Study on damage of Gd2O3-CeO2 under electronic energy loss: comparison between bulk-like and nanostructure.

To understand the physical phenomena responsible for radiation damage of the materials used in nuclear reactors, and thus study their operation life and/or efficiency, it is required to simulate the conditions by exposing the materials to energetic ions. Ceria (CeO2) has been proposed as one of the inert matrices for the transmutation of minor actinides in the futuristic inert matrix fuel (IMF) concept. The inert matrix should also contain burnable poison to compensate for the initial reactivity of fuel. In this context, gadolinium (Gd) is an excellent burnable poison with a high neutron absorption cross-section. In view of this, Gd2O3-CeO2 nano-powders were synthesized and sintered at 800 °C and 1300 °C to obtain different grain sizes and morphologies. FESEM and TEM were carried out to study the grain size of pristine pellets. The sintered pellets were irradiated with 80-MeV Ag ions (electronic energy loss (Se) regime) at room temperature to emulate the effect of fission fragments. For analysis of the effect of grain size on the irradiation-induced structural degradation at different fluences, GIXRD and Raman spectroscopy were performed. Significantly large damage has been observed for the smaller grain-sized samples (sintered at 800 °C) as compared to the large grain-sized sample (sintered at 1300 °C). Neither of the samples amorphized under the present experimental conditions as indicated by the presence of the Raman-active T2g mode (centred at 462 cm-1) and all the XRD peaks of fluorite cubic structure up to the highest fluence employed (1 × 1014 ions cm-2). X-ray photoelectron spectroscopy results demonstrate that Ce4+ to Ce3+ and vacancy-related isolated clusters are the main defects produced in the systems. The radiation tolerance behaviour of the samples is understood with the help of thermal spike simulation, which indicates higher transient lattice temperatures with longer duration in the smaller grain-sized sample upon irradiation. Gd-doped ceria thus possesses good radiation stability in the Se regime, indicating its potential for application in IMFs.

Physical properties and photocatalytic activity of Cr-doped TiO2 nanoparticles.

Nanocrystalline Ti1- x Crx O2 (0 ≤ x ≤ 0.20) samples were synthesised via acid-modified sol-gel process and characterised with various techniques, such as HRTEM, FESEM, Raman, XPS, DTA and VSM. The TEM image of TiO2 exhibits elongated nanoparticles with an average size of 10 nm. The HRTEM in combination with selected area electron diffraction (SAED) reveals the interplanar spacing and polycrystalline nature of the samples, respectively. FESEM micrographs divulge nonuniform morphologies and less aggregation of the particles in the doped sample. Raman spectra ensure the phase purity of the samples and a blue shift on Cr doping. X-ray photoelectron spectra (XPS) predict the chemical state of the elements and oxygen vacancies in the prepared samples. Room temperature magnetic measurements exhibit a significant variation in the magnetic parameters on Cr doping in TiO2 . The differential thermal analysis (DTA) shows the structural phase transition at ∼630°C. The photocatalytic performance is studied for the degradation of methylene blue (MB) dye under visible light irradiation. A higher photocatalytic efficiency is found for the 20% of Cr-doped TiO2 . These studies propose that the appropriate incorporation of Cr ions makes TiO2 very efficient for visible light-driven photocatalysts required for applications in wastewater treatment. LAY DESCRIPTION: In the present study, nanoparticles of TiO2 and Cr-doped TiO2 have been synthesised by a cost-effective acid-modified sol-gel process. The effect of Cr doping on the microstructure, thermal, magnetic and photocatalytic properties of TiO2 were explored in detail. The transmission electron microscopy (TEM) images exhibit the presence of elongated nanoparticles with an average size of 10 nm. Field emission scanning electron microscopy (FESEM) was used to study the surface morphology of the synthesised materials, which revealed nonuniform morphologies and less aggregation of the particles in the Cr-doped sample. Energy dispersive x-ray spectroscopy (EDS) confirms the elemental compositions with the appropriate stoichiometry of the elements. Raman spectra ensure the phase purity of the materials and also a blue shift with the incorporation of Cr ions in TiO2 . X-ray photoelectron spectra (XPS) predict the chemical state of the elements and oxygen vacancies in the prepared samples. The magnetic nature of all the synthesised samples was examined through the vibrating sample magnetometer (VSM) and revealed weak ferromagnetic behaviour of the samples. These results signify that the oxygen vacancies and defects play a crucial role in developing the ferromagnetic nature of oxide semiconductors. The differential thermal analysis (DTA) shows the structural phase transition at ∼630°C. The photocatalytic performance of the prepared samples was studied for the degradation of methylene blue (MB) dye under irradiation of visible light. A higher photocatalytic efficiency was found for the 20% of Cr-doped TiO2 . These studies propose that the appropriate incorporation of Cr ions makes TiO2 very efficient for visible light-driven photocatalysts required for applications in wastewater treatment.

