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1.
Swift heavy ion irradiation has been successfully used to modify the structural, optical, and gas sensing properties of SnO2 thin films. The SnO2 thin films prepared by sol-gel process were irradiated with 75 MeV Ni+ beam at fluences ranging from 1 × 1011 ion/cm2 to 3 × 1013 ion/cm2. Structural characterization with glancing angle X-ray diffraction shows an enhancement of crystallinity and systematic change of stress in the SnO2 lattice up to a threshold value of 1 × 1013 ions/cm2, but decrease in crystallinity at highest fluence of 3 × 1013 ions/cm2. Microstructure investigation of the irradiated films by transmission electron microscopy supports the XRD observations. Optical properties studied by absorption and PL spectroscopies reveal a red shift of the band gap from 3.75 eV to 3.1 eV, and a broad yellow luminescence, respectively, with increase in ion fluence. Gas response of the irradiated SnO2 films shows increase of resistance on exposure to ammonia (NH3), indicating p-type conductivity resulting from ion irradiation.  相似文献   

2.
In order to understand the properties of ion tracks and the microstructural evolution under accumulation of ion tracks in UO2, 100 MeV Zr10+ and 210 MeV Xe14+ ions irradiation examinations have been done at a tandem accelerator facility of JAEA-Tokai, and it has been observed the microstructure by means of a transmission electron microscope (TEM) and a scanning electron microscope (SEM) in CRIEPI.Comparison of the diameter of ion tracks between UO2 and CeO2 under irradiation with 100 MeV Zr10+ and 210 MeV Xe14+ ions at room temperature clarify that the sensitivity on high density electronic excitation of UO2 is much less than that of CeO2. By the cross-sectional observation of UO2 under irradiation with 210 MeV Xe14+ ions at 300 °C, elliptical changes of fabricated pores that exist till ∼6 μm depth and the formation of dislocations have been observed in the ion fluence over 5 × 1014 ions/cm2. The drastic changes of surface morphology and inner structure in UO2 indicate that the overlapping of ion tracks will cause the point defects, enhance the diffusion of point defects and dislocations, and form the sub-grains at relatively low temperature.  相似文献   

3.
The SHI irradiation induced effects on magnetic properties of MgB2 thin films are reported. The films having thickness 300-400 nm, prepared by hybrid physical chemical vapor deposition (HPCVD) were irradiated by 200 MeV Au ion beam (S∼ 23 keV/nm) at the fluence 1 × 1012 ion/cm2. Interestingly, increase in the transition temperature Tc from 35.1 K to 36 K resulted after irradiation. Substantial enhancement of critical current density after irradiation was also observed because of the pinning provided by the defects created due to irradiation. The change in surface morphology due to irradiation is also studied.  相似文献   

4.
The sputtering and surface state evolution of Bi/Si targets under oblique incidence of 120 keV Ar+ ions have been investigated over the range of incidence angles 0° ? θi ? 60°. Increasing erosion of irradiated samples (whose surface thickness reduced by ∼3% at normal incidence up to ∼8% at θ = 60°) and their surface smoothing with reducing grain sizing were pointed out using Rutherford backscattering (RBS), atomic force (AFM) and X-ray diffraction (XRD) techniques. Measured sputtering yield data versus θi with fixed ion fluence to ∼1.5 × 1015 cm−2 are well described by Yamamura et al. semi-empirical formula and Monte Carlo (MC) simulation using the SRIM-2008 computer code. The observed increase in sputter yield versus incidence angle is closely correlated to Bi surface topography and crystalline structure changes under ion irradiation.  相似文献   

5.
We have studied electronic and atomic structure modifications of Cu3N films under 100 keV Ne and 100 MeV Xe ion impact. Cu3N films were prepared on R(11-2 surface)-cut-Al2O3 substrates at 250 °C by using a RF-magnetron sputter deposition method. X-ray diffraction (XRD) shows that unirradiated films are polycrystalline with (1 0 0) orientation of cubic structure. We find that the electrical resistivity (∼10 Ω cm before ion impact) decreases by more than two orders of magnitude after the Ne impact at a fluence of ∼1013 cm−2, where no Cu phase separation is observed. For further ion impact (larger than ∼1015 cm−2), XRD shows Cu diffraction peak (Cu phase separation), and the resistivity decreases further (three orders of magnitude). Decomposition and phase separation are discussed based on these results, as well as temperature dependence of the resistivity and optical absorption. The results of 100 MeV Xe ion impact are compared with those of Ne ion impact.  相似文献   

