Swift Heavy Ion Beam Research Articles

Influence of Swift Heavy Ion Beam Irradiation on Optical, Structural, and Surface Morphological Properties of WO3 Thin Films Grown by RF Sputtering Method

Influence of Swift Heavy Ion Beam Irradiation on Optical, Structural, and Surface Morphological Properties of WO3 Thin Films Grown by RF Sputtering Method

Metallic Ca Aggregates Formed Along Ion Tracks and Optical Anisotropy in CaF2 Crystals Irradiated with Swift Heavy Ions

It is known that swift heavy ion (SHI) irradiation induces the shape elongation of metal nanoparticles (NPs) embedded in transparent insulators, which results in anisotropic optical absorption. Here, we report another type of the optical anisotropy induced in CaF2 crystals without including intentionally embedded metal NPs. The CaF2 samples were irradiated with 200 MeV Xe14+ ions with an incident angle of 45° from the surface normal. With the increasing fluence, an absorption band at ~550 nm, which is ascribed to Ca aggregates, increases both the intensity and the anisotropy. XTEM observation clarified the formation of the continuous line structures and the discontinuous NP chains parallel to the SHI beam. Numerical simulations of the optical absorption spectra suggested the NP chains but not the continuous line structures as the origin of the anisotropy. The optical anisotropy in CaF2 irradiated with SHIs is different from the shape elongation of NPs.

Suspended nanoporous graphene produced by swift heavy ion bombardment

In the present work, Raman spectroscopy measurements and molecular dynamics simulations were used to investigate damage production in suspended single-layer graphene when irradiated by 23 MeV I, 3 MeV Cu and 18 MeV Cu beams. Despite the high energies of the used swift heavy ion beams, we found no evidence of ion track formation, i.e. all damage imparted to graphene was due to elastic collisions between ions and carbon atoms. Comparing experimental results with simulations, we conclude that a significant amount of energy (at least 40 % in the case of 23 MeV I irradiation) is dissipated away from graphene following the ion impact, and is a likely reason for the absence of ion tracks.

Magnetic field control and swift heavy ion beam assisted tuning of resistive switching properties of BSFO/CFO/LNO heterostructures

Resistive switching (RS) behavior in mixed oxide insulators has shown a great promise as memristors or non-volatile resistive random-access memory (RRAM) applications. For dilute magnetic oxide multilayers, a novel approach of controlled defects induced and the magnetic field control of RS behavior is proposed. Resistive switching in Bi0.6Sr0.4FeO3 /CoFe2O4 /LaNiO3 (BSFO/CFO/LNO) multilayer heterostructures has been investigated as a case study. All oxide junctions consisting of conducting LaNiO3 (LNO) bottom electrode and BSFO-CFO active layers were fabricated by using chemical solution deposition. A set of samples were irradiated with 150 MeV Ag11+ ions for three different ion fluence of ∼1 × 10+11 ions cm−2, 1 × 10+12 ions cm−2 and 5 × 10+12 ions cm−2. Polycrystalline phase pure films with smooth, crack free surfaces were observed for pristine and irradiated samples. Optical spectroscopy revealed a decrease in the transmittance upon increasing ion fluence due to increase in the light scattering centres. The optical band gap showed a systematic decrease from 2.09 eV to 1.65 eV with increasing ion fluence. Room temperature I-V characteristics showed consistent and pronounced bipolar switching for all samples below ± 5 V. Upon applied magnetic fields of 0.58 T, the resistive switching ratios were found to increase significantly and were further tuned by 150 MeV Ag11+ ion beam irradiations. The magnetic field control of electrical transport properties in the controlled defect assisted oxide heterojunctions offers new insights to the existing understanding of oxide-based RS mechanism.

Metallic water: Transient state under ultrafast electronic excitation.