Electronic structure and defect-induced luminescence study of phase-stabilized t-ZrO2 nanocrystals.

Luminescent tetragonal-ZrO2 (t-ZrO2 ) nanocrystals were synthesized using an optimized combustion method without post-synthesis annealing and characterized using X-ray diffraction, electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, UV-Vis. spectroscopy, photoluminescence spectroscopy, thermoluminescence (TL), and vibrating sample magnetometry. The as-synthesized t-ZrO2 nanocrystals have a bandgap of 4.65 eV and exhibit defect-assisted blue emission (Commission Internationale de I'Elcairage coordinates 0.2294, 0.1984) when excited at 270 nm. The defect states were qualitatively and quantitatively analyzed using TL after irradiating nanocrystals with γ- and UV radiations at various doses. The TL glow curves show intense emission in the high-temperature region from 523 to 673 K for both UV- and γ-irradiated samples; however, another less-intense TL peak was also observed in the low-temperature region from 333 to 453 K with γ irradiation at higher doses, indicating the formation of shallow trapping states. The activation energies, frequency factor, and order of kinetics were estimated using the computerized glow curve deconvolution method for the shallow and deep traps for γ- and UV-irradiated samples. The present study shows that phase-stabilized t-ZrO2 nanocrystals are potential candidates for luminescence-based applications.

Luminescence properties of Ce-doped ZrO2 phosphors synthesized by combustion method.

Zr1-x Cex O2 with x = 0.005, 0.01, 0.02, and 0.03 samples were synthesized using a combustion technique. The X-ray diffraction results revealed that Ce-doped ZrO2 nanoparticles were in a monoclinic structure up to 1 mol% Ce concentration. The increase in the Ce concentration caused more distortion in the monoclinic structure of zirconia. The samples showed a mixed phase (monoclinic + tetragonal) beyond 1 mol% Ce content. The crystallite size (D) and strain (ε) were calculated from the Williamson-Hall equation. The D decreased from 25 ± 1 to 20 ± 1 nm and ε increased from 0.03 to 0.28% with an increase in Ce concentration. Photoluminescence (PL) spectra of Zr1-x Cex O2 showed emission in the blue region under an excitation wavelength of 290 nm. Zr0.995 Ce0.005 O2 showed the highest PL intensity with an average lifetime of 0.93 µs, and the PL intensity decreased with the increase in the Ce concentration. Thermoluminescence (TL) glow curves of Zr1-x Cex O2 were measured after gamma irradiation (500 Gy) with a heating rate of 5 K s-1 . The TL curve of Zr0.995 Ce0.005 O2 showed two prominent peaks at 412 K (peak 1) and 600 K (peak 2). The first TL glow peak was shifted towards a higher temperature at 440 K above 1 mol% Ce concentration. Repetitive TL measurements on the same aliquot exhibited excellent repeatability. Kinetic parameters associated with the TL peaks were calculated using the curve fitting method. Peak 1 followed non-first-order kinetics. The value of the activation energy of the 440 K peak was found to be 0.95 ± 0.01 eV for Zr0.99 Ce0.01 O2 . These findings showed that Zr1-x Cex O2 might be used in lighting and radiation dosimeter applications.

