Thermal,electrical and optical properties of proton-irradiated Makrofol DE 7-2 nuclear track detector

Samples from sheets of the polymeric material Makrofol DE 7-2 have been exposed to 1 MeV protons of fluences in the range 2.5×10¹³–5×10¹⁵ p/cm². The resultant effect of proton irradiation on the thermal properties of Makrofol has been investigated using thermogravimetric analysis and differential thermal analysis (DTA). The onset temperature of decomposition T _o and the activation energy of thermal decomposition E _a were calculated, and the results indicated that the Makrofol detector decomposes in one weight loss stage. Also, the proton irradiation in the fluence range 7.5×10¹³–5×10¹⁵ p/cm² led to a more compact structure of Makrofol polymer, which resulted in an improvement in its thermal stability with an increase in the activation energy of thermal decomposition. The variation of transition temperatures with proton fluence has been determined using DTA. The Makrofol thermograms were characterized by the appearance of an endothermic peak due to the melting of the crystalline phase. The melting temperature of the polymer, T _m, was investigated to probe the crystalline domains of the polymer. At a fluence range of 7.5×10¹³–5×10¹⁵ p/cm², the defect generated destroys the crystalline structure, thus reducing the melting temperature. In addition, the V–I characteristics of the polymer samples were investigated. The electrical conductivity was decreased with the increasing proton fluence up to 5×10¹⁵ p/cm². Further, the refractive index, transmission of the samples and any color changes were studied. The color intensity Δ E was greatly increased with the increasing proton fluence and was accompanied by a significant increase in the red and yellow color components.     

50 MeV Li3+ ion irradiation effect on structural, electrical, and dielectric properties of PVA-based nanocomposite polymer electrolytes

Nanocomposite polymer electrolyte thin films of polyvinyl alcohol (PVA)-orthophosphoric acid (H₃PO₄)-Al₂O₃ have been prepared by solution cast technique. Films are irradiated with 50 MeV Li³⁺ ions having four different fluences viz. 5?×?10¹⁰, 1?×?10¹¹, 5?×?10¹¹, and 1?×?10¹² ions/cm². The effect of irradiation on polymeric samples has been studied and characterized. X-ray diffraction spectra reveal that percent degree of crystallinity of samples decrease with ion fluences. Glass transition and melting temperatures have been also decreased as observed in differential scanning calorimetry. A possible complexation/interaction has been shown by Fourier transform infrared spectroscopy. Temperature-dependent ionic conductivity shows an Arrhenius behavior before and after glass transition temperature. It is observed that ionic conductivity increases with ion fluences and after a critical fluence, it starts to decrease. Maximum ionic conductivity of ～2.3?×?10^?5 S/cm owing to minimum activation energy of ～0.012 eV has been observed for irradiated electrolyte sample at fluence of 5?×?10¹¹ ions/cm². The dielectric constant and dielectric loss also increase with ion fluences while they decrease with frequency. Transference number of ions shows that the samples are of purely ionic in nature before and after ion irradiation.     

Swift heavy ion provoked structural, optical and electrical properties in SnO2 thin films

SnO₂ thin films grown on glass substrates at 300 ^°C by reactive thermal evaporation and annealed at 600 ^°C were irradiated by 120 MeV Ag⁹⁺ ions. Though irradiation is known to induce lattice disorder and suppression of crystallinity, we observe grain growth at a certain fluence of irradiation. X-ray diffraction (XRD) revealed the crystalline nature of the films. The particle size estimated by Scherrer’s formula for the irradiated films was in the range 10–25 nm. The crystallite size increases with increase in fluence up to 1×10¹² ions?cm^?2, whereas after that the size starts decreasing. Atomic force microscope (AFM) results showed the surface modification of nanostructures for films irradiated with fluences of 1×10¹¹ ions?cm^?2 to 1×10¹³ ions?cm^?2. The UV–visible spectrum showed the band gap of the irradiated films in the range of 3.56 eV–3.95 eV. The resistivity decreases with fluence up to 5×10¹² ions?cm^?2 and starts increasing after that. Rutherford Backscattering (RBS) reveals the composition of the films and sputtering of ions due to irradiation at higher fluence.     

