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Cation and anion disordering affect the structural and electronic properties of the isometric A2B2O7 pyrochlore materials. Here, we report a study on the structural response of La2Zr2O7 at two different temperatures (300 K and ~88 K) as a function of ion fluence (1 × 1013, 5 × 1013, and 1 × 1014 ions/cm2). The effect of ion fluence and irradiation temperature on the structural properties have been investigated using the grazing angle x-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy. GIXRD results confirmed that the weakening/broadening of the diffraction peaks and lattice volume expansion increases monotonically as a function of ion fluence at both the temperatures and are more pronounced at ~88 K. The cation and anion disordering appear to be ion fluence and irradiation temperature-dependent. Raman spectroscopy shows that the atomic disordering is more pronounced with enhanced ion fluence and revealed the involvement of the X48f parameter in the enhancement of disordering in the system. The HRTEM analysis revealed that the deterioration in the atomic ordering (amorphization) is significantly more pronounced at ~88 K. The qualitative analysis of cation/anion disordering and structural deformation revealed that irradiation parameters play a crucial role in developing and altering the properties of the pyrochlore materials for the technological applications.

Structural and spectroscopy studies have been carried out on conducting polymer poly(3-octylthiophene) (P3OT) and its copper-doped ZnO (Cu-ZnO/P3OT) hybrid nanocomposites (HNCs) under swift heavy ion (SHI) irradiation at different electronic energy depositions. The photoluminescence (PL) spectra of irradiated films exhibit a significant decrease in the intensity of emissions at higher ion fluences which is ascribed to the trapping of a photo-induced electron-hole by irradiation-induced free radicals and extrinsic non-radiative trap centers leading to the quenching effects. The generation of such free radicals and non-radiative recombination centers occurred through a chemical transformation of polymers in terms of polymer chain disordering, chain scission, chain aggregation, and bond breaking by ion irradiation depending upon the electronic energy depositions and ion fluences. The structural, vibrational, morphological, and optical properties of the irradiated P3OT and Cu-ZnO/P3OT HNCs films have been studied. Interestingly, the glancing-angle x-ray diffraction patterns of irradiated films reveal that the polymer and HNC films retain their chemical structures after high electronic deposition at lower ion fluences which leads to insignificant degradation of polymer and HNCs. However, a relative change in the intensity of characteristic peaks of polymer and ZnO was observed at higher ion fluences and is attributed to the disordering of polymer chains by high electronic depositions. Fourier transform infrared spectroscopy (FTIR) measurements also show similar observation, attributed to a decrease in the intensity of a few methyl and octyl functional groups of P3OT and HNCs. Further, optical study has shown a significant modification in the process of inter-chain and interfacial charge transfer. Finally, from these concurrent effects, PL quenching and photo-induced charge carrier transfer processes are understood by developing a schematic charge transfer diagram.

Understanding the radiation tolerance of ceramics against low energy heavy ions is important for evaluating their stability against alpha recoils, which are a significant source of damage for their...

In the present study, crystallization of amorphous-Si (a-Si) in Al/a-Si bilayer thin films under thermal annealing and ion irradiation has been investigated for future solar energy materials applications. In particular, the effect of thickness ratio (e.g. in Al : a-Si, the ratio of the Al and a-Si layer thickness) and temperature during irradiation on crystallization of the Si films has been explored for the first time. Two sets of samples with thickness ratio 1 : 1 (set-A: 50 nm Al/50 nm a-Si) and thickness ratio 1 : 3 (set-B: 50 nm Al/150 nm a-Si) have been prepared on thermally oxidized Si-substrates. In one experiment, thermal annealing of the as-prepared sample (of both the sets) has been done at different temperatures of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C. Significant crystallization was found to initiate at 200 °C with the help of thermal annealing, which increased further by increasing the temperature. In another experiment, ion irradiation on both sets of samples has been carried out at 100 °C and 200 °C using 100 MeV Ni7+ ions with fluences of 1 × 1012 ions per cm2, 5 × 1012 ions per cm2, 1 × 1013 ions per cm2, and 5 × 1013 ions per cm2. Significant crystallization of Si was observed at a remarkably low temperature of 100 °C under ion irradiation. The samples irradiated at 100 °C show better crystallization than the samples irradiated at 200 °C. The maximum crystallization of a-Si has been observed at a fluence of 1 × 1012 ions per cm2, which was found to decrease with increasing ion fluence at both temperatures (i.e. 100 °C & 200 °C). The crystallization of a-Si is found to be better for set-B samples as compared to set-A samples at all the fluences and irradiation temperatures. The present work is aimed at developing the understanding of the crystallization process, which may have significant advantages for designing crystalline layers at lower temperature using appropriate masks for irradiation at the desired location. The detailed mechanisms behind all the above observations are discussed in this paper.

Zirconolite, a potential candidate for the immobilization of actinides was investigated for the induced effects of α-particles simulated through ion beam irradiation. Nd-doped zirconolite pellets (Ca0.8Nd0.2ZrTi1.8Al0.2O7) synthesized through two step solid state sintering were irradiated with 30 keV He+ ions and analyzed for irradiation induced structural modulations through glancing angle X-ray diffraction technique. Diffraction patterns showed reduction in peak intensity and broadening of peaks with increasing fluence, indicating loss of crystallinity. Though zirconolite didn’t amorphize even upon irradiation at the maximum fluence used i.e. 1 × 1017 ions/cm2. Measured lattice strain enhanced with fluence, further suggesting distortion of the structure.