120 MeV swift Au9+ion induced phase transition in ZrO2: monoclinic to tetragonal and cubic to tetragonal structure.

This study reports the effect of 120 MeV swift Au9+ion irradiation on the structures of monoclinic, tetragonal and cubic ZrO2, probed through x-ray diffraction (XRD) and Raman spectroscopy. Three phases of ZrO2were prepared using the solution combustion method. The tetragonal and cubic phases of ZrO2were stabilized at room temperature by adding 6% and 10% of yttrium ions, respectively. Both the XRD and Raman results confirm the partial phase transition from monoclinic to tetragonal, which was approximately 74%. Tetragonal ZrO2is stable under 120 MeV Au9+ion irradiation. Interestingly, a phase transition from cubic to tetragonal ZrO2was observed under 120 MeV Au9+ion irradiation. The roles of transient temperature, defects and strain in the lattice induced by swift heavy ions are discussed. This study reveals the structural stability of different phases of ZrO2under swift heavy ion irradiation and should be helpful in choosing potential hosts for various applications such as inert fuel matrix inside the core of nuclear reactors, oxygen sensors and accelerators, and radiation shielding.

Gas sensing response of ion beam irradiated Ga-doped ZnO thin films.

The ion beam induced modified gallium doped ZnO thin films are studied for their gas sensing applications. The Ag9+ and Si6+ irradiated gallium doped zinc oxide thin films were exposed to various concentrations of ethanol and acetone gas for gas sensing applications. The Ag9+ ion irradiated Ga-doped ZnO thin was optimized at different operating temperature. It was observed that gas sensing response for both ethanol and acetone gas increases with increasing Ag9+ ion fluence. This indicates that the swift heavy ions have improved the sensitivity of Ga-doled ZnO thin film by reducing the particle size. The Si6+ ion irradiated Ga-doped ZnO thin films were also exposed to ethanol and acetone gas for gas sensing applications. In comparison to Ag9+ ion irradiated thin film, the film irradiated with Si6+ ion beam exhibits a greater sensing response to both ethanol and acetone gas.

Signature of strong localization and crossover conduction processes in doped ZnO thin films: synergetic effect of doping fraction and dense electronic excitations.

GaxZn1-xO thin films with varying Ga fraction within the solubility limit were irradiated with high-energy heavy ions to induce electronic excitations. The films show good transmittance in the visible region and a reduction of about 20% in transmittance was observed for irradiated films at higher ion fluences. The Urbach energy was estimated and showed an augmenting response upon increase in doping fraction and ion irradiation, this divulges an enhancement of localized states in the bandgap or disorder in the films. The evolution of such localized states plays a vital role in charge transport and thus the temperature dependent electrical conductivity of irradiated thin films was studied to elucidate the dominant conduction mechanisms. The detailed analysis unfolds that in the high-temperature regime (180 K

Annealing Effects on Gas Sensing Response of Ga-Doped ZnO Thin Films.

The high thermal conductivity, high electron mobility, the direct wide band gap, and large exciton binding energy of zinc oxide (ZnO) make it appropriate for a wide range of device applications like light-emitting diodes, photodetectors, laser diodes, transparent thin-film transistors, and so forth. Among the semiconductor metal oxides, zinc oxide (ZnO) is one of the most commonly used gas-sensing materials. The gas sensor made of nanocomposite ZnO and Ga-doped ZnO (ZnO:Ga) thin films was developed by the sol-gel spin coating method. The gas sensitivity of gallium-doped ZnO thin films annealed at 400, 700, and 900 °C was studied for ethanol and acetone gases. The variation of electrical resistance of gallium-doped ZnO thin films with exposure of ethanol and acetone vapors at different concentrations was estimated. Ga:ZnO thin films annealed at 700 °C show the highest sensitivity and shortest response and recovery time for both ethanol and acetone gases. This study reveals that the 5 at. % Ga-doped ZnO thin film annealed at 700 °C has the best sensing property in comparison to the film annealed at 400 and 900 °C. The sensing response of ZnO:Ga thin films was found higher for ethanol gas in comparison to acetone gas.