Enhancement in electrochemical properties of ionic liquid-based nanocomposite polymer electrolytes by 100 MeV Si9+ swift heavy ion irradiation

Swift heavy ion (SHI) irradiation has been used as a tool to enhance the electrochemical properties of ionic liquid-based nanocomposite polymer electrolytes dispersed with dedoped polyaniline (PAni) nanorods; 100 MeV Si⁹⁺ ions with four different fluences of 5?×?10¹⁰, 1?×?10¹¹, 5?×?10¹¹, and 1?×?10¹² ions cm^?2 have been used as SHI. XRD results depict that with increasing ion fluence, crystallinity decreases due to chain scission up to fluence of 5?×?10¹¹ ions cm^?2, and at higher fluence, crystallinity increases due to cross-linking of polymer chains. Ionic conductivity, electrochemical stability, and dielectric properties are enhanced with increasing ion fluence attaining maximum value at the fluence of 5?×?10¹¹ ions cm^?2 and subsequently decrease. Optimum ionic conductivity of 1.5?×?10^?2 S cm^?1 and electrochemical stability up to 6.3 V have been obtained at the fluence of 5?×?10¹¹ ions cm^?2. Ac conductivity studies show that ion conduction takes place through hopping of ions from one coordination site to the other. On SHI irradiation, amorphicity of the polymer matrix increases resulting in increased segmental motion which facilitates ion hopping leading to an increase in ionic conductivity. Thermogravimetric analysis (TGA) measurements show that SHI-irradiated nanocomposite polymer electrolytes are thermally stable up to 240–260 °C.     

Structural modifications induced in Bayfol polycarbonate due to heavy highly energetic ions irradiations

The effects of 28 GeV ⁵⁶Fe and 13.72 GeV ²⁸Si ion irradiation on the structural properties of two types of Bayfol, namely DPF 5023 and CR 1–4 polycarbonates, have been investigated. It is worth mentioning that this report is almost the first one dealing with the topic of material changes in such a high energy range. Samples from each type of Bayfol were classified into two groups. The first group has been exposed to Fe ion fluences at levels between 2000 and 8000 ion/cm². The second group has been exposed to Si ions with similar fluences. The total energy deposited is between 27.44 and 224 E12 eV. The modifications induced in Bayfol samples due to ion irradiation have been studied using X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy. The results indicate that the Fe ion irradiation causes crosslinking in Bayfol DPF 5023, reflected as a decrease in the ordering character. Also, the tendency of Bayfol CR 1–4 to crosslinking due to Fe ion irradiation is lower than that of Bayfol DPF 5023. On the other hand, the Si ion irradiation causes mainly chain scission at the carbonate site of both types of Bayfol associated with the formation of hydroxyl group.     

Modifications induced by swift heavy ions in rapidly solidified Sn–8.5Sb–5.5Cu alloy

Alloys of composition Sn–8.5Sb–5.5Cu (in atomic percent) were rapidly solidified by a melt-spinning technique. The samples were irradiated at room temperature with GeV uranium ions of fluences between 9×10⁸ and 9×10¹¹ ions cm^?2. X-ray diffraction analysis revealed the formation of a new-phase Cu₁₁Sb₃ as well as a reduction in the axial ratio (c/a) of the matrix (β -Sn) indicating the regular re-arrangement of atoms. Scanning force microscopy showed no surface topographic changes with the ion fluence. The mechanical properties (Young's modulus and hardness) of the irradiated alloys were studied as a function of ion fluence. The radiation-annealing process is discussed in terms of the evolution of both resistivity and hardness as a function of ion fluence.     

An investigation on the variations in properties of Ni+ irradiated ZnO thin films

