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Tracks of heavy ions in muscovite mica: Analysis of the rate of production of radiation defects
Abstract
The rate of formation of extended defects by heavy energetic ions in track-forming minerals shows a pronounced nonlinear dependence on the linear ionization rate. It is suggested that the formation of an extended defect-as recorded by small-angle x-ray scattering-requires a certain threshold ionization density. As a consequence, the mean number of observable defects per ion track is related more directly to the fluctuation in ionization density than to its mean value.
... As shown in Fig. 3 (e) and (f), due to the increasing electronic energy loss and energy deposition on the surface ( E ele -peak region) of the Kr 17 + -irradiated sample, the lattice temperature increased to 3500 K, substantially exceeding the melting point (2353 K) and leading to the formation of discontinuous tracks, including individual spherical defects and discontinuous cylindrical damage zones in the SrTiO 3 crystal. The formed discontinuous tracks in the Kr 17 + -irradiated sample could be ascribed to the statistical fluctuations in the ion charge state owing to the electron capture and loss processes along the ion path and the further induced nonhomogeneous energy deposition [53,54] . The statistical fluctuations in the ion charge state are immediately followed by the fluctuations in the momentary energy loss: if the momentary energy loss is only slightly higher than the threshold value for damage production, then the capture of electrons by the penetrating ion would reduce the momentary energy loss below the threshold value, resulting in an undamaged lattice structure; if the momentary energy loss is only slightly lower than the threshold value, then the loss of electrons by the penetrating ion would increase the momentary energy loss above the threshold value, resulting in the formation of lattice damage. ...
The primary motivation for studying ion-solid interactions and the responses of various materials to energetic irradiation is the fundamental necessity and importance to get a deeper understanding of how irradiation changes the lattice structures and physico-chemical properties of solid materials. Under the action of extreme electronic energy deposition induced by swift Kr¹⁷⁺, Ar¹²⁺ and Ni¹⁹⁺ irradiation, the formation mechanism of latent tracks with different damage morphologies in pristine and predamaged SrTiO3 crystals are analyzed utilizing experimental characterizations of the lattice damage and numerical calculations from the inelastic thermal spike model. In contrast to Ar¹²⁺ and Ni¹⁹⁺ irradiation, Kr¹⁷⁺ irradiation, with an ion energy of 2.35 MeV/u and electronic energy loss of 16.7 keV/nm, increased the lattice temperature of the pristine crystal to 3500 K, and via a subsequent rapid quenching process, discontinuous tracks including individual spherical defects and discontinuous cylindrical damaged zones were formed. The related damage morphology demonstrates the threshold value of the lattice-temperature change induced by irradiation for track production in pristine SrTiO3, which is fundamental and essential for comparing irradiating-ion velocities and electronic energy losses. Owing to the decrease in thermal conductivities and increase in electron-phonon coupling in Au⁺-irradiation-damaged SrTiO3, subsequent Si³⁺, Ar¹²⁺ and Kr¹⁷⁺ irradiation significantly increased the lattice temperature of predamaged crystals to greater than 3500 K, leading to discontinuous and continuous track production in the predamaged crystals. Thus, the pre-existing damage produced by nuclear energy loss interacted synergistically with the electronic energy loss and effectively enhanced the lattice-temperature increase and promoted track formation.
... The irregular length increments of individual tracks past the break in slope favor a discontinuous (Dartyge et al. 1981;Pellas and Perron 1984;Dartyge and Sigmund 1985;Green et al. 1986;Paul and Fitzgerald 1992;Hejl 1995;Villa et al. 1999;Jaskierowicz et al. 2004;Li et al. 2011Li et al. , 2012Li et al. , 2014) over a continuous (Carlson 1990;Afra et al. 2011;Kluth et al. 2012;) damage model. The high etch rate before the break in slope (40-50 μm/min) in the length vs. etch-strength plot (Fig. 1) suggests a more continuous central track section. ...
Fossil and induced confined fission-tracks in the Durango apatite do not etch to their full etchable lengths with the current protocols. Their mean lengths continue to increase at a diminished rate past the break in slope in a length vs. etch-time plot. The mean length of the fossil tracks increases from 14.5(1) to 16.2(1) μm and that of the induced tracks from 15.7(1) to 17.9(1) μm between 20 and 60 s etching (5.5 M HNO3; 21 °C); both are projected to converge toward ~18 μm after ~180 s. This increase is due to track etching, not bulk etching. The irregular length increments of individual tracks reveal a discontinuous track structure in the investigated length intervals. The mean lengths of the fossil and induced tracks for the standard etch time (20 s) for the (5.5 M HNO3; 21 °C) etch are thus not the result of a shortening of the latent fission tracks but instead of a lowering of the effective track-etch rate νT. The rate of length increase of individual fossil confined tracks correlates with their length: older tracks are shorter because they etch slower. Step etching thus makes it possible to some extent to distinguish between older and younger fossil fission tracks. Along-track νT measurements could reveal further useful paleo-temperature information. Because the etched length of a track at standard etch conditions is not its full etchable length, geometrical statistics based on continuous line segments of fixed length are less secure than hitherto held.
