Effect Of Swift Heavy Ion Irradiation Research Articles

Relaxation and charge transport phenomena in polyaniline nanofibers: Swift heavy ion irradiation effects

Relaxation and charge transport mechanisms in hydrochloric acid (HCl) doped polyaniline (PAni) nanofibers synthesized using interfacial polymerization technique and the swift heavy ion irradiation effects have been investigated by dielectric relaxation spectroscopy. Non-Debye type relaxation with a distribution of relaxation times observed in PAni nanofibers is dominated by hopping of trapped charges. Swift heavy ion irradiation induces a benzenoid to quinoid transition in PAni nanofibers. Dynamic processes occurring at different frequencies in PAni nanofibers exhibit the same activation energy which reveals an enhanced coupling among the localized short range dipolar motions. The increase in conductivity relaxation time upon irradiation indicates an increase in the carrier hopping length thereby impeding charge transport. The ac conductivity of the pristine and irradiated PAni nanofibers has been found to obey the universal power law of frequency. Although charge transport in both the pristine and irradiated PAni nanofibers follows the correlated barrier hopping (CBH) model with polarons as major charge carriers, significant decrease in conductivity has been observed upon irradiation.

SHI irradiation induced effects in functionalized MWCNTs

Multi-walled carbon nanotubes (MWCNTs) have attracted extensive attention globally due to their applications in modern nanotechnology. It is very important to study the effects on these MWCNTs under swift heavy ion (SHI) irradiation since ion irradiation has been recognized as one of the best tools for nanostructuring of materials, in general. Here, we present the effects of 80 MeV Ni ions with a fluence ranging from 3×1012 to 3×1013 ions/cm2 on functionalized MWCNT mats. The properties of pristine and irradiated samples were studied using X-ray diffraction, Raman spectroscopy and transmission electron microscopy. The effects of SHI irradiation on these samples are discussed in detail.

Study of swift heavy ion irradiation effect on Rhodamine 6G dye for dye sensitize solar cell application

The Rhodamine 6G (R6G) dye sample synthesized by thermal evaporation method is irradiated by 120 MeV Ag+9 ions at different fluences from 1 × 1011 ion/cm2 to 3 × 1012 ion/cm2. These samples are characterized by X-ray diffraction (XRD), ultraviolet–visible (UV–Vis) absorption spectroscopy and photo-conductivity measurements. In XRD, it is observed that amorphous nature of dye films increases with fluence and hence aggregates of dye molecules spread homogeneously on the substrate after irradiation. The absorption spectroscopy and photoconductivity results show maximum absorption and minimum photoresistivity at lowest fluence. The properties of the dye films such as increase in amorphous nature, increase in absorption peak area and marginal increase in photoconductivity are favorable for Dye-sensitize solar cell (DSSC) applications.

Structural, Optical And Gas Evolution Studies Of 60 MeV Si5+ Ion Irradiated PoT-PVC Blends

Swift Heavy Ion (SHI) irradiation induces chemical and structural changes in polymers by evolving various gases and gaseous fragments. The evolution of gases as a result of chain scissoring and bond breaking leads to cross-linking and cluster formation. Study of the evolved gases helps in understanding the various chemical and structural changes occurring within the polymer under the effect of SHI irradiation. In the present work, Poly (o-toluidine) (PoT), a derivative of polyaniline, is prepared by chemical oxidation polymerization and is blended with polyvinylchloride (PVC) to achieve self supported films. These PoT-PVC blend films were irradiated by 60 MeV Si 5+ ions at different fluences and evolved gases were monitored on-line by Residual Gas Analyzer (RGA). Pre and post irradiation FTIR, UV-Visible absorption and XRD studies have been carried out on these films to observe the changes in chemical/structural and optical properties. An effort has been made to correlate the evolved gases and structural properties after irradiation.Copyright © 2011 VBRI press.