Synroc minerals have been studied since decades for immobilization of high-level radioactive wastes released from nuclear weapons and nuclear reactors. Among them, the zirconolite, due to its high radiation and aqueous resistance and high waste loading, is considered as a potential candidate for containment purposes. Though irradiation damage effects of swift heavy ions in the material remain a major concern of study, a single phase Nd-doped zirconolite samples prepared through conventional solid-state reaction were irradiated with 120 MeV Au+ ions to study radiation damage effects. Irradiation-induced effects were investigated using ex-situ XRD and micro-Raman spectroscopic techniques. Zirconolite has been observed to undergo amorphization which is confirmed through disappearance of characteristic x-ray diffraction peaks and appearance of broad diffuse scattering bands. Amorphization trend with fluence appeared linear at lower fluences followed by saturation at higher fluences inferring therewith the formation of ion tracks. The ion fluence dependent Raman examination was also found to be in line with the XRD observations. However, the presence of Raman modes, characteristic of zirconolite in the 100–1000 cm−1 region, showed intact behavior of the local structure. To sum up, the 120 MeV heavy Au+ ions developed columnar defects, vacancies and induced micro-strains that lead to the bonds distortion and eventually amorphization of the zirconolite though retaining local ordering.

The electrical transport properties of Ti/n-Si Schottky barrier structure irradiated by 100 MeV O7+ ion has been studied between 120 K and 320 K and compared with unirradiated Ti/n-Si structure to gain the understanding of carrier transport mechanism in irradiated devices. The barrier parameters have been extracted using the current-voltage (I–V) characteristics in forwarding bias. It is found that Schottky barrier height (zero bias) increases while the value of ideality factor becomes smaller with increasing temperature. Recent models consisting of inhomogeneous barrier potential at the metal-semiconductor (MS) interface have been used to explain the behavior of barrier parameters. The role played by the high energy ions at MS interface during irradiation is considered to understand the observed behavior.

The nanocomposite thin films of Tin oxide (SnO2) and Titanium dioxide(TiO2) were deposited on silicon and ITO substrate by RF magnetron sputtering technique using sintered pellet formed by mixing S...

The physical and chemical properties of soft polymer–ceramic composites with 50 MeV swift heavy, Li3+ ion irradiation were studied. A solution-casting technique was employed to synthesize free standing, flexible composite films of ferroelectric polymer PVDF and ferroelectric ceramic BNBT mixtures with 0–3 connectivity. However, only 35 wt% ceramic was chosen for the study as it showed the highest dielectric constant and enhanced ferroelectric properties without irradiation. The effects of ion irradiation on the structural, microstructural, morphological, dielectric and ferroelectric properties of this particular composition were systematically investigated and conclusions were drawn. The mechanism for the enhancement of the electroactive β-phase due to the swift heavy ion irradiation was discussed and the enhancement was well correlated with its ferroelectric and dielectric properties.

The difference in the defect structures produced by different ion masses in a tungsten lattice is investigated using 80 MeV Au7+ ions and 10 MeV B3+ ions. The details of the defects produced by ions in recrystallized tungsten foil samples are studied using transmission electron microscopy. Dislocations of type b = 1/2[111] and [001] were observed in the analysis. While highly energetic gold ion produced small clusters of defects with very few dislocation lines, boron has produced large and sparse clusters with numerous dislocation lines. The difference in the defect structures could be due to the difference in separation between primary knock-on atoms produced by gold and boron ions.

State of the art applications (nuclear waste host, scintillators, piezoelectric, SOFCs, etc.) of isometric pyrochlore, A2B2O7, are very sensitive to the structural assessment upon ion irradiation. In the present study, La2Zr2O7 is irradiated using 1 MeV Xe4+ ions with fluence of 1 × 1013, 5 × 1013, and 1 × 1014 ions/cm2 at ~ 88 K and 300 K. The impact of irradiation temperature and ion fluence on the structural properties of the La2Zr2O7 are investigated using the GIXRD, Raman spectroscopy and high resolution transmission electron microscopy (HR-TEM). The GIXRD and Raman results indicate that the degradation of the crystallinity (i.e., damage/amorphization) are significantly higher with enhanced fluence at ~ 88 K than that of 300 K. The induced lattice strain also increases with an increase of ion fluence and it is more pronounced at ~88 K. The HR-TEM results of the La2Zr2O7 samples exhibit that degradation of the atomic ordering are more pronounced at ~ 88 K. The prominent induced strain and degradation of crystallinity (i.e., damage/amorphization) at ~ 88 K appear to be ion fluence and irradiation temperature-dependent. This study is enlightening the effect of the ion fluence and irradiation temperature on the degradation of crystallinity (i.e., damage/amorphization).

Grain size driven effects on electronic excitation-induced structural modifications have been investigated in nanocrystalline (NC) Nd2Zr2O7 on irradiation with 100 MeV iodine ions. Characterizations have been performed with in situ x-ray diffraction, Raman spectroscopy, and plane-view high-resolution transmission electron microscopy techniques. NC-powders of Nd2Zr2O7 were synthesized by auto gel-combustion and sintered at different temperatures to obtain different grain-sized samples. XRD analysis of the smallest grain-sized sample reveals the highest order–disorder transition (from pyrochlore to a more radiation-resistant phase; anion-deficient fluorite) rate at initial ion fluences followed by least amorphization at higher ion fluences. A strong correlation of the transformation build-up with the double ion impact model confirms the two step amorphization process in NC-Nd2Zr2O7 with the disordered anion-deficient fluorite structure as an intermediate phase. TEM result supports the formation of circular ion track consisting of randomly distributed regions (anion-deficient fluorite structure and amorphous regions), surrounded by a microstrain induced defect-rich pyrochlore superstructure. Lesser ordering at cationic sites and a relatively larger number of grain boundaries are responsible for the highest radiation tolerance exhibited by the smallest grain-sized sample. The present study reports a relatively higher radiation stability of NC-ternary pyrochlore oxide, Nd2Zr2O7, with a grain size of a few tens of nm, which establishes its application as a potential inert matrix for nuclear applications.

