Effect Of Heavy Ion Irradiation Research Articles

Investigation of heavy ion irradiation effects on a charge trapping memory capacitor by C–V measurement

Heavy ion irradiation effects on charge trapping memory (CTM) capacitors with TiN/Al2O3/HfO2/Al2O3/HfO2/SiO2/p-Si structure have been investigated. The ion-induced interface charges and oxide trap charges were calculated and analyzed by capacitance–voltage (C–V) characteristics. The C–V curves shift towards the negative direction after swift heavy ion irradiation, due to the net positive charges accumulating in the trapping layer. The memory window decreases with the increase of ion fluence at high voltage, which results from heavy ion-induced structural damage in the blocking layer. The mechanism of heavy ion irradiation effects on CTM capacitors is discussed in detail with energy band diagrams. The results may help to better understand the physical mechanism of heavy ion-induced degradation of CTM capacitors.

Effects of swift heavy ion irradiation on the InAs and Zn-based nanoparticles ion-beam synthesized in silica

Till now, a shape elongation effect under swift heavy ions (SHI) irradiation was observed predominantly for metal nanoparticles (NPs). We report this effect for InAs and Zn(core)/ZnO(shell) NPs embedded in silica matrix. In case of InAs NPs, SHI irradiation results in the formation of nanorods. A diversity of elongated features is observed for Zn-based NPs: chains of small ZnO clusters, elongated (Zn)core/(ZnO)shell structures and drop-like elongated Zn particles. The intense silica sputtering due to electronic excitations has been found for the “SiO2 + Zn-based NPs” composite. Photoluminescence (PL) spectroscopy reveals an emission in the visible range for both nanocomposites before SHI irradiation. This emission is attributed to the oxygen excess-related defect (NBOHC) as well as to the oxygen deficiency-related centres created in silica matrix during the implantation of cluster-forming ions (In + As or Zn). An intensive band in the spectral region of 2.8–3.1 eV is observed in PL spectrum of annealed “SiO2 + InAs NPs” composite. SHI irradiation results in its quenching and formation of an asymmetrical band centred at 1.9 eV. In case of “SiO2 + Zn-based NPs”, SHIs irradiation results in substantial increase of PL in orange spectral range.

Effects of swift heavy ion irradiation and annealing on the microstructure and recrystallizationof SiC pre-implanted with Sr ions

Polycrystalline SiC wafers were implanted with 360 keV strontium (Sr) ions at room temperature (RT)to a fluence of 2 × 1016 cm−2. Some of the implanted samples were irradiated with xenon (Xe) ions of 167 MeV to a fluence of 3.4 × 1014 cm−2 and 8.4 × 1014 cm−2at RT. The as-implanted and implanted then irradiated samples were vacuum annealed (isochronally) at temperatures ranging from 1,100 to 1,400°C in steps of 100°C for 5 h. Annealing induced modification of the microstructure of the implanted and swift heavy ions (SHIs) irradiated SiC was studied by Raman spectroscopy, scanning electron microscopy (SEM) and backscattering spectrometry (RBS). Sr ions bombardment caused formation of an amorphous layer in SiC, while irradiation by Xe ions led to partial recrystallization of the amorphized layer. After annealing at 1,100°C, the samples with low Sr retained ratio showed full recrystallization, while the samples with high Sr retained ratio showed poor recrystallization. This suggests that the presence of Sr within the implanted region inhibited the recrystallization of SiC. Annealing of the as-implanted samples at temperatures from 1,100°C and 1,200°Cresulted in larger average crystal size compared to the SHIsirradiated samples annealed in the same temperature range. The difference in the average crystal sizes between the as-implanted and SHIs irradiated samples was due to the differences in the nucleation rate per amorphous area in the two samples. Ramanspectroscopy results showedthat the intensity of the LO mode of SiC increases with increasing crystal size. However, several factors such as pores and defects in SiC play a role in the decrease of the LO mode intensity of SiC (even if the average crystal size is large).