ZnO thin films, irradiated by 80 MeV Ni⁺ ions, were analysed with the help of different characterization techniques like X-ray diffraction, optical absorption, transmission, photoluminescence (PL), electrical resistivity, photosensitivity (PS) and thermally stimulated current (TSC) measurements. Crystallinity and absorption edge were hardly affected by irradiation. PL spectrum of pristine sample showed a broad peak at 517 nm, whereas irradiated film had two emissions at 517 and 590 nm. Intensity ratio between these two emissions (I₅₁₇/I₅₉₀) decreased with the fluence, and finally at a fluence of 3×10¹³ ions/cm², the emission at 517 nm completely disappeared. Electrical resistivity of the sample irradiated with a fluence of 1×10¹³ ions/cm² drastically increased. However, on increasing the fluence to 3×10¹³ ions/cm², resistivity decreased, probably due the onset of hopping conduction through defects. PS also decreased due to irradiation. TSC measurements on pristine sample could reveal only one defect level at 0.6 eV, due to interstitia1 zinc (Zn_I). But, irradiation at a fluence of 1×10¹² ions/cm², resulted in three different defect levels as per TSC studies. Interestingly, the sample irradiated at a fluence of 3×10¹³ ions/cm² had only one defect level corresponding to a deep donor. The possible origin of these defect levels is also discussed in the paper.     

Induced absorption in yttrium aluminium perovskite crystals irradiated by 12C and 235U ions

The present work is devoted to investigation of optical absorption in pure and neodymium-doped YAlO₃ (YAP) single crystals in the spectral range 0.2–1.1 μm induced by the influence of ¹²C ions irradiation with energy 4.50 MeV/u (MeV per nucleon) and a fluence 2 × 10⁹ cm^?2 or of ²³⁵U ion irradiation with energy 9.35 MeV/u and a fluence 5 × 10¹¹ cm^?2. The induced absorption in the case of ¹²C ions irradiation is caused by recharging of point growth defects and impurities under the radiation influence. After irradiation by ²³⁵U ions with fluence 5 × 10¹¹ cm^?2 the strong absorption rise is probably caused by contribution of the lattice destruction as a result of heavy ion bombardment.     

Carbon (70 MeV) and copper (120 MeV) ions irradiation effects in Makrofol-N

Makrofol-N polycarbonate was irradiated with carbon (70 MeV) and copper (120 MeV) ions to analyze the induced effects with respect to optical and structural properties. In the present investigation, the fluence for carbon and copper beams was kept in the range of 1×10¹¹– 1×10¹³ ions/cm² to study the swift heavy ion induced modifications. UV–VIS, FTIR and XRD techniques were utilized to study the induced changes. The analysis of UV–VIS absorption studies revealed that the optical energy gap was reduced by 17% on carbon irradiation, whereas the copper beam leads to a decrease of 52% at the highest fluence of 1×10¹³ ions/cm². The band gap can be correlated to the number of carbon atoms, N, in a cluster with a modified Robertson's equation. In copper (120 MeV) ions irradiated polycarbonate, the number of carbon atoms in a cluster was increased from 63 to 269 with the increase of ion fluence from 0 to 1×10¹³ ions/cm², whereas N is raised only up to 91 when the same polymer films were irradiated with carbon (70 MeV) ions under similar conditions. FTIR analysis showed a decrease in almost all characteristic absorption bands under irradiation. The formation of hydroxyl (? OH) and alkene (C?C) groups were observed in Makrofol-N at higher fluence on irradiation with both types of ions, while the formation alkyne end (R? C≡ CH) group was observed only after copper ions irradiation. The radii of the alkyne production of about 3.3 nm were deduced for copper (120 MeV) ions. XRD measurements show a decrease in intensity of the main peak and an increase of the average intermolecular spacing with the increase of ion fluence, which may be attributed to the structural degradation of Makrofol-N on swift ion irradiation.     

Ion track effect on point defect production in SiC

Low-temperature (40 K) photoluminescence (PL) measurements were used to follow the defect formation induced in the 4H-SiC epitaxial layer by irradiation with 200 keV H⁺ and 800 keV C⁺ in the fluence range of 5×10⁹–3.5×10¹² ions/cm². After irradiation, the PL spectra show the formation of some sharp lines, called “alphabet lines”, located in the wavelength range of 425–443 nm, due to the recombination of excitons at structural defects induced by ion beams. The analysis of luminescence line intensity versus ion fluence allows us to mark two different groups of peaks, namely the P1 group (e, f and g lines) and the P2 group (a, b, c and d lines). The normalised yield of P1 group lines increases with ion fluence and reaches a maximum value, while the normalised yield of P2 group lines exhibits a threshold fluence and then increases until a saturation value is reached. These different trends indicate that, while the P1 group lines are related to the primary defects created by ion beams (interstitial defects, vacancies), the P2 group lines can be associated with some complex defects (divacancy, antisites). The trends are similar for irradiation with H⁺ and C⁺ ions; however, the defect formation occurs in the fluence range of 5×10⁹–10¹¹ ions/cm² for C⁺ irradiation and 10¹¹–4×10¹² ions/cm² for H⁺ irradiation. Taking into account the different values of energy deposited in elastic collision, a dependence on the ion type was found: the C⁺ ion results in being less effective in defect production as a higher defect recombination occurs inside its dense cascade.     