6.
Micro-indentation creep tests were performed at 25 °C on radial-normal samples cut from Zr-2.5Nb CANDU pressure tube material in both the as-fabricated condition and after irradiation with 8.5 MeV Zr+ ions. The average indentation stress, and hence the yield stress, was found to increase with decreasing indentation depth and with increasing levels of ion irradiation. The activation energy of the indentation creep rate and hence the, activation energy of the obstacles that limit the rate of dislocation glide, was independent of indentation depth but increased from ΔG0 = 0.185 to 0.215 μb3 with increasing ion irradiation damage. The magnitude of the activation energy indicates that ion irradiation introduces a new type of obstacle into the microstructure which reduces the low temperature indentation creep rate of Zr-2.5Nb pressure tubes. This is supported by TEM images showing that Zr+ ion irradiation produces small, nanometer size, dislocation loops which act as obstacles to dislocation glide and thus influence both the yield stress and the activation energy of the low-temperature thermal creep of Zr-2.5Nb pressure tube material. These findings suggest that neutron irradiation will have similar effect upon yield stress and low-temperature thermal creep as the Zr+ ion irradiation since both create similar crystallographic defects in Zr-2.5Nb pressure tubes.  相似文献   

7.
The effect of swift heavy ion (72.5 MeV 58Ni6+) irradiation on Au/n-GaAs Schottky barrier characteristics is studied using in situ current-voltage measurements. Diode parameters are found to vary as a function of ion irradiation fluence. The Schottky barrier height (SBH) is found to be 0.55(±0.01) eV for the as deposited diode, which decreases with ion irradiation fluence. The SBH decreases to a value of 0.49(±0.01) eV at the highest ion irradiation fluence of 5 × 1013 ions cm−2. The ideality factor is found to be 2.48 for unirradiated diode, and it increases with irradiation to a value of 4.63 at the highest fluence. The modification in Schottky barrier characteristics is discussed considering the energy loss mechanism of swift heavy ion at the metal-semiconductor interface.  相似文献   

8.
Characterization of ion induced modifications in the physical, chemical and structural properties of polymethylmethacrylate (PMMA) polymer induced by 145 MeV Ne6+ ions has been carried out by FTIR, UV-Visible, Differential scanning calorimetry (DSC) and X-ray diffraction. Heavy ion irradiation was carried out under a vacuum of ∼10−6 torr at Variable Energy Cyclotron Centre, Kolkata, India using a low beam current (∼15 nA). Ion fluences of 1010, 1011, 1012, 1013 ions/cm2 were used. The optical band gap (Eg), calculated from the absorption edge of the UV-Vis spectra of these films in 200-800 nm region varied from 2.167 eV to 1.512 eV for virgin and irradiated samples. In FTIR spectra appreciable changes have been observed after irradiation, indicating the molecular fragmentation, cross-linking, formation of unsaturated groups and free radicals. DSC thermograms give information about the thermal stability and type of thermal reactions (exothermic/endothermic) on the application of heat to the polymer. XRD analyses show slight shift of peak position and significant changes in peak intensity. XRD results show a decrease of ∼4.12% in crystallite size of irradiated sample at the higher fluence of 1012 ions/cm2.  相似文献   

9.
Wurtzite GaN epilayers irradiated at room temperature with 308 MeV 129Xe35+ ions to fluences of 1 × 1013 and 3 × 1013 cm−2 have been studied by contact mode atomic force microscopy (AFM), high-resolution X-ray diffraction (HRXRD), micro-Raman scattering and photoluminescence (PL) spectroscopy. The AFM images showed that the surface of GaN films was etched efficiently due to the Xe ion irradiation. The initial step-terrace structure on GaN surface was eliminated completely at a fluence of 3 × 1013 cm−2. HRXRD and Raman results indicated that the Xe ion irradiation led to a homogenous lattice expansion throughout the entire ∼3 μm-thick GaN films. The lattice expansion as well as the biaxial compressive stress of the films was increasing with the increase of ion fluence. PL measurements showed that a dominant yellow luminescence band in the as-grown GaN films disappeared, but a blue and a green luminescence bands were produced after irradiation. Based on these results, the strong electronic excitation effect of 308 MeV Xe ions in GaN is discussed.  相似文献   