Swift heavy ion irradiation-induced amorphous iron and Fe–Si oxide phases in metallic57Fe layer vacuum deposited on surface of SiO2/Si

57Fe conversion electron Mössbauer (CEM) spectroscopy, SEM and magnetization measurements were used to study the effect of swift heavy ion irradiation on metallic 57Fe (10 nm) thin layer vacuum deposited onto SiO2/Si. About 85% of the total iron content of the surface layer detected by CEM was present as metallic, crystalline alpha iron before the irradiation, while upon irradiation with 160 MeV Xe ions, with a fluence of 5 × 1013 ion cm−2, ~ 21% was converted to amorphous iron and ~ 47% to silicon-containing iron oxide phases. The presence of pure iron in the amorphous state was evidenced by CEM in agreement with magnetization measurements. Temperature dependence of CEM measurements and the FC/ZFC curves of the irradiated deposit indicated superparamagnetic nature of the iron-silicon-oxide phases. The results are discussed in terms of the thermal spike model for the formation of the amorphous iron phase that can be essential for the formation of silicon-iron-oxides. Graphical abstract

Structure and magnetic properties of Fe nanoparticles in amorphous silica implanted with Fe ions and effect of subsequent energetic heavy ion irradiation

Amorphous silicon dioxide (hereafter SiO2) samples were implanted with 380 keV Fe ions at room temperature. After the implantation, some samples were irradiated with 16 MeV Au ions. The magnetic property was investigated by using a SQUID magnetometer, and the morphology of Fe-implanted SiO2 samples was examined by using a transmission electron microscope and x-ray absorption spectroscopy (extended x-ray absorption fine structure and x-ray absorption near edge structure). The size of Fe nanoparticles increases with an increase in the amount of Fe implantation. A part of Fe nanoparticles consists of Fe oxides, and with an increase in the amount of Fe implantation, the valence state of Fe atoms and the structure of Fe nanoparticles gets close to those of metallic α-Fe. The room temperature magnetism was observed in Fe-implanted SiO2 samples. The magnetization–magnetic field curves for samples implanted with a small amount of Fe are reproduced by the Langevin equation, implying that Fe nanoparticles present the superparamagnetic behavior. For a large amount of Fe implantation, the magnetization–magnetic field curve shows the ferromagnetic state. Such a result of magnetic property is consistent with the results of the x-ray absorption. By the subsequent 16 MeV Au irradiation, the Fe nanoparticles were fragmentated, resulting in the decrease in magnetization. The optical absorption property of the SiO2 samples is briefly discussed.

Investigation of Nano-Scale Segregation in Nanostructured Ferritic Alloy 14YWT after Heavy Ion Irradiation.

Oxide-dispersion-strengthened (ODS) steels, which contain nano-scale Y-Ti-O particles, are being considered for high-temperature radiation environments of nuclear reactors. It is important to accurately characterize the structure of grain boundaries and understand the behavior of segregation at grain boundaries in ODS steels during irradiation. The effect of heavy ion irradiation at 700 °C on Nanostructured Ferritic Alloy 14YWT was investigated using Atom Probe Tomography. Enrichment of Cr occurs at the grain boundaries as well as at nano oxide particle surfaces in the unirradiated sample. The enrichment of Ti and Y at a grain boundary corresponds with Y-Ti-O nano oxide particles with larger size compared to those in the grain, and the Cr enrichment is particularly accentuated at these larger nano oxide particles. The segregation of W occurs at the grain boundaries that are without nano oxide particles. O is segregated at grain boundaries without oxide particles after irradiation. The segregation behavior of Cr, W, Ti, and Y at the grain boundary in the irradiated samples is similar to that in the unirradiated sample. The nano oxide particles embedded in the grain boundary are a primary reason for the increase in Cr segregation at the grain boundary.

