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1

TEM study of damage recovery in SiC by swift Xe ion irradiation  

NASA Astrophysics Data System (ADS)

The microstructure of 4H–SiC samples subsequently irradiated with low energy He (10 keV), Ti (220 keV) and high energy (167 MeV) Xe ions has been studied using cross-sectional transmission electron microscopy. It was found that xenon ions with fluences above 1013 cm?2 restore crystallinity in a heavily damaged partially amorphous zone. No, or negligible damage recovery is observed in fully amorphized layers of silicon carbide.

Skuratov, V. A.; O’Connell, J.; Sohatsky, A. S.; Neethling, J.

2014-05-01

2

Phase transformations in Y2O3 thin films under swift Xe ions irradiation  

NASA Astrophysics Data System (ADS)

Yttrium oxide (Y2O3) thin films deposited on silicon (Si) by an ion beam sputtering technique have been irradiated by 92 MeV xenon ions at room temperature. The microstructure of the irradiated thin film has been studied by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). A complete structural conversion from the cubic C-type to a monoclinic B-type phase is obtained. These results were compared with the phase transformation obtained in Y2O3 thin films by medium energy Xe ion irradiation. In both cases the oxygen network behaviour under irradiation is the key parameter of the phase transformation.

Gaboriaud, R. J.; Jublot, M.; Paumier, F.; Lacroix, B.

2013-09-01

3

Anisotropic deformation of Au nanoparticles by highly charged ion Xe21+ irradiation  

NASA Astrophysics Data System (ADS)

We present a detailed study of the deformation of Au nanoparticles (NPs) caused by the irradiation of highly charged ions (HCIs). When spherical Au NPs with a diameter of 19.8 nm were irradiated by 1 MeV Xe21+ ions with a fluence of 2 × 1014 cm-2, their anisotropic deformation was observed by atomic force microscopy. The results show that spherical Au NPs expand perpendicular to the ion beam changing their shape to oblate ellipsoidal. The size aspect ratio (major over minor axis) of the observed deformed Au NPs is about 1.23. The deformation process is described by a viscoelastic thermal spike model. The HCI beam deformation technique provides a unique method to tailor the shape of noble metal NPs.

Liu, Xueliang; Xu, Zhongfeng; Zhao, Yongtao; Liu, Lili; Wang, Yuyu; Chen, Liang; Li, Dehui; Zeng, Lixia; Zhao, Di; Xiao, Guoqing

2013-09-01

4

Quasi-two-dimensional Ag nanoparticle formation in silica by Xe ion irradiation and subsequent Ag ion implantation  

SciTech Connect

Ag nanoparticles were fabricated in silica by Xe ion irradiation and subsequent Ag ion implantation, which distributed in a depth range from 4.8 to 14.3 nm, rather than dispersed from surface to a depth of 24.7 nm when no irradiation was made in advance. In addition, the suppression of Ag implants' sputtering loss was also evidenced by a greatly increased Ag content in the prepared sample. These results are mainly due to the defect-enhanced in-beam particle growth. Further, formation of polycrystalline Ag nanoparticles was revealed, whose effect on optical absorption was discussed according to the electron mean-free-path mode.

Wang, Jun; Jia, Guangyi; Mu, Xiaoyu [School of Science, Tianjin University, Tianjin 300072 (China)] [School of Science, Tianjin University, Tianjin 300072 (China); Liu, Changlong [School of Science, Tianjin University, Tianjin 300072 (China) [School of Science, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, Institute of Advanced Materials Physics Faculty of Science, Tianjin 300072 (China)

2013-04-01

5

In situ TEM investigation of Xe ion irradiation induced defects and bubbles in pure molybdenum single crystal  

NASA Astrophysics Data System (ADS)

In order to study irradiation damage and inert gas bubble formation and growth behaviors, and to provide results and insights useful towards the validation of a multi-scale simulation approach based on a newly developed Xe-Mo inter-atomic potential, in situ Transmission Electron Microscopy (TEM) studies of Xe implantations in pure single crystal Molybdenum (Mo) have been conducted. 300 keV and 400 keV Xe+ ion beams were used to implant Xe in pre-thinned TEM Mo specimens. The irradiations were conducted at 300 °C and 600 °C to ion fluence up to 4 × 1016 ions/cm2. In situ TEM characterization allows detailed behaviors of defect clusters to be observed and is very useful in illustrating defect interaction mechanisms and processes. Dislocation loops were found to form at relatively low irradiation fluence levels. The characterization results showed that the free surfaces, formed in the process of producing pre-thinned specimens, play an important role in influencing the behaviors of dislocation loops. Similar characterizations were conducted at high fluence levels where Xe gas bubbles can be clearly observed. Xe gas bubbles were observed to form by a multi-atom nucleation process and they were immobile throughout the irradiation process at both temperatures. Measurements on both the number density and the size of dislocation loops and gas bubbles were taken. The results and implications of the measurements are discussed in this paper.

Yun, Di; Kirk, Marquis A.; Baldo, Peter M.; Rest, Jeffrey; Yacout, Abdellatif M.; Insepov, Zinetula Z.

2013-06-01

6

Defect production in silicon carbide irradiated with Ne and Xe ions with energy of 2.3 MeV\\/amu  

Microsoft Academic Search

In the present work specimens of mono-crystalline silicon carbide (4H polytype) were irradiated to three successively increasing ion fluences ranging from 7.2×1014 to 6.0×1016ions\\/cm2 (corresponding to the peak displacement damage of 1, 4 and 13dpa) with Ne and Xe ions respectively with the energy of 2.3MeV\\/amu. The irradiated specimens were subsequently annealed at temperatures of 1173 and 1273K. Defect structure

C. H. Zhang; Y. M. Sun; Y. Song; T. Shibayama; Y. F. Jin; L. H. Zhou

2007-01-01

7

Color center creation in LiF crystals irradiated with Xe, Kr and N ions: Dependence on fluence and beam current density  

NASA Astrophysics Data System (ADS)

Single LiF crystals were irradiated with Xe (195 MeV), Kr (117 MeV), and N (18 MeV) ions. Using absorption spectroscopy, color center creation was analyzed as a function of the ion energy loss, fluence, and flux. The concentration of single F centers and F 2 centers versus fluence and flux exhibits a nonlinear evolution with saturation at higher fluences. For LiF irradiated with N ions at high fluence, the concentration of F centers is proportional to the cube root of the flux indicating the strong interaction of primary hole centers. Macroscopic hillocks were observed in all irradiated LiF crystals by atomic force microscopy.

Dauletbekova, A. K.; Akilbekov, A. T.; Zdorovets, M. V.; Vassil'eva, A. F.; Akilbekova, D. A.

2010-10-01

8

Phase stability, grain growth and photoluminescence property of nanocrystalline yttria-stabilized zirconia film under 500 keV Xe6+ ion irradiation  

NASA Astrophysics Data System (ADS)

Nanocrystalline yttria stabilized zirconia (YSZ) film (with 8 mol% Y2O3) was synthesized via a sol-gel method. Phase stability, grain-growth and defects of the YSZ film were investigated under 500 keV Xe6+ ions irradiation to doses up to an average value of 22.2 displacements per atom (dpa). Atomic force microscope results show that the surface of the as-grown YSZ film is quite smooth and free of cracks. Transmission electron microscope results reveal that the average grain-size of the as-grown samples is around 12.6 nm. With increasing irradiation does up to 22.2 dpa, the average grain size increases, no phase transformation or amorphization is observed, which indicates that the phase structure of the nanocrystalline cubic YSZ film is quite stable. Two strong and broad emission peaks were detected in the YSZ film, and the emission intensity decreases obviously after irradiation. The possible mechanism of the grain growth was also discussed.

Chen, Lin; Chang, Yongqin; Guo, Qiang; Zhang, Jing; Wan, Farong; Long, Yi

2014-06-01

9

Nanoparticle ejection from Au by single Xe ion impacts.  

SciTech Connect

In situ transmission electron microscopy has been used to observe sputtered Au during Xe ion irradiation in transmission geometry. The sputtered Au was collected on an electron transparent carbon foil. Nanoparticles were observed on the collector foil after they were ejected by single ion impacts. The ejection is from the melt zone formed during the thermal spike phase of a displacement cascade produced near the surface by a single ion impact. Such single ion impacts are also capable of producing craters. Ejected nanoparticles can make a significant contribution to sputtering.

Birtcher, R. C.; Donnelly, S. E.; Schlutig, S.; Materials Science Division; Univ. of Salford; CIRIL Lab. CEA /CNRS

2000-12-04

10

Photoionization of Xe in a Fullerene Ion Cage  

NASA Astrophysics Data System (ADS)

Photoionization of Xe@C60^+ endohedral fullerene ions was investigated in the photon energy range 76 - 170 eV by merging beams of ions and synchrotron radiation. A solid sample containing 5 ppm of Xe@C60 was prepared by thermally evaporating and depositing C60 onto a rotating metal cylinder that was simultaneously bombarded by a 500 eV beam of Xe^+ ions for several weeks. The sample was then evaporated into a low-power discharge in an ECR ion source, yielding a 30 - 40 fA beam of Xe@C60^+ at 6 keV. Despite a low photoionization signal count rate of approximately 0.1 Hz, a signature due to photoexcitation of the Xe 4d giant resonance is evident in the measurements. The energy position of this feature suggests that the Xe atom donates electrons to the carbon cage of Xe@C60^+. The data show no evidence for a predicted splitting of the Xe 4d giant resonance in Xe@C60 into multiple components due to interference caused by reflection of electron waves by the carbon cage. This research was supported by the Division of Chemical Sciences, Geosciences and Biosciences of the U.S. Department of Energy.

Phaneuf, Ronald; Aryal, Nagendra; Esteves, David; Thomas, Christopher; Kilcoyne, David; Aguilar, Alejandro; Cisneros, Carmen

2010-03-01

11

Surface morphology and phase stability of titanium foils irradiated with 136 MeV 136Xe  

NASA Astrophysics Data System (ADS)

A stack of titanium foils was irradiated with 136 MeV 136Xe to study microstructure damage and phase stability of titanium upon irradiation. X-ray diffraction, scanning electron microscopy/energy dispersive spectroscopy and atomic force microscopy were used to study the resulting microstructure damage and phase stability of titanium. We observed the phase transformation of polycrystalline titanium from alpha-Ti (hexagonally closed packed (hcp)) to face centered cubic (fcc) after irradiation with 2.2 × 1015 ions/cm2. Irradiation of Ti with 1.8 × 1014-2.2 × 1015 ions/cm2 resulted in the formation of voids, hillocks, dislocation loops, dislocation lines, as well as polygonal ridge networks.

Sadi, S.; Paulenova, A.; Loveland, W.; Watson, P. R.; Greene, J. P.; Zhu, S.; Zinkann, G.

2014-06-01

12

LETTER TO THE EDITOR: Dynamics of Coulomb explosion of large Xe clusters irradiated by a super-intense ultra-short laser pulse  

Microsoft Academic Search

Dynamics of large Xe clusters irradiated by a super-intense ultra-short laser pulse is investigated within the frames of the simple Bethe model. Inner and outer classical above-barrier multiple ionization of the clusters, and also the Coulomb expansion of the cluster ion are calculated. As a typical example we consider a Xe cluster with 1000 atoms irradiated by a laser pulse

V. P. Krainov; A. S. Roshchupkin

2001-01-01

13

Molecular dynamic studies on anisotropic explosion of laser irradiated Xe cluster  

SciTech Connect

A three dimensional molecular dynamic model is used to investigate the dynamics of Xe clusters of various radii irradiated by laser of moderate intensities ({approx}10{sup 14}-10{sup 16}W/cm{sup 2}). The FWHM pulse duration of the laser is varied from few laser cycles to hundreds of femtosecond. For cluster of radius 50 A irradiated by a laser of 170 fs pulse duration, it is observed that ion yield is more along the direction of laser polarization than perpendicular to it. This trend reverses (more ions are emitted along the direction perpendicular to laser polarization than parallel to it) when laser pulses of few cycles are used. This reversal of anisotropy is explained on the basis of spatial shielding of ions due to the oscillating inner electron cloud along direction of laser electric field. The nature of anisotropy remains same with variations in laser intensity and cluster size.

Mishra, Gaurav; Gupta, N. K. [Theoretical Physics Division, Bhabha Atomic Research Centre, Mumabi-400085 (India)

2012-09-15

14

Microstructure evolution in Xe-irradiated UO2 at room temperature  

NASA Astrophysics Data System (ADS)

In situ Transmission Electron Microscopy was conducted for single crystal UO2 to understand the microstructure evolution during 300 keV Xe irradiation at room temperature. The dislocation microstructure evolution was shown to occur as nucleation and growth of dislocation loops at low irradiation doses, followed by transformation to extended dislocation segments and tangles at higher doses. Xe bubbles with dimensions of 1-2 nm were observed after room-temperature irradiation. Electron Energy Loss Spectroscopy indicated that UO2 remained stoichiometric under room temperature Xe irradiation.

He, L. F.; Pakarinen, J.; Kirk, M. A.; Gan, J.; Nelson, A. T.; Bai, X.-M.; El-Azab, A.; Allen, T. R.

2014-07-01

15

1.2 MeV/amu Xe ion induced damage recovery in SiC  

NASA Astrophysics Data System (ADS)

The microstructural changes of 4H-SiC samples dual irradiated with either low energy He (10 keV) or Ti (220 keV) and high energy (167 MeV) Xe ions has been studied using cross-sectional transmission electron microscopy. It was found that xenon ions with fluences above 1013 cm?2 restore crystallinity in a heavily damaged partially amorphous zone. No significant damage recovery was observed in fully amorphized layers of silicon carbide apart from a 5% reduction in the amorphous layer thickness.

O’Connell, J. H.; Skuratov, V. A.; Sohatsky, A. S.; Neethling, J. H.

2014-05-01

16

Heavy Ion Irradiation Effects in Zirconium Nitride  

SciTech Connect

Polycrystalline zirconium nitride (ZrN) samples were irradiated with He{sup +}, Kr{sup ++}, and Xe{sup ++} ions to high (>1.10{sup 16} ions/cm{sup 2}) fluences at {approx}100 K. Following ion irradiation, transmission electron microscopy (TEM) and grazing incidence X-ray diffraction (GIXRD) were used to analyze the microstructure and crystal structure of the post-irradiated material. For ion doses equivalent to approximately 200 displacements per atom (dpa), ZrN was found to resist any amorphization transformation, based on TEM observations. At very high displacement damage doses, GIXRD measurements revealed tetragonal splitting of some of the diffraction maxima (maxima which are associated with cubic ZrN prior to irradiation). In addition to TEM and GIXRD, mechanical property changes were characterized using nano-indentation. Nano-indentation revealed no change in elastic modulus of ZrN with increasing ion dose, while the hardness of the irradiated ZrN was found to increase significantly with ion dose. Finally, He{sup +} ion implanted ZrN samples were annealed to examine He gas retention properties of ZrN as a function of annealing temperature. He gas release was measured using a residual gas analysis (RGA) spectrometer. RGA measurements were performed on He-implanted ZrN samples and on ZrN samples that had also been irradiated with Xe{sup ++} ions, in order to introduce high levels of displacive radiation damage into the matrix. He evolution studies revealed that ZrN samples with high levels of displacement damage due to Xe implantation, show a lower temperature threshold for He release than do pristine ZrN samples. (authors)

Egeland, G.W.; Bond, G.M. [New Mexico Institute of Mining and Technology, Socorro, NM 87801 (United States); Valdez, J.A.; Swadener, J.G.; McClellan, K.J.; Maloy, S.A.; Sickafus, K.E. [Los Alamos National Lab (United States); Oliver, B. [Pacific Northwest National Lab (United States)

2004-07-01

17

Ion acceleration in Ar-Xe and Ar-He plasmas. II. Ion velocity distribution functions  

NASA Astrophysics Data System (ADS)

Ion velocity distribution functions (ivdfs) are investigated by laser induced fluorescence in Ar-Xe and Ar-He expanding helicon plasmas as a function of gas composition. In the case of Ar-Xe plasma, it was found that in the helicon source, both the Ar+ and Xe+ vdfs are unimodal. Their parallel speeds are subsonic and unaffected by changes in gas composition. At the end of the source, the argon ivdf shows a bimodal structure indicative of an electric double layer upstream of the measurement location. The fast argon ion component parallel velocity increases with Xe fraction from 6.7 to 8 km/s as the Xe fraction increases from 0% to 4%. In the expansion region, the bimodal character of Ar ivdf is maintained with a supersonic fast component reaching parallel speeds of 10.5 km/s. For all the studied plasma conditions and different spatial locations, the Xe+ vdf exhibits a unimodal structure with a maximum parallel flow velocity of 2.2 km/s at the end of the source. For Ar-He plasma, the Ar ivdf is bimodal with the fast ion component parallel velocity increasing from 5.2 to 7.8 km/s as the He fraction increases from 0% to 30%. For the same He fraction range, the slow argon ion population distribution changes from a single Gaussian to a wide distribution extending all the way from the speed of the fast population to 0 m/s.

Biloiu, Ioana A.; Scime, Earl E.

2010-11-01

18

I-Xe dating - Intercomparisons of neutron irradiations and reproducibility of the Bjurbole standard  

NASA Technical Reports Server (NTRS)

Previously unpublished data from the stepwise heating analysis of the Valecitos 1 (V1) Bjurbole standard are presented together with the results of an isotopic dilution measurement of a KI monitor included in the V1 irradiation package. The results of these analyses are compared with the values observed in other irradiations. Apparent I-Xe 'formation' ages are reproducible for three different samples of Bjurbole, suggesting isotopic homogeneity for initial iodine in the bulk material. The systematics of neutron capture in Xe-135 (produced from U-235 neutron fission) are examined and verified in irradiated BCR-1.

Hohenberg, C. M.; Kennedy, B. M.

1981-01-01

19

Calculation of Ion Charge State Distributions After Inner-Shell Ionization in Xe Atom  

SciTech Connect

The vacancy cascades following initial inner-shell vacancies in single and multi-ionized atoms often lead to highly charged residual ions. The inner-shell vacancy produced by ionization processes may decay by either a radiative or non-radiative transition. In addition to the vacancy filling processes, there is an electron shake off process due to the change of core potential of the atom. In the calculation of vacancy cascades, the radiative (x-ray) and non-radiative (Auger and Coster-Kronig) branching ratios give valuable information on the de-excitation dynamics of an atom with inner-shell vacancy. The production of multi-charged ions yield by the Auger cascades following inner shell ionization of an atom has been studied both experimentally and theoretically. Multi-charged Xe ions following de-excitation of K-, L{sub 1}-, L{sub 2,3}-, M{sub 1}-, M{sub 2,3}- and M{sub 4,5} subshell vacancies are calculated using Monte-Carlo algorithm to simulate the vacancy cascade development. Fluorescence yield (radiative) and Auger, Coster- Kronig yield (non- radiative) are evaluated. The decay of K hole state through radiative transitions is found to be more probable than non-radiative transitions in the first step of de-excitation. On the other hand, the decay of L, M vacancies through non-radiative transitions are more probable. The K shell ionization in Xe atom mainly yields Xe{sup 7+}, Xe{sup 8+}, Xe{sup 9+} and Xe{sup 10+} ions, and the charged X{sup 8+} ions are the highest. The main product from the L{sub 1}- shell ionization is found to be Xe{sup 8+}, Xe{sup 9+} ions, while the charged Xe{sup 8+} ions predominate at L{sub 2,3} hole states. The charged Xe{sup 6+}, Xe{sup 7+} and Xe{sup 8+} ions mainly yield from 3s{sub 1/2} and 3p{sub 1/2,3/2} ionization, while Xe in 3d{sub 3/2,5/2} hole states mainly turns into Xe{sup 4+} and Xe{sup 5+} ions. The present results are found to agree well with the experimental data.

Mohammedein, Adel M.; Ghoneim, Adel A.; Kandil, Kandil M.; Kadad, Ibrahim M. [Applied Sciences Department, College of Technological Studies, P.O. Box 42325, Shuwaikh 70654 (Kuwait)

2010-01-05

20

Modification of Optical Band-Gap of Si Films After Ion Irradiation  

NASA Astrophysics Data System (ADS)

Amorphous silicon (a-Si), nanocrystalline silicon (nc-Si) and hydrogenated nanocrystalline silicon (nc-Si:H) films were fabricated by using chemical vapor deposition (CVD) system. The a-Si and nc-Si thin films were irradiated with 94 MeV Xe-ions at fluences of 1.0 × 1011 ions/cm2, 1.0 × 1012 ions/cm2 and 1.0 × 1013 ions/cm2 at room temperature (RT). The nc-Si:H films were irradiated with 9 MeV Xe-ions at 1.0 × 1012 Xe/cm2, 1.0 × 1013 Xe/cm2 and 1.0 × 1014 Xe/cm2 at RT. For comparison, mono-crystalline silicon (c-Si) samples were also irradiated at RT with 94 MeV Xe-ions. All samples were analyzed by using an UV/VIS/NIR spectrometer and an X-ray powder diffractometer. Variations of the optical band-gap (Eg) and grain size (D) versus the irradiation fluence were investigated systematically. The obtained results showed that the optical band-gaps and grain size of the thin films changed dramatically whereas no observable change was found in c-Si samples after Xe-ion irradiation. Possible mechanism underlying the modification of silicon thin films was briefly discussed.

Zhu, Yabin; Wang, Zhiguang; Sun, Jianrong; Yao, Cunfeng; Wei, Kongfang; Gou, Jie; Ma, Yizhun; Shen, Tielong; Pang, Lilong; Sheng, Yanbin

2012-07-01

21

Separation of spin–orbit coupled metastable states of Kr+ and Xe+ by ion mobility  

Microsoft Academic Search

The spin–orbit coupled ground states of Kr+? and Xe+? (RG 2P1\\/2 and RG 2P3\\/2, RG=rare gas) are separated on the basis of ion mobility. Ion mobility separation of Kr+? and Xe+? is based on different interaction potentials of the 2P1\\/2 and 2P3\\/2 ionic states with helium. The ion mobility instrument used for these studies is a novel instrument based on

Brian K. Bluhm; Simon W. North; David H. Russell

2001-01-01

22

Separation of spin-orbit coupled metastable states of Kr+ and Xe+ by ion mobility  

Microsoft Academic Search

The spin-orbit coupled ground states of Kr+. and Xe+. (RG 2P1\\/2 and RG 2P3\\/2, RG=rare gas) are separated on the basis of ion mobility. Ion mobility separation of Kr+. and Xe+. is based on different interaction potentials of the 2P1\\/2 and 2P3\\/2 ionic states with helium. The ion mobility instrument used for these studies is a novel instrument based on

Brian K. Bluhm; Simon W. North; David H. Russell

2001-01-01

23

Observation of hyperfine mixing in measurements of a magnetic octupole decay in isotopically pure nickel-like 129Xe and 132Xe ions  

SciTech Connect

We present measurements of high statistical significance of the rate of the magnetic octupole (M3) decay in nickel-like ions of isotopically pure {sup 129}Xe and {sup 132}Xe. On {sup 132}Xe, an isotope with zero nuclear spin and therefore without hyperfine structure, the lifetime of the metastable level was established as (15.06 {+-} 0.24) ms. On {sup 129}Xe, an additional fast (2.7 {+-} 0.1 ms) decay component was established that represents hyperfine mixing with a level that decays by electric quadrupole (E2) radiation.

Trabert, E; Beiersdorfer, P; Brown, G V

2006-12-21

24

Modifications in structure and optical property of Cu nanoparticles in SiO2 by post heavy ion irradiation  

NASA Astrophysics Data System (ADS)

The implantation-synthesized Cu nanoparticles (NPs) in silica were irradiated with 500 keV Xe and Ar ions, respectively. After Xe ion irradiation at a fluence of 2 × 1016/cm2, the average diameter of Cu NPs was increased from 7.3 to 8.5 nm, and especially, Cu NPs with a diameter of 11–14 nm were formed beyond the projected range of Cu ions and nearly aligned at the same depth, which presented a higher volume fraction. As a result, the Cu surface plasmon resonance (SPR) absorption peak was enhanced. However, if Xe ion fluence was less than 1 × 1016/cm2, no clear variation of the Cu SPR absorption peak could be found. Further, it was also revealed that Xe ion irradiation caused the Cu SPR absorption peak to more drastically change than Ar ion irradiation at the same ion fluence. The underlying processes for the above findings were discussed and tentatively proposed.