2.0-MeV Er+ implanted in silicon: depth distribution, damage profile and annealing behaviour

Si crystals were implanted with 2.0- MeV Er⁺ at the doses of 5×10¹² ions/cm², 1×10¹⁴ ions/cm², 5×10¹⁴ions/cm², 1×10¹⁵ ions/cm² and 2.5×10¹⁵ ions/cm². Conventional furnace thermal annealing was carried out in the temperature range from 600 °C to 1150 °C. The depth distribution of Er, associated damage profiles and annealing behavioar were investigated using the Rutherford backscattering spectrometry and channelling (RBS/C) technique. A proper convolution program was used to extract the distribution of Er from the experimental RBS spectrum. The obtained distribution parameters, projected range R_p, projected range straggling ΔR_p and skewness SK were compared with those of TRIM96 calculation.The experimental R_p and SK values agree well with the simulated values, while the experimental ΔR_p is larger than TRIM 96 simulated value by a factor of 18%. The damage profile of silicon crystal induced by 2.0-MeV Er⁺ at a dose of 1×10¹⁴ ions/cm² was extracted using the multiple-scattering dechannelling model based on Feldman’s method, which is in a good agreement with the TRIM96 calculation. For the samples with dose of 5×10¹⁴ ions/cm² and more, an abnormal annealing behavioar was found and a qualitative explaination has been given. Received: 11 October 1999 / Accepted: 28 March 2000 / Published online: 5 July 2000     

Modification induced by gamma irradiation in Bayfol CR 1-4 polycarbonate

Bayfol CR 1-4 polycarbonate is a class of polymeric solid state nuclear track detector which has many applications in various radiation detection fields. Samples from sheets of Bayfol have been irradiated with gamma doses ranging from 100 to 620 kGy. The structural modifications in the gamma-irradiated Bayfol samples have been studied as a function of dose, using different characterization techniques such as X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, intrinsic viscosity and refractive index. The results indicate that the carbonyl group (C?O) degraded under irradiation up to 200 kGy. This degradation, reported by FTIR spectroscopy enhanced the degree of ordering in the degraded samples as revealed by the XRD technique. Above 200 and up to 620 kGy, cross-linking is achieved, leading to an increase in the intrinsic viscosity from 0.41 to 0.78 at 35°C, indicating an increase in the average molecular mass. On the other hand, the resultant effect of gamma irradiation on the thermal properties of Bayfol has been investigated using thermo-gravimetric analysis, results indicating that the gamma irradiation in the dose range 200–620 kGy led to a more compact structure of Bayfol polymer, which resulted in an improvement in its thermal stability with an increase in the activation energy of thermal decomposition due to cross-linking. In addition, the V–I characteristics of the polymer samples were performed, results indicated that at higher voltage, the conduction mechanism of Bayfol CR 1-4 was identified as the Poole–Frenkel type.     

Electrical and structural properties of the swift heavy ion irradiated Au/n-GaAs schottky barrier diodes

Abstract

Au/n-GaAs Schottky Barrier Diodes (SBDs) have been fabricated on LEC grown silicon doped (100) GaAs single crystals. The SBDs were irradiated using high energy (120 MeV) silicon ion with fluences of 1 × 10 ¹¹ and 1 × 10¹² ions/cm². Current-Voltage (I-V) characteristics of unirradiated and irradiated diodes were analyzed. The change in the reverse leakage current increases with increasing ion fluence. This is due to the irradiation induced defects at the interface and its increase with the fluence. The diodes were annealed at 573 and 673 K. to study the effect of annealing. The rectifying behavior of the irradiated (fluence of 1 × 10¹² ions/cm¹²) SBDs improves upon as the annealing temperature increases and is attributed to the in situ self-annealing during irradiation. Scanning Electron Microscopic analysis was carried out on the irradiated samples to delineate the projected range and to observe defects.     