Effect of swift heavy ion irradiation on the resistive random access memory performance of sputter deposited zinc rich zinc oxide thin films

Resistive Random-Access Memory (RRAM) devices are synthesized by sandwiching (i) ZnO thin film and (ii) Zn-rich ZnO thin film between top and bottom conducting electrodes consisting of Au thin layer and ITO substrate respectively. DC Sputtering was used to create the metal contact at the top of the device, while simultaneous RF and DC magnetron sputtering was used to form the ZnO and metal-rich oxide layer-based devices. The RRAM device was irradiated with 100 MeV Ag at a fluence of 1013 ions/cm2. The I-V characteristics of pristine and irradiated Au/ZnO/ITO and Au/Zn rich ZnO/ITO were measured using a semiconductor device analyser B1500. The thickness, stoichiometry, and crystallinity of zinc oxide thin films were determined using Rutherford Back Scattering, X-ray diffraction and Raman Spectroscopy. The present work shows that the performance of RRAM devices both in the ZnO and Zn rich ZnO significantly improves by ion irradiation.

Effects of 120 MeV Ag9+ swift heavy ion irradiation on the structural, optical and electrical properties of pristine and Ni doped BiFeO3 thin films grown by pulsed laser deposition

In this work, the effects of swift heavy ion (SHI) irradiation on the structure, morphology, optical and electrical properties of pristine and Ni-doped BiFeO3 thin films have been explored. The thin films with composition of BiFe1-xNixO3 (x = 0, 0.01, 0.03 and 0.05) were deposited on the n-type single crystal Si(100) substrates through pulsed laser deposition technique. Further, irradiation on the thin films was performed with 120 MeV Ag9+ ions at different ion fluences, i.e., 1 × 1013, 5 × 1013 and 1 × 1014 ions/cm2. To investigate the effects of SHI irradiation on the aforementioned properties, all the films have been characterized by various analytical techniques, such as X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, UV-visible diffuse reflectance spectroscopy and two-probe resistivity setup. The effects of the irradiation on the crystal structure and phase of the thin films were analyzed by the XRD and Raman measurements, and it has been observed that irradiation tends to amorphize the thin films. A decrease in the band gap has been observed for the irradiated thin films with the increase of ion fluence. The current-voltage plots of all the unirradiated and irradiated thin films demonstrate the rectifying diode type characteristics.

Suppression of Superconductivity in Heavy-ion Irradiated 2H-NbSe2 Caused by Negative Pressure

Effects of columnar defects created by 320 MeV Au irradiation on 2H-NbSe2 single crystals with a dose equivalent matching field up to 16 T were studied. Critical temperature is found to be suppressed almost linearly at a rate of 0.07 K/T. At the same time, the lattice parameters a and c are found to be expanded at rates of 0.016%/T and 0.030%/T, respectively. Such a lattice expansion should work as negative pressure to affect Tc. By separating the effect of heavy-ion irradiation on Tc suppression through lattice expansion and disorder, it is found that Tc is suppressed more by lattice expansion rather than by disorder.

The reliabilities of HfO2-based ferroelectric devices under swift heavy ion irradiation

The effects of heavy ion irradiation on the electrical response of HfO2-based ferroelectric capacitors have been studied. All the hysteresis loops measured from the irradiated samples shifted toward the positive voltage. The remanent polarization and relative permittivity of the capacitors decrease with increasing ion fluence. The leakage current exhibit negligible change after irradiation. The main reason causing the phenomena is swift heavy ions (SHIs) induced the pinning of domain walls, attributed to the phase transition. This work provides the possible physical mechanisms of SHIs irradiation on HfO2-based ferroelectrics, which is of significance for the space application of HfO2-based ferroelectric random access memory.

Investigation of effects of swift heavy ion irradiation on few-layer graphene: A molecular dynamics simulation study

The molecular dynamics simulation has been utilized to investigate the structural damage via heavy ion irradiation in graphene. The effects of stacking and incident angle of ion on the structural damage are mainly explored. The growth of stacking layers makes structural damage of overall and surface layer more and more serious. The damage of each layer shows obvious differences, the damage becomes weaker toward the centre. The effect of incident angle on damage is discussed in 3-layer graphene. The two surface layers are not affected while the damage of intermediate layer is weak with the decrease of incident angle. The driving force for structural damage is the stress wave propagating from the energy deposition region to the surrounding.

