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The material exposed to energetic radiation may change its properties and performance. Ion beam irradiation is an established method to investigate radiation damage in materials. In the present study, SRIM code is employed as a tool to determine the electronic and nuclear energy losses and displacement per atom (DPA) associated with the damage induced in Al2O3 using 100 MeV Au ion. We have further studied the creation of 100 MeV Au ion induced molten zone along the ion track in Al2O3 in the framework of the thermal spike (TS) model. Using the in-elastic thermal spike model, elastic thermal spike model, and unified thermal spike model, the evolution of lattice temperature and latent track radius as a function of depth of Al2O3 for 100 MeV Au ion irradiation are investigated. The current results demonstrate that the latent track radius shows a U-shaped variation based on the combined effect of electronic stopping power and nuclear stopping power. In order to corroborate these results, an additional irradiation experiment was performed using swift heavy ion (SHI), 100 MeV Au ions with fluence 1×1014 ions/cm2 for Al2O3. To investigate the structural properties, surface morphology and to identify the defects in the samples, pristine and irradiated Al2O3 samples were characterized by Grazing Incident X-Ray Diffraction (GIXRD), Atomic Force Microscopy (AFM) and Photoluminescence Spectroscopy (PL). AFM study shows the increase in roughness after SHI irradiation. A decrease in intensity of PL spectra upon SHI irradiation indicates the formation of new defects and disordered structures in the material, which is quite in agreement with the theoretical results. [ABSTRACT FROM AUTHOR]

The effect of 120 MeV Au9+ ion irradiation and thermal annealing on [W(25 Å)/Ni(25 Å)]×10 multilayers, grown on float-glass and silicon substrates, has been studied. Wide-angle x-ray diffraction studies of pristine, as well as irradiated W/Ni multilayers, show deterioration of the superlattice structure, but x-ray reflectivity (XRR) studies reveal a nearly unaffected multilayer structure. Analysis of the XRR data using “Parratt’s formalism” does show a significant increase of W/Ni interface roughness. The observed differences in wide-angle and low-angle scattering results of the irradiated W/Ni multilayers suggest significant difference in the interlayer and intralayer mixing induced by swift heavy ion irradiation. XRR results also reveal the fluence dependence of layer densification. Plane, as well as cross-sectional transmission electron microscopy, carried out in imaging and diffraction modes very clearly shows that at higher fluence the intralayer microstructure becomes nanocrystalline (1–2 nm) and at some places amorphous too. But, the definition of the W and Ni layers still remains intact. This has been understood in terms of competition between low miscibility at the W/Ni interface and ion-beam mixing kinetics. [ABSTRACT FROM AUTHOR]

Conducting nanowires parallel to each other, embedded in fullerene matrix are synthesized by high energy heavy ion irradiation of thin fullerene film at low fluence (up to 5×1011 ions/cm2). The conductivity of the conducting zone is about seven orders of magnitude higher than that of the fullerene matrix. The conducting nanowires are evidenced by conducting atomic force microscopy. The typical diameter of the conducting tracks is observed to be about 40–100 nm. The creation of conducting wires is explained by transformation of fullerene to conducting form of carbon in the ion track, surrounded by the polymerized zone. The polymerization of fullerene is evidenced by Fourier transform infrared spectroscopy. [ABSTRACT FROM AUTHOR]

Spray pyrolyzed ZnO films prepared using solution containing ethanol and water (volume ratio 1:1), exhibited optical transmission of 85% in the visible range and electrical resistivity of 78 Ω cm. These samples were irradiated using 120 MeV Au ion beam and then characterized using optical absorption and transmission, x-ray diffraction (XRD), electrical resistivity measurements, x-ray photoelectron spectroscopy (XPS), and photoluminescence studies. It appears that irradiation does not affect absorption edge while optical transmittance was slightly reduced. But intensities of peaks of XRD and photoluminescence were found to decrease continuously with increasing ion fluence. Electrical resistivity of the films decreased considerably (from 78 to 0.71 Ω cm) with increase in ion fluence. Atomic concentration from XPS analysis showed that Zn/O ratio is getting increased due to ion beam irradiation. Variations in carrier concentration were also measured using Hall measurements. [ABSTRACT FROM AUTHOR]

