Change of microstructure of Ni films irradiated with He+-ions

Microstructure of high purity Ni films irradiated with 20 and 100 keV He+-ions up to fluences of 5 · 1017 and 1018 cm-2 at 300 K was investigated. In polycrystalline Ni-films the grain size was found to decrease after irradiation. Irradiation of single crystalline films leads to their fragmentation into crystallites with misorientation amounting to ±3...5 degree at fluences of about 1018 cm-2. In the energy range of 20 to 100 keV radiation-induced fragmentation depends essentially on irradiation dose, rather than on He+ energy. He+ implantation into Ni results in development of helium porosity. At fluences of about 1018 cm-2 helium bubbles in the single crystalline films form a superlattice