Liu, Changlong; Wang, Nana; Wang, Jun; Liu, Huixian; Jia, Guangyi; Mu, Xiaoyu

2014-05-01

25

Photoinduced Desorption of Xe from Porous Si following Ultraviolet Irradiation: Evidence for a Selective and Highly Effective Optical Activity  

NASA Astrophysics Data System (ADS)

Photoinduced desorption (PID) of Xe from porous silicon (PSi) following UV irradiation has been studied. A nonthermal, morphology, and wavelength dependent phenomenon with more than 3 orders of magnitude enhancement of Xe PID within pores over atoms adsorbed on top of flat surfaces has been recorded, displaying extraordinary large cross sections up to ?Xe/PSi=2×10-15cm2. A long-lived, photoinduced, charge separated silicon-xenon complex is proposed as the precursor for this remarkable photodesorption process.

Toker, Gil; Asscher, Micha

2011-10-01

26

Fully stripped heavy ion yield vs energy for Xe and Au ions  

NASA Astrophysics Data System (ADS)

The Bevalac is now capable of accelerating U-238 ions to approximately 1 GeV/amu and measurements have shown that fully stripped U-238 ions are produced with good yield at these energies. However, knowing the stripping yields at different energies for U-238 does not allow an accurate prediction for other, lower Z projectiles. Consequently, extensive stripping yield measurements were made for Au-197 and Xe-139 ions. In addition to the stripping measurements from the direct Bevalac beam, pickup measurements were also made with specially prepared bare, one electron, and two electron ions. Since many research groups are considering heavy ion storage rings and/or synchrotrons, the pickup cross section for bare ions is important to estimate beam lifetime in terms of the average machine vacuum. Since the Mylar target provides a pickup probability similar to air, a preliminary analysis of the Xe(54+) and U(92+) data are presented along with predictions for other ions ranging down to Fe(26+).

Thieberger, P.; Wegner, H. E.; Alonzo, J.; Gould, H.; Anholt, R. E.; Meyerhof, W. E.

27

Dielectronic recombination of lithiumlike Xe51+ ions: Storage ring experiment and theoretical calculations  

NASA Astrophysics Data System (ADS)

Absolute rate coefficients for dielectronic recombination (DR) of Li-like 136Xe51+ have been measured at the heavy-ion storage ring ESR. The experimental results are compared with relativistic distorted-wave calculations employing the multiconfiguration Dirac-Fock method. Based on the DR measurements the 2s-2p1/2 and 2s-2p3/2 excitation energies in Li-like Xe51+ were determined with a relative accuracy of ~400 ppm.

Bernhardt, D.; Brandau, C.; Harman, Z.; Kozhuharov, C.; Müller, A.; Schippers, S.; Böhm, S.; Bosch, F.; Jacobi, J.; Kieslich, S.; Knopp, H.; Mokler, P. H.; Nolden, F.; Shi, W.; Stachura, Z.; Steck, M.; Stöhlker, Th

2014-04-01

28

TiO2 films photocatalytic activity improvements by swift heavy ions irradiation  

NASA Astrophysics Data System (ADS)

TiO2 thin films synthesized by sol-gel on glass substrates are irradiated by 90 MeV Xe ions at various fluences and room temperature under normal incidence. The structural, electrical, optical and surface topography properties before and after Xe ions irradiation are investigated. X-ray diffraction (XRD) reveals that the crystallinity is gradually destroyed, and the films become amorphous above 5×1012 ions/cm2. The band gap is not affected by Xe ions irradiation as evidenced from the optical measurements. By contrast, the conductivity increases with raising Xe fluence. The energy band diagram established from the electrochemical characterization shows the feasibility of TiO2 films for the photo-electrochemical chromate reduction. Xe ion irradiation results in enhanced photocatalytic activity in aquatic medium, evaluated by the reduction of Cr(VI) into trivalent state. TiO2 films irradiated at 1013 Xe/cm2 exhibit the highest photoactivity; 69% of chromate (10 ppm) is reduced at pH ~3 after 4 h of exposure to sunlight (1120 mW cm-2) with a quantum yield of 0.06%.

Rafik, Hazem; Mahmoud, Izerrouken; Mohamed, Trari; Abdenacer, Benyagoub

2014-08-01

29

Optima XE Single Wafer High Energy Ion Implanter  

SciTech Connect

The Optima XE is the first production worthy single wafer high energy implanter. The new system combines a state-of-art single wafer endstation capable of throughputs in excess of 400 wafers/hour with a production-proven RF linear accelerator technology. Axcelis has been evolving and refining RF Linac technology since the introduction of the NV1000 in 1986. The Optima XE provides production worthy beam currents up to energies of 1.2 MeV for P{sup +}, 2.9 MeV for P{sup ++}, and 1.5 MeV for B{sup +}. Energies as low as 10 keV and tilt angles as high as 45 degrees are also available., allowing the implanter to be used for a wide variety of traditional medium current implants to ensure high equipment utilization. The single wafer endstation provides precise implant angle control across wafer and wafer to wafer. In addition, Optima XE's unique dose control system allows compensation of photoresist outgassing effects without relying on traditional pressure-based methods. We describe the specific features, angle control and dosimetry of the Optima XE and their applications in addressing the ever-tightening demands for more precise process controls and higher productivity.

Satoh, Shu; Ferrara, Joseph; Bell, Edward; Patel, Shital; Sieradzki, Manny [Axcelis Technologies, Inc. 108 Cherry Hill Drive, Beverly, MA 01915 (United States)

2008-11-03

30

Effect of XeCl laser irradiation on the defect structure of Nd:YAG crystals  

NASA Astrophysics Data System (ADS)

This paper presents the effect of XeCl laser irradiation on Nd:YAG single crystal samples with various number of pulses at different repetition rates and laser fluences. Effects of the irradiation on the optical and structural properties of the crystal are analyzed by UV-vis-NIR spectroscopy. Annihilation of some point defects of the crystal structure is observed following laser irradiation at a fluence of 100 mJ cm-2 with 100 and 500 pulses. Increasing the laser fluence and pulse numbers leads to saturation and new defects are found to be formed in the crystal. Additional absorption spectra of the irradiated samples show that oxygen vacancies in the Nd:YAG crystals are removed during the low-dose irradiation. The laser irradiation is compared to the thermal annealing process for Nd:YAG crystal modification. Additional absorption spectrum of an annealed sample reveals that induced negative absorption band at 236 nm is correlated with the annihilation of the oxygen vacancy center. Our results also demonstrate that XeCl laser treatment has several advantages upon annealing at high temperatures in the Nd:YAG crystal quality improvement. Thus, the present work can give a new approach to modify Nd:YAG crystals to be used in a wide variety of solid-state laser engineering.

Panahibakhsh, S.; Jelvani, S.; Maleki, M. H.; Mollabashi, M.; Abolhosseini, S.

2014-09-01

31

Secondary ion emission from arachidic acid LB-layers under Ar +, Xe +, Ga + and SF 5 + primary ion bombardment  

Microsoft Academic Search

The influence of primary ion energy, mass and composition on sputtering and secondary ion emission of arachidic acid Langmuir–Blodgett mono- and multilayers, deposited on gold substrates, has been investigated. Ga+, Ar+, 129Xe+ and SF5+ in the energy range 5–25 keV were used as primary ions. Yields Y, damage cross-sections ?, and ion formation efficiencies E have been determined for selected

D. Stapel; O. Brox; A. Benninghoven

1999-01-01

32

Simultaneous imaging electron- and ion-feature Thomson scattering measurements of radiatively heated Xe.  

PubMed

Uniform density and temperature Xe plasmas have been produced over >4 mm scale-lengths using x-rays generated in a cylindrical Pb cavity. The cavity is 750 ?m in depth and diameter, and is heated by a 300 J, 2 ns square, 1054 nm laser pulse focused to a spot size of 200 ?m at the cavity entrance. The plasma is characterized by simultaneous imaging Thomson scattering measurements from both the electron and ion scattering features. The electron feature measurement determines the spatial electron density and temperature profile, and using these parameters as constraints in the ion feature analysis allows an accurate determination of the charge state of the Xe ions. The Thomson scattering probe beam is 40 J, 200 ps, and 527 nm, and is focused to a 100 ?m spot size at the entrance of the Pb cavity. Each system has a spatial resolution of 25 ?m, a temporal resolution of 200 ps (as determined by the probe duration), and a spectral resolution of 2 nm for the electron feature system and 0.025 nm for the ion feature system. The experiment is performed in a Xe filled target chamber at a neutral pressure of 3-10 Torr, and the x-rays produced in the Pb ionize and heat the Xe to a charge state of 20±4 at up to 200 eV electron temperatures. PMID:23127005

Pollock, B B; Meinecke, J; Kuschel, S; Ross, J S; Shaw, J L; Stoafer, C; Divol, L; Tynan, G R; Glenzer, S H

2012-10-01

33

Simultaneous imaging electron- and ion-feature Thomson scattering measurements of radiatively heated Xe  

SciTech Connect

Uniform density and temperature Xe plasmas have been produced over >4 mm scale-lengths using x-rays generated in a cylindrical Pb cavity. The cavity is 750 {mu}m in depth and diameter, and is heated by a 300 J, 2 ns square, 1054 nm laser pulse focused to a spot size of 200 {mu}m at the cavity entrance. The plasma is characterized by simultaneous imaging Thomson scattering measurements from both the electron and ion scattering features. The electron feature measurement determines the spatial electron density and temperature profile, and using these parameters as constraints in the ion feature analysis allows an accurate determination of the charge state of the Xe ions. The Thomson scattering probe beam is 40 J, 200 ps, and 527 nm, and is focused to a 100 {mu}m spot size at the entrance of the Pb cavity. Each system has a spatial resolution of 25 {mu}m, a temporal resolution of 200 ps (as determined by the probe duration), and a spectral resolution of 2 nm for the electron feature system and 0.025 nm for the ion feature system. The experiment is performed in a Xe filled target chamber at a neutral pressure of 3-10 Torr, and the x-rays produced in the Pb ionize and heat the Xe to a charge state of 20{+-}4 at up to 200 eV electron temperatures.

Pollock, B. B. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94550 (United States); University of California, San Diego, 9500 Gilman Dr., La Jolla, California 92093 (United States); Meinecke, J. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94550 (United States); University of Oxford, Wellington Square, Oxford, OX1 2JD (United Kingdom); Kuschel, S.; Ross, J. S.; Divol, L.; Glenzer, S. H. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94550 (United States); Shaw, J. L. [University of California, Los Angeles, 405 Hilgard Ave., Los Angeles, California 90095 (United States); Stoafer, C. [Columbia University, 116th Street and Broadway, New York, New York 10027 (United States); Tynan, G. R. [University of California, San Diego, 9500 Gilman Dr., La Jolla, California 92093 (United States)

2012-10-15

34

Dielectronic recombination of berylliumlike Xe50+ ions: Measurement and theoretical calculations  

NASA Astrophysics Data System (ADS)

Absolute rate coefficients for dielectronic recombination (DR) of Be-like 136Xe50+ have been measured at the heavy-ion storage ring ESR. The experimental results are compared with relativistic distorted-wave calculations employing the multiconfiguration Dirac-Fock method. Based on the DR measurements, multiple intra-L-shell excitation energies were determined.

Bernhardt, D.; Brandau, C.; Kozhuharov, C.; Müller, A.; Schippers, S.; Böhm, S.; Bosch, F.; Harman, Z.; Jacobi, J.; Kieslich, S.; Knopp, H.; Mokler, P. H.; Nolden, F.; Shi, W.; Stachura, Z.; Steck, M.; Stohlker, Th

2014-04-01

35

Simultaneous imaging electron- and ion-feature Thomson scattering measurements of radiatively heated Xe  

NASA Astrophysics Data System (ADS)

Uniform density and temperature Xe plasmas have been produced over >4 mm scale-lengths using x-rays generated in a cylindrical Pb cavity. The cavity is 750 ?m in depth and diameter, and is heated by a 300 J, 2 ns square, 1054 nm laser pulse focused to a spot size of 200 ?m at the cavity entrance. The plasma is characterized by simultaneous imaging Thomson scattering measurements from both the electron and ion scattering features. The electron feature measurement determines the spatial electron density and temperature profile, and using these parameters as constraints in the ion feature analysis allows an accurate determination of the charge state of the Xe ions. The Thomson scattering probe beam is 40 J, 200 ps, and 527 nm, and is focused to a 100 ?m spot size at the entrance of the Pb cavity. Each system has a spatial resolution of 25 ?m, a temporal resolution of 200 ps (as determined by the probe duration), and a spectral resolution of 2 nm for the electron feature system and 0.025 nm for the ion feature system. The experiment is performed in a Xe filled target chamber at a neutral pressure of 3-10 Torr, and the x-rays produced in the Pb ionize and heat the Xe to a charge state of 20+/-4 at up to 200 eV electron temperatures.

Pollock, B. B.; Meinecke, J.; Kuschel, S.; Ross, J. S.; Shaw, J. L.; Stoafer, C.; Divol, L.; Tynan, G. R.; Glenzer, S. H.

2012-10-01

36

Anisotropic proton-conducting membranes prepared from swift heavy ion-beam irradiated ETFE films  

Microsoft Academic Search

Poly(ethylene-co-tetrafluoroethylene) (ETFE) films were irradiated by swift heavy ion-beams of 129Xe23+ with fluences of 0, 3×106, 3×107, 3×108 and 3×109ions\\/cm2, followed by ?-ray pre-irradiation for radiation grafting of styrene onto the ETFE films and sulfonation of the grafted ETFE films to prepare highly anisotropic proton-conducting membranes. The fluence of Xe ions and the addition of water in the grafting solvent

Yosuke Kimura; Jinhua Chen; Masaharu Asano; Yasunari Maekawa; Ryoichi Katakai; Masaru Yoshida

2007-01-01

37

Generation of strongly coupled Xe cluster nanoplasmas by low intensive soft x-ray laser irradiation  

SciTech Connect

A seeding gas jet including Xe clusters was irradiated with a laser-driven plasma soft x-ray laser pulse ({lambda}=13.9 nm, {approx}7 ps, {<=}5 Multiplication-Sign 10{sup 9} W/cm{sup 2}), where the laser photon energy is high enough to ionize 4d core electrons. In order to clarify how the innershell ionization followed by the Auger electron emission is affected under the intense laser irradiation, the electron energy distribution was measured. Photoelectron spectra showed that the peak position attributed to 4d hole shifted to lower energy and the spectral width was broadened with increasing cluster size. Moreover, the energy distribution exhibited that a strongly coupled cluster nanoplasma with several eV was generated.

Namba, S.; Hasegawa, N.; Kishimoto, M.; Nishikino, M.; Kawachi, T. [Graduate School of Engineering, Hiroshima University,Kagamiyama 1-4-1, Higashi-Hiroshima, Hiroshima, 739-8527 (Japan); Quantum Beam Science Directorate, Japan Atomic Energy Agency, Umemidai 8-1, Kizugawa, Kyoto, 619-0215 (Japan)

2012-07-11

38

Effects of high-energy heavy ion irradiation on the crystal structure in CeO2 thin films  

NASA Astrophysics Data System (ADS)

We studied the change in crystal structure of 200 MeV Xe and 10 MeV I ion irradiated CeO2 thin films by means of X-ray diffraction (XRD). The experimental result showed that the average lattice parameter of CeO2 decreased and the full width at half maximum increased by the ion irradiation. Their changes are well correlated with the electronic stopping powers for I and Xe ions. The dependence of lattice parameter on the electronic energy loss was analyzed by using the Poisson's law, and the radii of the regions affected by the irradiation were determined.

Kishino, T.; Shimizu, K.; Saitoh, Y.; Ishikawa, N.; Hori, F.; Iwase, A.

2013-11-01

39

Influence of deposition conditions and ion irradiation on thin films of amorphous Cu?Zr superconductors  

Microsoft Academic Search

Amorphous films of Cu?Zr have been prepared by electron-beam (e-beam) codeposition and ion beam mixing. Various treatments, such as deposition onto liquid nitrogen cooled substrates and ion irradiation with 1 MeV Xe2+ ions or 500 keV Ar+ ions at 100 K and at 300 K, were used to vary the level of disorder in the amorphous state. The residual resistance

N. Karpe; J. Bøttiger; J. P. Krog; A. Nordström; Ö. Rapp

1996-01-01

40

Secondary ion emission from polycrystalline Al under Cs + irradiation  

NASA Astrophysics Data System (ADS)

Work function and secondary ion intensity variations apparent during the initial stages of sputtering with 1 keV Cs + ions have been recorded from Al under Cs + irradiation. These are compared with each other and ion-induced L 23MM Auger emissions induced through Ar + and Xe + irradiation. As expected, the Al + and Al - intensities scale with the substrate work function in a manner consistent with the electron tunneling model. Likewise, the Al 2+ population scales with the Auger signal consistent with a surface excitation initiated process. Furthermore, only single 2p vacancies were noted indicating that Al 2+ forms from the sputtered Al + population and Al + forms from the sputtered Al 0 population. The work function dependence exhibited by Al + reveals that this is a minor process, at least for these ions under these conditions.

van der Heide, P. A. W.

2004-06-01

41

New process observed in collisions between highly charged protonated protein and Xe8+ Xe5+ He2+ ions  

NASA Astrophysics Data System (ADS)

Electron multicapture processes have been studied in collisions between cytochrome C protein and highly charged Xe and He projectile at keV kinetic energy range. In competition with single and double electron capture, a new and unexpected channel attributed to deprotonation process of the protein has been observed.

Martin, S.; Chen, L.; Brédy, R.; Vernier, A.; Dugourd, P.; Antoine, R.; Ortéga, C.; Ji, M.; Bernard, J.; Gonzalez Maganad, O.; Reitsma, G.; Schlathölter, T.

2014-04-01

42

Unexpected transverse velocity component of Xe+ ions near the exit plane of a Hall thruster  

NASA Astrophysics Data System (ADS)

The velocity component of singly charged xenon ions in a plane perpendicular to the thrust axis of the 1 kW-class PPS100-ML Hall effect thruster is deduced from laser induced fluorescence measurements on the 5d 2F7/2-->6p 2D5/20 electronic transition at 834.72 nm. Measurements are carried out at several locations in the near field of the channel exhaust. Thruster operating parameters, such as magnetic field strength, discharge voltage, and xenon mass flow rate, are varied over a wide range. The initial aim of this work was to measure the azimuthal velocity of the ions due to their weak magnetic deflection. Surprisingly, experimental results cannot be explained by the one and only Lorentz force acting on Xe+ ions. A realistic picture of the ion trajectory in the E×B drift plane is obtained when adding a velocity component directed toward the external cathode.

Bourgeois, G.; Mazouffre, S.; Sadeghi, N.

2010-11-01

43

A guided-ion beam study of the reactions of Xe{sup +} and Xe{sup 2+} with NH{sub 3} at hyperthermal collision energies  

SciTech Connect

We have measured the absolute cross sections for reactions of Xe{sup +} and Xe{sup 2+} with NH{sub 3} at collision energies in the range from near-thermal to {approx}34 and {approx}69 eV, respectively. For Xe{sup +}, the cross section for charge transfer, the only exothermic channel, decreases from {approx}200 A{sup 2} below 0.1 eV to {approx}12 A{sup 2} at the highest energies studied. The production of NH{sub 3}{sup +} is the only channel observed below 5 eV, above which a small amount of NH{sub 2}{sup +} is also formed. In Xe{sup 2+} reactions, the main products observed are NH{sub 3}{sup +} and NH{sub 2}{sup +}. The charge transfer cross section decreases monotonically from {approx}80 to {approx}6 A{sup 2} over the studied energy range. The NH{sub 2}{sup +} cross section is similar to the charge transfer cross section at the lowest energies, and exhibits a second component above 0.4 eV, with a maximum of 65 A{sup 2} at 0.7 eV, above which the cross section decreases to {approx}30 A{sup 2} at the highest energies studied. At energies above 10 eV, a small amount of NH{sup +} is also observed in Xe{sup 2+} collisions. Product recoil velocity distributions were determined at selected collision energies, using guided-ion beam time-of-flight methods.

Levandier, Dale J. [Boston College Institute for Scientific Research, Chestnut Hill, Massachusetts 02159 (United States); Chiu, Yu-Hui [Air Force Research Laboratory, Space Vehicles Directorate, Hanscom AFB, Massachusetts 02452 (United States)

2010-10-21

44

Ion-radical synergy in HfO2 etching studied with a XeF2/Ar+ beam setup  

NASA Astrophysics Data System (ADS)

To gain more insight into fundamental aspects of the etching behavior of Hf-based high-k materials in plasma etch reactors, HfO2 films were etched in a multiple-beam setup consisting of a low energy Ar+ ion beam and a XeF2 radical beam. The etch rate and etch products were monitored by real-time ellipsometry and mass spectrometry, respectively. Although etching of HfO2 in XeF2/Ar+ chemistry is mainly a physical effect, an unambiguous proof of the ion-radical synergistic effect for the etching of HfO2 is presented. The etch yield for 400 eV Ar+ ions at a substrate temperature of 300 °C was 0.3 atoms/ion for Ar+ sputtering and increased to 2 atoms/ion when XeF2 was also supplied. The etch yield proved to follow the common square root of ion energy dependence both for pure sputtering and radical enhanced etching, with a threshold energy at room temperature of 69+/-17 eV for Ar+ ions and 54+/-14 eV for Ar+ ions with XeF2.

Gevers, P. M.; Beijerinck, H. C. W.; van de Sanden, M. C. M.; Kessels, W. M. M.

2008-04-01

45

Characteristics of the evolution of a plasma jet during the irradiation of a metal surface by a pulsed XeCl laser  

NASA Astrophysics Data System (ADS)

Results of experiments in which various metal targets were irradiated at an angle of 10 deg by 0.3-J, 20-ns pulses of a XeCl laser are reported. In addition to two regions of plasma evolution at the metal surface noted in an earlier study (Kagawa et al., 1983), a third region is identified where the plasma has the shape of a narrow core normal to the surface. At 1-2 mm from the surface, the core contains various metal ion lines. The spectrograms of the jet do not contain any lines of the atoms or ions of the gas surrounding the target (e.g., air, helium, or argon), indicating that the breakdown occurs only in the expanding metal vapors and not in the buffer gas.

Anisimov, V. N.; Bol'Shov, L. A.; Gaidarenko, D. V.; Derkach, O. N.; Kanevskii, M. F.

1987-07-01

46

Measurement and interpretation of CO and Kr + Xe in irradiated ThOâ-containing HTGR fuel particles  

Microsoft Academic Search

The irradiation of microspheres of ThOâ and Thâ ââUââOâ in the form of high-temperature gas-cooled reactor (HTGR) particles resulted in the buildup of CO as well as Kr + Xe within the particle. The particles were later equilibrated at 1325 less than or equal to T less than or equal to 2270 K, crushed, and the CO and Kr +

T. B. LINDEMER

1977-01-01

47

Ion-irradiation effect on high-temperature behaviors of advanced SiC fibers  

NASA Astrophysics Data System (ADS)

Heavy ion beam irradiation is usually chosen to simulate neutron irradiation damages in materials. However, there has the difficulty to study macro-properties of irradiated materials due to the very small affected depth. In this study, we have explored macro-properties of the ion-irradiated materials, owing to very fine diameter of Tyranno™-SA SiC fibers. The fibers were irradiated at a National Large Accelerator of Heavy Ions facility, GANIL (Caen, France), under 95 MeV Xe ions at room-temperature. To prevent the damage gradient in fiber, the fibers were irradiated on two sides with two fluence levels. According to TRIM-code calculation, the irradiation damages in the fibers affected the entire volume of the fibers with estimations of 0.05 and 0.2 dpa. The high-temperature behaviors of the ion-irradiated fibers from room temperature to 1200 °C were investigated by a specific tensile test device of single fiber, named MacaSiC. The thermo-elastic modulus of the ion-irradiated fibers showed the recovering, which started from 600 °C during heating. The thermo-electrical conductivity of the ion-irradiated fibers gradually increased until 900 °C and then saturated during heating and gradually decreased during cooling. The normalized value of electrical conductivity for 0.05 dpa irradiated fibers had higher than that of 0.02 dpa irradiated fibers after heating and cooling.

Shimoda, K.; Colin, C.; Kishimoto, H.; Doriota, S.