... At present, the discontinuous character of the track damage is not well understood, but it may result from the non-homogeneous energy deposition along the ion path since the energy transfer from the incident ion to the target atoms is a statistical process (Dartyge and Sigmund, 1985). Spherical defects may also be related to criteria responsible for the Rayleigh instability. ...
Few-nm sized gold, platinum and palladium nanoparticles were deposited on amorphous silicon nitride films. These films were irradiated with 420 MeV Au and 100 MeV Xe ions. Temperature distributions of thermal spikes produced by these ions were evaluated by observing desorption of the nanoparticles from the target surfaces upon ion impact. It was found that the temperature of the thermal spike produced by 420 MeV Au is higher than 100 MeV Xe. The observed temperature of the thermal spike at the entrance surface is slightly lower than that at the exit surface both for 420 MeV Au and 100 MeV Xe ions. These results can be well explained by the inelastic thermal spike model.
... In case of Gd 2 TiZrO 7 , the random distribution of Ti and Zr atoms on the B-site increases the relative stability of the crystallized defect-fluorite structure, which is characterized by the random occupation of the cation sites by Gd, Ti or Zr. This random mixing of Zr with Ti increases the stochastic nature of the local energy dissipation and initiates a competition between defect fluorite and amorphous phase formation 2,23,24 . This competition between defect fluorite and amorphous phase formation during the crystallization process, which is maximized in the Gd 2 ZrTiO 7 composition, is believed to be the primary driving force for the dramatic diametric variations in track morphology observed in this material. ...
We report on unexpected dramatic radial variations in ion tracks formed by irradiation with energetic ions (2.3 GeV 208Pb) at a constant electronic energy-loss (~42 keV/nm) in pyrochlore-structured Gd2TiZrO7. Though previous studies have shown track formation and average track diameter measurements in the Gd2TixZr(1−x)O7 system, the present work clearly reveals the importance of the recrystallization process in ion track formation in this system, which leads to more morphological complexities in tracks than currently accepted behavior. The ion track profile is usually considered to be diametrically uniform for a constant value of electronic energy-loss. This study reveals the diameter variations to be as large as ~40% within an extremely short incremental track length of ~20 nm. Our molecular dynamics simulations show that these fluctuations in diameter of amorphous core and overall track diameter are attributed to the partial substitution of Ti atoms by Zr atoms, which have a large difference in ionic radii, on the B-site in pyrochlore lattice. This random distribution of Ti and Zr atoms leads to a local competition between amorphous phase formation (favored by Ti atoms) and defect-fluorite phase formation (favored by Zr atoms) during the recrystallization process and finally introduces large radial variations in track morphology.
We report the narrowing of bandgap of the topmost layer of muscovite mica by low energy Ar+ ion beam induced defect formation. Variation of sputtering rate of the constituent elements of mica leads to organized defects creation. The first principle (DFT) calculation
shows a bandgap of 4.63 eV for a single layer of muscovite mica, whereas the absence of specified atoms in that layer results in a reduction of bandgap to 1.3 eV. To examine the change of bandgap of a single mica layer, the top most layer of the muscovite mica is selected, and controlled atomic vacancies are created by low energy Ar+ ion sputtering at glancing angle. The bombarding ion energy and incidence angle are chosen by Monte Carlo Simulation (SRIM) to create the desired defects on the top most layer. Removal of the
constituent atoms is probed by X-ray photoelectron spectroscopy and the change in bandgap is experimentally estimated by UV-Vis reflectance spectroscopy and conducting Atomic Force Microscopy (c-AFM). The experimental measurements of bandgap change are found to be consistent with the first principle calculation. The key features of bandgap alteration of the top layer of muscovite mica by ion induced sputtering are discussed.
We report surface pattern formation and simultaneous optical band gap reduction of multi-elemental muscovite mica due to differential sputtering of constituent elements and defect creation by various energetic ion bombardments. 14 keV Ar⁺, O2⁺, NO⁺, N2⁺, and C⁺ ions bombardment exhibits projectile mass dependent ripple like surface structure formation, and band gap alteration. It is observed that the lightest C⁺ ion is less effective, while the heaviest Ar⁺ ion is most suitable for well-defined ripple pattern formation as well as band gap reduction. Investigation of mica surface by X-ray Photoelectron Spectroscopy (XPS) shows projectile dependent depletion of different elements, specifically, potassium (K) atoms, which link the aluminosilicate layers, and also reside on the top of the surface. A remarkable sputter erosion of K atoms by Ar⁺ ion is observed due to similar mass of Ar and K. The optical band gap, estimated from the UV-VIS-IR data, shrinks from 3.6 eV (virgin) to 1.8 eV (Ar⁺ ion bombarded) in case of indirect transition. Urbach energy is also estimated from the optical absorption data and is correlated with the ion induced damage to explain the defect mediated change of the band gap.
