The Effect of Fast-Neutron Irradiation at Ambient Temperature on the Lattice Parameters of Silicon and Germanium Crystals

The change in the lattice parameter of nearly perfect silicon and germanium crystals irradiated with 4.2 × ${10}^{19}$ fast neutrons/${\mathrm{cm}}^2$ at about 40°C has been measured. The results show an expansion $\frac{\Delta a}{a}$ equal to about 1 × ${10}^{-4\mathrm{}}$ in both kinds of crystals. Isochronal annealing experiments on irradiated germanium indicate at least two well-defined annealing regions centered at 150 and 400°C, coinciding with previous anomalous x-ray transmission experiments.