2011-10-01

48

Composition of sputtered material from Cu?Ni alloy during Xe + ion sputtering at elevated temperatures  

NASA Astrophysics Data System (ADS)

Polycrystalline Cu?Ni alloys were sputtered by 3 kV Xe + ions at elevated temperatures to analyze the ion-beam-induced diffusion. The time evolution of the composition of the sputtered materials from the start of the sputtering was measured by TOF-SNMS (time-of-flight sputtered neutral mass spectrometry). During removal of the Gibbsian segregation layer of copper, the sputtered flux consisted of almost only copper atoms. Then, the copper content gradually decreased due to the formation of a sputter-induced copper-depleted surface layer, and reached an almost steady state with still higher copper content than the bulk composition. From the temperature dependence of the composition at the quasi-steady state the activation energy of copper transportation through a high diffusivity path was derived to be 54 kJ mol -1 (0.56 eV). The high diffusivity path was assigned to copper diffusion through grain boundaries.

Sekine, Shigeyuki; Shimizu, Hazime; Ichimura, Singo

1995-04-01

49

Dose Control System in the Optima XE Single Wafer High Energy Ion Implanter  

NASA Astrophysics Data System (ADS)

Photoresist outgassing can significantly compromise accurate dosimetry of high energy implants. High energy implant even at a modest beam current produces high beam powers which create significantly worse outgassing than low and medium energy implants and the outgassing continues throughout the implant due to the low dose in typical high energy implant recipes. In the previous generation of high energy implanters, dose correction by monitoring of process chamber pressure during photoresist outgassing has been used. However, as applications diversify and requirements change, the need arises for a more versatile photoresist correction system to match the versatility of a single wafer high energy ion implanter. We have successfully developed a new dosimetry system for the Optima XE single wafer high energy ion implanter which does not require any form of compensation due to the implant conditions. This paper describes the principles and performance of this new dose system.

Satoh, Shu; Yoon, Jongyoon; David, Jonathan

2011-01-01

50

Optical absorption and thermoluminescence of MgAl 2O 4 spinel crystals implanted with Xe ++ ions  

Microsoft Academic Search

We have studied changes in optical absorption of MgAl2O4 spinel crystals implanted with 340 keV Xe++ ions at about 120 K, to fluences ranging from 1015–1021 ions\\/m2. With increasing ion fluence, we observe an increase in optical absorption, especially in the vicinity of two absorption bands: one centered at 5.3 eV, the other at 6.9 eV. The absorption band at

I. V Afanasyev-Charkin; V. T Gritsyna; D. W Cooke; B. L Bennett; C. R Evans; M. G Hollander; K. E Sickafus

1999-01-01

51

Zn nanoparticles irradiated with swift heavy ions at low fluences: Optically-detected shape elongation induced by nonoverlapping ion tracks  

SciTech Connect

Elongation of metal nanoparticles (NPs) embedded in silica (SiO{sub 2}) induced by swift heavy-ion (SHI) irradiation, from spheres to spheroids, has been evaluated mainly by transmission electron microscopy (TEM) at high fluences, where tens to thousands of ion tracks were overlapped each other. It is important to clarify whether the high fluences, i.e., track overlaps, are essential for the elongation. In this study the elongation of metal NPs was evaluated at low fluences by linearly polarized optical absorption spectroscopy. Zn NPs embedded in silica were irradiated with 200-MeV Xe{sup 14+} ions with an incident angle of 45 deg. The fluence ranged from 1.0x10{sup 11} to 5.0x10{sup 13} Xe/cm{sup 2}, which corresponds to the track coverage ratio (CR) of 0.050 to 25 by ion tracks. A small but certain dichroism was observed down to 5.0x10{sup 11} Xe/cm{sup 2} (CR = 0.25). The comparison with numerical simulation suggested that the elongation of Zn NPs was induced by nonoverlapping ion tracks. After further irradiation each NP experienced multiple SHI impacts, which resulted in further elongation. TEM observation showed the elongated NPs whose aspect ratio (AR) ranged from 1.2 to 1.7 at 5.0x10{sup 13} Xe/cm{sup 2}. Under almost the same irradiation conditions, Co NPs with the same initial mean radius showed more prominent elongation with AR of {approx}4 at the same fluence, while the melting point (m.p.) of Co is much higher than that of Zn. Less efficient elongation of Zn NPs while lower m.p. is discussed.

Amekura, H.; Mitsuishi, K.; Nakayama, Y.; Kishimoto, N. [National Institute for Materials Science (NIMS), 3-13 Sakura, Tsukuba, Ibaraki 305-0003 (Japan); Ishikawa, N.; Okubo, N. [Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki (Japan); Ridgway, M. C.; Giulian, R. [Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Canberra (Australia); Buchal, Ch.; Mantl, S. [Institut fuer Bio- und Nanosysteme (IBN1-IT), Forschungszentrum Juelich GmbH, D-52425, Juelich (Germany)

2011-05-15

52

Radiation tolerance of nanostructured ZrN coatings against swift heavy ion irradiation  

NASA Astrophysics Data System (ADS)

Nano-structured zirconium nitride layers - on Si substrates - of various thicknesses (0.1, 3, 10 and 20 ?m) were irradiated with 167 MeV Xe, 250 MeV Kr and 695 MeV Bi ions to fluences in the range from 3 × 1012 to 2.6 × 1015 cm-2 for Xe, 1 × 1013 to 7.06 × 1013 cm-2 for Kr and 1012 to 1013 cm-2 for Bi. The purpose of these irradiation experiments is to simulate the effects of fission fragment bombardment on nanocrystalline ZrN. The irradiated layers where subsequently analysed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and nano-indentation hardness testing (NIH) techniques. XRD, TEM and NIH results indicate that ZrN has a very high tolerance to the effects of high energy irradiation.

Janse van Vuuren, A.; Skuratov, V. A.; Uglov, V. V.; Neethling, J. H.; Zlotski, S. V.

2013-11-01

53

High-energy ion irradiation effects on atomic structures and optical properties of copper oxide and electronic sputtering  

Microsoft Academic Search

We have investigated high-energy ion irradiation effects on atomic structures and optical properties of copper oxide (Cu2O) film on MgO substrate. X-ray diffraction shows that the diffraction intensity decreases to half of as-deposited film for 100MeV Xe ion irradiation at 3×1012cm?2 and no amorphization has been observed, while the optical absorption shows little change and no shift of the bandgap

N. Matsunami; M. Sataka; S. Okayasu; N. Ishikawa; M. Tazawa; H. Kakiuchida

2008-01-01

54

Study of the Ionization of C, N, O, Nr, Kr and Xe Positive Ions by Electron Impact.  

National Technical Information Service (NTIS)

A description of the methods used for measuring and the results for all positive ions of C, N, O, Ne, and Ar, excluding Ne(1+) and Ar(1+ 2+), as well as qualitative data for Kr and Xe, are presented. A comparison is presented with theoretical values in th...

E. D. Donets V. P. Ovsyannikov

1980-01-01

55

Multifragmentation in intermediate energy {sup 129}Xe-induced heavy-ion reactions  

SciTech Connect

The {sup 129}Xe-induced reactions on {sup nat}Cu, {sup 89}Y, {sup 165}Ho, and {sup 197}Au at bombarding energies of E/A = 40 & 60 MeV have been studied theoretically and experimentally in order to establish the underlying mechanism of multifragmentation at intermediate energy heavy-Ion collisions. Nuclear disks formed in central heavy-ion collisions, as simulated by means of Boltzmann-like kinetic equations, break up into several fragments due to a new kind of Rayleigh-like surface instability. A sheet of liquid, stable in the limit of non-interacting surfaces, is shown to become unstable due to surface-surface interactions. The onset of this instability is determined analytically. A thin bubble behaves like a sheet and is susceptible to the surface instability through the crispation mode. The Coulomb effects associated with the depletion of charges in the central cavity of nuclear bubbles are investigated. The onset of Coulomb instability is demonstrated for perturbations of the radial mode. Experimental intermediate-mass-fragment multiplicity distributions for the {sup 129}Xe-induced reactions are shown to be binomial at each transverse energy. From these distributions, independent of the specific target, an elementary binary decay probability p can be extracted that has a thermal dependence. Thus it is inferred that multifragmentation is reducible to a combination of nearly independent emission processes. If sequential decay is assumed, the increase of p with transverse energy implies a contraction of the emission time scale. The sensitivity of p to the lower Z threshold in the definition of intermediate-mass-fragments points to a physical Poisson simulations of the particle multiplicities show that the weak auto-correlation between the fragment multiplicity and the transverse energy does not distort a Poisson distribution into a binomial distribution. The effect of device efficiency on the experimental results has also been studied.

Tso, Kin

1996-05-01

56

Production of highly charged ion beams Kr32+, Xe44+, Au54+ with Electron String Ion Source (ESIS) Krion-2 and corresponding basic and applied studies  

NASA Astrophysics Data System (ADS)

Electron String Ion Source (ESIS) Krion-2 (JINR, Dubna) was used for basic and applied research in various aspects of multiply charged heavy ions production. Energy recuperation mode in ESIS has been proofed first and used for production of highly charged ions 84Kr28+÷84Kr32+, 124Xe40÷124Xe44 and Au51+÷ Au54+. Krion-2 ESIS was mounted on high voltage (HV) platform of LU-20 Linac and used as an injector of highly charged ions during Nuclotron run N° 41. Krion-2 ESIS has produced 3.0.107 124Xe42+ ions per pulse of 7 ?s duration. This ion beam was injected into LU-20 and Nuclotron, accelerated up to energy of 186 GeV and the extracted Xe beam was used for physics experiments. Electron String Ion Source Krion-2 demonstrated the high reliability and stability running during 30 days on HV platform. We believe that it is due to an extremely low electron beam power, provided by using the electron string mode of operation: 50 W pulse power and about 10 W average power. Other possible application of ESIS could be its use in injection complexes of synchrotrons and cyclotrons for cancer therapy. Slow and fast extraction of C4+ and C6+ beams from Krion-2 ESIS were preliminary studied towards ESIS optimization for medical accelerators requirements.

Donets, D. E.; Donets, E. D.; Donets, E. E.; Salnikov, V. V.; Shutov, V. B.

2010-09-01

57

SNMS characterization of ion irradiated GaAs surfaces  

NASA Astrophysics Data System (ADS)

This study deals with the phenomena that influence the relative intensity of the sputtered neutral yields when altered layers of GaAs are analysed by using sputtered neutral mass spectrometry (SNMS) technique. The altered layers were obtained by irradiation with He +, Ne +, Ar +, Kr +, Xe + and O 2+ ions of various energies, in order to explore different nuclear stopping power regimes. The main result is a considerable change both of the absolute and relative yields of As and Ga as a function of the bombarding time, type and energy of primary ions. The absolute variation in the sputtered neutral signal is probably related with the amorphization of the outer layers. The relative variation in the yield of As with respect to Ga is not due to true preferential sputtering but to surface segregation followed by removal of the segregated species during the bombardment.

Scandurra, A.; Licciardello, A.; Torrisi, A.; Weigert, R.; Puglisi, O.

1996-09-01

58

Effects of ion irradiation on solid oxide fuel cells  

NASA Astrophysics Data System (ADS)

The solid oxide fuel cell (SOFC) is an electrochemical device that converts chemical to electrical energy. It is usually based around an oxide conducting ceramic electrolyte that requires temperatures above 800°C to operate. There are many advantages to lowering this operation temperature such as more gas sealing options and more efficient startup. One of the key limitations is in the transport of ions across the electrolyte. The most common electrolyte material used is Yttria-Stabilized Zirconia (YSZ). The ionic conductivity can be greatly affected by grain boundaries, dislocations, and point defects. In this study, dislocations were introduced by heavy ion irradiation. Irradiation with Xe+ or Ar+ produced a large number of point defects and dislocations via a mechanism similar to Frank partial dislocation formation. The dislocation density was on the order of 1012/cm2 and the Burgers vector was 1/2<110>. Heat treatment at temperatures from 800-1400°C changed the defect structure, eliminated point defects, and allowed dislocations to react and grow. Thin films of YSZ were deposited on silicon substrates using pulsed laser deposition (PLD). Films deposited on a metallized substrate were polycrystalline while films deposited directly onto conductive silicon could be epitaxially grown. Ion irradiation caused the film conductivity to drop by a factor of 2-3 due to additional point defects in the film. Heat treatment removed these point defects allowing the conductivity to recover. A novel method was developed to produce freestanding YSZ membranes without a silicon substrate by using the Focused Ion Beam (FIB). Thick, single-crystal YSZ pieces were thinned using in-situ X-Ray Energy Dispersive Spectroscopy (EDS) for end point detection. The final membranes were single crystal, less than 350nm thick, and pinhole free. IV curves and impedance measurements were made after irradiation and heat treatment. The conductivity showed similar trends to the PLD deposited thin films. In addition to the ohmic losses from the electrolyte, ion implantation also affected the activation losses of the electrode. Single crystal electrolytes were implanted with various species. The exchange current density improved by an order of magnitude following irradiation with Na+ and Xe+ on the cathode side.

Cheng, Jeremy

59

Preparation of ion-track membranes of poly( p-phenylene terephthalamide): Control of pore shape by irradiation with different ion beams  

NASA Astrophysics Data System (ADS)

The preparation of ion-track membranes of thermally stable poly( p-phenylene terephthalamide) (PPTA) was performed by ion beam irradiation followed by chemical etching with a sodium hypochlorite solution. Cylindrical pores were observed in the membrane irradiated with 197Au and 238U ions at an energy of 11.1 MeV/n. In contrast, funnel shape pores appeared in the membrane irradiated with 84Kr, 102Ru and 129Xe ion at energies of 6.2, 3.6 and 3.5 MeV/n, respectively. The 197Au and 238U ion irradiation was found to exhibit more than four times larger sensitivity to the track etching under the same etching conditions. Consequently, the pore shape can be controlled by the masses and energies of the irradiated ions, in close relation to the etching sensitivity of the track.

Suzuki, Yasuyuki; Yamaki, Tetsuya; Koshikawa, Hiroshi; Asano, Masaharu; Voss, Kay-Obbe; Neumann, Reinhard; Yoshida, Masaru

2007-07-01

60

Ion beam mixing of ZnO/SiO2 and Sb/Ni/Si interfaces under swift heavy ion irradiation  

NASA Astrophysics Data System (ADS)

We have investigated the irradiation induced interface mixing in ZnO/SiO2 (?-quartz) and Sb/Ni/Si thin layer systems under swift heavy ion irradiation in the electronic stopping power regime. The irradiations were carried out at 77 K using 100 MeV Ar, 260 MeV Kr, and 200 MeV Xe ions. For the ZnO/SiO2 system experiments were also carried out at lower ion energies (300, 600, and 900 keV, respectively) where nuclear stopping dominates. The alterations of the interface concentration profiles were determined by means of Rutherford backscattering spectrometry performed subsequently at the irradiated and the nonirradiated parts of the samples. While for the semimetal/metal Sb/Ni interface almost no mixing could be found after high-energy irradiation (mixing efficiency for Xe ions: k/Se<0.02 nm5/keV) the ceramic system ZnO/SiO2 strongly reacts upon high energy ion irradiation (Xe: k/Se=2.1 nm5/keV). The Ni/Si interface shows an intermediate effect (Xe: k/Se=0.2 nm5/keV). The mixing behavior found at high ion energies is in contrast to that found in the nuclear stopping regime, where Sb/Ni shows very strong mixing and phase formation while ZnO/SiO2 exhibits only weak ballistic mixing. As was previously observed for the formation of ion tracks, interface mixing due to electronic energy deposition also sets in only if the electronic stopping power exceeds a threshold value.

Kraft, Saskia; Schattat, Beate; Bolse, Wolfgang; Klaumünzer, Siegfried; Harbsmeier, Felix; Kulinska, Agnieszka; Löffl, Anton

2002-02-01

61

Ion irradiation induced order-to-disorder transformation in ?-phase Lu4Hf3O12  

NASA Astrophysics Data System (ADS)

In this study, polycrystalline ?-phase Lu4Hf3O12 was irradiated with 6 MeV Xe26+ ions to fluences ranging from 2 × 1013 to 1 × 1015 ions/cm2. Ion irradiation-induced microstructural evolution was examined by using grazing incidence X-ray diffraction (GIXRD). A complete phase transformation from ordered rhombohedral to disordered fluorite (O-D) was observed by a fluence of 1 × 1015 ions/cm2, equivalent to a peak ballistic damage dose of ˜3.49 displacements per atom (dpa). To research the different irradiation effect between light ion and heavy ion on ?-Lu4Hf3O12, 400 keV Ne2+ ions were implanted to ion fluences ranging from 1×1014 to 1×1015 ions/cm2. A complete O-D crystal structure transformation was observed by a fluence of 5×1014 ions/cm2 (˜0.22 dpa). This threshold dose was found to be observably lower than the threshold dose to produce order-to-disorder transformation using Xe26+ ions on ?-Lu4Hf3O12. This suggests that heavy ions are less efficient than light ions in producing the retained defects that are responsible for the O-D transformation. The theoretical calculations show that the O-D transformation of ?-phase was attributed to the anion oxygen Frenkel pair defect. The ion irradiation-induced transformation of ?-phase Lu4Hf3O12 into disordered fluorite structure observed here is also discussed in relation to the temperature-composition (T-C) phase diagrams for the compound.

Wen, J.; Gao, C.; Li, Y. H.; Wang, Y. Q.; Zhang, L. M.; Hu, B. T.; Chen, L. J.; Su, X.

2013-09-01

62

Electron cyclotron resonance ion source related development work for heavy-ion irradiation tests  

SciTech Connect

The European Space Agency (ESA) uses the facilities at the Accelerator Laboratory (Department of Physics, University of Jyvaeskylae: JYFL) for heavy-ion irradiation tests of electronic components. Electron cyclotron resonance ion source related development work has been carried out in order to meet the requirements set by the project. During the irradiation tests several beam changes are performed during the day. Therefore, the time needed for the beam changes has to be minimized. As a consequence, a beam cocktail having nearly the same m/q ratio is used. This makes it possible a quick tuning of the cyclotron to select the required ion for the irradiation. In addition to this requirement, very high charge states for the heavy elements are needed to reach a penetration depth of 100 {mu}m in silicon. In this article we present some procedures to optimize the ion source operation. We also present results of the first three-frequency heating tests. The main frequency of 14 GHz was fed from a klystron and both secondary frequencies were launched from a traveling-wave tube amplifier (TWTA). Two separate frequency generators were used simultaneously to provide different signals for the TWTA. During the test an improvement of about 20% was observed for {sup 84}Kr{sup 25+} and {sup 129}Xe{sup 30+} ion beams when the third frequency was applied.

Koivisto, H.; Suominen, P.; Tarvainen, O.; Virtanen, A.; Parkkinen, A. [Department of Physics, University of Jyvaeskylae, P.O. Box. 35 (Y5), FIN-40014 Jyvaeskylae (Finland); Finnish Airforce C4IS MC, 41160, Tikkakoski (Finland)

2006-03-15

63

Electron cyclotron resonance ion source related development work for heavy-ion irradiation tests  

NASA Astrophysics Data System (ADS)

The European Space Agency (ESA) uses the facilities at the Accelerator Laboratory (Department of Physics, University of Jyväskylä: JYFL) for heavy-ion irradiation tests of electronic components. Electron cyclotron resonance ion source related development work has been carried out in order to meet the requirements set by the project. During the irradiation tests several beam changes are performed during the day. Therefore, the time needed for the beam changes has to be minimized. As a consequence, a beam cocktail having nearly the same m/q ratio is used. This makes it possible a quick tuning of the cyclotron to select the required ion for the irradiation. In addition to this requirement, very high charge states for the heavy elements are needed to reach a penetration depth of 100 ?m in silicon. In this article we present some procedures to optimize the ion source operation. We also present results of the first three-frequency heating tests. The main frequency of 14 GHz was fed from a klystron and both secondary frequencies were launched from a traveling-wave tube amplifier (TWTA). Two separate frequency generators were used simultaneously to provide different signals for the TWTA. During the test an improvement of about 20% was observed for 84Kr25+ and 129Xe30+ ion beams when the third frequency was applied.

Koivisto, H.; Suominen, P.; Tarvainen, O.; Virtanen, A.; Parkkinen, A.

2006-03-01

64

Study of the effect of high electronic excitations in quasicrystals irradiated with heavy ions  

NASA Astrophysics Data System (ADS)

We have studied the effect of irradiation with 900 MeV Pb and 780 MeV Xe ions on quasicrystals Al 62Cu 25.5Fe 12.5 and the related cubic ?-phase Al 55Cu 27Fe 11Si 7. The fluences ranged from 10 10 to 5.8 × 10 13 ions/cm 2. Irradiations were performed at 80 K and at room temperature. The structural changes induced by the electronic excitations were studied by high-resolution X-ray diffraction. Whereas one might have expected the irradiations to induce important structural transformations, e.g. a phase transition from an icosahedral to a rhombohedral phase, only minor structural modifications are observed in the icosahedral phase and none in the ?-phase. The defects created are not phasonic. Our results suggest a remarkable structural stability of these phases with respect to heavy-ion irradiation.

Coddens, Gerrit; Dunlop, Annie; Dammak, Hichem; Chatterjee, Ratnamala; Calvayrac, Yvonne; Quiquandon, Marianne; Elka??m, Erik; Gailhanou, Mark; Rouzière, Stéphan

2003-09-01

65

Interdigitated 50 nm Ti electrode arrays fabricated using XeF2 enhanced focused ion beam etching  

NASA Astrophysics Data System (ADS)

The fabrication of interdigitated titanium nanoelectrode arrays of 50 nm in width and spacing is described in this work. The nanoarrays have been realized using a Ga+ focused ion beam (FIB). FIB milling is typically accompanied by redeposition of removed material, which represents an important hindrance for milling closely spaced nanostructures. Redeposition effects have been reduced by means of XeF2 gas assistance, which increases the etch yield by a factor of seven compared with pure ion milling. Furthermore, we used a simple adsorption model, which led to the conclusion that dwell time and refresh time should be <500 ns and >30 ms, respectively, for optimized XeF2 assisted Ti milling. The measured resistance R of the electrodes is higher than 1 G?.

Santschi, Ch; Jenke, M.; Hoffmann, P.; Brugger, J.

2006-06-01

66

Atomistic simulation of track formation in nuclear fuels due to heavy ion irradiation  

NASA Astrophysics Data System (ADS)

At moving of the swift heavy ion (e.g. Xe ion - the typical fission fragment), the track formation takes place in nuclear materials. There is a large interest in understanding of the mechanisms of this process. In this work, the atomistic simulation of track formation due to the swift heavy ion irradiation is performed for various nuclear materials (U, UO2). The two-temperature atomistic model with explicit account of electron pressure and electron thermal conductivity is used. This two-temperature model describes ionic subsystem by means of molecular dynamics while the electron subsystem is considered in the continuum approach. The various mechanisms of track formation are examined.

Starikov, S.; Stegailov, V.; Pisarev, V.

2014-06-01

67

Azimuthal angular distributions of Xe + and Kr + ion-induced Al L 23 auger electrons  

NASA Astrophysics Data System (ADS)

Azimuthal angular distributions of L 23 Al Auger electrons emitted in collisions between 40 keV Xe + and Kr + ions and single crystal aluminium were studied. The azimuthai profiles of Auger electrons arising from L 23MM atomic-like transitions were compared to theoretical angular distributions. In this single step model, the wave function of the outgoing electron is well matched at the surface and takes into account multiple scattering and absorption processes through the use of a LEED formalism. The three other particle states are represented by atomic wave functions. From the comparison of experimental and calculated results it appears that the narrow line centred at 63.5 eV displays a low azimuthal angular anisotropy. Given this anisotropy is always lower than that of L 23VV electrons, it could be deduced that the L 23MM Auger electrons are not emitted from deep in the solid but however are emitted close enough to the surface to be still influenced by the crystal lattice.