Nanostructured CdS films are prepared on glass substrates by chemical bath deposition (CBD) method at room temperature and the samples are subjected to 120 MeV Ag SHI irradiation at various fluences from 1 × 10 to 3 × 10 ions/cm. Analysis of the samples by XRD exhibits both pristine as well as irradiated films are of cubic phase structure and shifting of diffraction peaks towards lower diffraction angle is observed upon irradiation. Structural phase transition from cubic to hexagonal is observed for the sample at high fluence 3 × 10 ions/cm. Crystallite size is found to increase for irradiated samples. Surface morphology observed using AFM shows that films consist of several nanoparticles (grains) and several small grains of CdS nanoparticles are grouped to form cluster. Increase in grain size due to irradiation is also observed from AFM picture. The optical absorption spectra exhibit shift in the fundamental absorption edge and hence the optical band gap energy decreases but the refractive index as well as dielectric constant increase with increasing ion fluence. Two intense and one weak Raman lines for pristine as well as irradiated CdS have been observed and all the samples show shift in Raman lines relative to bulk CdS due to phonon localization. [ABSTRACT FROM AUTHOR]

Thin films of Fe dispersed polyimide (PI) were prepared on glass and silicon substrates by RF sputtering technique. Different concentrations of Fe viz 0.5, 1 and 5% were dispersed by simultaneous sputtering of polymer and Fe-metal. These films were irradiated with 120 MeV Ni10+ ion beam at a fluence of 5 × 1012 ions/cm2. Ion induced modification in optical, structural, surface and magnetic properties were studied. Optical study of these samples was carried out by using UV-VIS spectroscopy. Small shift in band gap is observed with increase in metal concentration. However no significant change was observed after irradiation as polyimide is highly radiation resistive material. AFM analysis reveals that average surface roughness of the samples increases after irradiation. Magnetic properties were studied by means of MFM and SQUID. MFM images reveal that the magnetic contrast increases with increasing the concentration of Fe in the composites which shows strong magnetization due to metal doping. However the contrast decreases after irradiation. SQUID also supports the MFM results. [ABSTRACT FROM AUTHOR]

Ionoluminescence (IL) of natural kyanite crystals was studied during 120 MeV Au9+ ion irradiation in the fluence range 1.50-12 × 1011 ions/cm2. The IL spectrum exhibits sharp peaks at ∼689, 694, 705, 713 and 716 nm, along with a broad emission peak at 530 nm recorded for all samples investigated. The sharp emission peaks at 689 and 694 nm are attributed to R2 and R1 lines of Cr3+ impurities, and they are related to the transition 2Eg → 4A2g. The peaks at 705-716 nm are attributed to Fe3+ impurities and are related to the transition 4T1g → 6A1g. It was observed that up to a given fluence, the IL peak intensity grows, reaches a maximum and gradually decreases with increase of Au9+ ion fluence. The decrease in IL intensity might be attributed to disorder produced by dense electronic excitation under swift heavy ion irradiation. The stability of the chemical species was studied both with and without irradiation by means of FTIR spectroscopy. The results confirm that the Si-O-Al, Al-O and Si-O (2ν3) type species are destroyed due to amorphization. [ABSTRACT FROM AUTHOR]

Abstract: The influence of 200MeV Au ion irradiation on the surface properties of polycrystalline fullerene films has been investigated. The X-ray photoelectron and X-ray Auger electron spectroscopies are employed to study the ion-induced modification of the fullerene, near the surface region. The shift of C 1s core level and decrease in intensity of shake-up satellite were used to investigate the structural changes (like sp2 to sp3 conversion) and reduction of π electrons, respectively, under heavy ion irradiation. Further, X-ray Auger electron spectroscopy was employed to investigate hybridization conversion qualitatively as a function of ion fluence. [Copyright &y& Elsevier]

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 (ZnI). 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. [ABSTRACT FROM AUTHOR]

A Nickel Dimethylglyoxime (Ni-DMG) compound was dispersed in polymethyl methacrylate (PMMA) films at different concentrations. PMMA was synthesized by a solution polymerization technique. These films were irradiated with 120 MeV Ni10+ ions at the fluences of 1×1011 and 1×1012 ions/cm2. The radiation induced changes in dielectric properties and average surface roughness were investigated by using an LCR meter in the frequency range 50 Hz to 10 MHz and atomic force microscopy (AFM), respectively. The electrical properties of irradiated films are found to increase with the fluence and also with the concentration of Ni-DMG. From the analysis of frequency, f, dependence of dielectric constant, ε, it has been found that the dielectric response in both pristine and irradiated samples obey the Universal law given by ε α f n-1. The dielectric constant/loss is observed to change significantly due to the irradiation. This suggests that ion beam irradiation promotes (i) the metal to polymer bonding (ii) convert the polymeric structure in to hydrogen depleted carbon network due to the emission of hydrogen gas and/or other volatile gases. Atomic force microscopy (AFM) shows that the average surface roughness and surface morphology of irradiated films are observed to change. [ABSTRACT FROM AUTHOR]