10.
In this report, we present preliminary ion irradiation experiments performed using a new medium energy (up to ∼20 MeV), high temperature ion irradiation capability that we developed at Los Alamos National Laboratory. Details of ion fluence and irradiation temperature (including ion beam heating) control, measurements procedure and accuracy are described. In particular, we investigated irradiation-induced atomic intermixing in a layered structure composed of MgO and HfO2 thin films deposited on a sapphire substrate. This multi-layered structure represents a dispersion nuclear fuel form surrogate. To simulate a nuclear reactor environment, we performed ion irradiation using 10 MeV Au ions to a fluence of 5 × 1015 cm−2 at a substrate temperature of 1000 °C. The degree of atomic intermixing was assessed from depth profiles of Mg, Hf, and Al atoms, which were obtained using Rutherford backscattering spectrometry. We found considerable interlayer mixing for sample regions in close proximity to the sapphire substrate.  相似文献   

11.
WO3 films were prepared by sol-gel deposition process on Corning 2947, microscope slide substrates. The effects of irradiation on the solar parameters of WO3 films were investigated between ∼1 and 21 kGy absorbed dose by Co-60 radioisotope. Three characteristic optical density bands explained the causes of color due to the absorption of sunlight at induced color centers of the transition elements such as W, Fe and Zr after the gamma irradiation. These bands lead to variations on the solar control in terms of shading coefficient. The absorbed dose plays a key role in the improvement of the shading coefficient dramatically, hence the solar parameters changed considerably depending on the induced color centers of the transition elements and the variations of the grains and the void sizes of the film. The results of the solar parameters of irradiated WO3 films were compared with the unirradiated WO3 films and uncoated corning in the solar range.  相似文献   

12.
The total secondary electron emission yields, γT, induced by impact of the fast ions Neq+ (q = 2-8) and Arq+ (q = 3-12) on Si and Neq+ (q = 2-8) on W targets have been measured. It was observed that for a given impact energy, γT increases with the charge of projectile ion. By plotting γT as a function of the total potential energy of the respective ion, true kinetic and potential electron yields have been obtained. Potential electron yield was proportional to the total potential energy of the projectile ion. However, decrease in potential electron yield with increasing kinetic energy of Neq+ impact on Si and W was observed. This decrease in potential electron yield with kinetic energy of the ion was more pronounced for the projectile ions having higher charge states. Moreover, kinetic electron yield to energy-loss ratio for various ion-target combinations was calculated and results were in good agreement with semi-empirical model for kinetic electron emission.  相似文献   

13.
Large erosion (∼1.1 × 104 atoms/ion) of H from hydrogenated MCT wafers is observed due to the bombardment with 80 MeV Ni9+ ions. The initial H areal concentration and hydrogen depletion rate is monitored by elastic recoil detection analysis. The ion-damaged zones from where depletion of H takes place have been calculated from fluence-dependent hydrogen areal content analysis. The results are explained on the basis of the thermal spike model of ion-solid interaction.  相似文献   

14.
The diffusion of La, a trivalent cation dopant, actinide surrogate, and high-yield fission product, in CeO2, a UO2 nuclear fuel surrogate, during 1.8 MeV Kr+ ion bombardment over a temperature range from 673 K to 1206 K has been measured with secondary ion mass spectroscopy. The diffusivity under these irradiation conditions has been analyzed with a model based on a combination of sink-limited and recombination-limited kinetics. This analysis yielded a cation vacancy migration energy of  ∼ 0.4 eV below ∼800 K, were recombination-limited kinetics dominated the behavior. The thermal diffusivity of La in the same system was measured over a range of 873-1073 K and was characterized by an activation enthalpy of . The measurement of both the migration enthalpy and total activation enthalpy separately allows the vacancy formation enthalpy on the cation sublattice to be determined;  ∼ 1 eV. The mixing parameter under energetic heavy-ion bombardment at room temperature was measured as well and found to be ∼4 × 10−5 nm5/eV.  相似文献   

15.
Pure and Ytterbium (Yb) doped Calcium fluoride (CaF2) single crystals were irradiated with 100 MeV Ni7+ ions for fluences in the range 5 × 1011-2.5 × 1013 ions cm−2. The irradiated crystals were characterized by Optical absorption (OA) and Thermoluminescence (TL) techniques. The OA spectra of ion irradiated pure CaF2 crystals showed a broad absorption with peak at ∼556 nm and a weak one at ∼220 nm, whereas the Yb doped crystals showed two strong absorption bands at ∼300 and 550 nm. From the study of OA spectra, the defect centers responsible for the absorption were identified. TL measurements of Ni7+ ion irradiated pure CaF2 samples indicated a strong TL glow with peak at ∼510 K. However, the Yb doped crystals showed two TL glows at ∼406 and 496 K. The OA and TL intensity were found to increase with increase of ion fluence upto 1 × 1013 ions cm−2 and thereafter it decreased with further increase of fluence. The results obtained are discussed in detail.  相似文献   