Nègre, Michel; Mischler, Josette; Benazethy, Nicole

1985-07-01

68

Fragmentation of DNA components by hyperthermal heavy ion (Ar+ and Xe+) impact in the condensed phase  

NASA Astrophysics Data System (ADS)

The overriding environmental factor that presently limits human endeavors in space is exposure to heavy ion radiation. While knowledge of its damage to living tissue is essential for radiation protection and risk estimates for astronauts, very little data exists at the molecular level regarding the nascent DNA damage by the primary particle track, or by secondary species during subsequent reaction cascades. This persistent lack of a basic understanding of nascent damage induced by such low dose, high LET radiation, introduces unacceptable errors in radiation risk estimates (based mainly on extrapolation from high dose, low LET radiation), particularly for long term exposure. Mutagenic effects induced by heavy ion radiation to cells are largely due to DNA damage by secondary transient species, i.e. secondary ballistic ions, electrons and radicals generated along the ion tracks; the secondary ions have hyperthermal energies up to several 100 eV, which they will deposit within a few nm in the surrounding medium; thus their LET is very high, and yields lethal clustered DNA lesions. We present measurements of molecular damage induced in films of DNA components by ions with precisely such low energies (1-100 eV) and compare results to conventional electron impact measurements. Experiments are conducted in UHV using a mass selected low energy ion source, and a high-resolution quadrupole MS to monitor ion yields desorbing from molecular films. Among the major fragments, NH4 + is identified in the desorption mass spectra of irradiated films of Adenine, Guanine, Cytosine, indicating efficient deamination; in cells this results in pre-mutagenic lesions. Experiments with 5-amino-Uracil, and comparison to previous results on uracil and thymine show that deamination is a key step in the NH4 + fragment formation. For Adenine, we also observe formation of amine aducts in the films, viz. amination of Adenine, and global fragmentation in all ion impact mass spectra, attributed mainly to kinetic & potential ion scattering.[Funded by NSERC and the Canadian Space Agency].

Sarabipour, Sarvenaz; Sarvenaz Sarabipour, Ms; Michaud, Marc; Deng, Zongwu; Huels, Michael A.

69

Damage creation in porous silicon irradiated by swift heavy ions  

NASA Astrophysics Data System (ADS)

Mesoporous silicon (PS) samples were processed by anodising p+ Si wafers in (1:1) HF–ethanol solution. Different current densities were used to obtain three different porosities (41%, 56% and 75%). In all cases the morphology of the PS layer is columnar with a mean crystallite size between 12 nm (75% porosity) and 19 nm (41% porosity). These targets were irradiated at the GANIL accelerator, using different projectiles (130Xe ions of 91 MeV and 29 MeV, 238U ions of 110 MeV and 850 MeV) in order to vary the incident electronic stopping power Se. The fluences ranged between 1011 and 7 × 1013 cm?2. Raman spectroscopy and cross sectional SEM observations evidenced damage creation in the irradiated nanocrystallites, without any degradation of the PS layer morphology at fluences below 3 × 1012 cm?2. For higher doses, the columnar morphology transforms into a spongy-like structure. The damage cross sections, extracted from Raman results, increase with the electronic stopping power and with the sample porosity. At the highest Se (>10 keV nm?1) and the highest porosity (75%), the track diameter coincides with the crystallite diameter, indicating that a single projectile impact induces the crystallite amorphization along the major part of the ion path. These results were interpreted in the framework of the thermal spike model, taking into account the low thermal conductivity of the PS samples in comparison with that of bulk silicon.

Canut, B.; Massoud, M.; Newby, P.; Lysenko, V.; Frechette, L.; Bluet, J. M.; Monnet, I.

2014-05-01

70

In situ RBS measurements for the effect of swift heavy ion irradiation on metal-insulator interfaces  

NASA Astrophysics Data System (ADS)

We have studied the effect of 200 MeV Xe ion irradiation on Bi-Al2O3 and Au-Al2O3 interfaces by means of in situ Rutherford backscattering spectrometry (RBS). For the Bi-Al2O3 interface, we could observe a systematic change in RBS spectrum as a function of Xe ion fluence or the irradiation time. On the other hand, for Au-Al2O3 system, we could not observe any change in RBS spectrum. The experimental result confirmed our previous result that atomic mixing at Bi-Al2O3 interface surely occurs by the Xe ion irradiation. We analyzed the RBS spectra by the simulation software SIMNRA, and discussed the Bi-Al2O3 mixing quantitatively. From the irradiation time dependence of the mixing layer thickness, we estimated the effective diffusion constant for the atomic mixing at Bi-Al2O3 interface. Its value corresponds to the self-diffusion near the melting temperature of Al2O3. The result implies that Bi and Al2O3 are in molten forms during the ion irradiation, resulting in the atomic mixing at Bi-Al2O3 interface.

Hayashi, M.; Matsuda, M.; Asozu, T.; Sataka, M.; Nakamura, M.; Iwase, A.

2013-11-01

71

Ion irradiation-induced diffusion in bixbyite-fluorite related oxides: Dislocations and phase transformation  

NASA Astrophysics Data System (ADS)

Ion-irradiation induced diffusion and the phase transformation of a bixbyite-fluorite related rare earth oxide thin films are studied. This work is focused on yttrium sesquioxide, Y2O3, thin films deposited on Si (1 0 0) substrates using the ion beam sputtering technique (IBS). As-deposited samples were annealed ant then irradiated at cryogenic temperature (80 K) with 260 keV Xe2+ at different fluences. The irradiated thin oxide films are characterized by X-ray diffraction. A cubic to monoclinic phase transformation was observed. Analysis of this phenomenon is done in terms of residual stresses. Stress measurements as a function of irradiation fluences were realised using the XRD-sin2? method. Stress evolution and kinetic of the phase transformation are compared and leads to the role-played by the nucleation of point and extended defects.

Rolly, Gaboriaud; Fabien, Paumier; Bertrand, Lacroix

2014-05-01

72

Development of function-graded proton exchange membrane for PEFC using heavy ion beam irradiation  

NASA Astrophysics Data System (ADS)

The graded energy deposition of heavy ion beam irradiation to polymeric materials was utilized to synthesize a novel proton exchange membrane (PEM) with the graded density of sulfonic acid groups toward the thickness direction. Stacked Poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) films were irradiated by Xe 54+ ion beam with the energy of 6 MeV/u under a vacuum condition. The induced trapped radicals by the irradiation were measured by electron spin resonance (ESR) spectroscopy. Irradiated films were grafted with styrene monomer and then sulfonated. X-ray photo-electron spectroscopy (XPS) spectra showed that the densities of sulfonic acid groups were controlled for injection "Surface" and transmit "Back" sides of the fabricated PEM. The membrane electrode assembly (MEA) fabricated by the function-graded PEM showed improved fuel cell performance in terms of voltage stability. It was expected that the function-graded PEM could control the graded concentration of sulfonic acid groups in PEM.

Shiraki, Fumiya; Yoshikawa, Taeko; Oshima, Akihiro; Oshima, Yuji; Takasawa, Yuya; Fukutake, Naoyuki; Gowa Oyama, Tomoko; Urakawa, Tatsuya; Fujita, Hajime; Takahashi, Tomohiro; Oka, Toshitaka; Kudo, Hisaaki; Murakami, Takeshi; Hama, Yoshimasa; Washio, Masakazu

2011-08-01

73

Anisotropic proton-conducting membranes prepared from swift heavy ion-beam irradiated ETFE films  

NASA Astrophysics Data System (ADS)

Poly(ethylene-co-tetrafluoroethylene) (ETFE) films were irradiated by swift heavy ion-beams of 129Xe 23+ with fluences of 0, 3 × 10 6, 3 × 10 7, 3 × 10 8 and 3 × 10 9 ions/cm 2, followed by ?-ray pre-irradiation for radiation grafting of styrene onto the ETFE films and sulfonation of the grafted ETFE films to prepare highly anisotropic proton-conducting membranes. The fluence of Xe ions and the addition of water in the grafting solvent were examined to determine their effect on the proton conductivity of the resultant membranes. It was found that the polymer electrolyte membrane prepared by grafting the styrene monomer in a mixture of 67% isopropanol and 33% water to the ETFE film with an ion-beam irradiation fluence of 3.0 × 10 6 ions/cm 2 was a highly anisotropic proton-conducting material, as the proton conductivity was three or more times higher in the thickness direction than in the surface direction of the membrane.

Kimura, Yosuke; Chen, Jinhua; Asano, Masaharu; Maekawa, Yasunari; Katakai, Ryoichi; Yoshida, Masaru

2007-10-01

74

Photoionization Cross Section of Xe{sup +} Ion in the Pure 5p{sup 5} {sup 2}P{sub 3/2} Ground Level  

SciTech Connect

Coupling an ion trap with synchrotron radiation is shown here to be a powerful approach to measure photoionization cross sections on ionic species relaxed in their ground state. The photoionization efficiency curve of Xe{sup +} ions stored in a Fourier transform ion cyclotron resonance ion trap was recorded at ELETTRA in the 20-23 eV photon energy range. Absolute cross sections were derived by comparison of the photoionization yield of Xe{sup +} with measurements from the ASTRID merged-beam experiment. Multiconfiguration Dirac-Fock calculations were performed for the interpretation of these new data.

Thissen, R. [Laboratoire de Planetologie de Grenoble, UMR 5109 du CNRS, Batiment D de Physique, B.P. 53, 38041 Grenoble (France); Bizau, J. M. [Laboratoire d'Interaction des Rayons X avec la Matiere (LIXAM), UMR 8624 du CNRS, Universite Paris-Sud, Batiment 350, 91405 Orsay cedex (France); Blancard, C. [CEA DAM Ile-de-France, DPTA, Bruyeres-le-Chatel, 91297 Arpajon Cedex (France); Coreno, M. [CNR-IMIP, Rome Branch, c/o GasPhase Beamline, Sincrotrone Trieste, I- 34012 Basovizza, Trieste (Italy); Dehon, C.; Lemaire, J. [Laboratoire de Chimie Physique, UMR 8000 du CNRS, Universite Paris-Sud, Batiment 350, 91405 Orsay cedex (France); Franceschi, P. [Sincrotrone Trieste, SS-14 in Area Science Park, I-34012 Basovizza, Trieste (Italy); Giuliani, A. [Synchrotron SOLEIL, L'Orme des Merisiers, Saint Aubin, B.P. 48, 91192 Gif-sur-Yvette (France); Cepia, Institut National de la Recherche Agronomique (INRA), B.P. 71627, 44316 Nantes Cedex 3 (France); Nicolas, C. [Synchrotron SOLEIL, L'Orme des Merisiers, Saint Aubin, B.P. 48, 91192 Gif-sur-Yvette (France)

2008-06-06

75

Oxygen intake in ion irradiated fullerene films  

NASA Astrophysics Data System (ADS)

The present work reports the change in the oxygen content in energetic ion irradiated fullerene films. The oxygen contents in irradiated films have been studied using on-line elastic recoil detection analysis (ERDA) and off-line X-ray photo electron emission (XPS) and nuclear reaction analysis (NRA) techniques. The XPS and NRA techniques show that the oxygen content increases with ion fluence, whereas on-line ERDA measurements reveal that the oxygen content decreases with ion fluence. These experiments give clear evidence that oxygen content in irradiated films increases after exposure to the atmospheric oxygen.

Kumar, Amit; Khan, S. A.; Kumar, Manvendra; Agarwal, D. C.; Singh, Fouran; Tripathi, A.; Govind; Shivaprasad, S. M.; Salomon, J.; Pichon, L.; Pivin, J. C.; Avasthi, D. K.

2008-04-01

76

Melting of crystalline and amorphous silicon by Ruby, XeCl and KrF laser irradiation  

SciTech Connect

Pulses of radiation from a ruby laser (lambda = 693 nm, FWHM = 12 ns), a XeCl excimer laser (lambda = 308 nm, FWHM = 25 and 70 ns), and a KrF excimer laser (lambda = 248 nm, FWHM = 32 ns) have been used to induce melting of crystalline silicon and thin (<1 ..mu..m) amorphous layers of Si on crystalline silicon substrates. Depths of melting in crystalline Si were measured by TEM observations of the removal of dislocation loops created by low-dose ion implantation. Depths of melting of amorphous Si layers were monitored by observing the boundaries between a large polycrystalline region, assumed to form by normal melting from and resolidification back to the free surface, and a fine polycrystalline region, assumed to form by the explosive propagation inward of a thin buried liquid layer. In this work we report the comparison of predictions of heat flow calculations to the measured depth of melting in both crystalline and amorphous silicon. Excellent agreement is found with the Ruby and the XeCl results. Reasonable agreement with the KrF results is obtained only if the silicon liquid phase reflectivity at 249 nm is significantly less than that obtained by extrapolation of the optical parameters from longer wavelengths.

Aziz, M.J.; White, C.W.; Narayan, J.; Stritzker, B.

1985-06-01

77

The effects of nuclear and electronic stopping powers on ion irradiated novolac diazoquinone films  

NASA Astrophysics Data System (ADS)

The structure and surface modifications induced in ion irradiated AZ-1350 J photoresist films as function of energy, fluence and the amount of electronic and nuclear deposited energy density are investigated in detail. The films have been irradiated with 380 keV He +, 4 MeV I 2+ and 800 keV Xe 2+ ions, in a fluence range from 10 13 to 10 16 cm -2. At these energies, the ranges of the ions are larger than the thickness of the films and the transferred energy to the films extends from nearly pure electronic (for He +) to predominantly nuclear stopping power (for Xe 2+). The structural, chemical and mechanical properties of the samples were investigated through the techniques of nuclear reaction analysis, elastic recoil detection analysis, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and nanoindentation. When the electronic stopping prevails, as for 380 keV He + irradiation at low and intermediate fluences, the deposited electronic energy density is the main cause for the observed increase of hardness ( H), Young modulus ( E) and gel fraction through the cross-linking process, preserving most of the chemical characteristics of the original material. When nuclear stopping is large (Xe and I irradiations) the cross-linking process is only present at very low fluences. At intermediate and higher fluences the transference of nuclear energy density induces a large loss of oxygen and hydrogen and the photoresist is progressively transformed into an amorphous carbon layer. At the highest fluences, the hardness, Young modulus, density and Raman spectra are characteristics of a hydrogenated amorphous carbon system. We also show that the loss of hydrogen as function of fluence is well explained by the bulk molecular recombination model, which assumes that the hydrogen leaves the irradiated materials in molecular form.

Garcia, Irene T. S.; Zawislak, F. C.; Samios, D.

2004-04-01

78

Calibration of the Galileo micro channel plate with the Xe7+ +Xe43+ ions in the energy range from 2 keV\\/1 up to 154 keV\\/q  

Microsoft Academic Search

The procedure of calibration of the detector assembly consisting of the two Galileo micro channel plates (MCPs) operated in a Chevron configuration is described. The current gains and the analog particle gains of the MCPs for Xe ions with charge states from q=7+ to q=43+ and ion impact energies to charge state ratios from 2 keV\\/q to 154 keV\\/q have

W. Mroz; D. Fry; A. Prokopuik; M. P. Stockli; B. Walch

1998-01-01

79

Particle emission induced by the interaction of highly charged slow Xe-ions with a SiO2 surface  

NASA Astrophysics Data System (ADS)

Sputtering of surface atoms by low energy (a few keV) heavy ions is a commonly used technique in material science and applied physics. In general, sputtering occurs via nuclear energy transfer processes and is determined mainly by the atom-atom interaction potentials. In the energy range of interest, these potentials depend only slightly on the charge state of one collision partner if the other is neutral. The development of new ion-sources, however, allows for the use of ions with charged states of q greater than 50. For these highly charged ions it is conceivable that electronic processes come into play as well. If, for example, the density of charged surface atoms exceeds a certain limit, then particle emission can occur via the electrostatic repulsion of target atoms, the so-called Coulomb explosion. Indications for such electronic effects have been found in a few investigations of ion-induced sputtering Si (q less than 12 in Ar(q+)). However, the order of magnitude of this effect was not clear until now. In this work, we present preliminary data on sputtering, ion backscattering, and electron and photon emission from SiO2 surface induced by incident Xe ions of very high charge states (q=30 to 50). The experiment was performed at the electron beam ion trap (EBIT) of the Lawrence Livermore National Laboratory using a time-of-flight (TOF) ion analyzer-system from the Hahn-Meitner-Institute, Berlin.

Schiwietz, G.; Skogvall, B.; Schneider, D.; Clark, M.; Dewitt, D.; McDonald, J.

1991-10-01

80

Fabrication of micro/nano-structures using focused ion beam implantation and XeF2 gas-assisted etching  

NASA Astrophysics Data System (ADS)

A micro/nano-structure fabrication method is developed using focused ion beam implantation (FIBI) and FIB XeF2 gas-assisted etching (FIB-GAE). Firstly, the FIB parameters' influence on the FIBI depth is studied by SEM observation of the FIBI cross-section cutting by FIB. Nanoparticles with 10-15 nm diameter are found to be evenly distributed in the FIBI layer, which can serve as a XeF2-assisted etching mask when the ion dose is larger than 1.4 × 1017 ions cm-2. The FIBI layers being used as the etching mask for the subsequent FIB-GAE process are explored to create different micro/nano-structures such as nano-gratings, nano-electrode and sinusoidal microstructures. It is found that the method of combining FIBI with subsequent FIB-GAE is efficient and flexible in micro/nano-structuring, and it can effectively remove the redeposition effect compared with the FIB milling method.

Xu, Z. W.; Fang, F. Z.; Fu, Y. Q.; Zhang, S. J.; Han, T.; Li, J. M.

2009-05-01

81

Fe K-shell ionization induced by Xe20+ ions near the Bohr velocity  

NASA Astrophysics Data System (ADS)

Fe K-shell ionization cross sections by 2.4-6.0 MeV Xe20+ impact were investigated. It was found that the BEA model corrected both by the Coulomb repulsion and the effective nuclear charge gives the best agreement with the experimental data.

Xianming, Zhou; Yongtao, Zhao; Rui, Cheng; Jieru, Ren; Shidong, Liu; Yu, Lei; Yuanbo, Sun; Yuyu, Wang; Ge, Xu; Guoqing, Xiao

2014-04-01

82

3-10 keV Xe + ion beam machining of ultra low thermal expansion glasses for EUVL projection optics: Evaluation of surface roughness  

NASA Astrophysics Data System (ADS)

In order to obtain surface figure error of 0.15 nm rms and surface roughness ( R rms) of 0.12 nm rms for aspherical substrates in EUVL tools, ion beam figuring may be adopted to final surface figure error correction of aspherical substrates. During figure error correction, machined surface of the substrate becomes rougher than the pre-finished one. Therefore, we investigated the machined depth and ion energy dependences of R rms (measured by an AFM) of substrates machined by 3-10 keV Xe + ion beam, and compared them with the results obtained for Ar + ion beam. Result shows that the R of CLEARCERAM®-Z, Zerodur® and ULE® substrates machined to the depth of 50 nm by 3-10 keV Xe + ion beam at the normal ion incidence angle become approximately 0.25, 0.28 and 0.15 nm rms, respectively. Those values are larger than the pre-finished substrates (0.07-0.09 nm rms), but smaller than that (0.60 nm rms for CLEARCERAM®-Z, 0.61 nm rms for Zerodur® and 0.18 nm rms for ULE®) of the substrates machined by Ar + ion beam. Moreover, the R merely increase with increasing ion energy. The R of the ULE® substrate machined by 3-10 keV Xe + ion beam rapidly increase with increasing machined depth, then saturate at machined depth of 10-50 nm. The saturated values of the R are 0.12 and 0.15 nm rms for 3 and 10 keV Xe + ion beam respectively. We suggest that the 3 keV Xe + ion beam machining can be applicable for final shape correction of ULE® substrates for EUVL projection optics in association with considering further ultra smoothing process such as Si deposition or low energy ion beam smoothing.

Morikawa, K.; Kamijo, K.; Morijiri, K.; Pahlovy, S. A.; Aikawa, N.; Miyamoto, I.

2012-02-01

83

Swift heavy ion irradiation of diamond powder  

NASA Astrophysics Data System (ADS)

Sub-micrometer sized diamond powder was irradiated with 1.4 GeV uranium ions at fluences of 5 × 1012, 1 × 1013 and 8 × 1013 ions/cm2. The resulting structure of the irradiated diamond powder was investigated by synchrotron X-ray diffraction (XRD), Raman scattering and transmission electron microscopy. The high-resolution XRD measurements show that the diamond unit cell parameter increases with irradiation, and the unit cell volume increases by about 1.3‰ for the highest fluence. However, no peak broadening was observed and an ion-induced sharpening was evident after irradiation. Raman, TEM and EELS analysis confirmed that the diamond undergoes a radiation-induced transformation to a graphite-like carbon.

Zhang, Fuxiang; Lang, Maik; Zhang, Jiaming; Ewing, Rodney C.

2012-09-01

84

Damage accumulation in gallium nitride irradiated with various energetic heavy ions  

NASA Astrophysics Data System (ADS)

In this work a study of damage production in gallium nitride via elastic collision process (nuclear energy deposition) and inelastic collision process (electronic energy deposition) using various heavy ions is presented. Ordinary low-energy heavy ions (Fe + and Mo + ions of 110 keV), swift heavy ions ( 208Pb 27+ ions of 1.1 MeV/u) and slow highly-charged heavy ions (Xe n+ ions of 180 keV) were employed in the irradiation. Damage accumulation in the GaN crystal films as a function of ion fluence and temperature was studied with RBS-channeling technique, Raman scattering technique, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For ordinary low-energy heavy ion irradiation, the temperature dependence of damage production is moderate up to about 413 K resulting in amorphization of the damaged layer. Enhanced dynamic annealing of defects dominates at higher temperatures. Correlation of amorphization with material decomposition and nitrogen bubble formation was found. In the irradiation of swift heavy ions, rapid damage accumulation and efficient erosion of the irradiated layer occur at a rather low value of electronic energy deposition (about 1.3 keV/nm 3), which also varies with irradiation temperature. In the irradiation of slow highly-charged heavy ions (SHCI), enhanced amorphization and surface erosion due to potential energy deposition of SHCI was found. It is indicated that damage production in GaN is remarkably more sensitive to electronic energy loss via excitation and ionization than to nuclear energy loss via elastic collisions.

Zhang, C. H.; Song, Y.; Sun, Y. M.; Chen, H.; Yang, Y. T.; Zhou, L. H.; Jin, Y. F.

2007-03-01

85

Swift heavy ion irradiation of InP: Thermal spike modeling of track formation  

NASA Astrophysics Data System (ADS)

Irradiation of single-crystalline InP with swift heavy ions (SHI’s) causes the formation of ion tracks for certain irradiation temperatures if the electronic energy deposition exceeds a threshold value. With increasing SHI fluence, more and more ion tracks are formed, until a continuous amorphous layer is produced due to the multiple overlapping of the tracks at high ion fluences. Single-crystalline InP samples were irradiated either at liquid nitrogen temperature (LNT) or at room temperature (RT) with Kr, Xe, or Au ions with specific energies ranging from ca. 0.3to3.0MeV/u . Afterwards, the samples were investigated by means of Rutherford backscattering spectrometry and transmission electron microscopy in the plan-view and cross-section geometry. We show that the experimental data obtained can be qualitatively and quantitatively described on the basis of the inelastic thermal spike (TS) model, which was originally used only for metallic targets. The presented extension of the TS model on semiconductors covers mainly the very first stage of the energy transfer from SHI’s (so-called “ionization spikes”). Our results show that the extended TS model offers a self-consistent way to explain the influence of various irradiation conditions (ion mass, ion energy, irradiation temperature, etc.) on the ion track formation and damage accumulation in InP and, therefore, can make a contribution to a better understanding of the underlying mechanisms. Further, our results prejudice the amenity of a single value of the threshold electronic energy loss as a fundamental quantity that is commonly used for the description of track formation in solids irradiated with different ion species. There is no universal RT threshold for track formation in InP, but it is noticeably higher for lighter ions (12.0 and 14.8keV/nm for RT irradiations with Au and Xe, respectively). Our experimental and simulation results support the idea that the formation of visible tracks requires a predamaging of the material, unless each SHI penetrating perfectly ordered virgin InP directly produces a track that is large enough to be stable.

Kamarou, A.; Wesch, W.; Wendler, E.; Undisz, A.; Rettenmayr, M.