Nano hillock and complex crater formation by low-energy proton implantation with incident angle into lithium niobate single crystal

The formation of nano-size hillocks and simple and complex craters was observed as a result of ion–surface collisions with a lithium niobate single crystal on proton implantation. The low-energy ion implantation process is considered as a controllable and versatile tool for surface and near-surface modifications down to an atomic scale as an alternative to the swift heavy ion irradiation effect. Lithium niobate samples implanted by proton ions with a low energy of 120 keV at various fluences (1015 and 1016 protons/cm2) were studied using atomic force microscopy (AFM). The images of surface modification appear as simple and complex crater formation in the case of incident ions at normal to the surface. Varying the angle of incidence to θ=30° with respect to the normal to the surface, hillocks and multi-hillocks were observed. The complex craters with central uplifted, cone-shaped hillocks with a height of up to 4.3 nm are surrounded by low-height (1 nm) rims. The hillock height varies from a few nanometers to 16 nm with the basal diameter from 200 to 340 nm depending on the ion implantation conditions. The complex crater and hillock formation on the lithium niobate sample surface at the collision spot with the impact of incident angle is discussed.

Study of swift heavy ion irradiation effect on indium tin oxide coated electrode for the dye-sensitized solar cell application

Our long term objective is to study the swift heavy ion (SHI) irradiation effect on photoanode of dye-sensitized solar cell (DSSC) with the aim to investigate the stability of DSSC component in space irradiations and possibility of improvement in efficiency of DSSC due to ion induced effects in oxide layer. The DSSC photoanode consists of three layers viz; transparent conducting oxide (TCO), porous oxide with wide band gap and monolayer of dye molecule on top of corning glass substrate respectively. In the present study, procured radio frequency (RF) sputtered indium tin oxide (ITO) film on corning glass substrate were irradiated by SHI using 110 MeV Ni 8+ ions at different fluences ranging from 3.0 × 10 11 ion/cm 2 to 1.0 × 10 14 ion/cm 2. After irradiation significant changes have been observed in the structural, optical and electrical properties using X-ray diffraction (XRD), UV–Vis and Four Probe measurements, respectively. Overall there is 13% increase in optical transmittance which is favorable and moderate increase in sheet resistance from 8 Ω/□ to 18 Ω/□ which is still within acceptable limits for DSSC applications.

Fourier transform infrared and ultraviolet-visible investigation of swift heavy 100 MeV Ag-ion- and 75 MeV oxygen-ion-irradiated polyvinylidene fluoride thin films

Polyvinylidene fluoride (PVDF) polymer films (9, 12, and 20 μm) were irradiated with 100 MeV Ag ion (fluence: 1.875×1011 ions/cm2) and 75 MeV oxygen ion (fluences: 5.625×1011 and 5.675×1012 ions/cm2) using the PELLETRON facility at the Inter University Accelerator Centre, New Delhi, to study swift heavy ion (SHI) irradiation effects in thin films. The change in chemical, optical, and structural properties was analysed by comparing Fourier transform infrared (FTIR) and ultraviolet (UV)-visible spectra of pristine and irradiated films. The FTIR spectra show no major change in characteristic bands on irradiation, except that some weak bands appear because of the evolution of volatile species, unsaturated bond formation, decomposition of the free radicals, and subsequent cross-linking. The spectra of the irradiated films show some broadening and a decrease in intensity in characteristic bands when compared with the pristine samples. The FTIR results indicate that the overall chemical structure of PVDF is stable under SHI irradiation. The UV-visible absorption spectra of irradiated samples reveal hyperchromic shift, bathochromic shift, and hypsochromic shift. The spectra also estimate the direct optical band gap around 3.6 eV. The band gap decreases on irradiation, and the decrease is dependent on ion beam and fluence rate. The present study opens up the scope for the applicability of SHI-irradiated PVDF thin films as microsensors and actuators.