Gigantic deformations were found for the copper sulfide (Cu1.4S and Cu2S) thin films irradiated with 100 MeV Au8+ swift heavy ions (SHI) for 1011 and 1012 ions cm-2 fluencies. It was observed that the deformation due to SHI is dependent on the chemical composition of the film. The optical band gap (Eg) of the Cu1.4S was blue shifted, whereas that of Cu2S was red shifted. The surface modifications were also different for these two compositions. These effects were studied by using the atomic force microscopy and scanning electron microscopy. The results are explained in the light of thermal spike model. [ABSTRACT FROM AUTHOR]

Abstract: Three phase transitions (face centered to simple cubic, surface rearrangement from (2×2) to (1×1) and glass transition) in fullerene thin films and the effect of 150MeV Ti ion irradiation on these transitions have been studied, using temperature dependence of electrical resistivity measurements. The structural properties of the C60 thin films are studied by X-ray diffraction, atomic force microscopy and UV–vis spectroscopy. It is observed that defect creation by ion irradiation in the films lead to quenching and broadening of structural phase transitions but the transition temperatures did not show significant shifting under ion irradiation. [Copyright &y& Elsevier]

Abstract: Effects of swift heavy ions irradiation on silica films containing Fe under the form of solute ions or metal particles have been investigated, using electron spin resonance and magnetometry. The results indicate that electronic excitations induce the reduction of solute ions and the precipitation of metal particles when the Fe concentration is not too low. The hammering effect of ions on the silica matrix causes a tilt of easy magnetization axis when the volume fraction of particles is of a few percents, but this axis remains in the film plane for fraction over 10%. [Copyright &y& Elsevier]

Abstract: The influence of swift heavy ion (SHI) irradiation on electronic transport properties of epitaxial thin films of La0.75Ca0.25MnO3 is studied. The films were irradiated with 250MeV Ag17+ beam at fluence range 1010–1012 ions/cm2. A systematic variation in metal–insulator transition temperature (T p) and peak resistivity have been observed. At low fluence value (3×1010 ions/cm2) the T p is increased by 34K. With the increase in fluence it decreases but remain at upper side up to the fluence value of 3×1011 ions/cm2 as compared to the unirradiated film. The peak resistivity is also decreasing with the increase in fluence up to 3×1011 ions/cm2 and then increases with further increase of fluence. The temperature coefficient resistivity (TCR) is also increased with the fluence. The observed effects are correlated with the effects produced by the applications of hydrostatic pressure. The results are discussed in terms of SHI irradiation induced structural strains in the films. [Copyright &y& Elsevier]

Abstract: Sol–gel materials are converted into glassy ceramics when subjected to ion irradiation or heat treatments. In addition, a demixing occurs in the obtained glasses when their structure is metastable. In the present work, we have irradiated silicon-based gels with 120MeV and 2GeV Au ions at different fluences from 8×109 to 2×1013 ions/cm2. Ion irradiation leads to formation of carbon nanoclusters, which have semiconducting properties. Photoluminescence and optical absorption spectroscopies are used to identify the semiconducting properties of carbon clusters. High resolution transmission electron microscopy (HRTEM) and energy filtered imaging of C atoms show that C particles with a size of ∼4nm are produced and they are aligned along ion tracks. Elastic recoil detection analysis has been performed to determine the kinetics of the H evolution and to evaluate the track radius, which matches with the radius obtained from HRTEM. The obtained aligned carbon clusters (wires) would find useful applications as field emitters or nanocontacts. [Copyright &y& Elsevier]

Abstract: The effects of intense laser and energetic ion irradiation on Raman vibrational modes of Multiwalled Carbon Nanotubes have been investigated. The intensity ratio of D and G modes decreases with increase in laser power density and remains almost constant with decrease of laser power density. The intensity ratio of D mode to G mode for ion irradiated Multiwalled Carbon Nanotubes decreases at low fluence (4×1011 ions/cm2) and increases further with increase in ion fluence. The results show that ion irradiation at low fluence and laser irradiation lead to purification/ordering of the nanotubes. [Copyright &y& Elsevier]

The present work reports the synthesis of elongated Au nanoparticles (NPs) parallel to each other, embedded in silica matrix. Au NPs in silica, prepared using rf magnetron sputtering, were irradiated by 120 MeV Au ions at different fluences to induce elongation. Optical absorption study of irradiated film showed a clear splitting of surface plasmon bands corresponding to transverse and longitudinal modes. Transmission electron microscopy investigations of pristine and irradiated samples revealed an elongation (aspect ratio of ∼3.5) in Au NPs occurred as a result of irradiation. The results are discussed in the framework of thermal spike model. [ABSTRACT FROM AUTHOR]

Thin silica films containing Au nanoparticles were prepared by cosputtering. The kinetics of the growth of nanoparticles under 90 MeV Ni ion irradiation was studied by in situ x-ray diffraction. The growth of nanoparticles from 4 (for pristine) to 9 nm at a fluence of 1×1014 ions/cm2 was observed, in accordance with the observations made by transmission electron microscopy analyses. The present study shows that the ion irradiation is an effective tool for tailoring the size of nanoparticles. The results are discussed in the framework of thermal spike model. [ABSTRACT FROM AUTHOR]