2006-05-01

86

Ion beam irradiation in La2Zr2O7Ce2Zr2O7 pyrochlore  

Microsoft Academic Search

Generally, zirconate pyrochlores do not experience a radiation-induced transformation from the crystalline-to-amorphous state, but rather disorder to a defect fluorite structure-type. Thus Gd2Zr2O7 has been proposed as a nuclear waste form for the immobilization of plutonium because of its radiation ``stability''. In contrast, La2Zr2O7 can be amorphized by a 1.5 MeV Xe+ ion irradiation (~5.5 dpa at room temperature), and

J. Lian; L. M. Wang; R. G. Haire; K. B. Helean; R. C. Ewing

2004-01-01

87

Ion beam irradiation in La 2Zr 2O 7–Ce 2Zr 2O 7 pyrochlore  

Microsoft Academic Search

Generally, zirconate pyrochlores do not experience a radiation-induced transformation from the crystalline-to-amorphous state, but rather disorder to a defect fluorite structure-type. Thus Gd2Zr2O7 has been proposed as a nuclear waste form for the immobilization of plutonium because of its radiation “stability”. In contrast, La2Zr2O7 can be amorphized by a 1.5 MeV Xe+ ion irradiation (?5.5 dpa at room temperature), and

J. Lian; L. M. Wang; R. G. Haire; K. B. Helean; R. C. Ewing

2004-01-01

88

Heavy ion irradiation of astrophysical ice analogs  

NASA Astrophysics Data System (ADS)

Icy grain mantles consist of small molecules containing hydrogen, carbon, oxygen and nitrogen atoms (e.g. H2O, CO, CO2, NH3). Such ices, present in different astrophysical environments (giant planets satellites, comets, dense clouds, and protoplanetary disks), are subjected to irradiation of different energetic particles: UV radiation, ion bombardment (solar and stellar wind as well as galactic cosmic rays), and secondary electrons due to cosmic ray ionization of H2. The interaction of these particles with astrophysical ice analogs has been the object of research over the last decades. However, there is a lack of information on the effects induced by the heavy ion component of cosmic rays in the electronic energy loss regime. The aim of the present work is to simulate of the astrophysical environment where ice mantles are exposed to the heavy ion cosmic ray irradiation. Sample ice films at 13K were irradiated by nickel ions with energies in the 1-10 MeV/u range and analyzed by means of FTIR spectrometry. Nickel ions were used because their energy deposition is similar to that deposited by iron ions, which are particularly abundant cosmic rays amongst the heaviest ones. In this work the effects caused by nickel ions on condensed gases are studied (destruction and production of molecules as well as associated cross sections, sputtering yields) and compared with respective values for light ions and UV photons.

Duarte, Eduardo Seperuelo; Domaracka, Alicja; Boduch, Philippe; Rothard, Hermann; Balanzat, Emmanuel; Dartois, Emmanuel; Pilling, Sergio; Farenzena, Lucio; da Silveira, Enio Frota

89

Ion irradiation studies of oxide ceramics  

SciTech Connect

This paper presents the initial results of an investigation of the depth-dependent microstructures of three oxide ceramics following ion implantation to moderate doses. The implantations were performed using ion species that occur as cations in the target material; for example, Mg/sup +/ ions were used for MgO and MgAl/sub 2/O/sub 4/ (spinel) irradiations. This minimized chemical effects associated with the implantation and allowed a more direct evaluation to be made of the effects of implanted ions on the microstructure. 11 refs., 14 figs.

Zinkle, S.J.

1988-01-01

90

Effect of swift heavy ion irradiation on single- and multiwalled carbon nanotubes  

NASA Astrophysics Data System (ADS)

The effect of irradiation with swift heavy ions on the structure and properties of carbon nanotubes was investigated by Raman spectroscopy. It was found that disordering of the system occurred mainly at the surface. No ordering phenomena have been observed over a whole range of both fluences and electronic stopping powers studied. The disorder parameter (i.e., the ratio of the D and G band intensities (I/I)) increases non-linearly with the irradiation dose, showing a tendency to saturate at high fluences. The increase in the disorder parameter upon irradiation was proportional to the square root of the ion fluence. The radiation stability of the few-walled nanotubes was ca. 1.6 higher than that of the single-walled ones. The irradiation with both the Xe and Kr ions leads to essentially the same increase in the I/I ratio with respect to the deposited electronic energy density. In the case of the Ar ion irradiation, the observed increase in the I/I ratio is much lower, suggesting that the electronic stopping power threshold for defects creation in carbon nanotubes is lower than that for graphite.

Olejniczak, Andrzej; Skuratov, Vladimir A.

2014-05-01

91

Ion irradiation-induced phase transformations in bixbyite-fluorite related oxides: The role of dislocation loop nucleation  

NASA Astrophysics Data System (ADS)

The ion irradiation induced phase transformations of bixbyite-fluorite related oxides have been studied with thin films of Y2O3 grown on Si and SrTiO3 by an ion beam sputtering technique which allows to control the microstructure and stresses within the film. Y2O3 thin films are ion-irradiated with an xenon beam in an energy range 60-380 keV at a fluence of 4.4 × 1015 Xe/cm2 at 80 K. Depending on the energy of the xenon beam two different structural phase transformations are observed: cubic to nanocrystalline/amorphous and cubic to monoclinic phase transformations. The phase transformation are analysed in terms of structural extended defect nucleation like prismatic dislocation loops due to the oxygen network behaviour under ion irradiation.

Gaboriaud, Rolly J.; Lacroix, Bertrand; Paumier, Fabien

2012-04-01

92

Radiation effects on MgAl 2O 4–yttria stabilized ZrO 2 composite material irradiated with Ne + ions at high temperatures  

Microsoft Academic Search

Spinel (MgAl2O4) and yttria stabilized ZrO2 (YSZ) are candidates for fuel materials for use in nuclear reactors and the optical and insulating materials for fusion reactors. In our previous studies, the amorphization of spinel under 60keV Xe ion irradiation at RT was observed. On the other hand, amorphization could not be confirmed in YSZ single crystals under the same irradiation

T. Hojo; H. Yamamoto; J. Aihara; S. Furuno; K. Sawa; T. Sakuma; K. Hojou

2006-01-01

93

Amorphization of crystalline Si due to heavy and light ion irradiation  

SciTech Connect

The formation of amorphous silicon in crystalline silicon by bombardment with light (Si) and heavy (Xe) ions has been investigated by transmission electron microscopy with in situ ion irradiation. Experiments have been carried out at room temperature and low temperature (50 K) and the results are compared to a simple numerical model for amorphization. The results indicate that the amorphization mechanisms for both irradiations are heterogeneous in nature and that numerous overlaps of the collision cascade are generally required to render the crystal amorphous. Following from this, the nature of the material within the confines of collision cascades will be discussed and it will be shown that the individual cascade volume is not necessarily amorphous as previously described in the scientific literature but contains varying degrees of damage depending on the energy deposited within the cascade.

Edmondson, P. D.; Riley, D. J.; Donnelly, S. E. [Institute for Materials Research, University of Salford, Manchester M5 4WT (United Kingdom); Birtcher, R. C. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2009-08-15

94

Amorphization of crystalline Si due to heavy and light ion irradiation.  

SciTech Connect

The formation of amorphous silicon in crystalline silicon by bombardment with light (Si) and heavy (Xe) ions has been investigated by transmission electron microscopy with in situ ion irradiation. Experiments have been carried out at room temperature and low temperature (50 K) and the results are compared to a simple numerical model for amorphization. The results indicate that the amorphization mechanisms for both irradiations are heterogeneous in nature and that numerous overlaps of the collision cascade are generally required to render the crystal amorphous. Following from this, the nature of the material within the confines of collision cascades will be discussed and it will be shown that the individual cascade volume is not necessarily amorphous as previously described in the scientific literature but contains varying degrees of damage depending on the energy deposited within the cascade.

Edmondson, P. D.; Riley, D. J.; Birtcher, R. C.; Donnelly, S. E.; Materials Science Division; Univ. of Salford

2009-08-01

95

Enhanced light absorption of amorphous silicon thin film by substrate control and ion irradiation  

NASA Astrophysics Data System (ADS)

Large-area periodically aligned silicon nanopillar (PASiNP) arrays were fabricated by magnetic sputtering with glancing angle deposition (GLAD) on substrates coated by a monolayer of close-packed polystyrene (PS) nanospheres. The structure of PASiNP arrays could be manipulated by changing the diameter of PS nanospheres. Enhanced light absorptance within a wavelength range from 300 to 1,000 nm was observed as the diameter of nanopillars and porosity of PASiNP arrays increased. Meanwhile, Xe ion irradiation with dose from 1 × 1014 to 50 × 1014 ions/cm2 was employed to modify the surface morphology and top structure of thin films, and the effect of the irradiation on the optical bandgap was discussed.

Yuan, Fangda; Li, Zhengcao; Zhang, Tianci; Miao, Wei; Zhang, Zhengjun

2014-04-01

96

Enhanced light absorption of amorphous silicon thin film by substrate control and ion irradiation  

PubMed Central

Large-area periodically aligned silicon nanopillar (PASiNP) arrays were fabricated by magnetic sputtering with glancing angle deposition (GLAD) on substrates coated by a monolayer of close-packed polystyrene (PS) nanospheres. The structure of PASiNP arrays could be manipulated by changing the diameter of PS nanospheres. Enhanced light absorptance within a wavelength range from 300 to 1,000 nm was observed as the diameter of nanopillars and porosity of PASiNP arrays increased. Meanwhile, Xe ion irradiation with dose from 1?×?1014 to 50?×?1014 ions/cm2 was employed to modify the surface morphology and top structure of thin films, and the effect of the irradiation on the optical bandgap was discussed. PACS code 81.15.Cd; 78.66.Jg; 61.80.Jh

2014-01-01

97

Fabrication of Step-and-Flash Imprint Lithography (S-FIL) templates using XeF2 enhanced focused ion-beam etching  

NASA Astrophysics Data System (ADS)

The fabrication of Step-and-Flash Imprint Lithography (S-FIL) templates with line widths of 50 nm is described in this work. The structures have been patterned using a Ga+ focused ion beam (FIB) in a quartz template. FIB milling is generally accompanied with re-deposition effects, which represent a hindrance to densely patterned nanostructures required in most NIL applications. To reduce these re-deposition effects, in this research, xenon difluoride (XeF2) enhanced FIB etching was applied that also increases the material removal rates in comparison to pure kinetic ion sputtering. To optimise the process when using XeF2 gas the following ion scanning parameters have been examined: ion dose, beam current, dwell time and beam overlap (step size). It has been found that the assisting gases at very low doses do not bring significant etching enhancements whilst the sputtering rates have increased at high doses. Using the XeF2 gas-assisted etching, FIB structuring has been used to fabricate <100 nm structures onto quartz S-FIL templates. The presence of XeF2 considerably enhances the etching rate of quartz without any significant negative effects on the spatial resolution of the FIB lithographic process and reduces the template processing time.

Kettle, J.; Hoyle, R. T.; Dimov, S.

2009-09-01

98

THE IRRADIATION OF ION EXCHANGERS IN JEEP  

Microsoft Academic Search

Several organic and inorganic ion exchanger materials were irradiated in ; JEEP. Radiation effects are dcscribed and dependence on dose rate and quality of ; the radiation is discussed. By comparing the action of different kinds of ; ionizing radiation, possible reaction mechanisms are discussed. (authl;

Nater

1959-01-01

99

Deformation behavior of ion-irradiated polyimide  

SciTech Connect

We study nanoindentation hardness, Young's modulus, and tensile strength of polyimide (Kapton H) films bombarded with MeV light ions in the predominantly electronic stopping power regime. Results show that, for all the ion irradiation conditions studied, bombardment increases the hardness and Young's modulus and decreases the tensile strength. These changes depend close to linearly on ion fluence and superlinearly (with a power-law exponent factor of {approx}1.5) on electronic energy loss. Physical mechanisms of radiation-induced changes to mechanical properties of polyimide are discussed.

Kucheyev, S.O.; Felter, T.E.; Anthamatten, M.; Bradby, J.E. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Department of Electronic Materials Engineering, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200, (Australia)

2004-08-02

100

Neutron yields from thick C, Al, Cu, and Pb targets bombarded by 400 MeV\\/nucleon Ar, Fe, Xe and 800 MeV\\/nucleon Si ions  

Microsoft Academic Search

The angular and energy distributions of neutrons produced by 400 MeV\\/nucleon Ar, Fe, and Xe, and 800 MeV\\/nucleon Si ions stopping in thick C, Al, Cu, and Pb targets were measured using the Heavy-Ion Medical Accelerator in Chiba of the National Institute of Radiological Science (NIRS), Japan. The neutron spectra in the forward direction have broad peaks which are located

T. Kurosawa; N. Nakao; T. Nakamura; H. Iwase; H. Sato; Y. Uwamino; A. Fukumura

2000-01-01

101

Differential cross-section measurements of multiply charged xenon ions produced in 10-28keV e⁻Xe collisions  

Microsoft Academic Search

Partial single-differential ionization cross sections (PSDICSs) of a multiply ionized xenon atom (Xe{sup n+}, n=1-7) are measured for impact of 10-28 keV electrons with xenon by performing coincidences between the produced recoil ions and the electrons of indiscriminated energies detected at 90 deg. with respect to the incident electron beam direction. Values of relative PSDICSs for doubly charged ions are

S. Mondal; R. Shanker

2005-01-01

102

Mutation induced with ion beam irradiation in rose  

NASA Astrophysics Data System (ADS)

The effects of mutation induction by ion beam irradiation on axillary buds in rose were investigated. Axillary buds were irradiated with carbon and helium ion beams, and the solid mutants emerged after irradiation by repeated cutting back. In helium ion irradiation, mutations were observed in plants derived from 9 buds among 56 irradiated buds in 'Orange Rosamini' and in plants derived from 10 buds among 61 irradiated buds in 'Red Minimo'. In carbon ion, mutations were observed in plants derived from 12 buds among 88 irradiated buds in 'Orange Rosamini'. Mutations were induced not only in higher doses but also in lower doses, with which physiological effect by irradiation was hardly observed. Irradiation with both ion beams induced mutants in the number of petals, in flower size, in flower shape and in flower color in each cultivar.

Yamaguchi, H.; Nagatomi, S.; Morishita, T.; Degi, K.; Tanaka, A.; Shikazono, N.; Hase, Y.

2003-05-01

103

Anisotropic dewetting of ion irradiated solid films  

NASA Astrophysics Data System (ADS)

Experiments of irradiation with 30 keV Ga ions were conducted on ultrathin chromium films on rippled silicon substrates. The evolution of their surface morphology, as detected by real time scanning electron microscopy, shows an apparent differential sputtering yield for regions of positive and negative curvature which is in contrast with the standard theory for curvature depending sputtering yield. In particular, at the end of the irradiation process, chromium wires are left in the valleys of the substrate. This result was explained in terms of local melting caused by the ion impact and of a process of dewetting under the concurring actions of surface tension and Van der Waals forces while ion sputtering is active. The interpretation of the reported experimental results are fully supported by numeric simulations implementing the same continuum model used to explain ion induced spinodal dewetting. This hierarchical self-organization process breaks the symmetry of previously demonstrated ion induced dewetting, making possible to create new structures by using the same fundamental effects.

Repetto, L.; Šetina Bati?, B.; Firpo, G.; Piano, E.; Valbusa, U.

2013-11-01

104

New material for low-dose brachytherapy seeds: Xe-doped amorphous carbon films with post-growth neutron activated 125I.  

PubMed

We report a novel material for use in (125)I brachytherapy that consists of amorphous carbon films grown by ion-beam-assisted deposition and doped with Xe (5 at%) by implantation. Samples of these films grown on Si substrates were irradiated with neutrons in a TRIGA-I nuclear reactor for the production (125)Xe, and latter characterized by gamma spectroscopy. The results indicate that the (124)Xe was efficiently converted into (125)Xe, the precursor of (125)I, and support the activity calculations for a model brachytherapy seed. PMID:20729094

Gonçalves, R G F; Pinheiro, M V B; Lacerda, R G; Ferlauto, A S; Ladeira, L O; Krambrock, K; Leal, A S; Viana, G A; Marques, F C

2011-01-01

105

Amorphization and dynamic annealing of hexagonal SiC upon heavy-ion irradiation: Effects on swelling and mechanical properties  

SciTech Connect

Structural, mechanical, and dimensional evolutions of silicon carbide (SiC) induced by heavy-ion irradiations are studied by means of Rutherford backscattering spectrometry and channeling (RBS/C), nanoindentation, and surface profilometry measurements. 4H- and 6H-SiC single crystals were irradiated with 4 MeV Au{sup 2+} and 4 MeV Xe{sup +} ions at room temperature (RT) or 400 deg. C. Using a Monte Carlo program to simulate the RBS/C spectra (MCCHASY code), we find that Au ion irradiation at RT induces a total silicon sublattice disorder related to full amorphization at a dose of about 0.4 displacement per atom (dpa). A two-step damage process is found on the basis of the disordered fractions deduced from RBS/C data. Complete amorphization cannot be reached upon both Au and Xe ion irradiations at 400 deg. C up to about 26 dpa because of the dynamic annealing of defects. When complete amorphization is reached at RT, the Young's modulus and Berkovich hardness of irradiated 6H-SiC samples are lower by, respectively, 40% and 45% than those of the virgin crystals. The out-of-plane expansion measured by surface profilometry increases versus irradiation dose and the saturation value measured in the completely amorphous layer (normalized to the ion projected range) is close to 25%. We show that the modifications of the macroscopic properties are mainly due to the amorphization of the material. The macroscopic elasticity constants and dimensional properties are predicted for a composite material made of crystalline matrix containing dispersed amorphous inclusions using simple analytical homogenization models. Voigt's model seems to give the best approximation for disordered fractions larger than 20% in the second step of the damage process.

Kerbiriou, Xavier; Costantini, Jean-Marc; Sauzay, Maxime; Sorieul, Stephanie [CEA, DEN, SRMA, F-91191 Gif-sur-Yvette Cedex (France); Thome, Lionel [Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, CNRS/IN2P3/Univ. Paris-Sud, F-91405 Orsay-Campus (France); Jagielski, Jacek [Institute of Electronic Materials Technology, Wolczynska 133, PL-01-919 Warsaw, Poland and The Andrzej Soltan Institute for Nuclear Studies, 05-400 Swierk/Otwock (Poland); Grob, Jean-Jacques [InESS, 23 Rue du Loess, BP 20 CR, F-67037 Strasbourg (France)

2009-04-01

106

Temperature and ion-mass dependence of amorphization dose for ion beam irradiated zircon (ZrSiO{sub 4})  

SciTech Connect

The temperature dependence of amorphization dose for zircon under 1.5 MeV Kr ion irradiation has been investigated using the ANL HVEM-Tandem Facility. Three regimes were observed in the amorphization dose-temperature curve. In the first regime (15 to 300 K), the critical amorphization dose increased from 3.06 to 4.5 ions/nm{sup 2}. In the second regime (300 to 473 K), there is little change in the amorphizationdose. In the third regime (> 473 K), the amorphization dose increased exponentially to 8.3 ions/nm{sup 2} at 913 K. This temperature dependence of amorphization dose can be described by two processes with different activation energies (0.018 and 0.31 eV respectively) which are attributed to close pair recombination in the cascades at low temperatures and radiation-enhanced epitaxial recrystallization at higher temperatures. The upper temperature limit for amorphization of zircon is estimated to be 1100 K. The ion-mass dependence of the amorphization dose (in dpa) has also been discussed in terms of the energy to recoils based on data obtained from He, Ne, Ar, Kr, Xe irradiations and a {sup 238}Pu-doped sample.

Wang, L.M.; Ewing, R.C. [New Mexico Univ., Albuquerque, NM (United States). Dept. of Geology; Weber, W.J. [Pacific Northwest Lab., Richland, WA (United States); Eby, R.K. [Toronto Univ., ON (Canada). Dept. of Geological Sciences

1992-12-01

107

Temperature and ion-mass dependence of amorphization dose for ion beam irradiated zircon (ZrSiO[sub 4])  

SciTech Connect

The temperature dependence of amorphization dose for zircon under 1.5 MeV Kr ion irradiation has been investigated using the ANL HVEM-Tandem Facility. Three regimes were observed in the amorphization dose-temperature curve. In the first regime (15 to 300 K), the critical amorphization dose increased from 3.06 to 4.5 ions/nm[sup 2]. In the second regime (300 to 473 K), there is little change in the amorphizationdose. In the third regime (> 473 K), the amorphization dose increased exponentially to 8.3 ions/nm[sup 2] at 913 K. This temperature dependence of amorphization dose can be described by two processes with different activation energies (0.018 and 0.31 eV respectively) which are attributed to close pair recombination in the cascades at low temperatures and radiation-enhanced epitaxial recrystallization at higher temperatures. The upper temperature limit for amorphization of zircon is estimated to be 1100 K. The ion-mass dependence of the amorphization dose (in dpa) has also been discussed in terms of the energy to recoils based on data obtained from He, Ne, Ar, Kr, Xe irradiations and a [sup 238]Pu-doped sample.

Wang, L.M.; Ewing, R.C. (New Mexico Univ., Albuquerque, NM (United States). Dept. of Geology); Weber, W.J. (Pacific Northwest Lab., Richland, WA (United States)); Eby, R.K. (Toronto Univ., ON (Canada). Dept. of Geological Sciences)

1992-12-01

108

Void nucleation and phase stability in heavy ion irradiated materials  

Microsoft Academic Search

The response of a material to a fusion environment is one of the most important questions in fusion technology. Heavy ion irradiation can be used to further understanding of the microstructural evolution of an irradiated metal. Two aspects of heavy ion irradiation damage will be addressed: void nucleation and phase stability. A steady state void nucleation model was developed for

Plumton

1985-01-01

109

Irradiation effect of yttria-stabilized zirconia by high dose dual ion beam irradiation  

NASA Astrophysics Data System (ADS)

Yttria-stabilized zirconia (YSZ) is irradiated with 2.0-MeV Au2+ ions and 30-keV He+ ions. Three types of He, Au, Au + He (successively) ion irradiation are performed. The maximum damage level of a sequential dual ion beam implanted sample is smaller than single Au ion implanted sample. A comparable volume swelling is found in a sequential dual ion beam irradiated sample and it is also found in a single Au ion implanted sample. Both effects can be explained by the partial reorganization of the dislocation network into weakly damaged regions in the dual ion beam implanted YSZ. A vacancy-assisted helium trapping/diffusion mechanism in the dual ion beam irradiated condition is discussed. No phase transformation or amorphization behavior happens in all types of ion irradiated YSZ.

Zhang, Yan-Wen; Wang, Xu; Liu, Shi-Yi; Tang, Mei-Xiong; Zhao, Zi-Qiang; Zhang, Peng; Wang, Bao-Yi; Cao, Xing-Zhong

2014-06-01

110

Stress evolution in platinum thin films during low-energy ion irradiation  

SciTech Connect

Stress evolution of Pt thin films during low-energy ion irradiation is investigated by using wafer bending measurements and molecular dynamics simulations. Noble gas ions ranging in mass from He to Xe and energy from 0.5 to 5 keV are used. Depending on the type and energy of the ion, the change in stress can either be tensile or compressive. Heavier or higher-energy ions tend to create tensile stress, while lighter ions such as He always induce compressive stress. The stress evolution also depends on the initial state of stress in the thin films. The results are explained by a competition between the tensile stress induced by local melting along the ion track and the compressive stress induced by the accumulation of ion-induced interstitials in defect clusters or grain boundaries, often beyond the calculated ion penetration depth. Anisotropic diffusion of interstitials under an external stress field also plays an important role in the stress evolution. Molecular dynamics simulation is employed to evaluate the importance of each of these microscopic mechanisms.

Chan Wailun; Zhao Kai; Vo, Nhon; Cahill, David G.; Averback, Robert S. [Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Ashkenazy, Yinon [Racah Institute of Physics, Hebrew University of Jerusalem, 91904 Jerusalem (Israel)

2008-05-15

111

Study of local crystallization induced in FeSiNbZrB amorphous alloy by swift heavy ion (SHI) irradiation at room temperature  

NASA Astrophysics Data System (ADS)

Amorphous FeSiNbZrB alloy (metallic glass) ribbons were prepared by melt spinning and swift heavy ion (SHI) irradiation experiments were performed on the materials research terminal of the 320 kV ECR platform at the Institute of Modern Physics (IMP), Lanzhou. XRD, TEM and Mössbauer spectroscopy was used to reveal the irradiation-induced local crystallization, plastic deformation, damages and the magnetic moments rearrangements. The dimensions of our ribbons perpendicular to ion beam direction increased slightly , but the ribbon dimension along the ion beam shrunk; Irradiation of Xe-ions could cause local crystallization of amorphous FeSiNbZrB alloy ribbons and form finer ?-Fe(Si) phases precipitations with diameter of 1-2 nm; SHI irradiation could make the distribution of the magnetic moments of amorphous ribbons change their orientation from the in-plane orientation to the perpendicular one.