Change in Magnetic Anisotropy at the Surface and in the Bulk of FINEMET Induced by Swift Heavy Ion Irradiation.

57Fe transmission and conversion electron Mössbauer spectroscopy as well as XRD were used to study the effect of swift heavy ion irradiation on stress-annealed FINEMET samples with a composition of Fe73.5Si13.5Nb3B9Cu1. The XRD of the samples indicated changes neither in the crystal structure nor in the texture of irradiated ribbons as compared to those of non-irradiated ones. However, changes in the magnetic anisotropy both in the bulk as well as at the surface of the FINEMET alloy ribbons irradiated by 160 MeV 132Xe ions with a fluence of 1013 ion cm−2 were revealed via the decrease in relative areas of the second and fifth lines of the magnetic sextets in the corresponding Mössbauer spectra. The irradiation-induced change in the magnetic anisotropy in the bulk was found to be similar or somewhat higher than that at the surface. The results are discussed in terms of the defects produced by irradiation and corresponding changes in the orientation of spins depending on the direction of the stress generated around these defects.

Ion irradiation-induced effects on optical and structural properties of Ge nanoparticles synthesized by laser ablation

We present here the effects of swift heavy ion irradiation on the optical and structural properties of Germanium (Ge) nanoparticles (NPs) synthesized by using laser ablation of bulk Ge wafer in liquids. The Ge NPs have been irradiated with 120 MeV Ag ions of various fluences ranging from 5 × 1012 to 1 × 1014 ions/cm2. The effect of ion irradiation on optical and structural properties of the Ge NPs has been studied with transmission electron microscopy (TEM), Raman scattering, and photoluminescence (PL) emission measurements. We have observed a decrease in the average size of the Ge NPs upon increasing the fluence of irradiation, amorphization at high fluence, and smaller NPs started to grow in the vicinity of larger sized NPs under ion irradiation. Therefore, the proper selection of fluence can be tuned to modify the existing NPs and synthesize new NPs. The NPs became amorphous at the higher fluence with the core remaining crystalline while the shell transformed into an amorphous phase. From Raman scattering results, the shift observed in peak position and the increase in the broadening in the Ge phonon vibrational peak indicates a reduction in NPs size. The PL emission is also blue-shifted upon increasing the irradiation fluence.

Heavy-ion irradiation effects on electrical properties of yttrium oxide coatings

Ceramic coatings have been developed for nearly half a century to mitigate tritium leakage through steels and corrosion of the components in fusion reactor blanket systems. In recent years, irradiation effects of ceramic coatings on their characteristics and functions have been elucidated through heavy-ion irradiation tests. However, most of analytical methods used in these studies were destructive and time-consuming. In this study, yttrium oxide coatings were fabricated by radio-frequency magnetron sputtering, and the electrical impedance measurements were conducted for the coatings to develop a convenient approach for understanding of irradiation effects. The conductivity obtained from Nyquist plots showed lower values for the undamaged sample than for the damaged ones below 350 °C, while the relationship of the conductivity was reversed at 350 °C and higher temperatures. The ac conductivity of the undamaged sample showed a frequency dependence from 200 °C to 550 °C; however, that of the damaged ones did not show at 300 °C and lower temperatures and indicated a tendency similar to undamaged one above 300 °C. These tendencies of the conductivity at low temperatures were attributed to the partial recovery of the irradiation damage, while the remaining irradiation defects and/or irradiation-induced grain growth affected the electrical properties at higher temperatures. The electrical impedance spectroscopy methods have a potential to detect the influence of irradiation on the coating.