Defect-induced photoluminescence from gallium-doped zinc oxide thin films: influence of doping and energetic ion irradiation.

Herein, we present defect-induced photoluminescence behavior of Ga-doped ZnO (GZO) thin films with varying doping (Ga) concentrations and energetic ion irradiation. The Ga-doped ZnO thin films were prepared by a sol-gel spin-coating method. Micro-photoluminescence (µ-PL) was carried out to investigate the defect-related emission with the variation of doping concentration and ion irradiation. The PL spectra revealed that all films showed near-band-edge (NBE) emission along with a broad visible emission band, consisting of violet, blue, green, and yellow emission bands. The intensity of these emission bands was found to be strongly dependent on the Ga doping concentration and ion irradiation. Interestingly, a pronounced violet emission band around 2.99 eV (415 nm) was observed for the Ga-doped ZnO thin films with high Ga doping concentration, whereas an irradiated film with high ion fluence exhibited a strong green emission around 2.39 eV (519 nm); however, we concluded that the violet emission might have originated from zinc interstitial defects (Zni), and the concentration of Zni increased with the increasing doping concentration. The green emission is ascribed to the oxygen vacancies (VO), and the concentration of the VO defects increases with the increasing ion fluence. Thus, the µ-PL spectra of the irradiated films with emission dominating in the blue and green regions could be attributed to the formation of extended defects such as clusters and ionizing centers of Zni and VO. Herein, an in-depth understanding of the variation in defects related to the emission bands from these films is reported and correlated with the transport properties of these films for their possible optoelectronic applications.

Enhanced room temperature ferromagnetism and green photoluminescence in Cu doped ZnO thin film synthesised by neutral beam sputtering.

The Cu (3 to 15 at%) is incorporated into ZnO thin film by atomic beam co-sputtering has been investigated for enhancement in room temperature ferromagnetism and green photo-luminance. These Cu-ZnO thin films examined with Raman spectroscopy, X-Ray Diffraction (XRD), UV-Visible spectroscopy, Hall measurement, magnetic force microscopy (MFM) and magnetic hysteresis. Raman spectroscopy, XRD confirms wurtzite structure and improvement in the crystallinity of ZnO upto 7% Cu. Further increase in Cu concentration results in growth in Cu nanoparticles. On increasing Cu concentration, there is decrement in transparency and increase in band gap with increase in n-type carrier concentration as confirmed from UV-Visible and Hall measurement studies. Magnetic measurement exhibited unique feature of room temperature ferromagnetic ordering in undoped and doped sample upto 3% Cu. The enhancement in magnetic moment as well as green emission in photoluminescence response with increase in Cu doping indicates that generation of large defects in ZnO by Cu doping, which can be attributed to combined effect of the presence of oxygen vacancies and/or structural inhomogeneity as well as formation of bound magnetic polarons. Importantly, synthesised Cu doped ZnO thin films can be used as spin LEDs and switchable spin-laser diodes.

Fabrication of plasmonic dye-sensitized solar cells using ion-implanted photoanodes.

Plasmonic dye-sensitized solar cells containing metal nanoparticles suffer from stability issues due to their miscibility with liquid iodine-based electrolytes. To resolve the stability issue, herein, an ion implantation technique was explored to implant metal nanoparticles inside TiO2, which protected these nanoparticles with a thin coverage of TiO2 melt and maintained the localized surface plasmon resonance oscillations of the metal nanoparticles to efficiently enhance their light absorption and make them corrosion resistant. Herein, Au nanoparticles were implanted into the TiO2 matrix up to the penetration depth of 22 nm, and their influence on the structural and optical properties of TiO2 was studied. Moreover, plasmonic dye-sensitized solar cells were fabricated using N719 dye-loaded Au-implanted TiO2 photoanodes, and their power conversion efficiency was found to be 44.7% higher than that of the unimplanted TiO2-based dye-sensitized solar cells due to the enhanced light absorption of the dye molecules in the vicinity of the localized surface plasmon resonance of Au as well as the efficient electron charge transport at the TiO2@Au@N719/electrolyte interface.

