Ion tracks in silicon formed by much lower energy deposition than the track formation threshold

Abstract

Damaged regions of cylindrical shapes called ion tracks, typically in nano-meters wide and tens micro-meters long, are formed along the ion trajectories in many insulators, when high energy ions in the electronic stopping regime are injected. In most cases, the ion tracks were assumed as consequences of dense electronic energy deposition from the high energy ions, except some cases where the synergy effect with the nuclear energy deposition plays an important role. In crystalline Si (c-Si), no tracks have been observed with any monomer ions up to GeV. Tracks are formed in c-Si under 40 MeV fullerene (C60) cluster ion irradiation, which provides much higher energy deposition than monomer ions. The track diameter decreases with decreasing the ion energy until they disappear at an extrapolated value of ~ 17 MeV. However, here we report the track formation of 10 nm in diameter under C60 ion irradiation of 6 MeV, i.e., much lower than the extrapolated threshold. The diameters of 10 nm were comparable to those under 40 MeV C60 irradiation. Furthermore, the tracks formed by 6 MeV C60 irradiation consisted of damaged crystalline, while those formed by 40 MeV C60 irradiation were amorphous. The track formation was observed down to 1 MeV and probably lower with decreasing the track diameters. The track lengths were much shorter than those expected from the drop of Se below the threshold. These track formations at such low energies cannot be explained by the conventional purely electronic energy deposition mechanism, indicating another origin, e.g., the synergy effect between the electronic and nuclear energy depositions, or dual transitions of transient melting and boiling.

High-Energy Heavy Ion Irradiation of Al2O3, MgO and CaF2

“…Most recently, in our study of sequential ion irradiation of silicon, the removal of defects has been found after irradiation with a 23 MeV I beam (5 keV/nm). This is in contrast to previous works, whereby track formation in undamaged silicon has been found only after cluster ion irradiations [ 25 , 26 , 27 ]. Thus, the second aim of this work was to investigate Al 2 O 3 , MgO and CaF 2 materials’ behaviour when subjected to sequential heavy ion irradiation.…”

Integration of electronic effects into molecular dynamics simulations of collision cascades in silicon from first-principles calculations

“…Another argument that supports this point is that experimentally, amorphization of Si by electronic mechanisms occurs with swift irradiation of heavy ions of considerably greater energy than our 10-keV collision cascades, i.e. tens of MeV [47,48]. Thus, melting (amorphization) of the material via electron-phonon coupling as important as the one we observe with the TTM in scenario 1 is highly unrealistic.…”

Effect of irradiation with heavy Xe22+ ions with energies of 165–230 MeV on change in optical characteristics of ZrO2 ceramic

“…In particular, for ceramics, the theory most commonly used to describe radiation damage is the theory of the formation of so-called thermal bursts or thermal peaks arising along the trajectory of an incident particle, which are accompanied by the appearance of local temperature gradients comparable to the plasma temperature [29][30][31]. The formation of such local regions results in a large number of small point defects capable of making significant changes in the properties of materials, up to the formation of radiation damage, called latent tracks or disordering regions [32,33]. Moreover, if for metals the occurrence and subsequent evolution of radiation damage is well described and has a large number of experimental evidence of the proposed theoretical research, then for ceramics, in particular zirconia, such data are quite small, despite the great interest in this class of ceramics, both from a fundamental and practical point of view.…”