Hydrogen gas sensing response of RF sputtered nano-crystalline ZnO thin film is improved by $\sim 34.73$ % using swift heavy ion irradiation technique. X-ray diffraction reveals single crystalline wurtzite structure of ZnO thin films. Full width half maximum (FWHM) of (0002) diffraction peak is decreased with increase in ion fluences. However, at very high fluence $1\times 10^{13}$ ions/cm2, crystallinity is degraded while FWHM of diffraction peak increases. The ZnO films were grown under highly compressive stress, which was relaxed with incremental ion fluences up to $1\times 10^{13}$ ions/cm2. Cathodoluminenscence spectroscopy shows intense predominant peak around $\sim 3.23$ eV, which indicates good optical quality of the films. As ion fluence increases, a blue shift appears in near band emission peak from 3.23 to 3.33 eV, which indicates that in-plane stress is decreased. Surface morphology shows generation of self-affine nanostructure and grain fragments as ion fluences were increased. Grain fragmentations had enhanced the surface reaction, and as a result, gas sensor’s relative response has improved. It was observed that the gas sensor’s sensitivity is strongly dependent on ion fluences and operating temperature. The sensitivity was enhanced from 66.68% to 89.84% with fluence variations from pristine to $1\times 10^{12}$ ions/cm2 at 175 °C operating temperature.

Effect of 80 MeV 16 O 6+ ion irradiation in amorphous Fe 77 P 8 Si 3 C 5 Al 2 Ga 1 B 4 alloy is reported. Electronic energy loss induced modifications in the structural and, magnetic properties were monitored by synchrotron X-ray diffraction (SXRD), Mossbauer and, magnetic measurements. Broad amorphous hump seen in SXRD patterns reveals the amorphous nature of the studied specimens. Mossbauer measurements suggest that: (a) alignment of atomic spins within ribbon plane, (b) changes in average hyperfine field suggests radiation-induced decrease in the inter atomic distance around Mossbauer (Fe) atom, (c) hyperfine field distribution confirms the presence of non-magnetic elements (e.g. – B, P, C) in the first near-neighbor shell of the Fe atom, thus reducing its magnetic moment, and (d) changes in isomer shift suggests variation in average number of the metalloid near neighbors and their distances. Minor changes in soft magnetic behavior – watt loss and, coercivity after an irradiation dose of 2 × 10 13 ions/cm 2 suggests prospective application of Fe 77 P 8 Si 3 C 5 Al 2 Ga 1 B 4 alloy as core material in accelerators (radio frequency cavities).

The immobilization of minor actinides and alkaline-earth metal is a major concern in nuclear industry due to their long-term radioactive contribution to the high level waste (HLW). Materials having zirconolite, pyrochlore, and perovskite structure are promising candidates for immobilization of HLW. The zirconolite which exhibits high radiation stability and corrosion resistance behavior is investigated for its radiation stability against alpha particles in the present study. CaZrTi 2 O 7 pellets prepared using solid state reaction techniques, were irradiated with 30 keV He + ions for the ion fluence varying from 1 × 10 17 to 1 × 10 21 ions/m 2 . Scanning electron microscopy (SEM) images of the un-irradiated sample exhibited well separated grains with average size of about 6.8 μm. On the ion irradiation, value of the average grains size was about 7.1 μm, and change in the microstructure was insignificant. The X-ray photoelectron spectroscopy (XPS) studies showed a shift in the core level peak position (of Ca 2p, Ti 2p and Zr 3d) towards lower binding energy with respect to pristine sample as well as loss of oxygen was also observed for sample irradiated with the ion fluence of 1 × 10 20 ions/m 2 . These indicate a decrease in co-ordination number and the ionic character of M O bond. Moreover, core level XPS signal was not detected for sample irradiated with ion fluence of 1 × 10 21 ions/m 2 , suggesting surface damage of the sample at this ion fluence. However, X-ray diffraction (XRD) studies showed that zirconolite was not amorphized even on irradiation up to a fluence order of 1 × 10 21 ion/m 2 . But, significant decrease in peak intensity due to creation of defects and a marginal positive peak shift due to tensile strain induced by irradiation, were observed. Thus, XRD along with XPS investigation suggests that reduction, decrease in co-ordination number, and increase in covalency are responsible for the radiation damage in zirconolite.

Effect of (80 MeV) 16 O 6 + ion irradiation on the structural properties and cation distribution of the as-burnt samples (i.e. the samples are without any thermal/sintering treatment) with the following compositions: MnFe 2 O 4 , Mn 0.5 Zn 0.5 Fe 2 O 4 and ZnFe 2 O 4 prepared by sol–gel auto-combustion technique have been studied through in-situ and ex-situ X-ray diffraction (XRD) technique. Well characterized single phase MnFe 2 O 4 and Mn 0.5 Zn 0.5 Fe 2 O 4 samples were irradiated at fluence 1 × 10 11 , 1 × 10 12 , 1 × 10 13 and 1 × 10 14 ions/cm 2 to see the effect of the electronic energy loss induced changes in the structural properties and in cation distribution monitored through ex-situ XRD. ZnFe 2 O 4 samples were irradiated with ion fluence values ranging between 1 × 10 11 − 2 × 10 14 ions/cm 2 to observe the effect of in-situ XRD on structural properties and cation distribution. Results very clearly depict the redistribution of cations in the samples, which show noticeable changes in: ionic radii of A-site ( r A ) and B-site ( r B ), experimental and theoretical lattice parameter ( a exp. , a th. ), unit cell volume ( V ), Scherrer’s Grain diameter ( D ), oxygen positional parameter ( u ), tetrahedral and octahedral bond length ( R A , R B ), shared tetrahedral and octahedral edge ( d AE , d BE ) and bond angles ( θ 1 , θ 2 , θ 3 , θ 4 , θ 5 ). Results are interpreted in terms of irradiation induced changes in the above mentioned parameters.