Research on Ion Distribution and Stoping Power for Au Ions Irradiation Si, SiC

In order to predict the effect of heavy ion irradiation more accurately, the ion distribution and stoping power of Au irradiated silicon (Si) and silicon carbide (SiC) under various energy conditions were calculated by using SRIM program, and compared with the experimental values. It was found that the projeced range and divergence predicted by SRIM were significantly smaller, and the stopping power was significantly larger by about 25%. Therefore, the method of reducing the target density parameters was tried to make corrections. It was found that the gold ion distribution became deeper after the density decreased, the stopping power became smaller, and the curve was closer to the experiment with an error of only ~5%. The density reduction coefficient is introduced since there is no definite conclusion on how much density decreases. Based on a large number of previous experimental data, SRIM was used to calculate the density reduction coefficient values under different energy conditions repeatedly, and found that there is a corresponding relationship between the values and energy values. Finally, the polynomial regression fitting method was used to obtain their functional expressions, which laid a foundation for the prediction of Si and SiC irradiated by heavy ions.

Effect of swift heavy silicon ion irradiation on TiO2 thin film prepared by micro arc oxidized technique

Titanium dioxide (TiO2) thin films were fabricated via a micro arc oxidized process and its surface was modified using 100 MeV Swift Heavy Si7+ ion (SHI) irradiation. GIXRD analysis confirmed both the phases of rutile and anatase. Additionally, the analysis showed a gradual decrease in intensity which coincided with a rise in ion fluence at up to 5 × 1012 ions/cm2, whereas; at higher fluence (1 × 1013 ions/cm2), the intensity was enhanced. SEM images showed agglomerated particles in the range 0.1–9 µm for pristine whereas; at higher fluences (1 × 1012 and 1 × 1013 ions/cm2) the particle dimensions reduced to a range within 0.1–3 µm. AFM exhibited uniform agglomerates with reduced particle size in the range 0.1–0.5 µm for fluences>1 × 1012 ions/cm2. Enhancement in reflectance was observed for irradiated samples than what was seen in pristine. Irradiation led to a decrease in band gap to 1.4 eV (1 × 1013 ions/cm2) from 1.8 eV (pristine) due to an increase in the defects’ energy level. Surface wettability, roughness, in vitro bioactivity, and irradiated film attachment to the cells are enhanced. Hence, these analytical results demonstrate that the irradiated film is an excellent implant and would be useful in orthopedic applications.

Amifostine (WR-2721) Mitigates Cognitive Injury Induced by Heavy Ion Radiation in Male Mice and Alters Behavior and Brain Connectivity.

The deep space environment contains many risks to astronauts during space missions, such as galactic cosmic rays (GCRs) comprised of naturally occurring heavy ions. Heavy ion radiation is increasingly being used in cancer therapy, including novel regimens involving carbon therapy. Previous investigations involving simulated space radiation have indicated a host of detrimental cognitive and behavioral effects. Therefore, there is an increasing need to counteract these deleterious effects of heavy ion radiation. Here, we assessed the ability of amifostine to mitigate cognitive injury induced by simulated GCRs in C57Bl/6J male and female mice. Six-month-old mice received an intraperitoneal injection of saline, 107 mg/kg, or 214 mg/kg of amifostine 1 h prior to exposure to a simplified five-ion radiation (protons, 28Si, 4He, 16O, and 56Fe) at 500 mGy or sham radiation. Mice were behaviorally tested 2–3 months later. Male mice that received saline and radiation exposure failed to show novel object recognition, which was reversed by both doses of amifostine. Conversely, female mice that received saline and radiation exposure displayed intact object recognition, but those that received amifostine prior to radiation did not. Amifostine and radiation also had distinct effects on males and females in the open field, with amifostine affecting distance moved over time in both sexes, and radiation affecting time spent in the center in females only. Whole-brain analysis of cFos immunoreactivity in male mice indicated that amifostine and radiation altered regional connectivity in areas involved in novel object recognition. These data support that amifostine has potential as a countermeasure against cognitive injury following proton and heavy ion irradiation in males.

