Direct observation of cascade defect formation at low temperatures in ion-irradiated metals

Direct transmission electron microscopy observations of cascade defect formation have been carried out in gold, Type 316 stainless steel, and aluminum irradiated by Al+, Ar-, and Xe+ ions with energies between 80 and 400 keV. By utilizing a link of an ion accelerator to an electron microscope, in situ observations at low temperature (-1500C) have become possible. In gold, subcascade structures are clearly observed in all cases. Obvious dependence on projectile mass and energy is observed for cascade structure and vacancy clustering efficiency in gold and for defect visibility in aluminum and Type 316 stainless steel. A computer simulation calculation using MARLOWE shows subcascade distributions a little smaller in size and larger in number than the present observation