Surface damage appears on materials irradiated by highly charged ions (HCI). Since a direct link has been found between surface damage created by HCI with the one created by swift heavy ions (SHI), the inelastic thermal spike model (i-TS model) developed to explain track creation resulting from the electron excitation induced by SHI can also be applied to describe the response of materials under HCI which transfers its potential energy to electrons of the target. An experimental description of the appearance of the hillock-like nanoscale protrusions induced by SHI at the surface of CaF2 is presented in comparison with track formation in bulk which shows that the only parameter on which we can be confident is the electronic energy loss threshold. Track size and electronic energy loss threshold resulting from SHI irradiation of CaF2 is described by the i-TS model in a 2D geometry. Based on this description the i-TS model is extended to three dimensions to describe the potential threshold of appearance of protrusions by HCI in CaF2 and to other crystalline materials (LiF, crystalline SiO2, mica, LiNbO3, SrTiO3, ZnO, TiO2, HOPG). The strength of the electron-phonon coupling and the depth in which the potential energy is deposited near the surface combined with the energy necessary to melt the material defines the classification of the material sensitivity. As done for SHI, the band gap of the material may play an important role in the determination of the depth in which the potential energy is deposited. Moreover larger is the initial potential energy and larger is the depth in which it is deposited.
‘Tracks’ produced in response to the ionization energy deposited by energetic particles penetrating matter have a long history in physics. Initially identified in bubble chambers and as etchable tracks in dielectrics, 1 altered regions called ‘tracks’ have more recently been seen in semiconductors and metals when very fast heavy ions are incident.2,3 In addition to using etchable tracks to identify ions or to determine an ion’s energy, tracks seen in materials collected from space have proven useful, for instance, for identifying their solar flare exposure ages.4
The samples of natural mica (muscovite and biotite) were irradiated with energetic heavy ions [136Xe (11.56 MeV/n) and 197Au (11.40 MeV/n)] from universal linear accelerator (UNILAC) GSI, Darmstadt, Germany. The simple track etch technique has been used to develop and analyze the morphology of induced heavy ions and natural alpha recoil tracks with the help of atomic force microscopy. Defective structure and lattice disorder have been observed in the environs of the etch pits in these layered crystalline materials. The distribution of defects produced along the tracks, geometrical analysis of tracks shapes and shallowness and their correlations with the structural arrangement of the materials have been discussed in the present investigation. Importance of different ion track geometries in micaceous minerals for the fabrication of nanoterrace material with different stacks having sharp edges with unique properties has been elaborated in the present paper.
The principles of track etching are considered, taking into account the
formation of particle tracks, the basics of track etching, and methods
of nuclear particle identification. Earth and space sciences are
discussed, giving attention to fission track dating, modern energetic
particles in space, and ancient energetic particles in space. Aspects of
nuclear science and technology are also investigated, taking into
account nuclear physics at high and low energies, element mapping and
isotopic analysis, radiation dosimetry, and diverse applications in
science and technology.
Muscovite mica samples are studied by low angle scattering of x-rays, after irradiation by Krypton, Argon and Neon ions with an energy of 1 MeV/nucleon and Oxygen ions of 2 and 5 MeV/nucleon. Both point defects and larger defects are formed along the path of the ion; the latter defects have radii varying from 10 A to 30 A depending upon the type of incident ion. These large defects comprise the ″latent tracks″ which yield the visible tracks after etching. Their concentration is great enough at large irradiations (10**1**4 to 10**1**5 ions/cm**2) for the mica to become amorphous.
The microscopic structure of latent tracks in silicates is analyzed using small-angle x-ray scattering methods. Latent tracks are constituted of extended defects, separated by gap zones loaded with point defects. The variation of the linear density of extended defects along the path of the incident ions cannot be scaled with functions previously used, such as the primary rate of ionization. Upon a thermal annealing, the extended defects are much more stable than point defects. These latent tracks are chemically etched and their etching rates are inferred from optical and scanning electron-microscope observations. From these combined studies of latent and etched tracks, a model for the registration of etchable tracks in silicates is developed. In this model, the extended defects dominate the chemical etching and thermal annealing behavior of etchable tracks. The marked differences observed in the sensitivity of various silicates are no longer attributed to a radiation damage mechanism, which would operate much more efficiently in specific silicates, but to the etching behavior of each mineral. Indeed, for a given incident ion, the linear density of extended defects in a given part of the ion residual range appears to be similar in all silicates. This model is used in the framework of a Monte Carlo statistical code to predict etched track-length distributions in silicates, including those relevant to partially annealed tracks. The striking agreement between these predictions and the corresponding observations strongly support our model. It enables us to discuss the most important concepts previously proposed to account for the registration of etchable tracks in silicates, and to suggest a few preliminary guidelines for improving the use of solid-state track detectors.