The modern means of controlled irradiation by femtosecond lasers or swift heavy ion beams can transiently produce such energy densities in samples that reach collective electronic excitation levels of the warm dense matter state, where the potential energy of interaction of the particles is comparable to their kinetic energies (temperatures of a few eV). Such massive electronic excitation severely alters the interatomic potentials, producing unusual nonequilibrium states of matter and different chemistry. We employ density functional theory and tight binding molecular dynamics formalisms to study the response of bulk water to ultrafast excitation of its electrons. After a certain threshold electronic temperature, the water becomes electronically conducting via the collapse of its bandgap. At high doses, it is accompanied by nonthermal acceleration of ions to a temperature of a few thousand Kelvins within sub-100fs timescales. We identify the interplay of this nonthermal mechanism with the electron-ion coupling, enhancing the electron-to-ions energy transfer. Various chemically active fragments are formed from the disintegrating water molecules, depending on the deposited dose.

Recrystallization effects in spray-pyrolyzed Nb2O5 thin films induced by 100 MeV O7+ swift heavy ion beam irradiation

In this work, the influence of 100 MeV O7+ high energy swift heavy ion beam irradiation at varied fluences on the modification of properties of spray-deposited thin niobium pentoxide (Nb2O5) film is reported. The XRD patterns indicate tetragonal structure for pristine polycrystalline Nb2O5 film and partial amorphous nature for the irradiated samples in corroboration with the Raman spectra of the respective samples. The crystallite size is observed to reduce overall compared to that of the pristine film, however, a peaking is observed for 5x1012 ions/cm2 fluence within the irradiated films which is due to the high energy irradiation-induced defect formation and recrystallization effects. It is important to note that the defect density increases with fluence and recrystallisation occurs at 5x1012 ions/cm2, with further amorphization induced at much higher fluences. The generation of additional defect levels lowers the optical band gap. The direct and indirect band gaps were found to reduce upon irradiation compared to that of the pristine Nb2O5 film. The atomic force microscopic analysis reveals decrease in surface roughness of the irradiated samples from 5.9 nm to 10.1 nm compared to the pristine sample. Oxygen ion beam changes their morphology into network-like structures in a controllable manner which mainly depends on electronic energy loss occurring within the Nb2O5 lattice. Variations in transport parameters measured using Hall effect reveal that lower fluence yields less damage accumulation and does not cause significant change in properties of the sample. As fluence increases, vivid modifications originate from the production of significant density of point defects. At the critical fluence, recrystallisation is observed. These results are discussed in detail using the calculated parameters like crystallite size, Urbach energy, defect density and by correlating them with the observed optical and electrical data obtained from different techniques.

Linearly Modulated OSL in K\(_{3}\)Na(SO\(_{4}\))\(_{2}\):Eu\(^{3+}\) Phosphor Irradiated With 48 MeV Li\(^{3+}\) and 85 MeV C\(^{6+}\) Swift Heavy Ions Beam

K\({}_{3}\)Na(SO\({}_{4}\))\({}_{2}\):Eu\({}^{3+}\) shows OSL when irradiated with swift heavy ion beams of Li\({}^{3+}\) and C\({}^{6+}\) at different fluences. The micro sample is prepared through solid state diffusion method along with its counter parts of ball milled (7 days) nanophosphor and co-precipitated nanophosphor samples. The material was characterized by XRD to confirm its formation in a single phase. Comparison of the experimental data with that of the data available in the literature (JCPDS data file \#74 0398) shows formation of a single hexagonal phase, with the space group P3 m1. Study on the particle size effect shows that particle size in the 75--106 \(\mu\)m rangeis more suitable for the linearly modulated-optically stimulated luminescence (LM-OSL) dosimetry in micro form. Dosimetric properties of the phosphor material using LM-OSL technique for blue light stimulation (\(\lambda=470\) nm and \(t=120$\) seconds) show that it is highly sensitive in the linear dose range. Here in this paper, we tried to find a relationship between detrapping probabilities and photoionization cross section using curve fitting (deconvolution) method. We also calculated and converted the fluence into doses using SRIM software. Data are presented indicating that the LM-OSL peak is composed of three overlapping components originating from populated traps with optical cross sections of 10\({}^{-17}\)-10\({}^{-18}\) cm\({}^{2}\). It was found that micro and ball milled nanophosphor Carbon ion beam irradiated samples dominates the photoionization cross section as compared with lithium ion irradiated samples, but co-precipitated sample is dominant in lithium irradiated samples. Which infers about the different trapping level formation and also recombination processes involved during the preparation and in readouts of samples.