The isometric pyrochlore structure type A2B2O7 possesses a wide range of technological applications such as electrolytes in solid oxide fuel cell, thermal barrier coating, and nuclear waste form for actinides incorporation. Pyrochlore series Gd2Ti2-yZryO7 with y = 0.0, 0.4, 0.8, 1.2, 1.6, and 2.0 was prepared using standard solid-state method. X-ray diffraction along with SEM studies was carried out to investigate the effect of Zr content on microstructure and the swift heavy ion irradiation-induced effects on the structural integrity of Gd2Ti2-yZryO7 pyrochlore family. Rietveld refinement showed a systematic increase in the lattice parameter on increasing the value of y in Gd2Ti2-yZryO7 and an abrupt enhancement in the value of the O48f positional parameter at y ≥ 1.6. The intensity of superstructure peaks gradually decreases in the X-ray diffraction pattern on increasing the Zr content, which indicates the transformation from the ordered pyrochlore structure to disordered anion-deficient fluorite structure. On irradiation with swift heavy ion (120 MeV Au+9), the compositions with y = 0.0 and 0.4 were completely amorphized and the composition with y = 0.8 and 1.2 partially amorphized whereas no sign of amorphization was observed in the Zr rich (y = 1.6 and 2.0) compositions. The composition with y ≥ 1.6 retains its crystallinity even at higher ion fluence of 1 × 1014 ions/cm2. These results are explained on the basis of the ratio of cationic radii rA/rB and in turn the ‘x’ parameter of 48f oxygen.

SnO2 thin films have been deposited on Si substrates using RF-magnetron sputtering and implanted by 200 keV Cu− ions with ion fluence of 2.79 × 1016 ion/cm2 and 4 × 1016 ion/cm2. Post annealing is done on the pristine and Cu− ion-implanted SnO2 thin films. Samples were characterized using the grazing-incidence X-ray diffraction (GIXRD), field-emission scanning electron microscopy (FESEM) and near-edge X-ray absorption fine structure (NEXAFS). After the annealing, amorphous to crystalline phase transition and growth of particles are seen. It is also evidenced that Cu ions do not make metallic/oxide phases up to the implantation dose of 2.79 × 1016 ion/cm2. Cu L-edge NEXAFS has confirmed the Cu2+ ions in the samples. The O K-edge NEXAFS spectra of annealed films have shown diminished peak intensity of O 2p to Sn 5s hybridized orbitals which signify the O vacancy formation. A pre-edge peak in the O K-edge NEXAFS of Cu implanted films has evolved and confirms the additional hybridization of unoccupied Cu d orbitals with O 2p orbitals. The improved intensity of Sn M5,4-edge features is due to the enhanced crystallinity in annealed samples. Ion-solid interaction induced structural and electronic structure amendments are briefly discussed in the light of energy-loss mechanism.

The understanding of the influence of energetic ions on the transport properties of semiconductor materials is essential to design the devices for use in a radiation environment. In this article, an in-situ investigation of the effect of 100 MeV O7+ irradiation on the current-voltage characteristics of the Pd/n-Si Schottky barrier structure is carried out. It is observed that the interface barrier parameters (Ideality Factor, Schottky barrier height and reverse saturation current) are a strong function of ion fluence. The voltage dependence of conduction mechanisms indicates the presence of defects near the interface as well as in bulk silicon. The energy loss mechanisms of energetic ions in the Pd/n-Si structure are used to explain the observed results after irradiation.

The dependence of radiation stability of Gd 2 Zr 2 O 7 on stoichiometry and structure under swift heavy ion irradiation was investigated. Gd 2 Zr 2 O 7 , lies on the borderline of pyrochlore to fluorite phase transition, hence, it is highly sensitive to variations in the composition and/or synthesis conditions. The Gd 2 Zr 2 O 7 was synthesized in two sets (Set-A and -B) by solid state synthesis and gel combustion yielding different phases and stoichiometry as confirmed by Resonant Rutherford backscattering spectrometry (RRBS) and field emission scanning electron microscopy (FESEM). Both sets of Gd 2 Zr 2 O 7 were irradiated with 120 MeV Au ions with fluences varying from 3×10 11 to 1×10 14 ions/cm 2 . The pristine and irradiated samples were studied by X-ray diffraction (XRD) and Raman spectroscopy. The Set-A sample with pyrochlore structure remained crystalline upto the highest fluence 10 14 ions/cm 2 employed, whereas Set-B sample having anion-deficient fluorite structure lost crystallinity at the fluence of 5×10 13 ions/cm 2 , as revealed by in-situ XRD experiment. The in-situ XRD along with Raman studies elucidated that sample synthesized using solid state reaction process exhibits better stability under swift heavy ion irradiation, implying that the sample with perfect stoichiometric pyrochlore structure possess better radiation stability.