Highly selective and reversible NO2 gas sensor using vertically aligned MoS2 flake networks.

We demonstrate a highly selective and reversible NO2 resistive gas sensor using vertically aligned MoS2 (VA-MoS2) flake networks. We synthesized horizontally and vertically aligned MoS2 flakes on SiO2/Si substrate using a kinetically controlled rapid growth CVD process. Uniformly interconnected MoS2 flakes and their orientation were confirmed by scanning electron microscopy, x-ray diffraction, Raman spectroscopy and x-ray photoelectron spectroscopy. The VA-MoS2 gas sensor showed two times higher response to NO2 compared to horizontally aligned MoS2 at room temperature. Moreover, the sensors exhibited a dramatically improved complete recovery upon NO2 exposure at its low optimum operating temperatures (100 °C). In addition, the sensing performance of the sensors was investigated with exposure to various gases such as NH3, CO2, H2, CH4 and H2S. It was observed that high response to gas directly correlates with the strong interaction of gas molecules on edge sites of the VA-MoS2. The VA-MoS2 gas sensor exhibited high response with good reversibility and selectivity towards NO2 as a result of the high aspect ratio as well as high adsorption energy on exposed edge sites.

Facile Synthesis of Semiconducting Ultrathin Layer of Molybdenum Disulfide.

In this paper, we have reported a simple and efficient method for the synthesis of uniform, highly conducting single or few layer molybdenum disulfide (MoS2) on large scale. Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM) have been used for the confirmation of mono or few layered nature of the as-synthesized MoS2 sheets. X-ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD) and Raman Spectroscopy have also been used to study the elemental, phase, and molecular composition of the sample. Optical properties of as-synthesized sample have been probed by measuring absorption and photoluminescence spectra which also compliment the formation of mono and few layers MoS2 Current-voltage (I-V ) characteristics of as-synthesized sample in the pellet form reveal that MoS2 sheets have an ohmic character and found to be highly conducting. Besides characterizing the as-synthesized sample, we have also proposed the mechanism and factors which play a decisive role in formation of high quality MoS2 sheets.

Correlations of charge neutrality level with electronic structure and p-d hybridization.

The formation of charge neutrality level (CNL) in highly conducting Cadmium oxide (CdO) thin films is demonstarted by the observed variation in the band gap upon annealing and doping. It may be explained by the observation that Tin (Sn) doping breaks the perfect periodicity of CdO cubic crystal structure and creates virtual gap states (ViGS). The level of local CNL resides at the branch point of ViGS, making the energy at which native defect's character changes from predominantly donor-like below CNL to predominantly acceptor-like above the CNL and a schematic band diagram is developed to substantiate the same. Further investigations using soft x-ray absorption spectroscopy (SXAS) at Oxygen and Cadmium edges show the reduction of Sn4+ to Sn2+. The analysis of the spectral features has revealed an evidence of p-d interaction between O 2p and Cd 4d orbitals that pushes the valence band minima at higher energies which is symmetry forbidden at г point and causing a positive valance band dispersion away from the zone centre in the г ~ L, K direction. Thus, origin of the CNL is attributed to the high density of the Oxygen vacancies as confirmed by the change in the local electronic structure and p-d hybridization of orbitals.

Electronic structure modification and Fermi level shifting in niobium-doped anatase titanium dioxide thin films: a comparative study of NEXAFS, work function and stiffening of phonons.