Enhancement of photoelectric properties of Cu2ZnSnS4 thin films by electronic excitations induced by swift heavy ions

The structural, optical, and current–voltage characteristics including photosensitivity of copper zinc tin sulphide (Cu2ZnSnS4) thin films were modified significantly by the electronic excitations. These excitations were induced by swift heavy ion (SHI) beams of 100 –120 MeV of O, Ag, and Au. X-ray diffraction patterns confirm that the pristine and irradiated films crystallize in kesterite structure and the crystallite size increases after O, and Ag ion irradiations compared to Au ions. The micro-Raman spectra reveal the presence of lattice defects in the Au irradiated sample. The analysis shows that the crystallinity of the Cu2ZnSnS4 thin film increases with O ion irradiation indicating that the density of defect states decreases after SHI irradiation. The maximum photosensitivity is found to be 62% for O irradiated thin films compared to other ion beams due to the reduction in the band gap.

High energy (MeV) ion beam induced modifications in Al2O3-ZnO multilayers thin films grown by ALD and enhancement in photoluminescence, optical and structural properties

Atomic Layer Deposition (ALD) is employed for the growth of nanometric conformal layers on distinct substrates. In the present work, we demonstrated the attainable consequences on the examination of optical and structural peculiarities of pristine and SHI (swift heavy ions) irradiated ultrathin multilayer samples of Al2O3-ZnO fabricated on glass and silicon substrates using the technique based on ALD. Multilayer Al2O3-ZnO specimens were irradiated with 100 MeV SHI in the fluence range of 1E12 to 5E13 ions/cm2. For a better conception of the impact of ion beam irradiation with high energy on structural parameters like strain, dislocation density, crystallite size was demonstrated by X-Ray Diffraction (XRD). The coefficient of absorption was used to demonstrate the changes that occur in optical bandgap, urbach energy, skin depth and optical density with the function of ion fluence. Photoluminescence (PL) spectra were investigated at room temperature to comprehend the mechanism of changes in peak shifting and intensity of broad and strong emission luminescence spectra at excitation wavelengths of 300 nm were noteworthy. To evaluate the thickness, crystalline quality and quantitative composition of the elements Rutherford Backscattering Spectroscopy (RBS) employing utilizing the He2+ with high energy was used and reported. Regulation of optical peculiarities through swift heavy ion beam irradiation explores extensive opportunities for Al2O3-ZnO multilayer nanofabrication in optoelectronics domain.

Mixing nanostructured Ni/piezoPVDF composite thin films with e-beam irradiation: A beneficial synergy to piezoelectric response

Piezoelectric PVDF polymer thin films are nanostructured by swift heavy ion beam resulting in nanoporous structures. The nanocylindars are then partially filled with Ni(0) in order to create a composite of higher dielectric permittivity. In a second step, the composite is irradiated with electron beam, in order to induce chain scissions in the PVDF matrix and render it more flexible. It is found that e-beam irradiation does not affect the remanent polarization up to more than 1MGy. The energy harvesting properties are optimized with a maximum for 1MGy irradiation, delivering an output voltage of 4.1 V.cm−2 which corresponds to a maximum output power of 25μW. cm-2 and an integrated power of 0.46μW. cm−2 for 1 bar of external pressure (mechanical solicitations frequency of 10 Hz). The mechanisms responsible for the enhancement of the harvesting efficiency due to e-beam irradiation are discussed.