Enhancement of ferromagnetism in Ni-implanted HfO2 dielectric thin films

Abstract We report thermal annealing and 100 MeV Si 8+ swift heavy ion irradiation effects on the structural and magnetic properties of Ni-implanted HfO 2 thin films. At low Ni doping concentration (∼1%), HfO 2 thin films show ferromagnetic behavior. We clearly demonstrate the cluster free nature of our film using cross-sectional high resolution transmission microscopy and magnetization vs. temperature data. Rutherford backscattering spectrometry is used to estimate the film thickness and to establish that Ni-ions are placed in the HfO 2 matrix. By comparing the results for the annealed and swift heavy ion irradiated samples, it is concluded that the enhancement in magnetic signal is closely related to the dispersion/diffusion of implanted Ni and defect creation such as oxygen vacancies. The results of magnetic force microscopy supported the observation of room temperature ferromagnetism in Ni-implanted HfO 2 films.

Swift heavy ion irradiation effect on Cu-doped CdS nanocrystals embedded in PMMA

Semiconductor nanocrystals (NCs) have received much interest for their optical and electronic properties. When these NCs dispersed in polymer matrix, brightness of the light emission is enhanced due to their quantum dot size. The CdCuS NCs have been synthesized by chemical route method and then dispersed in PMMA matrix. These nanocomposite polymer films were irradiated by swift heavy ion (SHI) (100 MeV, Si+7 ions beam) at different fluences of 1 × 1010 and 1 × 1012 ions/cm2 and then compared their structural and optical properties by XRD, atomic force microscopy, photoluminescence, and UV-Vis spectroscopy before and after irradiation. The XRD spectra showed a broad hump around 2θ ≈ 11·83° due to amorphous PMMA and other peaks corresponding to hexagonal structure of CdS nanocrystals in PMMA matrix. The photoluminescence spectra shows a broad peak at 530 nm corresponding to green emission due to Cu impurities in CdS. The UV-Vis measurement showed red shift in optical absorption and bandgap changed from 4·38–3·60 eV as the irradiation fluency increased with respect to pristine CdCuS nanocomposite polymer film.

Swift heavy ion irradiation effects on carbonyl and trans-vinylene groups in high and low density polyethylene

In this work, we have studied the effects of swift heavy ion irradiation on the creation of new functional groups in high and low density polyethylene (HDPE and LDPE). Polymers were irradiated with different ions (6.77 MeV He and 47 MeV Li) and fluences. The induced changes were analyzed by Fourier transform infrared (FTIR) spectroscopy. Creation and damage cross sections for some groups were compared for two different types of PE.

60-MeV C5+ ion irradiation effects on conducting poly (o-toluidine)–poly vinyl chloride blend films

Poly (o-toluidine) was synthesized from a derivative of aniline (o-toluidine) monomer by chemical oxidative polymerization method. After polymerization, the polymer prepared was blended with poly vinyl chloride and irradiated by 60-MeV C5+ ions at five different fluences of 1×1011, 3.3×1011, 1×1012, 3.3×1012 and 1×1013 ions/cm2. The swift heavy ion irradiation effects on crystallinity and DC conductivity were studied. X-ray diffraction study showed variations in crystallinity of the blend films upon irradiation. The crystallinity, DC conductivity and activation energy were found to vary discontinuously with fluence. The DC conductivity and activation energy were obeying Meyer–Neldel rule.