The electronic structure and tuning of work function (WF) by electronic excitations (EEs) induced by swift heavy ions (SHIs) in anatase niobium-doped titanium dioxide (NTO) thin films is reported. The densities of EEs were varied using 80 MeV O, 130 MeV Ni and 120 MeV Ag ions for irradiation. The EE-induced modifications in electronic structure were studied by O K-edge and Ti L3,2 edge absorption spectra using near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The reduction of hybridized O 2p and Ti 3d unoccupied states in the conduction band with a decrease in energy of the crystal field strength of ∼ 480 meV and the correlated effect on the decrease in the WF value of ∼ 520 meV upon increasing the total energy deposition in the lattice are evident from the study of NEXAFS and scanning Kelvin probe microscopy (SKPM), respectively. The observed stiffening in the low frequency Raman mode (LFRM) of ∼ 9 cm(-1) further validates the electronic structure modification under the influence of EE-induced strain in TiO6 octahedra. The reduction of hybridized valence states, stiffening behavior of LFRM and decrease in WF by nano-crystallization followed by amorphization and defects in NTO lattice are explained in terms of continuous, discontinuous amorphous ion tracks containing intestinally created defects and non-stoichiometry in the lattice. These studies are very appropriate for better insights of electronic structure modification during phase transformation and controlled Fermi level shifting, which plays a crucial role in controlling the charge carrier injection efficiency in opto-electronic applications and also provides a deeper understanding of the involved physical processes.

Synthesis characterization and luminescence studies of gamma irradiated nanocrystalline yttrium oxide.

Nanocrystalline Y2O3 is synthesized by solution combustion technique using urea and glycine as fuels. X-ray diffraction (XRD) pattern of as prepared sample shows amorphous nature while annealed samples show cubic nature. The average crystallite size is calculated using Scherrer's formula and is found to be in the range 14-30 nm for samples synthesized using urea and 15-20 nm for samples synthesized using glycine respectively. Field emission scanning electron microscopy (FE-SEM) image of 1173 K annealed Y2O3 samples show well separated spherical shape particles and the average particle size is found to be in the range 28-35 nm. Fourier transformed infrared (FTIR) and Raman spectroscopy reveals a stretching of Y-O bond. Electron spin resonance (ESR) shows V(-) center, O2(-) and Y(2+) defects. A broad photoluminescence (PL) emission with peak at ~386nm is observed when the sample is excited with 252 nm. Thermoluminescence (TL) properties of γ-irradiated Y2O3 nanopowder are studied at a heating rate of 5 K s(-1). The samples prepared by using urea show a prominent and well resolved peak at ~383 K and a weak one at ~570 K. It is also found that TL glow peak intensity (I(m1)) at ~383 K increases with increase in γ-dose up to ~6.0 kGy and then decreases with increase in dose. However, glycine used Y2O3 shows a prominent TL glow with peaks at 396 K and 590 K. Among the fuels, urea used Y2O3 shows simple and well resolved TL glows. This might be due to fuel and hence particle size effect. The kinetic parameters are calculated by Chen's glow curve peak shape method and results are discussed in detail.

Purification/annealing of graphene with 100-MeV Ag ion irradiation.

Studies on interaction of graphene with radiation are important because of nanolithographic processes in graphene-based electronic devices and for space applications. Since the electronic properties of graphene are highly sensitive to the defects and number of layers in graphene sample, it is desirable to develop tools to engineer these two parameters. We report swift heavy ion (SHI) irradiation-induced annealing and purification effects in graphene films, similar to that observed in our studies on fullerenes and carbon nanotubes (CNTs). Raman studies after irradiation with 100-MeV Ag ions (fluences from 3 × 10(10) to 1 × 10(14) ions/cm(2)) show that the disorder parameter α, defined by I D/I G ratio, decreases at lower fluences but increases at higher fluences beyond 1 × 10(12) ions/cm(2). This indicates that SHI induces annealing effects at lower fluences. We also observe that the number of graphene layers is reduced at fluences higher than 1 × 10(13) ions/cm(2). Using inelastic thermal spike model calculations, we estimate a radius of 2.6 nm for ion track core surrounded by a halo extending up to 11.6 nm. The transient temperature above the melting point in the track core results in damage, whereas lower temperature in the track halo is responsible for annealing. The results suggest that SHI irradiation fluence may be used as one of the tools for defect annealing and manipulation of the number of graphene layers. PACS: 60.80.x; 81.05.ue.