In order to simulate radiation damages in tungsten, potential plasma facing materials in future fusion reactors, surrogate approach of heavy ion irradiation on polycrystalline tungsten is employed. Tungsten specimen is irradiated with gold heavy ions of energy 120 MeV at different fluences. Positron annihilation lifetime measurements are carried out on pristine and ion beam irradiated tungsten specimens. The variation in positron annihilation lifetime in ion irradiated specimens confirms evolution of vacancy clusters under heavy ion irradiation. The pristine and irradiated tungsten specimens have also been characterized for their microstructural, structural, electrical, thermal, and mechanical properties. X-ray diffractograms of irradiated tungsten specimens show structural integrity of polycrystalline tungsten even after irradiation. Nevertheless, the increase in microstrain, electrical resistivity and microhardness on irradiation indicates creation of lattice damages inside polycrystalline tungsten specimen. On the other hand, the thermal diffusivity has not change much on heavy ion irradiation. The induction of damages in metallic tungsten is mainly attributed to high electronic energy loss, which is 40 keV/nm in present case as obtained from SRIM program. Although, concomitant effect of nuclear losses on damage creation cannot be ignored. It is believed that the energy received by the electronic system is being transferred to the atomic system by electron-phonon coupling. Eventually, elastic nuclear collisions and the transfer of energy from electronic to atomic system via inelastic collision is leading to significant defect generation in tungsten lattice.

An in-situ high temperature (1000 K) setup is designed and installed in the materials science beam line of superconducting linear accelerator at the Inter-University Accelerator Centre (IUAC) for temperature dependent ion irradiation studies on the materials exposed with swift heavy ion (SHI) irradiation. The Gd 2 Ti 2 O 7 pyrochlore is irradiated using 120 MeV Au ion at 1000 K using the high temperature irradiation facility and characterized by ex-situ X-ray diffraction (XRD). Another set of Gd 2 Ti 2 O 7 samples are irradiated with the same ion beam parameter at 300 K and simultaneously characterized using in-situ XRD available in same beam line. The XRD studies along with the Raman spectroscopic investigations reveal that the structural modification induced by the ion irradiation is strongly dependent on the temperature of the sample. The Gd 2 Ti 2 O 7 is readily amorphized at an ion fluence 6 × 10 12 ions/cm 2 on irradiation at 300 K, whereas it is transformed to a radiation-resistant anion-deficient fluorite structure on high temperature irradiation, that amorphized at ion fluence higher than 1 × 10 13 ions/cm 2 . The temperature dependent ion irradiation studies showed that the ion fluence required to cause amorphization at 1000 K irradiation is significantly higher than that required at room temperature irradiation. In addition to testing the efficiency of the in-situ high temperature irradiation facility, the present study establishes that the radiation stability of the pyrochlore is enhanced at higher temperatures.

This paper reports an unusual extent of mixing in Bi/Te thin bilayer system using 90 MeV Au and 95 MeV Ag ions of energies having same electronic energy loss (S e ) value. The analysis is made using Rutherford backscattering spectroscopy and atomic force microscopy. The mixing variance as observed from the depth profiles extracted from RBS data using Rutherford universal manipulation program is found to be higher for Au irradiated samples. Similarly higher sputtering yield is observed for Au ions than Ag ions. These have been accounted to ion velocity effect of Bi/Te with Au ions having velocity ~1.3 times slower to Ag ions.

MeV Ag ions have been used to study the swift heavy ion (SHI) induced modification in Te/Bi bilayer system. The samples were analysed using Rutherford backscattering spectroscopy (RBS), Atomic force microscopy (AFM) and X-ray diffractometer (XRD). The elemental depth study with RBS results show a strong mixing between the top Te layer and the underlying Bi layer on irradiation. Surface roughness as calculated by AFM is found to increase from 8 to 30 nm on irradiation for the fluence 3x10 13 ions/cm 2 . XRD results confirm the formation of Bi-Te alloy phases on mixing and are expected to be formed due to the interfacial reaction taking place within the molten ion tracks. Ion beam mixing has the potential to induce the formation Bi-Te alloy thin films which are the promising candidate for thermoelectric applications near room temperature. Copyright © 2014 VBRI press.

The Al-induced crystallization of amorphous (a)-Si under thermal annealing and swift heavy ion irradiation has been investigated. The c-Al (50 nm)/a-Si (150 nm) thin films have been prepared on thermally oxidized Si-substrates. A set of samples have been annealed at temperatures ranging from 100 °C to 500 °C to achieve crystallization. Another set of similar samples have been irradiated at an elevated temperature of 100 °C using 100 MeV Ni+7 ions at fluences of 1 × 1012 ions-cm−2, 5 × 1012 ions-cm−2, 1 × 1013 ions-cm−2, and 5 × 1013 ions-cm−2. The crystallization of a-Si is observed at annealing temperature of 200 °C. The crystallinity increases with increasing temperature. On the other hand, irradiation using swift heavy ion leads to crystallization of a-Si at significantly lower temperature of 100 °C. The irradiation induced crystallization is explained in terms of creation of vacancies, interstitials and mixing of Si and Al atoms at a-Si/c-metal interface due to energy deposited by swift Ni ions.

The pyrochlore structure is of particular interest to the nuclear industry due to its potential for nuclear waste immobilization and as a host material for inert matrix fuels. Herein, the experimental results of the temperature and ion fluence dependence on the disordered ion tracks produced by the electronic excitation in the pyrochlore compound Nd2Zr2O7 are presented. The samples were exposed to extreme conditions of ion irradiation with 100 MeV 107Ag9+ ions at ion fluences ranging from 3 × 1011 ions/cm2 to 2 × 1013 ions/cm2 at temperatures of 300 K and 1000 K. The in-situ X-ray diffraction along with micro-Raman spectroscopic analysis on Nd2Zr2O7 samples irradiated at 300 K displays order-disorder phase transformation which is consistent with earlier reports. The direct-impact model is used to calculate the amorphous fraction which exists due to massive deposition of electronic-energy in a localized region, and the estimated value of track radius is 2.98 ± 0.56 nm. Furthermore, theoretical thermal spike simulations are performed to estimate the track radius (∼4.2 nm) which provides strong support for experimental results. To simulate the response of Nd2Zr2O7 under nuclear reactor environment, irradiation carried out at an elevated temperature that exhibits significant radiation tolerance. Its substantiality is revealed from comparative temperature dependent irradiation studies where a slow rate of amorphization is found at the elevated temperature because of the competition between defect production and thermal healing mechanism. Thus, obtained results strongly endorse the appositeness of Nd2Zr2O7 as inert matrix material for the fabrication of futuristic nuclear fuel.