Investigation of swift heavy ion irradiation effects on Au/CdTe and Au/CdZnTe Schottky barrier diode

The influence of 100 MeV Ag 7 + ion irradiation on current–voltage ( I – V ) and capacitance–voltage ( C – V ) characteristics of Au/CdTe and Au / Cd 0.9 Zn 0.1 Te Schottky barrier diodes as a function of fluence are investigated. The irradiation fluence was varied from 1 × 10 10 to 1 × 10 13 ions cm - 2 . The current transport across the metal–semiconductor junction for pure and irradiated Schottky barrier diodes has been described by the thermionic-field emission process. Also, there are several mechanisms such as barrier tunneling, carrier compensation and generation–recombination mechanism, which may account for the I – V and C – V characteristics after irradiation. This variation in various diode parameters such as ideality factor ( n ) , Schottky barrier height ( Φ b ) and saturation current ( I s ) has been studied as a function of irradiation fluence. The energy loss mechanism of swift heavy ions at the metal–semiconductor interface is used to explain the change in Schottky barrier diode parameters. The observed modification at interface states of Schottky barrier height over a wide fluence range are mainly due to intense electronic energy loss mechanism and latent ion track formation created by swift heavy ions.

Dielectric characteristics of substituted M-type strontium hexaferrite crystals and their modifications on swift heavy ion irradiation

Dielectric behaviour of flux grown substituted crystals bearing composition SrGa x In y Fe 12−( x+ y) O 19 ( x = 5, 7, 9; y = 0.8, 1.3, 1.0) is reported. Variation of dielectric constant ( ɛ /), dielectric loss (tan δ) and ac conductivity ( σ ac) with temperature in the range 30–500 °C under the frequency of the applied ac field in the range 1–10 4 kHz for all the varied compositions are analyzed and explained. Swift heavy ion irradiation effects on these parameters are investigated. On irradiation the crystals show changes in the values of dielectric constant ( ɛ /), dielectric loss (tan δ) and ac conductivity ( σ ac). The frequency variation of ɛ / and tan δ is explained by Koop's phenomenological theory and hopping frequency of electrons between Fe 2+ and Fe 3+ on octahedral sites for both irradiated and unirradiated crystals.

High-resolution XRD analysis of swift heavy ion irradiated InGaAs/GaAs heterostructures

Strain relaxation and swift heavy ion irradiation effects on molecular beam epitaxy grown InGaAs/GaAs heterostructures have been studied by high-resolution X-ray diffraction. Symmetric and asymmetric scans were analyzed to understand the irradiation effects on strain and defects. The broad layer peak of the experimental scans in the samples was observed. The excess width of the layer peak than the expected one has been attributed to the strain relaxation induced defects. Irradiated samples show an additional peak close to the substrate peak of compressive nature, which has been attributed to radiation damage in the substrate due to the heavy ions. Dynamical scattering theory based simulations have been compared with the experimental scans. It has also been used to deconvolute the additional peak. The simulation was comparable with the experimental scan and a satisfactory fit was obtained. The dislocation density has been reduced upon irradiation. The observed decrease in the defect density is attributed to the high electronic energy loss of the ions near the interface region. Also, the damage created by the heavy ions near the interface would enhance the diffusion of indium across the interface and hence reduce the relative mismatch at the interface.

Investigation of swift heavy ion irradiation effects in CdTe crystals

CdTe crystals grown by the Bridgman technique were irradiated by swift heavy ions (SHIs), 100 MeV Ag7+ ions, with fluences varying from 1011 to 1014 ions cm−2 and the damage is investigated by atomic force microscopy, x-ray diffraction, hall effect measurements and photoluminence. It is found that the behaviour of CdTe crystals under a SHI irradiation induces structural disorder, generation of optically active defects, decrease in the electron mobility but an increase in the carrier concentration compared with as-grown samples. The observed effects are mainly due to the intense electronic excitation created by SHIs.

Thickness dependent swift heavy ion irradiation effects on electronic transport of (La0.5Pr0.2)Ba0.3MnO3 thin films

Electrical resistivity and magnetoresistance measurements on (La0.5Pr0.2)Ba0.3MnO3 thin films of 50 and 200nm thicknesses, irradiated by 200MeV Ag+15 ions, have been carried out. Before irradiation, all the films exhibit insulator-metal transition at a temperature (Tp) of ∼200K. After irradiation, both resistivity and Tp remain mostly unaffected in 50nm thin film but vary largely in 200nm thin films. This disparity in irradiation effect on these films is explained to arise from the interplay of columnar defect induced (i) enhancement in resistivity with increasing thickness of the film and (ii) local release of strain at the interfaces of low thickness films, which decreases resistivity.