Effect of oxygen on gas emitted from polymer irradiated using Swift Heavy Ion beams

At the end of their life, polymers used in the nuclear industry are placed in Intermediate Level – Long Lived Waste packages. For safety purposes, the amount of gas emitted by these organic materials has to be estimated. γ irradiations are commonly used to simulate β and γ-emitters; α-emitters simulation are more problematic because of experimental difficulties. It is proposed in France to use particle accelerators with ions providing stopping power values in polymers equivalent to the one of α-emitters. This approach has been validated under inert atmosphere; the question now arises of the effect of the presence of oxygen. We showed that the hydrogen release is slightly affected by atmosphere of irradiation and increases with LET. The evolution with LET of CO2 release is dependent on the polymer: it increases for polymers with low G(CO2) at low LET and decreases for polymers presenting relatively high G(CO2) at low LET.

Investigation of Ion Irradiation Effects in Silicon and Graphite Produced by 23 MeV I Beam.

Both silicon and graphite are radiation hard materials with respect to swift heavy ions like fission fragments and cosmic rays. Recrystallisation is considered to be the main mechanism of prompt damage anneal in these two materials, resulting in negligible amounts of damage produced, even when exposed to high ion fluences. In this work we present evidence that these two materials could be susceptible to swift heavy ion irradiation effects even at low energies. In the case of silicon, ion channeling and electron microscopy measurements reveal significant recovery of pre-existing defects when exposed to a swift heavy ion beam. In the case of graphite, by using ion channeling, Raman spectroscopy and atomic force microscopy, we found that the surface of the material is more prone to irradiation damage than the bulk.

Effect of 100 MeV Ni ion irradiation on CdZnTe thin films

Modification of semiconductor thin films by Swift Heavy Ion (SHI) beam irradiation is a unique technique for property improvement. In the present investigation, Cadmium Zinc Telluride (CZT) thin films of thickness 100 nm are deposited on glass substrates by the thermal evaporation method. These films are irradiated with 100 MeV Ni ion beams at a fluence of 1×1012 ions/cm2 and 5×1012 ions/cm2. The SHIinduced surface modifications are studied by Atomic Force Microscopy (AFM). The structural properties are investigated using X-ray diffraction (XRD) technique. Optical characterization is carried out using UV–Vis spectroscopy. The SHI irradiation on CZT films results in grain fragmentation. Phase transformation and widening of bandgap is also observed after SHI irradiation. The SHIinduced property modifications are explained in the framework of ‘coulomb explosion and thermal spike model’.

Swift heavy ion beam modified MoS2- PVA nanocomposite free-standing electrodes for polymeric electrolyte based asymmetric supercapacitor

Swift heavy ion (SHI) beam irradiation technique is one of the sophisticated techniques used for modifying material properties to design efficient devices. In this report, the casted MoS2- PVA nanocomposite films have been irradiated with 80 MeV C6+, 100 MeV Si9+, and 120 A g9+ ion beams to achieve enhanced conductivity and have been exploited as an electrode material for asymmetric supercapacitor. PVDF-HFP: TPAI gel polymer electrolyte having 3 wt.% TPAI content showed the highest conductivity and was chosen for the iodide redox gel polymer electrolyte system. The pristine MoS2-PVA nanocomposite films having an electrical conductivity of 2.5E-5 S/cm exhibited specific capacitance of 65.27 F/g whereas the films irradiated with 120 MeV Ag9+ ion beams showed an electrical conductivity of 9.7E-3 S/cm and enhanced specific capacitance of 186.67 F/g. The enhanced capacitance is attributed to the high current density generated due to the increased conductivity of the electrodes.