The material exposed to energetic radiation may change its properties and performance. Ion beam irradiation is an established method to investigate radiation damage in materials. In the present study, SRIM code is employed as a tool to determine the electronic and nuclear energy losses and displacement per atom (DPA) associated with the damage induced in Al2O3 using 100 MeV Au ion. We have further studied the creation of 100 MeV Au ion induced molten zone along the ion track in Al2O3 in the framework of the thermal spike (TS) model. Using the in-elastic thermal spike model, elastic thermal spike model, and unified thermal spike model, the evolution of lattice temperature and latent track radius as a function of depth of Al2O3 for 100 MeV Au ion irradiation are investigated. The current results demonstrate that the latent track radius shows a U-shaped variation based on the combined effect of electronic stopping power and nuclear stopping power. In order to corroborate these results, an additional irradiation experiment was performed using swift heavy ion (SHI), 100 MeV Au ions with fluence 1×1014 ions/cm2 for Al2O3. To investigate the structural properties, surface morphology and to identify the defects in the samples, pristine and irradiated Al2O3 samples were characterized by Grazing Incident X-Ray Diffraction (GIXRD), Atomic Force Microscopy (AFM) and Photoluminescence Spectroscopy (PL). AFM study shows the increase in roughness after SHI irradiation. A decrease in intensity of PL spectra upon SHI irradiation indicates the formation of new defects and disordered structures in the material, which is quite in agreement with the theoretical results. [ABSTRACT FROM AUTHOR]

Abstract: Swift Heavy Ion (SHI) irradiation of the polymeric materials modifies their physico-chemical properties. Lexan polycarbonate films were irradiated with 95MeV oxygen ions to the fluences of 1010, 1011, 1012, 1013 and 2×1013 ions/cm2. Characterization of optical, chemical, electrical and structural modifications were carried out by UV–Vis spectroscopy, FTIR spectroscopy, Dielectric measurements and X-ray Diffraction. A shift in the optical absorption edge towards the red end of the spectrum was observed with the increase in ion fluence. The optical band gap (Eg ), calculated from the absorption edge of the UV–Vis spectra of these films in 200–800nm region varied from 4.12eV to 2.34eV for virgin and irradiated samples. The cluster size varied in a range of 69–215 carbon atoms per cluster. In FTIR spectra, appreciable modification in terms of breaking of the cleavaged C–O bond of carbonate and formation of phenolic O–H bond was observed on irradiation. A rapidly decreasing trend in dielectric constant is observed at lower frequencies. The dielectric constant increases with fluence. It is observed that the loss factor increases moderately with fluence and it may be due to scissoring of polymer chains, resulting in an increase in free radicals. A sharp increase in A.C. conductivity in pristine as well as in irradiated samples is observed with frequency and is attributed to scissoring of polymer chains. XRD analyses show significant change in crystallinity with fluence. A decrease of ∼9.02% in crystallite size of irradiated sample at the fluence of 2×1013 ions/cm2 is observed. [Copyright &y& Elsevier]

Abstract: The effects of 80MeV O6+ ions irradiation on polycarbonate (makrofol-DE) have been studied by different characterization techniques, viz. Fourier transform IR spectroscopy, Vickers’ microhardness tester, LCR meter, thermogravimetric analysis and differential scanning calorimetry. It is observed that the hardness of the film increases as fluence increases. This may be attributed to the cross-linking effects as corroborated with FTIR spectra. There is an exponential increase in conductivity with log frequency and the effect of irradiation is significant at higher fluences. The dielectric constant/loss is observed to change with the fluence. From the analysis of frequency dependence of dielectric constant it has been observed that the dielectric response in both pristine and irradiated samples obey Jonscher''s power law. The results are also explained on the basis of structural modification of polymer due to heavy ion irradiation. TGA/DSC thermograms indicate that there is no significant change in the stability of polymer and glass transition temperature up to the fluence of 2.4×1013 ions/cm2. [Copyright &y& Elsevier]