Yttria stabilized zirconia pellets with different crystallite sizes were irradiated with 80 MeV Ag6+ ions at room temperature and 1000 K to understand the effect of crystallite size/material microstructure and irradiation temperature on the radiation tolerance against high energy heavy ions [where electronic energy loss (Se) dominates]. XRD and Raman spectroscopy measurements reveal that, irrespective of the irradiation temperature, the nano-crystalline samples suffered more damage when compared with the bulk-like sample. A reduction in the irradiation damage, i.e., improvement in the radiation tolerance, was observed for all the samples irradiated at 1000 K. The reduction in the damage, however, was remarkably higher for the nano-crystalline samples compared with the bulk-like sample, and hence the difference in the damage between the bulk-like and nano-crystalline samples was also significantly lower at 1000 K than that at room temperature. The irradiation damage, against Se, was thus found to be critically dependent on the interplay between the irradiation temperature and the crystallite size. These results are explained on the basis of the “in-elastic thermal spike” model by taking into consideration the combined effects of crystallite size and environmental (irradiation) temperature on the electron-phonon coupling strength and the lattice thermal conductivity and hence on the resulting thermal spike. These results, besides being crucial from the fundamental prospect of comprehending the size and temperature dependent radiation damage against Se, may also be important from the perspective of designing highly nano-crystalline materials for applications in various radiation environments.

We report on the effect of 80 keV Xe+ ion irradiation on the commercially available, sectioned 10B pencil-graphite specimens subjected to normal and oblique angle incidence of ions (θ i = 0°–70°) and considering a fixed ion fluence of . The pristine and irradiated samples were characterized by powder x-ray diffraction, atomic force microscopy and Raman spectroscopy studies. Unlike pristine graphite and normal incidence cases, several ripple patterns can be visualized in the atomic force micrographs of the specimens irradiated with an oblique angle incidence. Moreover, apart from conventional G-band located at , a distinct diamond-like carbon (DLC) phase has been witnessed at in the Raman spectra of the graphitic specimens subjected to ion impact and for values of 50° and 70°. The formation of the DLC phase along with surface ripple formation would find numerous scopes while dealing with properties such as surface transport, field emission and mechanically hard coating in miniaturized devices.

Hydroxyapatite (HAp, Ca10(PO4)6(OH)2) is the main inorganic component of hard tissues like bone and teeth. HAp incorporated with magnetic ions, play an important role in cell separation, magnetic resonance imaging (MRI), targeted drug delivery and in hyperthermia treatment of cancer. In this study, the effect of 60 MeV Si 5+ ion on the hydrothermally synthesized Fe 3+ doped hydroxyapatite (Fe-HAp, 33 nm) was investigated. At higher fluences, partial amorphization with an increase in the cluster size and surface roughness was observed. Depending on the ion fluence, pores ranging from 300 to 360 nm in size were produced. Irradiated Fe-HAp samples showed enhanced haemocompatibility and bioactivity. The drug (amoxycillin, AMX) loaded irradiated samples exhibited high antimicrobial activity. Copyright © 2013 VBRI press.

CdTe polycrystalline thin films possessing hexagonal phase regions are obtained by spray deposition in presence of a high electric field. Thin film samples are irradiated with 100 MeV Ag ions using Pelletron accelerator to study the swift heavy ion induced effects. The ion irradiation results in the transformation of the metastable hexagonal regions in the films to stable cubic phase due to the dense electronic excitations induced by beam irradiation. The phase transformation is seen from the X-ray diffraction patterns. The band gap of the CdTe film changes marginally due to ion irradiation induced phase transformation. The value changes from 1.47 eV for the as deposited sample to 1.44 eV for the sample irradiated at the fluence 1 × 10 13 ions/cm2. The AFM images show a gradual change in the shape of the particles from rod shape to nearly spherical ones after irradiation.

High-energy ion beam irradiation of the polymers is a good technique to modify the properties such as electrical conductivity, structural behaviour and mechanial properties. Polyaniline thin films doped with hydrochloric acid (HCl) were prepared by oxidation of ammonium persulphate. The effect of Swift Heavy Ions irradiation on the electrical and structural properties of polyaniline has been measured in this study. Polyaniline films were irradiated by oxygen ions (energy 80 MeV, charge state O+7) with fluence varying from 1 × 1010 to 3 × 1012 ions/cm2. The studies on electrical and structural properties of the irradiated polymers were investigated by measuring V-I using four probe set-up and X-ray diffraction (XRD) using Bruker AXS, X-ray powder diffractometer. V-I measurements shows an increase in the conductivity of the film, XRD pattern of the polymer shows that the crystallinity improved after the irradiation with Swift Heavy Ions (SHI), which could be attributed to cross linking mechanism.