Investigations on the effect of swift heavy silicon ion irradiation on hydroxyapatite

The effect of swift heavy silicon ion irradiation on hydroxyapatite prepared by hydrothermal technique was analyzed. The physical and biological properties were studied using G1XRD, Micro-Raman, photoluminescence, AFM, SEM, EDX, in vitro bioactivity, antimicrobial activity and drug release. When compared with pristine the crystallinity increases with an increase in fluence. Slight reduction in crystallinity was noted for irradiated samples at higher fluence (1×1013 and 1×1014 ions/cm2) than lower fluence (1×1012 ions/cm2). After irradiation the υ4 O-P-O asymmetric bending mode peak at 583 cm−1 disappeared. The PL intensity increases with an increase in fluence and it had become narrow and showed red shift. This suggests the material could find application as phosphors. The enhancement in band gap was attained for irradiated samples than Hpris (5.38–5.5 eV). AFM studies revealed the enhancement of roughness, particle size and pores on irradiation. SEM exposed the creation of pores along with an increase in porosity (2 µm to 30 µm). Formation of platy crystals was noted for 1×1013 ions/cm2 sample. In vitro bioactivity results with the formation of spherical (2 µm) apatite deposition along with the presence of interconnected pores (2–10 µm) which could enhance osteointegration and osteoconduction. In addition, Ca/P ratio was found to increase after soaking in SBF. Initial burst release followed by sustained release was obtained upto 45 h. Therefore it could assist in the treatment of bone and joint infection. Hence, SHI had improved the material to be used in biomedical field as an implant due to its enhanced properties such as crystallinity, pore size, surface roughness, PL intensity, antimicrobial activity, drug release and bioactivity.

The heavy ions irradiation effects on advanced spin transfer torque materials

We investigate the heavy ions irradiation effect on the spin transfer torque film stacks with perpendicular magnetic anisotropy. Samples are exposed to 175 MeV Cl ion and 235 MeV Ge ion at the fluence of 1x105 ions/cm2 and 1x106 ions/cm2. Measurements of magnetization vs. magnetic field are performed on the film stacks before and after irradiation. The results exhibit that magnetic properties of free layer (CoFeB) in the spin transfer torque film keeps unchanged while magnetic properties of the synthetic antiferromagnet layer (Co/Pt) and the ferromagnetic exchange coupling between reference layer (CoFeB) and synthetic antiferromagnet layer through W layer have changed significantly when the fluence of the two kinds of ions reach 1x106 ions/cm2. We analysis the irradiation damage of the film stacks by SRIM simulation and give a reasonable explanation for this phenomenon. Thus, our work demonstrates that perpendicular spin transfer torque MRAM technology itself, the memory element construction, is subject to damage from heavy ions irradiation.

Defect-Induced Phase Transition in Hafnium Oxide Thin Films: Comparing Heavy Ion Irradiation and Oxygen-Engineering Effects

Hafnium oxide acts as a functional dielectric in a variety of traditional and emerging nonvolatile memory technologies. To investigate the effect of heavy ion irradiation on its crystalline structure, highly textured hafnium oxide films were irradiated with 1.635 GeV Au ions of fluences ranging from 1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> to 7×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> ions/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . For monoclinic hafnium oxide films, a fluence-dependent defect-induced phase transition to a defect-stabilized tetragonal phase is identified. In low-temperature tetragonal hafnium oxide films, the X-ray diffraction (XRD) patterns show an out-of-plane lattice constant decrease with increasing irradiation fluence. Observed crystalline changes are strikingly similar to trends found for oxygen-engineered hafnium oxide films, directly grown at varying oxidation conditions. The correlation of structural changes with in vacuo electron spectroscopy data of oxygen-engineered films suggests that the irradiation of hafnium oxide leads to an oxygen loss that increases with fluence. Therefore, the underlying mechanism of the monoclinic to tetragonal phase transition is obviously directly related to oxygen defects. This new information allows predictions of device stability under swift heavy ion irradiation of hafnium oxide-based devices.