Abstract: Ferric oxalate was used as organometallics fillers in polyvinyl chloride (PVC) to form polymer matrix composite films at different concentration of filler. These films were irradiated with 80MeV O6+ ions at the fluences of 1×1011 and 1×1012 ions/cm2. The radiation induced modifications in dielectric properties, microhardness, surface morphology and surface roughness of polymer composite films have been investigated at different concentration (i.e. 5%, 10% and 15%) of filler. It was observed that hardness and electrical conductivity of the films increase with the concentration of the dispersed ferric oxalate and also with the fluence. From the analysis of frequency, f, dependence of dielectric constant, ɛ, it has been found that the dielectric response in both pristine and irradiated samples obey the Universal law given by ɛ ∝ f n−1. The dielectric constant/loss is observed to change significantly due to the irradiation. This suggests that ion beam irradiation promotes (i) the metal to polymer bonding and (ii) convert the polymeric structure into hydrogen depleted carbon network. Thus irradiation makes the polymer harder and more conductive. Atomic force microscopy (AFM) shows that average roughness (R a) of the irradiated films is lower than that of unirradiated films. Surface morphology of irradiated polymer composite films is observed to change. Scanning electron microscopy (SEM) results show that partial agglomeration of fillers in the polymer matrix. [Copyright &y& Elsevier]

Abstract: Swift heavy ion irradiation of P(VDF–HFP)–(PC+DEC)–LiClO4 gel polymer electrolyte system with 48 MeV Li3+ ions having five different fluences was investigated with a view to increase the Li+ ion diffusivity in the electrolyte. Irradiation with swift heavy ion (SHI) shows enhancement of conductivity at lower fluences and decrease in conductivity at higher fluences with respect to unirradiated polymer electrolyte films. Maximum room temperature (303 K) ionic conductivity is found to be 2.2×10−2 S/cm after irradiation with fluence of 1011 ions/cm2. This interesting result could be ascribed to the fluence-dependent change in porosity and to the fact that for a particular ion beam with a given energy higher fluence provides critical activation energy for cross-linking and crystallization to occur, which results in the decrease in ionic conductivity. The XRD results show decrease in the degree of crystallinity upon ion irradiation at low fluences (≤1011 ions/cm2) and increase in crystallinity at high fluences (>1011 ions/cm2). The scanning electron micrographs (SEM) exhibit increased porosity of the polymer electrolyte films after low fluence ion irradiation. [Copyright &y& Elsevier]

Abstract: Electronically conducting polymers are suitable electrode materials for high performance supercapacitors, for their high specific capacitance and high dc conductivity in the charged state. Supercapacitors and batteries are energy storage and conversion systems which satisfies the requirements of high specific power and energy in a complementary way. Ion beam {energy>1MeV} irradiation on the polymer is a novel technique to enhance or alter the properties like conductivity, density, chain length and solubility. Conducting polymer polypyrrole thin films doped with LiClO4 are synthesized electrochemically on ITO coated glass substrate and are irradiated with 160MeV Ni12+ ions at different fluence 5×1010, 5×1011 and 3×1012 ionscm−2. Dc conductivity measurement of the irradiated films showed 50–60% increase in conductivity which is may be due to increase of carrier concentration in the polymer film as observed in UV–Vis spectroscopy and other effects like cross-linking of polymer chain, bond breaking and creation of defects sites. X-ray diffractogram study shows that the degree of crystallinity of polypyrrole increases in SHI irradiation and is proportionate to ion fluence. The capacitance of the irradiated films is lowered but the capacitance of the supercapacitors with irradiated films showed enhanced stability compared to the devices with unirradiated films while characterized for cycle life up to 10,000cycles. [Copyright &y& Elsevier]

Abstract: Studies of irradiation effects in inorganic polymers and gels performed at CSNSM during the last ten years are summarized, and new results concerning the effect of the density of transferred energy on the precipitation kinetics of C, Si and metal clusters are presented. The precipitation yield as a function of the fluence of ions with different masses and energies was investigated by means of various spectroscopies, depending on the particles nature. The rates of gel to ceramics conversion and of C, Si and metal precipitation are determined by the density of electronic excitations and nuclear collisions have little effect. Particles formed by ion irradiation show a narrower size distribution and, consequently, more interesting characteristics for magnetic or optical applications than those formed in heat treated gels. [Copyright &y& Elsevier]

Swift heavy ion irradiation is carried out on sapphire (α-Al2O3) for controlled modification of its optical properties. Single crystals of α-Al2O3 (0 0 0 1) were irradiated at room temperature with 190 MeV Ag ions having Se∼23 keV/nm with fluences varying from 1011 to 1013 ions/cm2. The pristine as well as irradiated sapphires were characterized by photoluminescence, Fourier transform infrared spectra, optical absorption and X-ray diffraction techniques. The intensity of the PL peak observed at 2.1 eV increases with fluence. X-ray diffraction analysis shows that the surface starts getting amorphized after the fluence of 1 × 1012 ions/cm2. Structural disorder and generation of optically active defect centers (color centers) occur after a fluence of 1 × 1012 ions/cm2. At this fluence the defected zones start overlapping due to multiple ion impact giving rise to cumulative optical response of defects. [Copyright &y& Elsevier]