Nous avons étudié, par diffusion des rayons X aux petits angles des échantillons de mica muscovite irradiés par des ions Krypton, Argon, Néon, d'énergie 1 MeV par nucléon et par des ions Oxygèene d'énergies 2 et 5 MeV par nucléon. Il se forme à la fois des défauts ponctuels et des défauts étendus de forme isotrope dont le rayon varie de 10 Å à 30 Å selon les irradiations. Ce sont ces défauts étendus, qui au cours de l'attaque chimique ultéricure à l'irradiation, donnent naissance aux traces visibles au microscope. La concentration volumique de ces défauts est importante et pour des doses élevées (10 à 10 ions par cm) les échantillons deviennent amorphes.Muscovite mica samples are studied by low angle scattering of x-rays, after irradiation by Krypton, Argon and Neon ions with an energy of 1 McV/nucleon and Oxygen ions of 2 and 5 MeV/nucleon. Both point defects and larger defects are formed along the path of the ion; the latter defects have radii varying from 10 Å to 30 Å depending upon the type of incident ion. These large defects comprise the “latent tracks” which yield the visible tracks after etching. Their concentration is great enough at large irradiations (to 10 to 10 ions/cm) for the mica to become amorphous.
The mechanism of track formation in muscovite mica was studied using X-ray small angle scattering. The samples were irradiated with Argon ions of minimum energy 1 MeV/nucleon, the integrated doses ranging from 3 × 10 to 10 Argon ions/cm.Experiments show that point defects are formed with a concentration of the order of 1 per cent. In the case of Argon ions of 1 MeV/nucleon energy (maximum energy loss rate), additional larger defects, with a size of about 20 Å, are also created.The effect of thermal annealing created. and chemical etching was also studied to relate the possibility of track development with the presence of such defects.Le mécanisme de formation des traces dans le mica moscovite a été étudié par la méthode de diffusion centrale des Rayons X. Les échantillons ont été irradiés avec des ions Argon d'énergie minimale 1 MeV/nucleon, la dose variant de 3 × 10 à 10 ions Argon par cm.Les échantillons contiennent alors essentiellement des défauts ponctuels, la concentration étant de l'ordre du %. Des Léfauts plus gros (20 Å) apparaissent lorsque la perte d'énergie des ions est maximale.L'influence du recuit et des attaques chimiques a également été étudiée pour établir une corrélation entre la présence de ces défauts et la possibilité de révéler les traces par attaque chimique.
I t is proposed that etchable damage is produced in dielectrics by energetic charged particles when a critical dosage of ionization energy is deposited a t a critical distance from the ion's path by secondary electrons. Within the critical cylinder, molecular fragments more soluble than the parent molecule are formed. The radius of the critical cylinder is taken to be approximately 20 b, as is appropriate to the passage of the etchant along the track and the diffusion of reaction products back to the surface. At the critical radius the dosage approximates doses producing bulk damage under y irradiation. The proposed criterion predicts the formation or nonformation of etchable tracks in Lexan polycarbonate, cellulose nitrate, and mica, in agreement with published data. The calculations have been extended to magnetic monopoles to establish criteria for their detection in dielectric track detectors.
Massive charged particles create regions of intense damage (tracks) by passing through bulk samples of insulating materials. These tracks are shown to result from the positively charged region created by ionization. An approximate model of an ``ion explosion spike'' is proposed in which the mutual repulsion of the positive ions ejects them into the surrounding lattice. This model is shown to be generally consistent with a wide range of experimental fact. An additional damage mechanism appears to apply to polymers, in some of which tracks are produced by light projectiles such as α particles. The data here are shown to be consistent with tracks consisting primarily of broken bonds caused by decay of directly excited electrons.
When a heavy charged particle such as a fission fragment traverses certain materials it leaves a trail of radiation damage which shows up as a track when a sample is viewed by transmission electron microscopy. If a sample of a silicate mineral containing such tracks is immersed in a suitable reagent such as hydrofluoric acid it has been found that the tracks are very selectively attacked. Fine hollow channels are formed along the particle paths while the rest of the material is untouched. A study of this effect in various silicate minerals is reported as a function of etching reagent, etching temperature, and etching time. The minimum width of the etched channels is considerably less than the apparent widths of the tracks prior to etching. It is concluded that the track images result in large part from elastic strains surrounding a damaged core. The etching effect also serves to ``develop'' and ``fix'' particle tracks and hence increases the usefulness of silicate minerals as particle detectors.