THE DISAPPEARANCE OF VOIDS DURING 180-KEV NI+ BOMBARDMENT OF NICKEL

Ni+-ions with 180 keV energy promote void nucleation, growth and shrin kage as a result of impinging on nickel substrates held at temperature s between 600 degrees C and 750 degrees C. Growth proceeds to fluences near 3 X 10(21) ions/m(2) and is followed by shrinkage and, at 650 de grees C and 700 degrees C, increasing void number densities at higher fluences. Voids formed at 650 degrees C, when ion bombarded at tempera tures between 25 degrees C and 550 degrees C, decrease in size and num ber density, ultimately disappearing after a fluence of similar to 2 x 10(21) ions/m(2) administered at the lower temperature. These observa tions are explained using rate theory modified to include the intersti tials injected by the ion beam, the changing dislocation density in th e irradiation damaged layer, and sputtering of the surface by the ion beam.