Single crystals of sapphire (α-Al2O3) were irradiated at room temperature with 100 and 190 MeV silver (Ag) ions from the 15 UD Pelletron at the Nuclear Science Centre, New Delhi. The pristine as well as irradiated sapphires are characterized by photoluminescence at room temperature under 2.8 eV blue excitation by a He–Cd laser, ultraviolet (UV)–Visible absorption and electron paramagnetic resonance (EPR). Photoluminescence studies show a peak at 2.2 eV, due to formation of a F22+ center. The intensity of this peak increases with fluence. A sudden increase in peak intensity has been observed after 5×1012 ions/cm2 where the defect zones started overlapping due to multiple ion impact. UV–Visible and EPR studies show formation of defects like F and F+ centers. [Copyright &y& Elsevier]

We report evolution of magnetic properties in zinc oxide (ZnO) single crystals and polycrystalline films induced by 500 KeV xenon ion (Xe 3+ ) irradiation. Room temperature ferromagnetism (RT-FM) behavior is observed in as deposited polycrystalline ZnO film and strength of FM enhances with ion fluence up to 2×10 17 ions/cm 2 and then decreases. However, RT-FM is not observed in ZnO single crystals even after irradiation with fluence up to 3.5×10 17 ions/cm 2 . The X-ray diffraction (XRD) and Raman measurements of ZnO single crystal reveal slightly disordered hexagonal wurtzite structure after irradiation. However, as deposited and irradiated polycrystalline ZnO films indicate excessive lattice defects in the wurtzite structure. X-ray photoelectron spectroscopy (XPS) reveals that Zn vacancy/interstitial defects are absent in all samples, although oxygen vacancy lattice defects are present. Density of oxygen vacancies is much higher in as deposited and irradiated polycrystalline ZnO films as compared to single crystals. This seems to be the determining factor for the presence and absence of RT-FM in ZnO films and single crystals respectively. The observed FM behavior in as deposited and irradiated polycrystalline ZnO films is explained on the basis of spin split impurity band formation from singly and doubly occupied oxygen vacancies which initiates d 0 ferromagnetism. [ABSTRACT FROM AUTHOR]

Abstract: Swift heavy ion (SHI) irradiation of polymeric materials results in the change of their free volume properties which have strong correlation with their macroscopic properties. The modification depends on the polymer and ion beam parameters, namely ion energy, fluence and ion species. Polystyrene films were irradiated with Li3+ ions of energy 50MeV from 15 UD Pelletron accelerators at Inter University Accelerator Centre (IUAC), New Delhi, India to the fluences of 1011, 1012 and 1013 ions/cm2. Nanosized free volume parameters in the polymer have been studied by positron annihilation lifetime spectroscopy (PALS) and Doppler broadening spectroscopy (DBS). From o-Ps lifetime τ 3, free volume hole radius, mean free volume of microvoids and fractional free volume are computed and modification in free volume with the fluence is studied. Free volume parameters change slowly with ion fluence with a decrease at the highest fluence of 1013 ions/cm2. The decrease in τ 3 and I 3 (reflecting the number of free volume holes) may be interpreted on the process of cross-linking. S parameter obtained from DBS measurements showed a minor decrease with increasing fluence. [Copyright &y& Elsevier]

Abstract: Modified chemical bath deposited (MCBD) bismuth sulphide (Bi2S3) thin films’ structural, optical and electrical properties are engineered separately by annealing in air for 1h at 300°C and irradiating with 100MeV Au swift heavy ions (SHI) at 5×1012 ions/cm2 fluence. It is observed that the band gap of the films gets red shifted after annealing and irradiation from pristine (as deposited) films. In addition, there is an increase in the grain size of the films due to both annealing and irradiation, leading to the decrease in resistivity and increase in thermoemf of the films. These results were explained in the light of thermal spike model. [Copyright &y& Elsevier]

Abstract: The present study compares structural and optical modifications of bare and silica (SiO2) coated ZnS quantum dots under swift heavy ion (SHI) irradiation. Bare and silica coated ZnS quantum dots were prepared following an inexpensive chemical route using polyvinyl alcohol (PVA) as the dielectric host matrix. X-ray diffraction (XRD) and transmission electron microscopy (TEM) study of the samples show the formation of almost spherical ZnS quantum dots. The UV–Vis absorption spectra reveal blue shift relative to bulk material in absorption energy while photoluminescence (PL) spectra suggests that surface state and near band edge emissions are dominating in case of bare and coated samples, respectively. Swift heavy ion irradiation of the samples was carried out with 160MeV Ni12+ ion beam with fluences 1012 to 1013 ions/cm2. Size enhancement of bare quantum dots after irradiation has been indicated in XRD and TEM analysis of the samples which has also been supported by optical absorption spectra. However similar investigations on irradiated coated quantum dots revealed little change in quantum dot size and emission. The present study thus shows that the coated ZnS quantum dots are stable upon SHI irradiation compared to the bare one. [Copyright &y& Elsevier]

