Bi nanowires modified by 400 keV and 1 MeV Au ions

Abstract

We report on the modification of the structure and morphology of Bi nanowires of two different diameters (80 or 130 nm) exposed to beams of 400 keV and 1 MeV Au+ until complete wire degradation. For fluences up to ∼1 ion/nm2, the main effect was a slight roughening of the originally smooth surface and the appearance of a damaged zone at the wire edges. After an exposure to ∼2 ions/nm2, shallow (∼5-7 nm deep) but wide (up to 120nm) depressions are seen, giving the wires a "wavy" morphology. At the largest fluence tested (10 ions/nm2), the thickest nanowires present an amorphized structure containing an embedded dispersion of small spherical metallic crystallites, while the thinner wires collapse into large (∼50nm) nanoparticles composed of a crystalline core surrounded by a disordered oxidized shell. The observed morphologic modifications are discussed considering sputtering and radiation induced surface diffusion effects.