiSi and NiGe alloys in the temperature range from 535 K to 735 K. The analysis of the Si and the Ge concentration in solid solution in Ni was performed by damage rate measurements at 86 K in the case of NiSi and 73 K in the case of NiGe. The results indicate a high efficiency of the radiation-induced Si segregation. Between two and ten Frenkel defects must be produced to transport one Si atom to the sinks, whereas radiation-induced segregation could not be detected in NiGe alloys by this method. The kinetics of the mass transport can be described consistently by the assumption of mobile but thermally unstable Si interstitial complexes. From the evaluation of the experimental data we obtain a value of 0.23 eV for the binding energy of the Si interstitial complex. (orig.)