Swift heavy ion irradiation effects in nanocrystalline gold

We have studied the effects of irradiation with energetic ions on defect accumulation in nanocrystalline gold (nano-Au). The specimens of nano-Au foil (3–5μm thickness) with various grain sizes (23–156nm) are prepared by the gas deposition method and subsequent thermal annealings. Irradiations of the specimens with 60-MeV 12C ions, 3.54-GeV 136Xe ions or 2.0-MeV electrons are performed at low temperature (below 17–18K). The defect accumulation behavior is observed by measuring the electrical resistivity change during irradiation. For comparison, irradiation and resistivity measurements are performed on ordinary polycrystalline gold (poly-Au) under similar conditions. Through an analysis of the defect accumulation behavior, the cross-sections for defect annihilation, σr, and production, σd, in nano-Au are found to increase monotonically as the grain size decreases. These results are considered to be caused by the existence of a large volume fraction of the regions near grain boundaries in nano-Au where the threshold energy for defect production, Ed, may become lower than in poly-Au. For 3.54-GeV 136Xe ion irradiation, in addition to the effect of decrease in Ed, the defect production seems more prominent in nano-Au than in poly-Au. It may suggest that electronic excitation contributes to the defect production effectively in nano-Au.

Swift heavy ion irradiation effects on structural and magnetic characteristics of RFeO3 (R = Er, Ho and Y) crystals

Magnetic studies have been carried out on single crystals of RFeO3 (R=Er, Ho and Y) using vibrating sample magnetometer before and after swift heavy ion irradiation. Highly anisotropic character of the crystals is maintained even after irradiation. Irradiation causes decrease in magnetization and increase in Neel temperature of the crystals studied. The decrease in magnetization is attributed to amorphization caused by irradiation. High-resolution X-ray diffraction studies confirm amorphization on irradiation of the RFeO3 (R=Er, Ho and Y) crystals.

Luminescence study of bare and coated CdS quantum dots: Effect of SHI irradiation and ageing

Bare and silica coated CdS quantum dots are prepared following chemical route. Swift heavy ion (SHI) irradiation of the samples was carried out with 160MeV Ni12+ ion beam with fluences 1012–1013ions/cm2. Photoluminescence (PL) studies of all the samples were carried out with excitation wavelength 325nm. The surface state emission is dominant in case of bare samples while e–h recombination is observed in case of coated samples. Red shift in the absorption response in the optical absorption spectra of bare samples reveal size enhancement of the quantum dots after irradiation. No such shift is observed for coated samples. The coated samples also exhibit enhanced photo stability.

Ionic conduction in 70 MeV C 5+ ion-irradiated P(VDF–HFP)–(PC + DEC)–LiCF 3SO 3 gel polymer electrolyte system

Swift heavy ion irradiation effects on ionic conduction in the P(VDF–HFP)–(PC + DEC)–LiCF 3SO 3 gel polymer electrolyte system have been investigated. Polymer gel electrolytes films were irradiated with 70 MeV C 5+ ions with seven different fluences in the range of 10 10–10 12 ions/cm 2. Irradiation of the polymer gel electrolyte films with swift heavy ions shows enhancement in conductivity at lower fluences (≤ 10 11 ions/cm 2) and decrease in conductivity at higher fluences. XRD results show decreased crystallinity below and increased crystallinity above the threshold fluence after ion irradiation. It appears that below the critical fluence, swift heavy ion irradiation increases Li + ion diffusivity in the polymer electrolyte. FTIR spectra suggest chain scission at low fluence and cross linking at higher fluence. Scanning electron micrographs exhibit increased porosity of the polymer electrolyte after ion irradiation.