Abstract: Alloy thin films of CuIn(S0.4Se0.6)2 material were deposited using the solution growth technique. The various deposition parameters such as pH of solution, time, concentration of ions and temperature have been optimized for the device grade thin films. The as-deposited films were annealed in a rapid thermal annealing (RTA) system at 450°C in air for 5min and subjected to high-energy Ag ion irradiations. Ag ion irradiation has been performed with an energy of 100MeV at a fluency of 5×1012 ions/cm2 on the thin film. The changes in optical and electrical properties that occurred before and after post-deposition treatments in CuIn(S0.4Se0.6)2 thin films were studied using X-ray diffraction (XRD) and AFM; increase in crystallinity was observed after annealing and irradiation. In addition, structural damages were observed in irradiated thin films. After annealing and irradiation, the surface roughness was seen to be increased. Decrease in resistivity was observed, which is consistent with the optical energy band gap. The results are explained by considering the high energy deposited due to the electronic energy loss upon irradiation, which modified the properties of the material. [Copyright &y& Elsevier]

Abstract: Polymer composites with different concentrations of organometallics (ferric oxalate) dispersed PMMA were prepared. PMMA was synthesized by solution polymerization technique. These films were irradiated with 120MeV Ni10+ ions in the fluence range 1011–5×1012 ions/cm2. The radiation induced modifications in dielectric properties, microhardness, structural changes and surface morphology of polymer composite films have been investigated at different concentrations of filler and ion-fluences. It was observed that electrical conductivity and hardness of the films increase with the concentration of the filler and also with the fluence. The dielectric constant (ɛ) obeys the Universal law given by ɛαfn −1. The dielectric constant/loss is observed to change significantly due to irradiation. This suggests that ion beam irradiation promotes the metal to polymer bonding and convert polymeric structure into hydrogen depleted carbon network. This makes the composites more conductive and harder. Surface morphology of the films has been studied using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The average surface roughness is observed to increase after irradiation as revealed by AFM studies. The SEM images show the blisters type of phenomenon on the surface due to ion beam irradiation. [Copyright &y& Elsevier]

Abstract: We report here the physico-chemical changes brought about by high electronic energy deposition of gold ions in HCl doped polyaniline (PANI) thin films. PANI thin films were synthesized by in situ polymerization technique. The as-synthesized PANI thin films of thickness 160nm were irradiated using Au7+ ion of 100MeV energy at different fluences, namely, 5×1011 ions/cm2 and 5×1012 ions/cm2, respectively. A significant change was seen after irradiation in electrical and photo conductivity, which may be related to increased carrier concentration, and structural modifications in the polymer film. In addition, the high electronic energy deposition showed other effects like cross-linking of polymer chains, bond breaking and creation of defect sites. AFM observations revealed mountainous type features in all (before and after irradiation) PANI samples. The average size (diameter) and density of such mountainous clusters were found to be related with the ion fluence. The AFM profiles also showed change in the surface roughness of the films with respect to irradiation, which is one of the peculiarity of the high electronic energy deposition technique. [Copyright &y& Elsevier]

Abstract: The formation of carbonaceous clusters in swift heavy ion irradiated polymer films has been investigated extensively. The information about these clusters may be obtained from Ultraviolet–Visible (UV−Vis) spectroscopic studies. The optical band gap (E g), calculated from the absorption edge of the UV spectra of these polymers can be correlated to the number of carbon atoms (N) in a cluster with the Tauc equation. Films of 50μm, 80μm, 125μm, 250μm thicknesses of PET, PTFE, PMMA and PES polymers, respectively, were irradiated with Si8+ ions of energy 100MeV to different fluences from 1010 to 1013 ions/cm2 at Pelletron accelerator, Inter University Accelerator Centre, New Delhi, India. UV–Vis absorption studies show that optical energy gap decreases with transferred energy density of the ion beams. The energy band gap (E g) values were computed from the absorption edge in the 200–800nm region with the Tauc relation. The values vary from 3.86 to 1.61eV for the pristine and various irradiated polymer samples. Maximum change of 40% is observed in PES irradiated to 1013 ions/cm2. The cluster size shows a variation in the range of 79–454carbon atoms per cluster for the polymers studied here. [Copyright &y& Elsevier]