Enhanced Upconversion Luminescence of Erbium–Nitrogen-Doped Zinc Oxide Nano-Wires by Implantation of Ytterbium Ions

Erbium–nitrogen codoped zinc oxide nanowires of ytterbium-doped are prepared by thermal evaporation and ion implantation methods. Ytterbium ions are doped into nanowires at a fluence of (0, 1, 3, 5, and 9) × 10¹⁵ cm^?2. Microstructural and optical properties of specimen are investigated by X-ray diffractometer, absorption spectra, Raman, and upconversion photoluminescence examinations. Upconversion photoluminescence emissions at 550 nm and 660 nm are obtained under 980-nm light excitation. Both intensities of green and red peaks are enhanced by the introduction of ytterbium ions. When ytterbium ion fluence is 5 × 10¹⁵ cm^?2, light emission intensity reaches maximum value. The energy transfer and cross-relaxation processes are responsible for the change of emission intensity.     

Investigations on the effect of argon ion bombardment on the structural and optical properties of crystalline gallium antimonide

The effects of bombardment of 250 keV argon ions in n-type GaSb at fluences 2×10¹⁵ and 5×10¹⁵ ions cm^?2 were investigated by high-resolution X-ray diffraction (HRXRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). HRXRD studies revealed the presence of radiation-damaged layer (strained) peak in addition to the substrate peak. The variation in the lattice constant indicates the strain in the bombarded region. The out-of-plane (?_⊥) and in-plane strains (?_|) determined from the profiles of several symmetric and asymmetric Bragg reflections, respectively, were found to change with the ion fluence. Simulations of XRD patterns using dynamical theory of X-ray scattering (single-layer model) for the damaged layer yielded good fits to the recorded profiles. FTIR transmission studies showed that the optical density (α·d) of GaSb bombarded with different fluences increases near the band edge with increase in ion fluence, indicating the increase in the defect concentration. The density of the defects in the samples bombarded with different fluences was in the range of 3.20×10²¹–3.80×10²¹ cm^?3. The tailing energy estimated from the transmission spectra was found to change from 12.0 to 58.0 meV with increasing ion fluences, indicating the decrease of crystallinity at higher fluences. SEM micrographs showed the swelling of the bombarded surface of about 0.33 μm for the fluence of 2×10¹⁵ ions cm^?2, which increased to 0.57 μm for the fluence of 5×10¹⁵ ions cm^?2.     

Formation of bubbles and blisters in hydrogen ion implanted polycrystalline tungsten

ABSTRACT

Tungsten (W) has been regarded as one of the most promising plasma facing materials (PFMs) in fusion reactors. The formation of bubbles and blisters during hydrogen (H) irradiation will affect the properties of W. The dependence of implantation conditions, such as fluence and energy, is therefore of great interest. In this work, polycrystalline tungsten samples were separated into two groups for study. The thick samples were implanted by 18?keV H₃⁺ ions to fluences of 1?×?10¹⁸, 1?×?10¹⁹ and 1?×?10²⁰ H⁺/cm², respectively. Another thick sample was also implanted by 80?keV H₂⁺ ions to a fluence of 2?×?10¹⁷ H⁺/cm² for comparison. Moreover, the thin samples were implanted by 18?keV H₃⁺ ions to fluences of 9.38?×?10¹⁶, 1.88?×?10¹⁷ and 5.63?×?10¹⁷ H⁺/cm², respectively. Focused ion beam (FIB) combined with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for micro-structure analysis, while time-of-flight ion mass spectrometry (ToF-SIMS) was used to characterize the H depth profile. It is indicated that bubbles and blisters could form successively with increasing H⁺ fluence. H bubbles are formed at a fluence of ～5.63?×?10¹⁷ H⁺/cm², and H blisters are formed at ～1?×?10¹⁹ H⁺/cm² for 18?keV H₃⁺ implantation. On the other hand, 80?keV H₂⁺ ions can create more trapping sites in a shallow projected range, and thus enhancing the blisters formation with a relatively lower fluence of 2?×?10^17?H⁺/cm². The crack-like microstructures beneath the blisters are also observed and prefer to form on the deep side of the implanted range.     