The films of polymethyl methacrylate (PMMA) were synthesized by solution polymerization technique. Nickel dimethylglyoxime (Ni-DMG) compound was dispersed in polymethyl methacrylate (PMMA) films at different concentrations. These films were irradiated with 120 MeV Ni10+ ions at the fluences of 1 × 1011 and 1 × 1012 ions/cm2. These irradiated films were characterized by means of X-ray diffraction (XRD), Vickers’ microhardness tester, atomic force microscopy (AFM) and scanning electron microscopy (SEM). X-ray diffraction patterns revealed that the particle size of Ni-DMG nanoparticles is reduced upon irradiation. It indicates that there is a significant interaction of ion beam with Ni-DMG particles in polymer matrix which leads to deposition of large amount of energy and resulted in splitting/melting of nanometric grains. It also revealed that semi crystalline phase of pristine films has been changed with respect to concentration and with the fluence. It is observed that the hardness of the film increases as fluence increases. This suggests that ion beam irradiation promotes (i) the metal to polymer bonding (ii) convert the polymeric structure in to hydrogen depleted carbon network due to the emission of hydrogen gas and/or other volatile gases. The surface average roughness increases as concentration of filler increases and decreases due to ion beam irradiation as revealed from AFM studies. SEM micrographs show partial agglomeration of filler and flake-like structure upon irradiation.

The effect of low temperature swift heavy ion (LT-SHI) implantation on InAs(1 0 0) and InSb(1 0 0) wafers have been investigated. SHI implantation was carried out with 70 MeV silicon (Si5+) ions with fluences of 1 × 1010, 1 × 1011, 1 × 1012 and 1 × 1013 ions/cm2 at room temperature (RT) and liquid nitrogen temperature (LNT). The X-ray diffraction peak intensity of the LT-SHI implanted sample increases with respect to the ion fluences, while the full width half maximum (FWHM) value decreases correspondingly with the increase of ion fluences for both InAs and InSb samples. Whereas the X-ray diffraction peak intensity decreases with respect to the increase of ion fluences for the samples implanted at RT. Scanning electron microscopy (SEM) was used in cross-sectional mode to analyze the penetration depth of silicon ions in InAs and InSb wafers. Atomic force microscopy revealed that the average surface roughness values (Rrms) of InAs and InSb samples implanted at LNT, decreased with the increase of ion fluences while an opposite effect has been observed in the case of RT implanted samples. The present study has confirmed the improvement in the structural and surface properties of InAs and InSb wafers when they are subjected to LT-SHI implantation with 70 MeV silicon (Si5+) ions.

The induced damage in single crystals of Sodium sulphanilate dihydrate (SSDH) irradiated at IUAC, New Delhi with 15 MV Pelletron accelerator with 100 MeV Ag7+ and 70 MeV Li3+ ions has been studied by optical measurements, mechanical hardness measurements, Electrical and ERDA measurements. Optical absorption measurements increase with the increase in fluence. The mechanical hardness of the crystal decreases on irradiation. The dielectric constant of SSDH increases on irradiation.

Swift heavy ion irradiations were carried out on metal organic chemical vapour deposition- grown GaN epilayers on sapphire (0 0 0 1) substrates at room temperature, with 100 MeV O7+ ions and fluences varying from 1×1012, 1×1013 and 5×1013 ions cm−2. The pristine and irradiated GaN samples were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) and UV–visible optical transmittance studies. XRD results indicate the presence of gallium oxide phases after O7+ ion irradiation and the increase in the Ga2O3 peak intensity and full-width half-maximum of irradiated GaN with increasing ion fluences. Surface morphology was observed from AFM analysis, which indicates a decrease in the root-mean square of roughness from 3.9 to 0.5 nm. PL measurements show a red shift as compared to the as-grown GaN. The UV–visible optical transmittance studies show a decrease in band gap after ion irradiation.

Pure single crystals of Potassiumtetrakisthioureabromide (KTTB) were irradiated at room temperature with 40 MeV lithium ions at fluences varying from 10 10 to 10 12 ions/cm 2 from the 15 UD Pelletron facility at Inter University Accelerator Centre (IUAC), New Delhi. The pristine as well as irradiated KTTB single crystals were characterized by photoluminescence at room temperature under 2.8 eV blue excitation by a He–Cd laser and UV–Vis absorption to study the radiation induced defects. The ion-induced changes have also been studied with respect to their mechanical response using Vickers micro hardness technique. The effect of swift heavy ion beam on dielectric dispersion is explained in detail. Surface morphology was also studied for pristine and irradiated crystals.

Organic nonlinear optical crystal l -asparaginium picrate was subjected to 100 MeV Ag 8+ ions and 100 MeV Si 8+ ions. The dielectric properties of the crystals were studied before and after irradiation from 100 Hz to 5 MHz at various temperatures (308 K to 358 K). A drastic increase in the dielectric constant is seen due to irradiation. The dielectric constant and dielectric loss increase with increasing irradiation fluence. The UV–vis spectra of the pristine and irradiated samples were recorded and quantified. There is a small shift in absorption edge towards lower wavelength for the irradiated crystals due to the decrease in bandgap of the material. The observed results are discussed in detail.

Ag:ZrO2 nanocomposite films have been synthesized by a sol-gel dip coating process at room temperature, followed by irradiation using swift heavy ions. The effect of electronic energy loss and fluences on the evolution and consequently on the tailoring of plasmonic properties of films has been studied. The optical study exhibits that color of films converts from transparent in pristine form into shiny yellow when films are irradiated by 100 MeV Ag ions at a fluence of 3 x 10(12) ions/cm(2). However, irradiation by 120 MeV O ions up to the fluence of 1 x 10(14) ions/cm(2) does not induce any coloration in films. The coloration is attributed to the evolution of plasmonic feature resulting in a surface plasmon resonance (SPR) induced absorption peak in the visible region. Increase in fluence from 3 x 10(12) to 6 x 10(13) ions/cm(2) of 100 MeV Ag ions induces a redshift in SPR induced peak position from 434 to 487 nm. Microstructural studies confirms the conversion of Ag2O3 (in pristine films) into cubic phase of metallic Ag and the increase of average size of particles with the increasing fluence up to 6 x 10(13) ions/cm(2). Further increase in fluence leads to the dissolution of Ag atoms in the ZrO2 matrix. (c) 2011 American Institute of Physics