Sun, Jianrong; Wang, Zhiguang; Wang, Yuyu; Chang, Hailong; Song, Peng; Shen, Tielong; Zhu, Yabin; Pang, Lilong; Li, Fashen

2013-07-01

112

High-selectivity reactive ion etching with CO\\/NH3\\/Xe gas for micro\\/nanostructuring of 20% Fe-Ni, Au, Pt, and Cu  

Microsoft Academic Search

Highly selective etch process for conductive metals (Au, Pt, and Cu) and magnetic metal (20%Fe-Ni) has been developed on a magnetron reactive ion etching system which uses a CO\\/NH3\\/Xe chemistry. Etch selectivities of these metals to titanium greater than 80:1 for Au, 40:1 for Pt, 30:1 for Cu, and 15:1 for Permalloy (20%Fe-Ni) were achieved at a titanium etch rate

T. Abe; Youn Gi Hong; Masayoshi Esashi

2003-01-01

113

Effect of spin--orbit states of Kr+ and Xe+ on the single-electron capture spectra of C2+ ions  

NASA Astrophysics Data System (ADS)

High resolution translational energy spectra have been obtained for state-selective single-electron capture by 8 keV C2+ in Ar and 6 keV C2+ in Kr and Xe. The Ar spectrum displays 12 well-resolved peaks which fall into two sequences corresponding to capture from the ground 1S state and the metastable 3P0 state of the C2+ ion. The only two capture channels which violate spin conservation in this range of energy gain are notably absent from this spectrum. The effect of spin--orbit splitting (0.18 eV) of the 2P3/2,1/2 ground state of the Ar+ ion is not apparent in this spectrum. By contrast the spin--orbit splitting of the 2P3/2,1/2 states of the Kr+ (at 0.67 eV) and Xe+ (at 1.31 eV) ions is strongly reflected in the respective spectra. The Kr+ spectrum reveals six pairs of neatly arranged doublet peaks, while the Xe+ spectrum displays a less obvious relationship between the doublets.

Lee, A. R.; Leather, C.; Brenton, A. G.

1995-09-01

114

Interactions of high-energy, highly charged Xe ions with buckyballs.  

National Technical Information Service (NTIS)

Ionization and fragmentation have been measured for C(sub 60) molecules bombarded by highly charged (up to 35+) xenon ions with energies ranging up to 625 MeV. The observed mass distribution of positively charged fragments is explained in terms of a theor...

R. Ali H. G. Berry S. Cheng

1994-01-01

115

The interactions of high-energy, highly charged Xe ions with buckyballs  

Microsoft Academic Search

Ionization and fragmentation have been measured for C60 molecules bombarded by highly charged (up to 35 +) xenon ions with energies ranging up to 625 MeV. The observed mass distribution of positively charged fragments is explained in terms of a theoretical model indicating that the total interaction cross section contains roughly equal contributions from (a) excitation of the giant plasmon

R. Ali; H. G. Berry; S. Cheng; R. W. Dunford; H. Esbensen; D. S. Gemmell; E. P. Kanter; T. Lebrun; L. Young; W. Bauer

1995-01-01

116

Study on effects of swift heavy ion irradiation on the crystal structure in CeO 2 doped with Gd 2O 3  

Microsoft Academic Search

To simulate the effects of Gd2O3-doping and high-energy fission products in UO2, Gd2O3-doped CeO2 pellets were irradiated with 200-MeV Xe14+ ions. Doping and irradiation effects were analyzed using X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS). The lattice constant of CeO2 decreases and the local structure is disordered with increased doping levels. However, the irradiation induces an expansion

Y. Tahara; B. Zhu; S. Kosugi; N. Ishikawa; Y. Okamoto; F. Hori; T. Matsui; A. Iwase

2011-01-01

117

Desorption of cluster ions from adsorbed methane under cryogenic condition by low-energy ion irradiation  

Microsoft Academic Search

We have investigated ion desorption from adsorbed methane following keV He+ ion irradiation. The thickness of the adsorbed layer was precisely controlled. For mono-layered methane, only monomer ions (CHx+) were desorbed by 1keV He+ ion irradiation. On the other hand, a large number of cluster ions (CnHx+) up to n=20 were desorbed from multi-layered film. Among cluster ions, molecular ions

Ayumi Narita; Mitsunori Honda; Norie Hirao; Yuji Baba; Tsuyoshi Yaita

2008-01-01

118

Hydrogen retention in ion irradiated steels  

SciTech Connect

In the future 1--5 MW Spallation Neutron Source, target radiation damage will be accompanied by high levels of hydrogen and helium transmutation products. The authors have recently carried out investigations using simultaneous Fe/He,H multiple-ion implantations into 316 LN stainless steel between 50 and 350 C to simulate the type of radiation damage expected in spallation neutron sources. Hydrogen and helium were injected at appropriate energy and rate, while displacement damage was introduced by nuclear stopping of 3.5 MeV Fe{sup +}, 1 {micro}m below the surface. Nanoindentation measurements showed a cumulative increase in hardness as a result of hydrogen and helium injection over and above the hardness increase due to the displacement damage alone. TEM investigation indicated the presence of small bubbles of the injected gases in the irradiated area. In the current experiment, the retention of hydrogen in irradiated steel was studied in order to better understand its contribution to the observed hardening. To achieve this, the deuterium isotope ({sup 2}H) was injected in place of natural hydrogen ({sup 1}H) during the implantation. Trapped deuterium was then profiled, at room temperature, using the high cross-section nuclear resonance reaction with {sup 3}He. Results showed a surprisingly high concentration of deuterium to be retained in the irradiated steel at low temperature, especially in the presence of helium. There is indication that hydrogen retention at spallation neutron source relevant target temperatures may reach as high as 10%.

Hunn, J.D.; Lewis, M.B.; Lee, E.H.

1998-11-01

119

The interactions of high-energy, highly charged Xe ions with buckyballs  

NASA Astrophysics Data System (ADS)

Ionization and fragmentation have been measured for C(60) molecules bombarded by highly charged (up to 35+) xenon ions with energies ranging up to 625 MeV. The observed mass distribution of positively charged fragments is explained in terms of a theoretical model indicating that the total interaction cross section contains roughly equal contributions from (1) excitation of the giant plasmon resonance, and (2) large-energy-transfer processes that lead to multiple fragmentation of the molecule. Preliminary results of measurements on VUV photons emitted in these interactions are also presented.

Ali, R.; Berry, H. G.; Cheng, S.

120

The interactions of high-energy, highly charged Xe ions with buckyballs  

NASA Astrophysics Data System (ADS)

Ionization and fragmentation have been measured for C 60 molecules bombarded by highly charged (up to 35 +) xenon ions with energies ranging up to 625 MeV. The observed mass distribution of positively charged fragments is explained in terms of a theoretical model indicating that the total interaction cross section contains roughly equal contributions from (a) excitation of the giant plasmon resonance, and (b) large-energy-transfer processes that lead to multiple fragmentation of the molecule. Preliminary results of measurements on VUV photons emitted in these interactions are also presented.

Ali, R.; Berry, H. G.; Cheng, S.; Dunford, R. W.; Esbensen, H.; Gemmell, D. S.; Kanter, E. P.; LeBrun, T.; Young, L.; Bauer, W.

121

The interactions of high-energy, highly charged Xe ions with buckyballs  

SciTech Connect

Ionization and fragmentation have been measured for C{sub 60} molecules bombarded by highly charged (up to 35+) xenon ions with energies ranging up to 625 MeV. The observed mass distribution of positively charged fragments is explained in terms of a theoretical model indicating that the total interaction cross section contains roughly equal contributions from (a) excitation of the giant plasmon resonance, and (b) large-energy-transfer processes that lead to multiple fragmentation of the molecule. Preliminary results of measurements on VUV photons emitted in these interactions are also presented.

Ali, R.; Berry, H.G.; Cheng, S. [and others

1994-12-31

122

Energy-loss and mean ranges of129Xe ions in mica and makrofol-Kg  

NASA Astrophysics Data System (ADS)

Calibrated Polyallyldiglycol Carbonate (PADC) detectors have been used to determine energy-loss and mean ranges of 13.04 MeV/u129Xeion in mica and Makrofol-KG using the nuclear track technique. The energy-loss rates (dE/dx) of the ion as a function of energy and depth of penetration in mica and Makrofol-KG have been derived from the respective energy-loss curves. Experimental data are compared with theoretical values obtained from four different sources. The significance and scope of the work is discussed.

Kutshreshtha, A.; Laldawnglana, C.; Mishra, R.; Ghosh, S.; Dwivedi, K. K.; Brandt, R.; Fink, D.

123

Surface Modification of Polymer Substrates by Oxygen Ion Irradiation  

SciTech Connect

Oxygen cluster ions and/or monomer ions were used for the sputtering and the surface modification of polymers such as polycarbonate (PC) and polyethylene terephthalate (PET). For the case of oxygen cluster ion irradiation, the sputtered depth increased with increase of the acceleration voltage, and the sputtering yield was much larger than that by the monomer ion irradiation. The sputtered particles represented the polymer structure, which indicated that the bond scission by the cluster ion irradiation resulted in an ejection of monomer molecule through the intermolecular collision. On the other hand, for the oxygen monomer ion irradiation, the implanted depth increased with increase of the acceleration voltage, and the bond scission occurred at the deep region through the binary collision with the high energetic ions. Therefore, the sputtering yield for the polymer surfaces decreased, and the sputtering effect became very small. Furthermore, the simultaneous use of oxygen cluster and monomer ions was more effective for oxidation of the PET surfaces rather than the monomer ion irradiation or the cluster ion irradiation. As a result, the contact angle measurement showed that the wettability of the PET surfaces irradiated by the simultaneous use of oxygen cluster and monomer ions was much enhanced.

Takaoka, G. H.; Ryuto, H.; Araki, R.; Yakushiji, T. [Photonics and Electronics Science and Engineering Center, Kyoto University, Nishikyo, Kyoto 615-8510 (Japan)

2008-11-03

124

RBS analyses of xenon-irradiated Ti and TiN films  

Microsoft Academic Search

TiN films of 30-300 nm thickness, deposited onto stainless steel via magnetron sputtering, and 10 mum thick Ti foils were irradiated with 80-360 keV Xe+ ions at influences of phi = 1015-1017 ions\\/cm2. The Xe content was depth-profiled by means of 900 keV He++ Rutherford backscattering. Irradiations of films with a thickness exceeding the ion range (at 80 and 250

Th. Weber; W. Bolse; K. P. Lieb

1990-01-01

125

Enhanced sputtering yields of carbon due to accumulation of low-energy Xe ions  

NASA Astrophysics Data System (ADS)

We have calculated the sputtering yields of carbon and molybdenum under xenon ion bombardment by a Monte Carlo code ACAT which simulates binary collision events in solids. The yields of carbon calculated with ACAT differ from the experimental data below the threshold energy predicted from the semi-empirical formula proposed by Yamamura and Tawara. Meanwhile, the results of ACAT with 14% xenon atoms retained in graphite are in good agreement with the experimental data and the xenon retention in carbon plays an important role in reducing the threshold energy for carbon sputtering. In order to estimate the experimental sputtering yields of carbon, a simplified formula is proposed in the frame of the semi-empirical formula. The formula predicts the yield curve close to the reported sputtering yields of carbon for the condition that carbon target retains 14% xenon atoms.

Kenmotsu, T.; Wada, M.; Hyakutake, T.; Muramoto, T.; Nishida, M.

2009-05-01

126

Spectroscopic characterization of ion-irradiated multi-layer graphenes  

NASA Astrophysics Data System (ADS)

Low-energy Ar ions (0.5-2 keV) were irradiated to multi-layer graphenes and the damage process, the local electronic states, and the degree of alignment of the basal plane, and the oxidation process upon ion irradiation were investigated by Raman spectroscopy, soft X-ray absorption spectroscopy (XAS) and in situ X-ray photoelectron spectroscopy (XPS). By Raman spectroscopy, we observed two stages similar to the case of irradiated graphite, which should relate to the accumulations of vacancies and turbulence of the basal plane, respectively. XAS analysis indicated that the number of sp2-hybridized carbon (sp2-C) atoms decreased after ion irradiation. Angle-resolved XAS revealed that the orientation parameter (OP) decreased with increasing ion energy and fluence, reflecting the turbulence of the basal plane under irradiation. In situ XPS shows the oxidation of the irradiated multi-layer graphenes after air exposure.

Tsukagoshi, Akira; Honda, Shin-ichi; Osugi, Ryo; Okada, Hiraku; Niibe, Masahito; Terasawa, Mititaka; Hirase, Ryuji; Izumi, Hirokazu; Yoshioka, Hideki; Niwase, Keisuke; Taguchi, Eiji; Lee, Kuei-Yi; Oura, Masaki

2013-11-01

127

Spectral properties of ion irradiated carbon rich solids  

NASA Astrophysics Data System (ADS)

Carbon rich solid materials have been studied before, during, and after ion irradiation (3-400 keV ions) by in situ reflectance spectroscopy (from UV to IR). Frozen hydrocarbons (benzene, methane, butane, acetylene, etc., also mixed with water ice) have been irradiated at low temperature with fast ions. Irradiation causes the formation of many molecular species and of a long chain polymer like material (organic refractory residue). The process mimics what occurs in space because of cosmic ion irradiation of the icy surfaces of some objects in the Solar System. Other irradiated materials include natural bitumens (Asphaltite, kerite) and polymers (i.e. polystyrene). Upon irradiation the originally transparent polymer samples are converted in a material that, already at low doses, strongly absorbs in the UV. Such materials could mimic a kind of organic material (i.e. a spectrally neutral one) freshly exposed at the surface of minor objects in the Solar System because of meteoritic impact.

Strazzulla, G.; Baratta, G.; Brunetto, R.; Garozzo, M.; Kanuchova, Z.

2009-04-01

128

Modifications of the magnetic properties of ferrites by swift heavy ion irradiations  

Microsoft Academic Search

Single crystal plates of ferrimagnetic yttrium iron garnet (111)-YIG:Si (Y3Fe4.94Si0.06O12) and barium hexaferrite (00.1)-BaM (BaFe12O19) or (00.1)-BaM:Co,Ti (BaFe9.1Co1.4Ti1.5O19) are irradiated with swift heavy ions (3.8 GeV 129Xe or 6.0 GeV 208Pb) in the electronic slowing down regime, above the threshold (~20 keV nm-1) of formation of continuous and homogeneous cylindrical amorphous tracks. The modifications of the magnetic properties are studied

Jean-Marc Costantini; Francis Studer; Jean-Claude Peuzin

2001-01-01

129

Longitudinal dilation behavior of ion-irradiated Tyranno™-SA SiC fibers at elevated-temperatures  

NASA Astrophysics Data System (ADS)

Advanced SiC fibers with low oxygen content, nearly-stoichiometric composition and high crystallinity, are envisaged as reinforcement in SiCf/SiC composites for next generation nuclear reactors. In this study, we performed ion-irradiation experiments at GANIL (Caen, France) on the advanced fiber, Tyranno™-SA grade-3, with 95 MeV Xe ions at room-temperature. To prevent the damage gradient in fiber, the fibers were irradiated on two sides with two fluence levels (2.46 × 1014 ions/cm2 for the first side +2.52 × 1014 ions/cm2 for the opposite side and 9.89 × 1014 ions/cm2 for the first side +1.02 × 1015 ions/cm2 for the opposite side). According to TRIM-code calculation, the ion irradiation damages in the fibers affected the entire volume of the fibers, with estimations of 0.05 and 0.2 dpa. The structural evolution under the ion irradiation was studied by transmission electron microscopy (TEM) and Raman spectroscopy. The results did not reveal a complete amorphization. The gradual transition in physical properties, such as deformation and coefficient of thermal expansion (CTE) and electrical conductivity, during heating and cooling up to 1800 °C were monitored by longitudinal dilation test of a single fiber. These physical property changes (or recoveries) of the ion-irradiated fibers were categorized in the following temperature regions (1st stage: <200 °C (no recovering), 2nd stage: 200-1400 °C (recovering) and 3rd stage: >1400 °C (almost completely recovered)). In particular, a linear recovery in the medium range of 800-1400 °C during heating had very limited property changes.

Shimoda, Kazuya; Colin, Christian

2012-10-01

130

Generation of colour centres in yttria-stabilized zirconia by heavy ion irradiations in the GeV range.  

PubMed

We have studied the colour centre production in yttria-stabilized zirconia (ZrO(2):Y(3 +)) by heavy ion irradiation in the GeV range using on-line UV-visible optical absorption spectroscopy. Experiments were performed with 11.4 MeV amu(-1) (127)Xe, (197)Au, (208)Pb and (238)U ion irradiations at 8 K or room temperature (RT). A broad and asymmetrical absorption band peaked at a wavelength about 500 nm is recorded regardless of the irradiation parameters, in agreement with previous RT irradiations with heavy ions in the 100 MeV range. This band is de-convoluted into two broad Gaussian-shaped bands centred at photon energies about 2.4 and 3.1 eV that are respectively associated with the F(+)-type centres (involving a singly ionized oxygen vacancy, VO· and T centres (i.e. Zr(3+) in a trigonal symmetry) observed by electron paramagnetic resonance (EPR) spectroscopy. In the case of 8 K Au ion irradiation at low fluences, six bands are used at about 1.9, 2.3, 2.7, 3.1 and 4.0 eV. The three bands near 2.0-2.5 eV can be assigned to oxygen divacancies (i.e. F(2)(+) centres). No significant effect of the irradiation temperature is found on the widths of all absorption bands for the same ion and fluence. This is attributed to the inhomogeneous broadening arising from the static disorder due to the native charge-compensating oxygen vacancies. However, the colour centre production yield is strongly enhanced at 8 K with respect to RT. When heating irradiated samples from 8 K to RT, the extra colour centres produced at low temperature do not recover completely to the level of RT irradiation. The latter results are accounted for by an electronically driven defect recovery process. PMID:21399362

Costantini, Jean-Marc; Beuneu, François; Schwartz, Kurt; Trautmann, Christina

2010-08-11

131

Carbon nanowires generated by ion irradiation of hydrocarbon ices  

NASA Astrophysics Data System (ADS)

In this paper we present the formation of carbon nanowires (polyynes and polycumulenes) in the solid state by ion irradiation of frozen hydrocarbons (C6H6 and C2H2). Irradiations have been performed using H+ ions in the 100's keV energy regime using fluences up to 5 × 1014 ions/cm2. Beyond the intrinsic significance of these results in the field of material science, this work has been motivated by the fact that ion beam irradiation of hydrocarbon ices is one of the most important process thought to happen in several extraterrestrial environments where many spectroscopic features of polyyne molecules have been identified.

Puglisi, O.; Compagnini, G.; D’Urso, L.; Baratta, G. A.; Palumbo, M. E.; Strazzulla, G.

2014-05-01

132

Heavy ion irradiation of U Mo/Al dispersion fuel  

NASA Astrophysics Data System (ADS)

The usage of high-density U-Mo/Al dispersion fuel for high burn up in research and test reactors seems to be limited by the unfavourable interdiffusion layer between the fuel and the Al-matrix, which develops during irradiation. This interdiffusion layer was observed up to now only after costly and time consuming in-pile irradiation and could not be created in out-of-pile experiments. This paper presents a new approach of creating such an interdiffusion layer out-of-pile by irradiation with heavy ions. An appropriate choice of heavy-ion irradiation simulates irradiation damage and deposition of fission fragments as it happens during in-pile irradiation and induces a diffusion process between the fuel and the Al matrix. An irradiation experiment and post-irradiation examinations are presented.

Wieschalla, N.; Bergmaier, A.; Böni, P.; Böning, K.; Dollinger, G.; Großmann, R.; Petry, W.; Röhrmoser, A.; Schneider, J.

2006-10-01

133

Formation of TiO2 nanorods by ion irradiation  

NASA Astrophysics Data System (ADS)

Ion beam irradiation is a powerful method to fabricate and tailor the nanostructured surface of materials. Nanorods on the surface of single crystal rutile TiO2 were formed by N+ ion irradiation. The dependence of nanorod morphology on ion fluence and energy was elaborated. With increasing ion fluence, nanopores grow in one direction perpendicular to the surface and burst finally to form nanorods. The length of nanorods increases with increasing ion energy under same fluence. The development of the nanorod structure is originated from the formation of the nanopores while N2 bubbles and aggregation of vacancies were responsible for the formation of nanopores and nanorods. Combining C+ ion irradiation and post-irradiation annealing experiments, two qualitative models are proposed to explain the formation mechanism of these nanorods.

Zheng, X. D.; Ren, F.; Cai, G. X.; Hong, M. Q.; Xiao, X. H.; Wu, W.; Liu, Y. C.; Li, W. Q.; Ying, J. J.; Jiang, C. Z.

2014-05-01

134

Transport and structure of ion irradiated HTSC thin films  

Microsoft Academic Search

Thin films of c-axis and a-axis oriented REBa2Cu3O7-delta (RE = Y, Gd, Eu) deposited by magnetron sputtering were irradiated with H+, He+ and Ar2+ ions. The changes of the transport properties were studied as a function of the crystal direction, the angle of incidence and the ion mass. The Tc-depression rates are lowered for aligned ion irradiation due to the

O. Meyer; T. Kroener; J. Remmel; J. Geerk; G. Linker; B. Strehlau; Th. Wolf

1992-01-01

135

A laser spectroscopic study on Xe{sup +} ion transport phenomena in the ExB discharge of a Hall effect thruster  

SciTech Connect

The Velocity Distribution Function (VDF) of metastable Xe{sup +} ions was measured along the channel axis of the 5 kW-class PPS registered X000 Hall effect thruster by means of Laser Induced Fluorescence spectroscopy at 834.72 nm for various voltages, magnetic fields and mass flow rates. Axial velocity and dispersion profiles are compared to on-axis profiles obtained with the 1.5 kW-class PPS100 thruster. Outcomes of the comparison are threefold. (i) The broadening of the FDV across the region of strong magnetic field is a general feature for Hall thrusters. It originates in the overlap between ionization and acceleration layers. The velocity dispersion increases with the discharge voltage; it reaches up to 200 eV in unit of kinetic energy at 700 V. (ii) Most of the acceleration potential ({approx_equal}70%) is localized outside the thruster channel whatever the thruster size and operating conditions. The electric field moves upstream when the applied voltage is ramped up; in other words the fraction of potential inside the channel increases with the voltage; (iii) A non negligible amount of very slow and very fast (kinetic energy higher than the applied potential) Xe{sup +} ions are always observed. Such ions may find their origin in space and temporal oscillations of the electric field as suggested by numerical simulations carried out with a hybrid model.

Mazouffre, S.; Gawron, D.; Kulaev, V. [ICARE, CNRS, 1c Avenue de la Recherche Scientifique, 45071 Orleans (France); Luna, J. Perez [LAPLACE, 118 Route de Narbonne, 31062 Toulouse (France); Sadeghi, N. [LSP, Joseph-Fourier University-CNRS, 140 Avenue de la Physique, BP87, 38402 St Martin d'Heres (France)

2008-03-19

136

Raman study of Kr ion irradiated sodium aluminoborosilicate glass  

NASA Astrophysics Data System (ADS)

Raman spectroscopy was used to investigate the microstructure evolution of sodium aluminoborosilicate glass after 4 MeV Kr17+ ions irradiation at various fluences from 3.1 × 1011 to 1.8 × 1015 ions/cm2. The Si-O-Si vibration band around 450 cm-1 was slightly shifted to higher Raman shift after irradiation, and stabilized after the nuclear deposited energy reached about 1024 eV/cm3. An increase in the population of 3-membered rings and decrease in the species of 4-membered rings were evidenced in the irradiated samples. These have been correlated to the densification process of glass. Depolymerization of glass network caused by Kr ion irradiation was also observed. These results indicate that the microstructural modifications caused by Kr ion irradiation are the consequence of ballistic effects.

Chen, L.; Wang, T. S.; Yang, K. J.; Peng, H. B.; Zhang, G. F.; Zhang, L. M.; Jiang, H.; Wang, Q.