Nanopatterning surfaces by grazing incidence swift heavy ion irradiation

Nanopatterned surfaces play a key role for many applications exploiting unique features such as an enhanced surface area, long- and short-ranged morphology modulations or a spatial variation of electronic and chemical properties. Ion beam irradiation has been frequently used for nanostructuring bulk materials because it is efficient, fast, and cost-effective. In this paper we show that ion irradiation under extremely grazing incidence in conjunction with other scalable processing methods such as wet etching and thermal annealing, is a perfect tool for nanopatterning of dielectric surfaces. We demonstrate that by tuning ion energy and fluence, one can select different surface nanopattern morphologies like individual chains of nanohillocks, nanostripes, or nanoscaled ripples. Furthermore, chemical etching of the irradiated surface can be used to create a negative replica of the nanopattern as only the material making up the surface track is susceptible to the etching process and is thus removed. Also, a removal of the surface track can be achieved by thermal annealing in vacuum. All these presented strategies open up new ways for achieving control over nanoscale surface modifications using swift heavy ion beams.

Electronic sputtering of solid N[formula omitted] by swift ions

Most sputtering yield measurements for solid N2 are reported for stopping powers lower than 10−13eV cm2/molecule. We measured the sputtering yield for solid N2 at stopping powers, in the electronic regime, above 10−12eV cm2/molecule, extending the range of such measurements by more than an order of magnitude, using a 33 MeV 58Ni9+ swift heavy ions beam. The evolution of the thin N2 ice films was monitored in-situ by mid-infrared spectroscopy (FTIR) during irradiation. As N2 is only weakly infrared active, and can be hardly monitored directly via an infrared absorption mode in such experiments, we use the Fabry–Perot interference fringes of the ice film to evaluate, via an optical model, the erosion of the N2 film as a function of ion fluence. A sputtering model including several sputtering crater shapes is developed and tested against experimental data. We derive the sputtering yield for a semi-infinite N2 ice film and its dependence with the ice thickness for thin film conditions, monitoring the N2 ice sputtering depth. We combine the results with previous measurements at lower stopping powers to derive the electronic sputtering of solid N2 over a large stopping power range.

Intense ionizing irradiation-induced atomic movement toward recrystallization in 4H-SiC

An ultrafast thermal spike within a time interval of a few pico-seconds generated by intense ionizing energy deposited using 100 MeV Ag ions is utilized to study the atomistic details of damage recovery in 4H-SiC. Sequential single ion irradiations were performed using 300 keV Ar and 100 MeV Ag in ⟨0001⟩ 4H-SiC to invoke swift heavy ion (SHI) beam induced epitaxial recrystallization in samples with different degrees of pre-damaged conditions. SHI irradiation was carried out at both room temperature and a low temperature of ∼80K. Low-temperature irradiation was carried out to arrest thermal diffusion of defects and to isolate ionization-induced defect migration in 4H-SiC. Insights into the thermal spike generated by ionizing events in crystalline and amorphous regions at both the temperatures predict a SiC response to SHI. The results emphasize the role of different degrees of pre-damage induced physico-chemical conditions and irradiation temperatures against SHI-induced recrystallization as evaluated by Rutherford backscattering/channeling, Raman spectroscopy, and hard x-ray photoelectron spectroscopy. Understanding the dependence of ion-beam damage accumulation and their recovery on the inelastic to elastic energy loss ratio is important for the performance prediction of SiC intended for extreme environments such as space, defense, and nuclear radiation. We report substantial damage recovery even at a near liquid nitrogen temperature of ∼80K. The recovery gets impeded mainly by the formation of complex defects having homonuclear bonds. The results are explained in the framework of the inelastic thermal spike model, and the role of phonon in the damage recovery process is emphasized.

Radiation impact of swift heavy ion beams on double-interface CoFeB/MgO magnetic tunnel junctions

A double-interface CoFeB/MgO magnetic tunnel junction (MTJ) has a high thermal stability barrier (E) and high-efficiency magnetization switching with the scaling of device dimensions. However, compared to a single-interface CoFeB/MgO MTJ, its more complicated film stacks and interfaces are more vulnerable to irradiation-induced swift heavy ions. We have studied the irradiation effects of Ta/Kr ions on double-interface CoFeB/MgO MTJs. Structural and physical analyses are performed through transmission electron microscopy, energy dispersive x-ray spectroscopy, and vibrating sample magnetometry. 1907 MeV Ta-ion irradiation damages the interfaces of the double-interface MTJ, resulting in the irreversible decrease in coercivity, while 2060 MeV Kr-ion irradiation damages the bulk properties of the MTJ, leading to the decrease in saturation magnetization. However, the electronic properties of the double-interface MTJ are almost immune to Kr-ion irradiation.