Zinc sulfide (ZnS) thin films in zinc-blende (ZB) and wurtzite (W) phases have been fabricated by pulsed laser deposition. 150 MeV Ni ion beam irradiation has been carried out at different fluences ranging from 10(11) to 10(13) ions/cm(2) at room temperature for ion induced modifications. Structural phase transformation in ZnS from W to ZB phase is observed after high energy ion irradiation which leads to the decrease in bandgap. Generation of high pressure and temperature by thermal spike during MeV Ion irradiation along the ion trajectory in the films is responsible for the structural phase transformation. (C) 2010 Elsevier Ltd. All rights reserved

The effects of swift heavy ion (SHI) irradiation in epitaxial thin film of magneto-electric GaFeO3 (GFO) deposited on (0 0 1) oriented yttria-stabilized zirconia substrate are reported. The structural modifications during the irradiation are studied using in-situ x-ray diffraction and it is observed that SHI induces stress. Thus the induced stress leads to the formation of elongated array of GFO nano-grains and the crystallographic tilting between film and substrate as observed from reciprocal space mapping (RSM). The epitaxy is found to persist even with a dose of ions cm−2 from the RSM. The irradiation is found to affect the magnetic properties of GFO viz., the transition temperature and the redistribution of iron at soft and hard magnetic sites. These observations indicate the possibility of tuning structural and magnetic properties of GFO with SHI.

Intermixing induced in W/Si multilayers by irradiation with 150 MeV Ag+ ions has been studied. In situ x-ray reflectivity measurements during heavy ion irradiation allows one to monitor the evolution of interface mixing as well as internal stresses as a function of time during irradiation. The technique of x-ray reflectivity is sensitive enough to measure diffusion length down to 0.1 nm. A finite intermixing occurs in the system, in spite of it having a positive heat of mixing. High accuracy of the technique allows one to discern subtle effects of factors like stress or film thickness, on swift heavy ion irradiation induced intermixing. The measurements provide clear evidence of an enhanced intermixing in the presence of tensile stress in the film. Mixing efficiency decreases with increasing film thickness. The film thickness dependence of mixing efficiency can be understood in terms of the thermal spike model by taking into consideration the changes in electron mobility due to scattering from surface and interfaces.

Zinc nanoparticles (NPs) embedded in silica were irradiated with swift heavy ions (SHIs) of seven different combinations of species and energies. The shape elongation induced by the irradiations was evaluated by optical linear dichroism (OLD) spectroscopy, which is a sensitive tool for determining the change in the mean aspect ratio (AR) of NPs. Although the mean AR change indicated a linear fluence dependence in the low- and medium-fluence regions, it indicated a nonlinear dependence in the high-fluence region. The data reveal that the elongation efficiency of Zn is correlated with the electronic stopping power 'Se in silica' and is not correlated with either the 'Se in Zn' or the nuclear stopping power. The elongation efficiency plotted as a function of the 'Se in silica' revealed a linear relationship, with a threshold value of ∼2 keV nm(-1), which is the same dependence exhibited by the ion-track formation in silica. The log-log plot showed that the elongation efficiency increased linearly with Se above a critical value of ∼3 keV nm(-1) and steeply decreased with Se to the power of 5 below the critical Se. The steep decrease can be ascribed to the discontinuous nature of the ion tracks, which is expected at Se ∼ 2-4 keV nm(-1) in silica. The fluence Φ dependences of AR - 1 under various irradiations are well-normalized with the electronic energy deposition of SHIs, i.e., the product of Se and Φ, with a Se greater than the same critical value of ∼3 keV nm(-1). The normalized data above the critical value fell on a linear relation, AR(Φ) - 1 ∝ SeΦ, for SeΦ2 keV nm(-3) and a sublinear relation, AR(Φ) - 1 ∝ (SeΦ)(1/2) for SeΦ2 keV nm(-3). On the basis of these experimental results, we discuss some insights into the elongation mechanism.

Softening and stiffening of phonons in rutile titanium dioxide films are investigated by in situ micro-Raman studies during energetic ion irradiation. The in situ study minimized other possible mechanisms of phonon dynamics. Initial softening and broadening of Raman shift are attributed to the phonon confinement by structural defects and loss of stoichiometry. The stiffening of A1g mode is ascribed to large distortion of TiO6 octahedra under the influence of lattice strain in the (110) plane, which gives rise to lengthening of equatorial Ti-O bond and shortening of apical Ti-O bond. The shortening of apical Ti-O bond induces stiffening of A1g mode in the framework of the bond-order-length-strength correlation mechanism.

This paper reports the effect of 100 MeV Ag swift heavy ion (SHI) irradiation with fluences ranging from 1 × 1011 to 1 × 1013 ions cm−2 on the optical properties of Ag0.10(Ge0.20Se0.80)0.90 thin films. It has been observed that the SHI irradiation changes the refractive index (n) and the oscillator strength (E d). The data on the dispersion of the refractive index, n(λ), have been determined using the single-effective-oscillator model. We observed an increase in E d and refractive index (n) at lower ion fluence (1 × 1011 ions cm−2), followed by the reversal in the trend at higher fluences. The optical gap has been determined by Tauc's plot. The values of decrease with ion fluence. Results have been explained in terms of the structural changes in thin films.

Single crystals of L-threonine were subjected to 50 MeV Li3+ ion irradiation at various ion fluences. Radiation induced changes in the structural, electrical, thermal and optical properties of the crystals have been studied in detail. The ion fluence dependence on these properties has also been discussed. Surface modifications in the crystals have been explored through atomic force microscopy. It has also been observed that the powder second-harmonic generation efficiency of irradiated L-threonine varies with the ion fluence studied.