2013-07-01

137

Time-of-Flight Measurements of Ion and Electron from Xenon Clusters Irradiated with a Soft X-Ray Laser Pulse  

NASA Astrophysics Data System (ADS)

The photoionization process in xenon clusters irradiated with a soft x-ray laser pulse (h?­=89.2 eV, intensity: ~1010 W/cm2) was examined using a time-of-flight mass spectrometer, where the laser photon energy was high enough to ionize Xe 4d inner electrons (threshold: 67.55 eV for 4d5/2 and 69.54 eV for 4d3/2). The dominant ion yield resulting from Auger decay of 4d hole was Xe3+ ion. This showed that the double Auger transition probability would be enhanced in the cluster environments. In order to clarify the decay dynamics of 4d inner holes, the electron energy spectrum was measured. It was found that the distinct photo- and Auger electron lines were not observed, while the energy distribution implies the production of a low temperature cluster plasma.

Namba, S.; Hasegawa, N.; Nishikino, M.; Kishimoto, M.; Kawachi, T.; Tanaka, M.; Ochi, Y.; Nagashima, K.; Takiyama, K.

138

Measured and calculated SF{sub 6}{sup -} collision and swarm ion transport data in SF{sub 6}-Ar and SF{sub 6}-Xe mixtures  

SciTech Connect

The measurement of the mobility of SF{sub 6}{sup -} in the mixtures SF{sub 6}-Ar and SF{sub 6}-Xe is reported over the density-reduced electric field strength E/N 1-180 Td (1 Townsend=10{sup -17} V cm{sup 2}), from a time-resolved pulsed Townsend technique. Simultaneously, the mobility of SF{sub 6}{sup -} in the same binary mixtures has been calculated from a set of collision cross sections for SF{sub 6}{sup -}-Ar, SF{sub 6}{sup -}-Xe, and SF{sub 6}{sup -}-SF{sub 6} using a Monte Carlo simulation procedure for ion transport. The good agreement between measured and calculated mobilities in these gas mixtures has led us to conclude that the validation of our cross section sets is confirmed. The elastic collision cross section, a predominant process for ion energies lower than about 10 eV, was determined from a semiclassical JWKB approximation using a rigid core potential model for the ion-neutral systems under consideration. This elastic cross section was then added to several other inelastic collision cross sections found in the literature for ion conversion, electron detachment of SF{sub 6}{sup -} and charge transfer. Moreover, the calculations of the mobility and the ratios of the transverse and longitudinal diffusion coefficients to the mobility were extended into a much wider E/N range from 1 to 4000 Td. Additionally, we have also calculated the energy distribution functions and the reaction coefficients for ion conversion and electron detachment. Finally, we have shown that the range of validity for the calculation of the mobility in gas mixtures from Blanc's law is only valid for the low E/N region, where the interaction is dominated by elastic collisions and the ion distribution function remains essentially Maxwellian.

Benhenni, M.; Yousfi, M.; Merbahi, N.; Eichwald, O. [Universite Paul Sabatier, CPAT, UMR 5002 du CNRS, 118 route de Narbonne, 31062 Toulouse cedex (France); Urquijo, J. de; Hinojosa, G. [Centro de Ciencias Fisicas, Universidad Nacional Autonoma de Mexico, Apartado Postal 48-3, 62251, Cuernavaca, Mor. (Mexico); Hernandez-Avila, J.L. [Universidad Autonoma Metropolitana, CBI-Energia, Av. San Pablo 180, 02200 Mexico, D.F. (Mexico)

2005-03-01

139

Light-emitting Si nanostructures formed in SiO{sub 2} on irradiation with swift heavy ions  

SciTech Connect

SiO{sub 2} layers containing implanted excess Si are irradiated with Xe ions with an energy of 130 MeV and doses of 3 x 10{sup 12}-10{sup 14} cm{sup -2}. In the samples irradiated with a dose of 3 x 10{sup 12} cm{sup -2}, {approx}10{sup 12} cm{sup -2} segregated clusters 3-4 nm in dimension are detected by transmission electron microscopy. With increasing dose, the dimensions and number of these clusters increase. In the photoluminescence spectrum, a 660- to 680-nm band is observed, with the intensity dependent on the dose. After passivation of the sample with hydrogen at 500 deg. C, the band disappears, but a new {approx}780-nm band typical of Si nanocrystals becomes evident. On the basis of the entire set of data, it is concluded that the 660- to 680-nm band is associated with imperfect Si nanocrystals grown in the tracks of Xe ions due to high ionization losses. The nonmonotonic dependence of the photoluminescence intensity on the dose is attributed to the difference between the diameters of tracks and the diameters of the displacements' cascades responsible for defect formation.

Kachurin, G. A., E-mail: kachurin@isp.nsc.ru; Cherkova, S. G. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Branch (Russian Federation); Skuratov, V. A. [Joint Institute for Nuclear Research (Russian Federation); Marin, D. V.; Cherkov, A. G. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

2010-04-15

140

The response of the pyrochlore structure-type to ion-beam irradiation  

NASA Astrophysics Data System (ADS)

Pyrochlore with the general formula of A3+2B4+2O7 (Fd3m; Z = 8) has been proposed as the candidate waste form for the immobilization of actinides, particularly plutonium from dismantled nuclear weapons. Because actinides decay by alpha-decay events, radiation effects on the waste form are a concern. The effects of radiation on different pyrochlore compositions, A2B2O7 (A = La ˜ Lu, and Y; B = Ti, Sn, and Zr), have been investigated by 50 KeV He+, 600 KeV Ar+, 1.0 MeV Kr+, and 1.5 MeV Xe+ ion irradiations. Titanate pyrochlores are generally sensitive to ion beam damage and can be amorphized at a low damage level (˜0.2 dpa). The critical amorphization temperature, Tc, increases from ˜480 to ˜1120 K with increasing A-site cation size. A dramatically increasing radiation "resistance" to ion beam induced-amorphization has been observed with increasing Zr-content in the Gd2Ti2-xZrxO7 system. The pure end-member, Gd2Zr2O7, cannot be amorphized, even at doses as high as ˜100 dpa. Although zirconate pyrochlores are generally considered to be radiation "resistant", ion beam-induced amorphization occurs for La2Zr2O7 at a dose of ˜5.5 dpa at room temperature. Stannate pyrochlores A2Sn 2O7 (A = La, Nd, Gd) are readily amorphized by ion beam damage at a relatively low dose (˜1 dpa) at room temperature; while no evidence of amorphization has been observed in A2Sn2O7 (A = Er, Y, Lu) irradiated with 1 MeV Kr+ ions at a dose of ˜6 dpa at 25 K. The factors that influence the response of different pyrochlore compositions to ion irradiation-induced amorphization are discussed in terms of cation radius ratio, defect formation energies, and the tendency of the pyrochlore structure-type to undergo an order-disorder transition to the defect-fluorite structure. The "resistance" of the pyrochlore structure to ion beam-induced amorphization is not only affected by the relative sizes of the A- and B-site cations, but also the cation electronic configurations. Pyrochlore compositions that have larger structural deviations from the ideal fluorite structure are more sensitive to ion beam-induced amorphization. These fundamental results provide insight into the structural and compositional controls on radiation-induced amorphization of pyrochlores. This understanding can be used for the design and selection of materials used for the immobilization of actinides.

Lian, Jie

141

Enhanced electrochemical etching of ion irradiated silicon by localized amorphization  

NASA Astrophysics Data System (ADS)

A tailored distribution of ion induced defects in p-type silicon allows subsequent electrochemical anodization to be modified in various ways. Here we describe how a low level of lattice amorphization induced by ion irradiation influences anodization. First, it superposes a chemical etching effect, which is observable at high fluences as a reduced height of a micromachined component. Second, at lower fluences, it greatly enhances electrochemical anodization by allowing a hole diffusion current to flow to the exposed surface. We present an anodization model, which explains all observed effects produced by light ions such as helium and heavy ions such as cesium over a wide range of fluences and irradiation geometries.

Dang, Z. Y.; Breese, M. B. H.; Lin, Y.; Tok, E. S.; Vittone, E.

2014-05-01

142

Atomistic simulations of MeV ion irradiation of silica  

NASA Astrophysics Data System (ADS)

We used molecular dynamics simulations to study 2.3 MeV Au ion irradiation of silica. In this energy regime, the energy loss of the ion is divided almost equally between electronic and nuclear energy loss. The inelastic thermal spike model was used to model the electron-phonon interactions due to the high electronic energy loss. Binary collision approximation calculations provided input for the recoil energies due to MeV ions. We performed simulations of the damage due to the separate damage mechanisms as well as together, and found that the inelastic thermal spike is needed to accurately simulate the irradiation damage from MeV ions.

Backman, M.; Djurabekova, F.; Pakarinen, O. H.; Nordlund, K.; Zhang, Y.; Toulemonde, M.; Weber, W. J.

2013-05-01

143

Fabrication of carbon nanostructures (nanodots, nanowires) by energetic ion irradiation  

Microsoft Academic Search

Carbon nanostructures were synthesized by energetic ion irradiation of Si-based gel films. These polymer-like films with different side groups and C concentrations were prepared by sol–gel chemistry and irradiated with Si or Au ions of different energies in the range 3 MeV–2 GeV. The shape and size of the formed carbon nanostructures was studied by energy filtered transmission electron microscopy.

Amit Kumar; Fouran Singh; J C Pivin; D K Avasthi

2007-01-01

144

Fabrication of carbon nanostructures (nanodots, nanowires) by energetic ion irradiation  

Microsoft Academic Search

Carbon nanostructures were synthesized by energetic ion irradiation of Si-based gel films. These polymer-like films with different side groups and C concentrations were prepared by sol-gel chemistry and irradiated with Si or Au ions of different energies in the range 3 MeV-2 GeV. The shape and size of the formed carbon nanostructures was studied by energy filtered transmission electron microscopy.

Amit Kumar; Fouran Singh; J. C. Pivin; D. K. Avasthi

2007-01-01

145

Formation of nanosized hills on Ti 3SiC 2 oxide layer irradiated with swift heavy ions  

NASA Astrophysics Data System (ADS)

The Ti 3SiC 2 refractory compound that combines properties of both metals and ceramics is a fuel cladding candidate under investigation for Gas-cooled Fast Reactor. Its behavior under swift heavy ion irradiation (Xe ions, 92 MeV, 10 19 m -2) was investigated. Significant and unexpected surface changes have been highlighted: hills have been observed by AFM on the surface of Ti 3SiC 2. Such a topographic modification has never been observed in other materials irradiated in similar conditions. The characterization of these hills by both XPS and X-TEM has highlighted that the surface modifications do not appear in Ti 3SiC 2 but in the amorphous oxide layer located on the sample surface before irradiation. Moreover, the thickness of this oxide layer grew under irradiation dose. The comparison with previous irradiations has led to the conclusion that this surface modification stems from electronic interactions in this amorphous layer, and that there is a threshold in the electronic stopping power to overcome to form hills.

Nappé, J. C.; Monnet, I.; Audubert, F.; Grosseau, Ph.; Beauvy, M.; Benabdesselam, M.

2012-01-01

146

Synthesis of Fe-C60 complex by ion irradiation  

NASA Astrophysics Data System (ADS)

In order to synthesize the Fe@C60 complex, iron ion beam irradiated to C60 thin films. The energy of the irradiated iron ions was controlled from 50 eV to 250 eV. The dose of that was controlled from 6.67 × 1012 to 6.67 × 1014 ions/cm2. By the analysis of the surface of the iron ion irradiated C60 thin films using laser desorption/ionization time-of-flight mass spectrometry, we could confirm the peak with mass/charge of 776. The mass/charge of 776 corresponds to Fe + C60. We obtained the maximum intensity of the peak with mass/charge of 776 under the irradiation iron ion energy and the dose were 50 eV and 3.30 × 1013 ions/cm2, respectively. Then, the separation of the material with mass of 776 was performed by using high performance liquid chromatography. We could separate the Fe + C60 from the iron ion irradiated C60 thin film. As a result, we could synthesize the Fe + C60 complex as a new material.

Minezaki, Hidekazu; Oshima, Kosuke; Uchida, Takashi; Mizuki, Toru; Racz, Richard; Muramatsu, Masayuki; Asaji, Toyohisa; Kitagawa, Atsushi; Kato, Yushi; Biri, Sandor; Yoshida, Yoshikazu

2013-09-01

147

Ion irradiation tolerance of graphene as studied by atomistic simulations  

SciTech Connect

As impermeable to gas molecules and at the same time transparent to high-energy ions, graphene has been suggested as a window material for separating a high-vacuum ion beam system from targets kept at ambient conditions. However, accumulation of irradiation-induced damage in the graphene membrane may give rise to its mechanical failure. Using atomistic simulations, we demonstrate that irradiated graphene even with a high vacancy concentration does not show signs of such instability, indicating a considerable robustness of graphene windows. We further show that upper and lower estimates for the irradiation damage in graphene can be set using a simple model.

Ahlgren, E. H.; Lehtinen, O. [Department of Physics, University of Helsinki, P.O. Box 43, 00014 Helsinki (Finland); Kotakoski, J. [Department of Physics, University of Helsinki, P.O. Box 43, 00014 Helsinki (Finland); Department of Physics, University of Vienna, Boltzmanngasse 5, 1190 Wien (Austria); Krasheninnikov, A. V. [Department of Physics, University of Helsinki, P.O. Box 43, 00014 Helsinki (Finland); Department of Applied Physics, Aalto University, P.O. Box 1100, 00076 Aalto (Finland)

2012-06-04

148

Formation, Dynamics, and Characterization of Nanostructures by Ion Beam Irradiation  

Microsoft Academic Search

Ion beam irradiation is a potential tool for phase formation and material modification as a non-equilibrium technique. Localized rise in temperature and ultra fast (?10 s) dissipations of impinging energy make it an attractive tool for metastable phase formation. As a matter of fact, a major component of materials science is dominated by ion beam methods, either for synthesis of

S. Dhara

2007-01-01

149

Multiple Charged Nitrogen Ion Beam Irradiation of Fullerene Thin Films  

Microsoft Academic Search

In this work, the results of structural modification of fullerene thin films bombarded by multiple charged nitrogen ions have been reported. The properties of as?deposited and irraditated fullerene thin films have been investigated by Raman and FTIR spectroscopy and AFM analysis. After irradiation by multiple charged nitrogen ions (N, N) new bondings in fullerene films have been formed and the

I. Dragani?; Z. Markovi?; Z. Stojanovi?; M. Mitri?; N. Rom?evi?; M. Rom?evi?; Z. Nikoli?

2007-01-01

150

Effect of ion irradiation on hydrogen gas sensitivity of polymer  

NASA Astrophysics Data System (ADS)

In search of economical hydrogen gas sensor material, polymer blend with polyvinyl chloride (PVC) and polyester (PET) has been investigated as sensor material. The polymer blend were irradiated with 50 MeV Li 3+ ions at different fluences. The changes in conductivity of the ion irradiated blend in the presence of hydrogen gas were studied. The sensitivity, response time and recovery time were studied as a function of ion fluences on exposing the sensor material to the H 2 gas at ambient condition. Preliminary results observed are encouraging.

Singh, N. L.; Shrinet, V.; Pandya, N. R.; Sharma, Anita; Patel, N. V.; Avasthi, D. K.

151

Ion exchange in glass using femtosecond laser irradiation  

SciTech Connect

We explain the occurrence of ion exchange and an index profile around the focal point inside a commercial crown glass formed by femtosecond laser irradiation. The index profile in the photoinduced area has a ring-shaped pattern, which indicates that local densification occurred in the glass. An irregular surface reflecting the density distribution is formed around the focal point by dry etching process using a focused ion beam. By the irradiation of femtosecond laser pulses, the effect of ion exchange between the focal point and the surrounding area is also observed in the area in which local densification occurred.

Kanehira, Shingo [Innovative Collaboration Center, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Miura, Kiyotaka; Hirao, Kazuyuki [Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan)

2008-07-14

152

University of Wisconsin Ion Beam Laboratory: A facility for irradiated materials and ion beam analysis  

NASA Astrophysics Data System (ADS)

The University of Wisconsin Ion Beam Laboratory (UW-IBL) has recently undergone significant infrastructure upgrades to facilitate graduate level research in irradiated materials phenomena and ion beam analysis. A National Electrostatics Corp. (NEC) Torodial Volume Ion Source (TORVIS), the keystone upgrade for the facility, can produce currents of hydrogen ions and helium ions up to ~200 ?A and ~5 ?A, respectively. Recent upgrades also include RBS analysis packages, end station developments for irradiation of relevant material systems, and the development of an in-house touch screen based graphical user interface for ion beam monitoring. Key research facilitated by these upgrades includes irradiation of nuclear fuels, studies of interfacial phenomena under irradiation, and clustering dynamics of irradiated oxide dispersion strengthened steels. The UW-IBL has also partnered with the Advanced Test Reactor National Scientific User Facility (ATR-NSUF) to provide access to the irradiation facilities housed at the UW-IBL as well as access to post irradiation facilities housed at the UW Characterization Laboratory for Irradiated Materials (CLIM) and other ATR-NSUF partner facilities. Partnering allows for rapid turnaround from proposed research to finalized results through the ATR-NSUF rapid turnaround proposal system. An overview of the UW-IBL including CLIM and relevant research is summarized.

Field, K. G.; Wetteland, C. J.; Cao, G.; Maier, B. R.; Dickerson, C.; Gerczak, T. J.; Field, C. R.; Kriewaldt, K.; Sridharan, K.; Allen, T. R.

2013-04-01

153

Charge transfer reactions in Xe plasma expansion  

SciTech Connect

Charge transfer reactions of fast Xe ions with hydrocarbons including methane (CH{sub 4}), ethene (C{sub 2}H{sub 4}), and propane (C{sub 3}H{sub 8}) are studied by adding these hydrocarbon gases into a cross flowing Xe plasma expansion. Branching ratios and relative reaction rates for the charge transfers of fast Xe{sup +} with each of the three hydrocarbon gases are measured under different rf powers of the inductively coupled Xe discharge. For CH{sub 4}/Xe system, we find that fast Xe{sup +} reacts readily with CH{sub 4} generating CH{sub 4}{sup +} and CH{sub 3}{sup +} in a ratio of 1:0.56, with an estimated rate coefficient of (2.3{+-}0.3)x10{sup -10} cm{sup 3}/s at 75 W rf power which slowly increases to (2.9{+-}0.3)x10{sup -10} cm{sup 3}/s at 250 W (error bars reflect only the uncertainties due to the unknown extent of the ion recombination that follows the charge transfer reaction). These observed charge transfer reactions are made possible by the kinetically excited Xe ions produced by free expansion of the plasma. For the C{sub 2}H{sub 4}/Xe system product ions C{sub 2}H{sub 4}{sup +} and C{sub 2}H{sub 2}{sup +} are observed, and for C{sub 3}H{sub 8}/Xe, C{sub 2}H{sub 4}{sup +} and C{sub 2}H{sub 5}{sup +} and minor product ions including C{sub 2}H{sub 2}{sup +} and C{sub 3}H{sub 7}{sup +} are observed.

Jiao, C. Q.; Garscadden, A.; Ganguly, B. N. [Innovative Scientific Solutions Inc., Dayton, Ohio 45440-3638 (United States); Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433-7251 (United States)

2007-04-15

154

Fast fluorescence decay of naphthalene induced by Ar ion irradiation  

NASA Astrophysics Data System (ADS)

A single photon counting system was constructed for a time resolved fluorescence measurement with pulsed heavy ions from the AVF cyclotron in Takasaki Ion Accelerators for Advanced Radiation Application (TIARA). Fluorescence spectra and decay of naphthalene in poly(vinyl butylal) (PVB) film were observed from the irradiation with Ar ions. Though fluorescence spectra were assigned to the first singlet excited state of naphthalene, the decay with Ar ion irradiation were faster than that excited by UV light. This faster decay results from quenching by the transient species produced. The relative initial concentration of the excited state of naphthalene to that of the radicals increases with increasing energy deposited along the incident ion's trajectory.

Taguchi, Mitsumasa; Aoki, Yaushi; Namba, Hideki; Watanabe, Ritsuko; Matsumoto, Yuuichi; Hiratsuka, Hiroshi

1997-02-01

155

Swift heavy ion irradiation of zirconium phosphate of various forms  

NASA Astrophysics Data System (ADS)

The zirconium phosphate and its various derivatives have good resistance against ionization radiation, as it was found earlier during the irradiation of them with ?-rays of high energy. Continuing these experiments amorphous and crystalline (both ?- and ?-forms) zirconium phosphate, its monosodium, and propylamine intercalated forms were irradiated with a fluence of 10 11-10 14 ion cm -2 with swift heavy ions of 203Bi and 84Kr. The irradiation was also performed with Si containing zirconium phosphate. The structure of the materials was characterized by XRD method. The comparison of the powder diffraction patterns reveals that the irradiation has practically no effect on the ?-zirconium phosphate, while the other materials more or less destroyed and some of them became amorphous. The propylamine intercalate form of zirconium phosphate is decomposed on ?-ZrP and organic radical.

Szirtes, L.; Megyeri, J.; Kuzmann, E.; Havancsák, K.

2003-06-01

156

Penetration controlled irradiation with ion beams for biological study  

NASA Astrophysics Data System (ADS)

To investigate the effect of local irradiation on biological systems, an apparatus for penetration controlled irradiation with ion beams was set up. By comparison of ranges of 1.5 MeV/u He 2+ between the theoretically calculated ranges and the practical ranges using chemical and biological materials, it was demonstrated that the range of an ion beam in a biological material could be controlled linearly by changing the distance from the beam window in the atmosphere to a target, although the fluence decreased at the range-end of the ion beams. In addition, the penetration controlled irradiation of tobacco pollen increased the frequency of leaky pollen. The increased frequency of the leaky pollen suggested that damage in the pollen envelope was induced at the range-end.

Tanaka, Atsushi; Watanabe, Hiroshi; Shimizu, Takashi; Inoue, Masayoshi; Kikuchi, Masahiro; Kobayashi, Yasuhiko; Tano, Shigemitsu

1997-06-01

157

Modeling ?-? coincidence spectra of 131m Xe, 133 Xe, 133m Xe, and 135 Xe  

Microsoft Academic Search

In support of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), improvements have been made to the model of the Automated\\u000a Radioxenon Sampler\\/Analyzer (ARSA) ?-? coincidence detector for radioxenon monitoring. MCNPX is used to simulate the detector\\u000a response for all the electrons and photons emitted from 131mXe, 133Xe, 133mXe, 135Xe, and 137Cs signals. A MatLab code was written to incorporate the MCNPX results

D. A. Haas; S. R. Biegalski; K. M. Foltz Biegalski

2008-01-01

158

Response of Strontium Titanate to Ion and Electron Irradiation  

SciTech Connect

Response of strontium titanate (SrTiO3) to ion and electron irradiation is studied at room temperature. For an accurate energy to depth conversion and a better determination of ion-induced disorder profile from Rutherford backscattering spectrometry measurement, a detailed iterative procedure is described and applied to ion channeling spectra to determine the dechanneling yield and the disorder profiles for the Sr and Ti sublattices. The result shows a large underestimation in disorder depth, ~ 40% at the damage peak, which indicates a large overestimation of the electronic stopping power for 1.0 MeV Au ions in SrTiO3 predicted by the SRIM (Stopping and Range of Ions in Matter) code. Overestimation of heavy ion stopping power may lead to an overestimation of the critical dose for amorphization. The current study also demonstrates possible ionization effects in SrTiO3 under ion and electron irradiation. Pre-amorphized SrTiO3 exhibits strong ionization-induced epitaxial recovery at the amorphous/crystalline interface under electron irradiation.

Zhang, Yanwen; Lian, Jie; Zhu, Zihua; Bennett, Wendy D.; Saraf, Laxmikant V.; Rausch, Julie L.; Hendricks, Catherine A.; Ewing, R. C.; Weber, William J.

