Atom ejection patterns from the Ge (100) and (110) surfaces have been studied for 100–800 eV Ne+, Ar+, Kr+, and Xe+ion bombardment as a function of target temperature in the range 0°–350°C. For ion energies below a critical value dependent on the bombarding ion, atom ejection patterns are always observed; while for higher bombarding energies the patterns appear only when the target temperature exceeds a certain value. From these data an activation energy of 1.3 eV for diffusion of defects was obtained. The experimental results indicate that very little damage to the lattice results from ion bombardment when the ion energy stays below a critical value (Ar, Ne: ∼200 eV; Kr, Xe: ∼400 eV). At higher ion energy the damage becomes more severe and higher target temperatures are required for annealing the damage between subsequent ion collisions.