16.
The effects of composition and structure on hydrogen incorporation in tungsten oxide films were investigated. Films were deposited on carbon and SiO2 substrates using a reactive sputtering by varying the substrate temperature from 30 to 600 °C in argon and oxygen mixture. The films were characterized using X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), elastic recoil detection analysis (ERDA) and Raman scattering. XRD patterns showed amorphous structure in the films deposited below 400 °C and (0 1 0) oriented monoclinic WO3 in the films deposited beyond 400 °C. The results of RBS and ERDA indicated that hydrogen concentration in the amorphous films increased from 0.1 to 0.7 H/W with changing the composition from WO0.25 to WO3. The hydrogen concentration in WO3 films decreased to 0.4 H/W with increasing the substrate temperature during deposition. The Raman spectra of the WO3 films revealed that decreasing of W6+O terminals was related to decreasing of the hydrogen concentration. It was considered that the incorporated hydrogen in tungsten oxide films was bonded at the end of W6+O terminals.  相似文献   

17.
We report the first investigation of the frequency dependent effect of 50 MeV Li3+ ion irradiation on the series resistance and interface state density determined from capacitance-voltage (C-V) and conductance-voltage (G-V) characteristics in HfO2 based MOS capacitors prepared by rf-sputtering. The samples were irradiated by 50 MeV Li3+ ions at room temperature. The measured capacitance and conductance were corrected for series resistance. The series resistance was estimated at various frequencies from 1 KHz to 1 MHz before and after irradiation. It was observed that the series resistance decreases from 6344.5 to 322 Ω as a function of frequency before irradiation and 8954-134 Ω after irradiation. The interface state density Dit decreases from 1.12 × 1012 eV−1 cm−2 before irradiation to 3.67 × 1011 eV−1 cm−2 after ion irradiation and further decreases with increasing frequency.  相似文献   

18.
CdTe polycrystalline thin films possessing hexagonal phase regions are obtained by spray deposition in presence of a high electric field. Thin film samples are irradiated with 100 MeV Ag ions using Pelletron accelerator to study the swift heavy ion induced effects. The ion irradiation results in the transformation of the metastable hexagonal regions in the films to stable cubic phase due to the dense electronic excitations induced by beam irradiation. The phase transformation is seen from the X-ray diffraction patterns. The band gap of the CdTe film changes marginally due to ion irradiation induced phase transformation. The value changes from 1.47 eV for the as deposited sample to 1.44 eV for the sample irradiated at the fluence 1×1013 ions/cm2. The AFM images show a gradual change in the shape of the particles from rod shape to nearly spherical ones after irradiation.  相似文献   

19.
A study of the effects of ion irradiation on the surface mechanical behavior and shrinkage of organic/inorganic modified silicate thin films was performed. The films were synthesized by sol-gel processing from tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) precursors and spin-coated onto Si substrates. The sol viscosity and the spin velocity were adjusted so that the films produced had a final thickness ranging from 580 to 710 nm after heat treatment. The ion species and incident energies used were selected such that the projected ion range was greater than the film thickness, resulting in fully irradiated films. After heat treatment at 300 °C for 10 min, the films were irradiated with 125 keV H+, 250 keV N2+ and 2 MeV Cu+ ions with fluences ranging from 1 × 1014 to 1 × 1016 ions/cm2. Both hardness and reduced elastic modulus were seen to exhibit a monotonic increase with fluence for all three ion species. Also, H loss was found to increase monotonically with increase in fluence, while the film thickness was found to decrease with increase in fluence.  相似文献   

20.
The response of a variety of W material grades to nanostructure ‘fuzz’ formation is explored. W targets are exposed to He or D2-0.2He plasmas in PISCES-B at 900-1320 K to below sputter threshold He+ ions of energy 25-60 eV for up to 2.2 × 104 s. SEM and XPS reveal nanoscopic reorganization of the W surface to a layer of ‘fuzz’ of porosity ∼90% as determined by a ‘fuzz’ removal/weight loss method. The variability of ‘fuzz’ growth is examined at 1120 K for 1 h durations: SR, SC and doped W grades - La2O3 (1% wt.), Re (5% and 10% wt.), and TiC (1.5% wt.) developed 2-3 μm thick ‘fuzz’ layers, while a VPS grade developed a layer 4 μm thick. An RC grade revealed additional ‘fuzz’ at deep (>100 μm) grain boundaries. However, heat treatment up to 1900 K produced reintegration of ‘fuzz’ with the bulk and He release at ∼1000 K and ∼1400-1800 K due to depopulation from vacancy complexes.  相似文献   

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