Sputtering yields, enhanced by more than an order of magnitude, have been observed for 80 keV Xe ion irradiation of monocrystalline Au nanorods. Yields are in the range 100-1900 atoms=ion compared with values for a flat surface of % 50. This enhancement results in part from the proximity of collision cascades and ensuing thermal spikes to the nanorod surfaces. Molecular dynamic modeling reveals that the range of incident angles occurring for irradiation of nanorods and the larger number of atoms in ''explosively ejected'' atomic clusters make a significant contribution to the enhanced yield. Flow processes resulting from single, heavy-ion impacts on flat surfaces of dense metals cause changes in surface topography involving the displacement of tens of thousands of atoms and resulting in features such as craters and protrusions with dimensions on the order of 10 nm [1][2][3]. Such processes have been observed primarily on Au surfaces but also for Ag, In, and Pb [4]. They occur where the mean free path between successive collisions, in the collision cascade resulting from the ion impact, is on the order of an atomic spacing. Under these conditions, the binary collision approximation [5], generally used successfully to model collision processes, may no longer be fully applicable and the energy dissipation may be better approximated by an energy-or thermal-spike model [6]. As the spike size is typically several nanometers, ion irradiation of nanostructures may yield enhancement of effects resulting from cascade interaction with the surface [7].In this Letter we report on an in situ transmission electron microscopy (TEM) study of Au nanorods under irradiation, at room temperature, with 80 keV Xe þ ions. Using volume calculations based on TEM image measurements, we have determined sputtering yields S, and have obtained values more than an order of magnitude larger than those for similar irradiations of flat Au surfaces. Estimations have been made of the maximum contribution to S expected from ballistic ejection and evaporative loss of material during the thermal spike. Although this yields an enhancement to S of a factor of about 4 over that for flat surfaces, it fails to account for the values measured. Molecular dynamics (MD) simulations reveal that a combination of varied angles of incidence and ''explosive'' ejection of nanoclusters by the thermal spike can contribute to the increased yield which may be further enhanced by the proximity of cascades to the surface. Au nanowires were fabricated by electrodeposition into an anodic Al 2 O 3 template with 20 nm diameter pores. The template was then dissolved in 0.1 M NaOH and the resulting nanowires rinsed in distilled water and deposited onto holey-Formvar-coated Cu TEM grids. Electron microscopy and diffraction indicated that the nanowires were approximately 20 nm in diameter, microns in length, and consisted of columnar grains on the order of 100 nm in length with no preferred growth direction.Specimens were irradiated at room temperature in a JEOL 2000FX TEM operat...

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Ion irradiation has been observed to induce a macroscopic flattening and in-plane shrinkage of graphene sheets without a complete loss of crystallinity. Electron diffraction studies performed during simultaneous in-situ ion irradiation have allowed identification of the fluence at which the graphene sheet loses long-range order. This approach has facilitated complementary ex-situ investigations, allowing the first atomic resolution scanning transmission electron microscopy images of ion-irradiation induced graphene defect structures together with quantitative analysis of defect densities using Raman spectroscopy.

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