Modification of optical and electrical properties of zinc oxide-coated porous silicon nanostructures induced by swift heavy ion.

Morphological and optical characteristics of radio frequency-sputtered zinc aluminum oxide over porous silicon (PS) substrates were studied before and after irradiating composite films with 130 MeV of nickel ions at different fluences varying from 1 × 1012 to 3 × 1013 ions/cm2. The effect of irradiation on the composite structure was investigated by scanning electron microscopy, X-ray diffraction (XRD), photoluminescence (PL), and cathodoluminescence spectroscopy. Current-voltage characteristics of ZnO-PS heterojunctions were also measured. As compared to the granular crystallites of zinc oxide layer, Al-doped zinc oxide (ZnO) layer showed a flaky structure. The PL spectrum of the pristine composite structure consists of the emission from the ZnO layer as well as the near-infrared emission from the PS substrate. Due to an increase in the number of deep-level defects, possibly oxygen vacancies after swift ion irradiation, PS-Al-doped ZnO nanocomposites formed with high-porosity PS are shown to demonstrate a broadening in the PL emission band, leading to the white light emission. The broadening effect is found to increase with an increase in the ion fluence and porosity. XRD study revealed the relative resistance of the film against the irradiation, i.e., the irradiation of the structure failed to completely amorphize the structure, suggesting its possible application in optoelectronics and sensing applications under harsh radiation conditions.

Swift heavy ion induced structural, iono and photoluminescence properties of ß-CaSiO3:Dy³âº nanophosphor.

CaSiO(3):Dy(3+) (1-5 mol%) nanophosphors have been prepared by a low temperature solution combustion method. The structural and luminescence (ionoluminescence; IL and photoluminescence; PL) studies have been carried out for pristine and ion irradiated samples. The XRD patterns of pristine sample show a prominent peak at (320) for the monoclinic structure of ß-CaSiO(3). Upon ion irradiation, the intensity of the prominent peak is decreased at the fluence of 7.81 × 10(12)ions cm(-2) and at higher fluence of 15.62 × 10(12)ions cm(-2), the prominent peak completely vanishes. The decrease in peak intensity might be due to the stress induced point defects. On-line IL and in situ PL studies have been carried out on pelletized samples bombarded with 100 MeV Si(7+) ions with fluences in the range (7.81-15.62)×10(12)ions cm(-2). The characteristic emission peaks at 481,574, 664 and 754 nm recorded in both IL and PL are attributed to the luminescence centers activated by Dy(3+) ions. It is found that IL and PL emissions intensity decreases with increase in Si(7+) ion fluence. The decrease in intensity can be due to the destruction of Si-O-Si and O-Si-O type species present on the surface of the sample. FTIR studies also confirm the Si-O-Si and O-Si-O type species observed to be sensitive for swift heavy ion (SHI) irradiated samples.

Ion beam induced amorphization and bond breaking in Zn2SiO4:Eu3+ nanocrystalline phosphor.

This paper reports on the ionoluminescence (IL) of Zn(2)SiO(4):Eu(3+) nanophosphors bombarded with 100 MeV Si(7+) ions with fluences in the range (3.91-21.48)×10(12) ions cm(-2). The prominent IL emission peaks recorded at 580, 590, 612, 650 and 705 nm are attributed to the luminescence centers activated by Eu(3+) ions. It is observed that IL intensity decreases and saturates with increase of Si(7+) ion fluence. Fourier transform infrared (FT-IR) studies confirm surface/bulk amorphization for a fluence of (3.91-21.48)×10(13) ions cm(-2). These results show degradation of SiO (2ν(3)) bonds present on the surface of the sample and/or due to lattice disorder produced by dense electronic excitation under heavy ion irradiation. These results are discussed in detail.