Ion implantation is a very energetic process, and the energy stored in the electronic lattice is especially high in insulators since the electrons are localised and the high Coulomb forces cannot relax quickly.

For just one recent example of implantation as an energetic process even in conductors you could look at Milosavljevic et al, App.Surf.Sci. (2013) 268:516; http://dx.doi.org/10.1016/j.apsusc.2012.12.158.

To see that insulators are a special case you can look at the "electronic sputtering" induced by heavy ion beams, the so-called "MeV-SIMS": see for example Wakamatsu et al Nucl.Instrum.Methods B (2011) 269:2251; http://dx.doi.org/10.1016/j.nimb.2011.02.069.

It depends on the system what exactly happens to the energy, but it is entirely believable that in at least some cases there will be radiation enhanced diffusion in the ion track.

Ion implantation is a very energetic process, and the energy stored in the electronic lattice is especially high in insulators since the electrons are localised and the high Coulomb forces cannot relax quickly.

For just one recent example of implantation as an energetic process even in conductors you could look at Milosavljevic et al, App.Surf.Sci. (2013) 268:516; http://dx.doi.org/10.1016/j.apsusc.2012.12.158.

To see that insulators are a special case you can look at the "electronic sputtering" induced by heavy ion beams, the so-called "MeV-SIMS": see for example Wakamatsu et al Nucl.Instrum.Methods B (2011) 269:2251; http://dx.doi.org/10.1016/j.nimb.2011.02.069.

It depends on the system what exactly happens to the energy, but it is entirely believable that in at least some cases there will be radiation enhanced diffusion in the ion track.

Dear Chris, I am curious about the specific case of swift heavy ion beam induced modifications of nanoparticles shape in a metal-insulator nanocomposite. Ion track size is the threshold size beyond which elongation of metal nanoparticles along ion beam direction has been observed. We have observed elongated metal nanoparticles of size smaller than the ion track size. I was wondering about the generality of the mechanism of ion beam induced deformation of embedded nanoparticles for different size ranges.

Dear Satyabrata, I would have thought that the "ion track size" is not well defined in a metal-insulator composite. The ion track is given by the energy loss, and the Coulomb effect in the ionisation induced by the heavy ion. But both of these are a strong function of the matrix - the energy loss is different both in size and in nature between insulators and metals, and in metals there is no Coulomb effect since the electrons are not localised. I would also have thought that radiation enhanced diffusion effects would be strong in a metal-insulator composite, for the same reason. Therefore I would not expect to see a strong size (threshold) effect when comparing the nanoparticle and average ion track diameters.

The process depends on ion type and energy.

Can we know more about your beams?

Dear Jerzy, Irradiation with different ions (90 MeV Ni, 100 MeV Ag or 120MeV Au) were carried out. The ion track size is different for these ions. It depends on the energy depositions.

Dear colleagues, especially for the ions of medium energies we have the large lateral size of damage cascades and observe internal sputtering of metal nanoparticles that also can lead to the change in the nanoparticle shape (https://www.researchgate.net/publication/256605531_Influence_of_Ion_Irradiation_on_the_Morphology_Structure_and_Optical_Properties_of_Gold_Nanoparticles_Synthesized_in_SiO2_and_Al2O3_Die-lectric_Matrices?ev=prf_pub).

Article Influence of Ion Irradiation on the Morphology, Structure, a...

For Satyabrata's multi-MeV beams the energy-loss regime is very definitely electronic. These high energies can penetrate quite thick targets, and one of the classical uses is the fabrication of very well controlled porous structures (filters!). This is done by developing the latent tracks with a suitable chemical treatment. Then the ion fluence determines the pore density and the chemical treatment determines the pore size.

Alexey's "medium energy" beams are in the regime of nuclear energy-loss where the displacement cascades (and corresponding sputtering and mixing) can be calculated by Monte Carlo programs like SRIM (www.srim.org). This is entirely different physics from Satyabrata's high energy regime.

Dear Dr. Jeynes, many thanks for your comment. I just tried to mention the particular case when the damage cascade size is larger than the size of nanoparticle and this is acheved for the high nuclear losses.

Elongation of a solid become charged is a common feature. Before charging, repulsion forces between atoms are counterbalanced by the surface tension. The charging decreases the surface tension value, thus, the elongation occurs. Among other factors induced the internal strains are also numerous defects: microstrains of the lattice, point defects, dislocations and intercrystalline boundaries (pores in poroud materials too). So, the more perfect solid particle in respect to crystallinity, the smaller relative elongation with charging will be. Small metal particles possess usualy perfect crystal structure. Big particles are often very defective: they have dislocations and micrograined structure.