Tailoring the properties of spray deposited V2O5 thin films using swift heavy ion beam irradiation

Swift heavy ion (SHI) beam irradiation can generate desirable defects in materials by transferring sufficient energy to the lattice that favours huge possibilities in tailoring of materials. The effect of Ag15+ ion irradiation with energy 200 MeV on spray deposited V2O5 thin films of thickness 253 nm is studied at various ion doses from 5 × 1011 to 1 × 1013 ions/cm2. The XRD results of pristine film confirmed orthorhombic structure of V2O5 and its average crystallite size was found to be 20 nm. The peak at 394 cm−1 in Raman spectra confirmed O–V–O bonding of V2O5, whereas 917 cm−1 arise because of distortion in stoichiometry by a loss of oxygen atoms. Raman peaks vanished completely above the ion fluence of 5 × 1012 ions/cm2. Optical studies by UV–Vis spectroscopy shows decrement in transmittance with an increase in ion fluence up to 5 × 1012 ions/cm2. The red shift is observed both in the direct and indirect band gaps until 5 × 1012 ions/cm2. The surface topography of the pristine film revealed sheath like structure with randomly distributed spherical nano-particles. The roughness of film decreased and the density of spherical nanoparticles increased upon irradiation. Irradiation improved the conductivity significantly for fluence 5 × 1011 ions/cm2 due to band gap reduction and grain growth.

Study of humidity sensing properties and ion beam induced modifications in SnO2-TiO2 nanocomposite thin films

Swift heavy ion beam induced dense electronic excitation in the nanocomposite thin film is a unique way to introduce various modifications such as track formation, atomic transport and phase transformation. Therefore, this work based on the modification in the properties of Titanium dioxide and Tin oxide nanocomposite thin films prepared by RF sputtering deposition technique in the mol% 50:50 on ITO coated glass and silicon substrates. The prepared nanocomposite thin films annealed at 500 °C and irradiated with SHI of 150 MeV Fe11+ ion beam with varied ion fluences ranging from 5 × 1012to 5 × 1013 ions.cm−2. The SRIM simulation was confirmed the electronic energy loss (Se) as 1.038 × 102 eV/nm, nuclear energy loss (Sn) as 1.33 × 10−1 eV/nm and the projectile depth of the iron ion inside the thin films was founded to be 17.18 um. Structural analyses of pristine and irradiated thin films were analyzed by X-ray diffraction technique. Changes observed in the peak intensity were confirmed by the significant variations in crystallite size, which was calculated by the Debye Scherrer equation. The crystallite size of all samples was found to be improved from 59 nm to 141 nm. The influence of ion irradiation on surface topography of nanocomposite thin films was analyzed by Atomic Force Microscopy (AFM). The sectional analysis of AFM images reveals that the grain size depends on the ion irradiation fluences. The grain size was increased from 52 nm to 129 nm. The optical properties were studied using UV–Visible spectroscopy and Photoluminescence (PL) spectroscopy. Tauc's method was used to calculate the optical energy band gap of the samples. The direct band gap was decreased as ion fluence increases may be due to creation of metastable energy states in between the valance and conduction band. The recombination and separation of photo generated charge carriers were studied by the photoluminescence spectroscopy. Rutherford Backscattering Spectrometry (RBS) was performed on all samples to ensure depth profiling, elemental composition and absence of impurities in titanium dioxide and tin oxide nanocomposite thin films. The response time, recovery time, repeatability and ageing effect after (one, two and three) weeks of nanocomposite thin films were obtained during humidity sensing measurements.