2005 Volume 46 Issue 10 Pages 2295-2297
A focused Ga+ ion beam (30 keV and 187 pA) have been irradiated at doses of 8.92×1016–2.68×1018 ions/cm2 in (001) plane of a single-crystalline Ni and an amorphous Ni75B15Si10 alloy and their surface evolution was investigated by atomic force microscopy. The root-mean-square (rms) roughness increased with increasing ion dose and the transition of surface morphology from dot structure to ripple structure occurred during FIB machining in the single-crystalline Ni. However, the amorphous Ni75B15Si10 alloy showed no such transition of surface morphology and held the rms roughness almost constant in an ion dose range more than about 1×1017 ions/cm2. Therefore, it is suggested that surface diffusion, which is the primary smoothing mechanism for crystalline surfaces, plays an important role in smoothening during FIB machining when the ion dose is low, while viscous flow, which is dominant for amorphous surfaces, contributes to smoothening when the ion dose is large.