Abstract: The effect of swift heavy ion irradiation on hydroxyapatite (HAp) ceramic – a bone mineral was investigated. The irradiation experiment was conducted using oxygen ions at energy of 100MeV with three different fluences of 1012, 1013, 1014 ions/cm2. The irradiated samples were characterized by glancing angle X-ray diffraction (GXRD), atomic force microscopy (AFM), dynamic light scattering (DLS), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). GXRD confirmed incomplete amorphisation of HAp with increase in fluence. There was considerable reduction in particle size on irradiation leading to nanosized HAp (upto 53nm). PL studies showed emission in the visible wavelength region. The irradiated samples exhibited better bioactivity than the pristine HAp. [Copyright &y& Elsevier]

Abstract: In an attempt to increase the Li ion diffusivity in gel polymer electrolytes, the effects of Li3+ ion irradiation in P(VDF–HFP)–(PC+DEC)–LiCF3SO3 electrolyte system, with five different fluences, is studied. Irradiation with swift heavy ions shows enhancement in conductivity at low fluences and decreased in conductivity at higher fluences with respect to pristine polymer electrolyte films. Maximum room temperature ionic conductivity after irradiation is found to be 2.6×10−3 S/cm. This interesting result could be attributed to the fact that, higher fluence provides critical activation energy for cross-linking and crystallization to occur, which results in decrease in ionic conductivity. XRD results show decrease in the degree of crystallinity upon ion irradiation at low fluences (⩽1011 ions/cm2) and increase in crystallinity at high fluences (>1011 ions/cm2). In FTIR spectra the absorption band intensities around 3025cm−1 and 2985cm−1 decrease upon irradiation with a fluence of 5×1010 ions/cm2 suggesting chain scission and increase upon irradiation with a fluence of 5×1012 ions/cm2 indicating cross-linking. FTIR analyses corroborate the conductivity and XRD results. [Copyright &y& Elsevier]

Abstract: Thermally evaporated ZnO thin films have been irradiated with 100MeV Au8+ ions at different fluence from 5×1011 ions/cm2 to 5×1013 ions/cm2. The optical and structural properties of the irradiated and pristine films were studied using Fourier transform infrared spectroscopy (FTIR), UV–visible absorption spectroscopy, photoluminescence (PL), atomic force microscopy (AFM) and XRD. FTIR results showed that for low fluence, the transmittance of the film decreased and increased again at higher fluence but Zn–O bond remains unaffected by irradiation. As revealed from the absorption spectra, absorption edge is not changed by the irradiation but the optical absorption is increased. The AFM study of the films implied that roughness decreased at low fluence values up to 5×1012 ions/cm2 and at higher fluences the roughness increased. [Copyright &y& Elsevier]

Abstract: Conducting polymer polypyrrole thin films doped with LiCF3SO3, [CH3(CH2)3]4NBF4 and [CH3(CH2)3]4NPF6 have been electrodeposited potentiodynamically on ITO coated glass substrate. The polymer films are irradiated with 160MeV Ni12+ ions at three different fluences of 5×1010, 5×1011 and 3×1012 ions cm−2. An increase in dc conductivity of polypyrrole films from ∼100S/cm to ∼170S/cm after irradiation with highest fluence is observed in four-probe measurement. X-ray diffractogram shows increase in the crystallinity of the polypyrrole films upon SHI irradiation, which goes on increasing with the increase in fluence. Absorption intensity increase in the higher wavelength region is observed in the UV–Vis spectra. The SEM studies show that the cauliflower like flaky microstructure of the surface of polypyrrole films turns globular upon SHI irradiation at fluence 5×1011 ions cm−2 and becomes smooth and dense at the highest fluence used. The cyclic voltammetry studies exhibit that the redox properties of the polypyrrole films do not change much on SHI irradiation. [Copyright &y& Elsevier]

Abstract: Conjugated polymers in the form of thin films play an important role in the field of materials science due to their interesting properties. Polymer thin films find extensive applications in the fabrication of devices, such as light emitting devices, rechargeable batteries, super capacitors, and are used as intermetallic dielectrics and EMI shieldings. Polymer thin films prepared by plasma-polymerization are highly cross-linked, pinhole free, and their permittivity lie in the ultra low k-regime. Electronic and photonic applications of plasma-polymerized thin films attracted the attention of various researchers. Modification of polymer thin films by swift heavy ions is well established and ion irradiation of polymers can induce irreversible changes in their structural, electrical, and optical properties. Polyaniline and polyfurfural thin films prepared by RF plasma-polymerization were irradiated with 92MeV silicon ions for various fluences of 1×1011 ionscm−2, 1×1012 ionscm−2, and 1×1013 ionscm−2. FTIR have been recorded on the pristine and silicon ion irradiated polymer thin films for structural evaluation. Photoluminescence (PL) spectra were recorded for RF plasma-polymerized thin film samples before and after irradiation. In this paper the effect of swift heavy ions on the structural and photoluminescence spectra of plasma-polymerized thin films are investigated. [Copyright &y& Elsevier]