DLTS and in situ C–V analysis of trap parameters in swift 50 MeV Li3+ ion-irradiated Ni/SiO2/Si MOS capacitors

Ni/SiO₂/Si MOS structures were fabricated on n-type Si wafers and were irradiated with 50 MeV Li³⁺ ions with fluences ranging from 1×10¹⁰ to 1×10¹² ions/cm². High frequency C–V characteristics are studied in situ to estimate the build-up of fixed and oxide charges. The nature of the charge build-up with ion fluence is analyzed. Defect levels in bulk Si and its properties such as activation energy, capture cross-section, trap concentration and carrier lifetimes are studied using deep-level transient spectroscopy. Electron traps with energies ranging from 0.069 to 0.523 eV are observed in Li ion-irradiated devices. The dependence of series resistance, substrate doping and accumulation capacitance on Li ion fluence are clearly explained. The study of dielectric properties (tan δ and quality factor) confirms the degradation of the oxide layer to a greater extent due to ion irradiation.     

Evolution,migration and clustering of helium-vacancy complexes in RAFM steel- depth resolved positron annihilation Doppler broadening study

Indian Reduced Activation Ferritic Martensitic steel is implanted with 130 keV helium ions to a fluence of 5 × 10¹⁴ and 1 × 10¹⁶ ions/cm² and investigated using positron annihilation spectroscopy. The samples were characterised by defect sensitive S and W-parameters using depth resolved slow positron beam. A dose dependency is observed in the nucleation and growth of helium bubbles with annealing temperature. An experimental evidence for the migration of smaller helium-vacancy complexes is observed via the variation in thickness/width of irradiated layer with temperature. The S–W plot clearly shows the regions corresponding to defect annealing, bubble nucleation and growth.     

Improvement of the pinning properties of (Bi/Pb)-2223 textured ceramics by columnar defects introduced by 6 GeV Pb ions

Pinning properties of (Bi/Pb)-2223 textured ceramics have been improved by 6 GeV Pb ions irradiation. Two samples were irradiated at fluencesφ _t=5 × 10¹⁰ ions/cm² and 2 × 10¹¹ ions/cm², respectively. The magnetic irreversibility is clearly improved in the intermediate range of temperature: (30–35) K<T<60 K for magnetic fields lower than the “fluence equivalent field”B _φ =φ _t.φ ₀. Moreover the irreversibility line is shifted towards higher fields. The results reported here show that the introduction of columnar defects or other extended defects is a route to improve the screening properties of tubes or cans based on (Bi/Pb)-2223 material and operating in liquid nitrogen.     

Study of optical band gap and carbon cluster sizes formed in 100 MeV Si8+ and 145 MeV Ne6+ ions irradiated polypropylene polymer

A wide variety of material modifications in polymers have been studied by using ion irradiation techniques. Extensive research has focused on to Swift Heavy Ions (MeV’s energy), probably because of good controllability and the large penetration length in polymers. High energy ion irradiation tends to damage polymers significantly by electronic excitation and ionization. It may result into the creation of latent tracks and can also cause formation of radicals such as ablation, sputtering, chain scission and intermolecular cross-linking, creation of triple bonds and unsaturated bonds and loss volatile fragments. Polypropylene polymer films of thickness 50 μm were irradiated to the fluences of 1 × 10¹⁰, 3 × 10¹⁰, 1 × 10¹¹, 3 × 10¹¹, 6 × 10¹¹ and 1 × 10¹² ions/cm² with Si⁸⁺ ions of 100 MeV energy from Pelletron accelerator at Inter University Accelerator Centre (IUAC), New Delhi and Ne⁶⁺ ions of 145 MeV to the fluences of 10⁸, 10¹⁰, 10¹¹, 10¹² and 10¹³ ions/cm³ from Variable Energy Cyclotron Centre, Kolkata. Optical modifications were characterized by UV towards the red end of the spectrum with the increase of the fluence. Value of optical band gap E _g shows a decreasing trend with ion fluence irradiated with both kinds of ions. Cluster size N, the number of carbon atoms per conjugation length increases with increasing ion dose. Cluster size also increases with the increase of electronic stopping power.