2009-04-20

159

Time-of-Flight Measurements of Ion and Electron from Xenon Clusters Irradiated with a Soft X-Ray Laser Pulse  

Microsoft Academic Search

The photoionization process in xenon clusters irradiated with a soft x-ray laser pulse (h?­=89.2 eV, intensity: ~1010 W\\/cm2) was examined using a time-of-flight mass spectrometer, where the laser photon energy was high enough to ionize Xe 4d inner\\u000a electrons (threshold: 67.55 eV for 4d5\\/2 and 69.54 eV for 4d3\\/2). The dominant ion yield resulting from Auger decay of 4d hole

S. Namba; N. Hasegawa; M. Nishikino; M. Kishimoto; T. Kawachi; M. Tanaka; Y. Ochi; K. Nagashima; K. Takiyama

2009-01-01

160

Ion irradiation of ammonia/carbon dioxide mixtures  

NASA Astrophysics Data System (ADS)

We present new experimental results on the thermal and ion irradiation processing of ammonia/carbon dioxide frozen mixtures. Mixtures deposited at low T (16 K) have then been warmed up to 160 K. During warm up complex chemical reactions occur leading to the formation of new molecules and, in particular, of ammonium carbamate. Other samples have been irradiated with 144 keV S9+ ions. Also in this case new chemical species are formed among which CO and OCN-. The results are discussed in the light of their relevance to understand the effects of different processes going on in the variegated superficial and sub-superficial layers of Enceladus.

Lv, X. Y.; Boduch, P.; Ding, J. J.; Domaracka, A.; Langlinay, T.; Palumbo, M. E.; Rothard, H.; Strazzulla, G.

2013-09-01

161

On the uptake of water vapor by ion irradiated polyimide  

NASA Astrophysics Data System (ADS)

It is known that ion-irradiated polymers are capable to adsorb dopants from solid, liquid or gaseous phases. For simple ambient atmosphere exposures, oxygen and water vapor are the most prominent dopants. Though the quantity of the latter one is not sufficient to be probed by conventional spectroscopic techniques, it can be detected indirectly via its ionic conductivity on applying a strong electric field along the track direction, as long as it is not yet masked by the intrinsic ion track conductivity, which is the case for low-fluence polymer irradiation. The conductivity is of similar order for most low-fluence irradiated polymers examined - namely 10-15-10-13 ?-1 cm-1. Water vapor uptake - as determined via the ion track conductivity - sensitively depends on the ambient air humidity, so that fresh low fluence irradiated polymers can act as humidity sensors. Aging however leads to rapid deterioration of this property within a week exposure time at ambient room temperature and pressure. The water vapor absorption process in tracks is reversible, and the amount of water retained depends specifically on the polymer. Thus, whereas for polyimide, polycarbonate, polypropylene, and polytetrafluoride some water vapor adsorption is detected, polymethylmethacrylate and polyethyleneterepthalate exhibit little or no effect. Moreover, uptake of water vapor is restricted to the latent ion tracks themselves, and is barely detectable in neighboring pristine material. It scales linearly with the deposition of electronic energy along the ion track.

Fink, D.; Klett, R.; Müller, M.; Hu, Xuanwen; Chadderton, L. T.; Wang, L.; Hillenbrand, J.

162

Defect production and accumulation under hydrogen and helium ion irradiation  

Microsoft Academic Search

The 316L stainless steel (316L SS) is a candidate material for the first wall of a fusion reactor, which will be irradiated with 14 MeV neutrons and escaped ions. This will produce helium and hydrogen in the matrix, which come both from the transmutation production and escaped ions of the plasma. The synergistic action of high-energy cascades and helium induces

Jinnan Yu; Xinjie Zhao; Wen Zhang; Wen Yang; Fengmin Chu

1997-01-01

163

Large conductivity changes in ion beam irradiated organic thin films  

Microsoft Academic Search

Using 2-MeV Ar+ ion beam irradiation, we have generated conducting patterns in otherwise high resistivity, organic thin films of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), 1,4,5,8-napthalenetetracarboxylic dianhydride (NTCDA), and Ni phthalocyanine (NiPc). The room-temperature resistivity of the films changes by 14 orders of magnitude from its as-deposited value of &rgr;?1010 ? cm to &rgr;?5×10?4 ? cm at ion doses of 1017 cm?2. The

S. R. Forrest; M. L. Kaplan; P. H. Schmidt; T. Venkatesan; A. J. Lovinger

1982-01-01

164

Optimized energetic particle emissions from Xe clusters in intense laser fields  

SciTech Connect

We have probed the interaction of intense laser fields with Xe clusters by measuring the energy and charge state distributions of emitted ions and electrons using ultrafast 20-fs pulses. This work demonstrates that the energetic particle emissions from laser-cluster interactions can be optimized by manipulating the character of ultrafast laser pulses, i.e., pulse duration and sign of chirp. The mean and maximum ion energies as high as 0.1 and 2 MeV, respectively, are achieved when Xe clusters are irradiated by 500-fs pulses with negative chirp as an optimal condition under a laser peak intensity of 2x10{sup 17} W/cm{sup 2}. The mean ion energy obtained from 500-fs pulses with negative chirp is found to be about 1.6 times larger than that with positive chirp.

Fukuda, Yuji; Yamakawa, Koichi; Akahane, Yutaka; Aoyama, Makoto; Inoue, Norihiro; Ueda, Hideki [Advanced Photon Research Center, Kansai Research Establishment, Japan Atomic Energy Research Institute, Kizu, Kyoto 619-0215 (Japan); Kishimoto, Yasuaki [Naka Fusion Research Establishment, Japan Atomic Energy Research Institute, Naka, Ibaraki 311-0193 (Japan)

2003-06-01

165

Time-dependent characteristics of the dielectric barrier discharge in Xe-Cl2 mixture and kinetics of the XeCl? molecules  

NASA Astrophysics Data System (ADS)

Time-dependent characteristics of the dielectric barrier discharge in Xe-Cl2 mixture at chlorine concentration of 0.5% and kinetic processes governing the generation of XeCl? molecules are studied using the 1D fluid model. It is shown that at low voltage amplitude (5 kV) a one-peak mode of the discharge is observed and at high voltage amplitude (7 kV) a two-peak mode of the discharge appears. The radiation power of the XeCl? band increases with amplitude of the supply voltage. It is demonstrated that the harpoon reaction Xe? + Cl2 ? XeCl? + Cl provides the greatest contribution into generation of XeCl? exciplex molecules during short current pulses and the ion-ion recombination Xe+ 2 + Cl- ? XeCl* + Xe provides the greatest contribution during afterglow. Quenching of XeCl? molecules is a result of the radiative decay XeCl? ? Xe + Cl + hv (308 nm). During current spike the great contribution into quenching of XeCl? provides also the dissociative ionization e + XeCl? ? Xe+ + Cl + 2e.

Avtaeva, Svetlana

2014-04-01

166

Enhanced diffusion processes during heavy-ion irradiation of glasses  

SciTech Connect

Alkali silicate glasses have been irradiated by using Ar ions at energy of and above 200 keV. The target temperature was varied in the range between liquid nitrogen temperature and 200/sup 0/C. The observed modifications in alkali depth distribution, determined by nuclear techniques, have been analyzed on the basis of phenomenological models. 12 refs., 3 figs.

Arnold, G.W.; Battaglin, G.; Della Mea, G.; De Marchi, G.; Mazzoldi, P.; Miotello, A.

1987-01-01

167

Enhanced Diffusion Processes During Heavy-Ion Irradiation of Glasses.  

National Technical Information Service (NTIS)

Alkali silicate glasses have been irradiated by using Ar ions at energy of and above 200 keV. The target temperature was varied in the range between liquid nitrogen temperature and 200 deg C. The observed modifications in alkali depth distribution, determ...

G. W. Arnold G. Battaglin G. Della Mea G. De Marchi P. Mazzoldi

1987-01-01

168

Magnetization and susceptibility of ion irradiated granular magnetite films  

SciTech Connect

Superparamagnetic granular magnetite (Fe3O4) films with an average grain size of 3 nm have been found to be magnetized following 5.5 MeV Si2+ ion irradiation to a fluence of 1.0E16 ions/cm2 near room temperature. The film underwent a phase transition to ferromagnetism after the irradiation. X-ray diffraction study shows that the average grain size increased to 23 nm. There is a dramatic change in the microstructure, featuring particle aggregation and material condensation. Magnetic domains in the irradiated film are observed in the size range of tens to several hundreds of nanometers. The change in the magnetic properties is attributed to irradiation induced grain growth and structural modifications that lead to occurrence of magnetic anisotropy. There are dipolar interactions between the nanoparticles in both the unirradiated and irradiated films. Data fits for the in-phase alternating current magnetic susceptibility of the unirradiated film indicate that the blocking temperature is ~150 K, depending on frequency. A gradual Verwey transition for the irradiated film occurs at ~75 K, above which the susceptibility exhibits unusual behavior: a linear decrease with decreasing temperature. There are irreversible processes of magnetic domains during cooling and warming up between 10 and 300 K.

Jiang, Weilin; McCloy, John S.; Lea, Alan S.; Sundararajan, J. A.; Yao, Qi; Qiang, Y.

2011-04-26

169

Irradiation resistance properties studies on helium ions irradiated MAX phase Ti3AlC2  

NASA Astrophysics Data System (ADS)

The study presents an investigation of irradiation resistance properties of Ti3AlC2 under 500 keV He ions irradiation with the doses ranging from 5.0 × 1016 to 1.0 × 1018 ions cm?2 at certain temperatures, like room temperature (RT), 300 and 500 °C. X-ray diffraction (XRD) and Transmission electron microscopy (TEM) are used to study the evolution of structural damage and the behavior of deposited He ions respectively. XRD analysis reveals that for the highest dose irradiation (˜52 dpa at peak), no amorphization occurs. And the structural recovery of Ti3AlC2 is more significant accompanied with the gradual disappearance of the irradiation-induced TiC phase as the temperature rises from RT to 300 and to 500 °C with the same dose irradiation. TEM observations show that He bubbles appear in the shapes of sphere, string and platelet but no big bubbles are formed for all irradiations. Moreover, no large cracks form in the sample implanted with the highest helium concentration of ˜6.4 × 105 appm.

Song, Peng; Sun, Jianrong; Wang, Zhiguang; Cui, Minghuan; Shen, Tielong; Li, Yuanfei; Pang, Lilong; Zhu, Yabin; Huang, Qing; Lü, Jinjun

2014-05-01

170

Multiphoton ionization of iodine atoms and CF 3I molecules by XeCl laser radiation  

NASA Astrophysics Data System (ADS)

We report about effective ionization of iodine atoms and CF3I molecules under the action of intense XeCl laser radiation (308 nm). The only ion fragment resulting from the irradiation of the CF3I molecules is the I+ ion. We have studied the influence of the intensity, spectral composition, and polarization of the laser radiation used on the intensity of the ion signal and the shape of its time-of-flight peak. Based on the analysis of the results obtained, we have suggested the mechanism of this effect. The conclusion drawn is that the ionization of the iodine atoms by the ordinary XeCl laser with a nonselective cavity results from a three- (2 + 1)-photon REMPI process. This process is in turn due to the presence of accidental two-photon resonances between various spectral components of the laser radiation and the corresponding intermediate excited states of the iodine atom. The probability of ionization of the atoms from their ground state I(2P3/2) by the radiation of the ordinary XeCl laser is more than two orders of magnitude higher than the probability of their ionization from the metastable state I*(2P1/2). The ionization of the CF3I molecules by the XeCl laser radiation occurs as a result of a four-photon process involving the preliminary one-photon dissociation of these molecules and the subsequent (2 + 1)-photon REMPI of the resultant neutral iodine atoms.

Lokhman, V. N.; Ogurok, D. D.; Ryabov, E. A.

2008-01-01

171

Effects of Ga ion-beam irradiation on monolayer graphene  

NASA Astrophysics Data System (ADS)

The effects of Ga ion on the single layer graphene (SLG) have been studied by Raman spectroscopy (RS), SEM, and field-effect characterization. Under vacuum conditions, Ga ion-irradiation can induce disorders and cause red shift of 2D band of RS, rather than lattice damage in high quality SLG. The compressive strain induced by Ga ion decreases the crystalline size in SLG, which is responsible for the variation of Raman scattering and electrical properties. Nonlinear out-put characteristic and resistance increased are also found in the I-V measurement. The results have important implications during CVD graphene characterization and related device fabrication.

Wang, Quan; Mao, Wei; Ge, Daohan; Zhang, Yanmin; Shao, Ying; Ren, Naifei

2013-08-01

172

Gel behavior of keV ion irradiated polystyrene  

SciTech Connect

Among the chemical and physical modifications induced by ion bombardment of polymers, the solubility changes are very important because of technological application for lithography in microelectronic devices. Solubility changes due to the occurrence of crosslinkings have been followed on monodisperse and polydisperse polystyrene after ion irradiations (10/sup 11/--10/sup 14/ ions/cm/sup 2/, keV energy). By using the Inokuty gel theory (M. Inokuti J. Appl. Phys. 38, 2999 (1963)), the chemical yield (crosslinking/eV) has been determined for different molecular weights and molecular weight distributions.

Calcagno, L.; Foti, G.; Licciardello, A.; Puglisi, O.

1988-10-17

173

Effects of Ga ion-beam irradiation on monolayer graphene  

SciTech Connect

The effects of Ga ion on the single layer graphene (SLG) have been studied by Raman spectroscopy (RS), SEM, and field-effect characterization. Under vacuum conditions, Ga ion-irradiation can induce disorders and cause red shift of 2D band of RS, rather than lattice damage in high quality SLG. The compressive strain induced by Ga ion decreases the crystalline size in SLG, which is responsible for the variation of Raman scattering and electrical properties. Nonlinear out-put characteristic and resistance increased are also found in the I-V measurement. The results have important implications during CVD graphene characterization and related device fabrication.

Wang, Quan; Mao, Wei; Zhang, Yanmin; Shao, Ying; Ren, Naifei [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China)] [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China); Ge, Daohan [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China) [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China); State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Shanghai 200050 (China)

2013-08-12

174

Microstructure and micromechanics of brazings under irradiation by ions  

NASA Astrophysics Data System (ADS)

In order to study the microstructural evolution under irradiation, of phosphides (M 2P and M 3P) present in junctions realized by brazing, irradiations with various ions have been performed at 300 and 523 K. Our irradiated materials are, a brazed junction of two stainless steel plates, two amorphous model alloys and a crystalline model alloy. We observe that at 300 K the amorphous state is stable for M 3P whereas a dislocation network develops in the other phases. At the higher temperature amorphous alloys recrystallize and a dislocation network develops in the three phases present in the junction. Micromechanical tests by submicronic indentation show that the most frequent M 2P phase is initially very hard and undergoes a softening when irradiated.

Boulanger, L.; Chen, J.; Jung, P.; Serruys, Y.

1994-09-01

175

Fabrication of carbon nanostructures (nanodots, nanowires) by energetic ion irradiation  

NASA Astrophysics Data System (ADS)

Carbon nanostructures were synthesized by energetic ion irradiation of Si-based gel films. These polymer-like films with different side groups and C concentrations were prepared by sol-gel chemistry and irradiated with Si or Au ions of different energies in the range 3 MeV-2 GeV. The shape and size of the formed carbon nanostructures was studied by energy filtered transmission electron microscopy. They exhibited a visible photoluminescence emission, due to their semiconducting nature and the confinement of excitons. The changes in the optical properties were correlated with the structural transformation of films, investigated by means of Fourier transformed infrared (FTIR) and Raman spectroscopies. The role of carbon concentration, structure and energy transferred by ions on the luminescence properties are discussed.

Kumar, Amit; Singh, Fouran; Pivin, J. C.; Avasthi, D. K.

2007-04-01

176

Effects on focused ion beam irradiation on MOS transistors  

SciTech Connect

The effects of irradiation from a focused ion beam (FIB) system on MOS transistors are reported systematically for the first time. Three MOS transistor technologies, with 0.5, 1, and 3 {mu}m minimum feature sizes and with gate oxide thicknesses ranging from 11 to 50 nm, were analyzed. Significant shifts in transistor parameters (such as threshold voltage, transconductance, and mobility) were observed following irradiation with a 30 keV Ga{sup +} focused ion beam with ion doses varying by over 5 orders of magnitude. The apparent damage mechanism (which involved the creation of interface traps, oxide trapped charge, or both) and extent of damage were different for each of the three technologies investigated.

Campbell, A.N.; Peterson, K.A.; Fleetwood, D.M.; Soden, J.M.

1997-04-01

177

Ion beam irradiated optical channel waveguides  

NASA Astrophysics Data System (ADS)

Nowadays, in the modern optical communications systems, channel waveguides represent the core of many active and passive integrated devices, such as amplifiers, lasers, couplers and splitters. Different materials and fabrication processes were investigated in order to achieve the aforementioned optoelectronic circuits with low costs and high performance and reproducibility. Nevertheless, the 2D guiding structures fabrication continues to be a challenging task in some of optical materials due to their susceptibility to mechanical and/or chemical damages which can occur during the different steps of the fabrication process. Here we report on channel waveguides demonstration in erbium doped Tungsten - Tellurite (Er3+:TeO2-WO3) glasses and BGO crystals by means of a masked ion beam and/or direct writing processes performed at different energy MeV and ions species. The evidence of the waveguides formation was investigated by microscopy techniques and micro Raman spectroscopy.

Bányász, I.; Rajta, I.; Nagy, G. U. L.; Zolnai, Z.; Havranek, V.; Pelli, S.; Veres, M.; Himics, L.; Berneschi, S.; Nunzi-Conti, G.; Righini, G. C.

2014-03-01

178

Structure alterations in microporous (Mg,Fe){sub 2}Al{sub 4}Si{sub 5}O{sub 18} crystals induced by energetic heavy-ion irradiation  

SciTech Connect

The microporous framework structure of (Mg{sub 1-x}Fe{sub x}){sub 2}Al{sub 4}Si{sub 5}O{sub 18} (=cordierite) has been subject to a comparative study on the effect of structural alterations originating from exposure to high-energy heavy ions. Oriented samples (with x=0.061, 0.122, and 0.170) were irradiated with swift {sup 124}Xe, {sup 197}Au and {sup 96}Ru ions with 11.1 MeV per nucleon energy and fluences of 1x10{sup 12} and 1x10{sup 13} ions/cm{sup 2}. Irradiated and non-irradiated samples were investigated by means of X-ray diffraction, Moessbauer spectroscopy and optical absorption spectroscopy. Structural investigations reveal an essentially unchanged Al,Si ordering, which appears to be unaffected by irradiation. The most remarkable macroscopic change is the ion-beam induced colouration, which could be assigned to electronic charge transfer transitions involving the Fe cations. Moessbauer spectra indicate an increased amount of {sup [4]}Fe{sup 3+} for the irradiated sample. The most noticeable structural alteration concerns irradiation-induced dehydration of extra-framework H{sub 2}O, which is accompanied by a reduction in the molar volume by {approx}0.2 vol%. - Graphical abstract: Cordierite single-crystal specimen showing the color change from pale blue (unirradiated) to a yellowish brown layer (irradiated) after exposure to relativistic {sup 124}Xe ions at a fluence of 1x10{sup 12} ions per cm{sup 2}.

Miletich, Ronald, E-mail: ronald.miletich@geow.uni-heidelberg.d [Institut fuer Geowissenschaften, Universitaet Heidelberg, Im Neuenheimer Feld 234-236, D-69120 Heidelberg (Germany); Diego Gatta, G. [Dipartimento di Scienze della Terra, Universita degli Studi di Milano, Via Botticelli 23, I-20133 Milano (Italy); Redhammer, Guenther J. [Fachbereich Materialforschung und Physik, Abteilung Mineralogie, Universitaet Salzburg, Hellbrunnerstrasse 34, A-5020 Salzburg (Austria); Burchard, Michael; Meyer, Hans-Peter [Institut fuer Geowissenschaften, Universitaet Heidelberg, Im Neuenheimer Feld 234-236, D-69120 Heidelberg (Germany); Weikusat, Christian [Institut fuer Geowissenschaften, Universitaet Heidelberg, Im Neuenheimer Feld 234-236, D-69120 Heidelberg (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung, Materials Research, Planckstrasse 1, D-64291 Darmstadt (Germany); Rotiroti, Nicola [Dipartimento di Scienze della Terra, Universita degli Studi di Milano, Via Botticelli 23, I-20133 Milano (Italy); Glasmacher, Ulrich A. [Institut fuer Geowissenschaften, Universitaet Heidelberg, Im Neuenheimer Feld 234-236, D-69120 Heidelberg (Germany); Trautmann, Christina; Neumann, Reinhard [GSI Helmholtzzentrum fuer Schwerionenforschung, Materials Research, Planckstrasse 1, D-64291 Darmstadt (Germany)

2010-10-15

179

Hydrogen retention in ion irradiated steels  

Microsoft Academic Search

In the future 1--5 MW Spallation Neutron Source, target radiation damage will be accompanied by high levels of hydrogen and helium transmutation products. The authors have recently carried out investigations using simultaneous Fe\\/He,H multiple-ion implantations into 316 LN stainless steel between 50 and 350 C to simulate the type of radiation damage expected in spallation neutron sources. Hydrogen and helium

J. D. Hunn; M. B. Lewis; E. H. Lee

1998-01-01

180

Ion emission from fused silica under 157-nm irradiation  

NASA Astrophysics Data System (ADS)

We present a summary of initial work on the etching of silica at 157 nm. At fluences well below the threshold for plasma formation, we have characterized the direct desorption of atomic ions from fused silica surfaces during 157-nm irradiation. The ion identities and kinetic energies were determined by time-resolved mass spectroscopy. The principal ions are Si+ and O+. The emission intensities are dramatically increased by treatments that are expected to increase the density of surfaces defects. Molecular dynamics simulations of the silica surface suggest that silicon ions bound at surface oxygen vacancies (analogous to E' centers) provide suitable configurations for emission. We propose that emission is best understood in terms of a hybrid mechanism involving both antibonding chemical forces (Menzel-Gomer-Redhead model) and repulsive electrostatic forces on the adsorbed ion after laser excitation of the underlying defect.

John, Sharon R.; Leraas, J. A.; Langford, S. C.; Dickinson, J. T.

2007-04-01

181

Properties of ion track in polystyrene irradiated with high energy 56Fe ions  

NASA Astrophysics Data System (ADS)

Polystyrene (PS) films were irradiated with 1.157 GeV 56Fe ions at room temperature to fluences of 1 × 1012 ions/cm2 at various electronic energy loss values. Ultraviolet-visible (UV-vis) spectra were measured to investigate the optical properties of the irradiated materials. Optical constants of virgin and irradiated PS were evaluated in the UV-vis frequence range through fitting of UV-vis spectra with the multi-Lorentz model. Furthermore, effective medium theory was applied to evaluate the optical constants of materials in the ion track area. It is found that the refractive index of ion track material decreased significantly in the ultraviolet-visible range whereas its extinction coefficient increased. Gas atom release and carbon atom conglomerating are believed to be the reason. The extracted track radius and its variation with electronic energy loss values are in good agreement with earlier studies.

Ma, Mingwang; Wu, Shengwei; Lin, Jun; Sun, Youmei; Jin, Yunfan; Zhu, Zhiyong

2012-09-01

182

Study of temperature and radiation induced microstructural changes in Xe-implanted UO2 by TEM, STEM, SIMS and positron spectroscopy  

NASA Astrophysics Data System (ADS)

Doppler broadening of annihilation gamma-line combined with a slow positron beam (SPB) was used to measure the momentum density distribution of annihilating pairs in a set of sintered UO2 samples implantated with 800-keV 136Xe2+ at fluences of 1 × 1015 and 1 × 1016 Xe cm-2. The effect of prolonged post-implantation annealing at 1673 and 1873 K, grain size, and 152-MeV Iodine irradiation were studied by analysis of S(E) profiles and S-W maps and discussed versus secondary ion mass spectroscopy (SIMS), scanning transmission electron microscopy results. Spectroscopy with SPB and SIMS is an excellent combination of complementary techniques for studying the formation and evolution of Xe-bubbles, and Xe retention.

Djourelov, Nikolay; Marchand, Benoît; Marinov, Hristo; Moncoffre, Nathalie; Pipon, Yves; Bérerd, Nicolas; Nédélec, Patrick; Raimbault, Louis; Epicier, Thierry

2013-11-01

183

Enhancement of Secondary Hydrocarbon Ion Emission Yield from Graphite Irradiated with Energetic Carbon Cluster Ion Beams  

NASA Astrophysics Data System (ADS)

When radiations, such as UV lights, X-rays, gamma-rays, and energetic electrons and ions, irradiate interstellar grains, excitation and ionization of the atoms and molecules around the surface of the grains occur, and chemical reactions are induced. Thus many kinds of organic and inorganic molecules are produced on the interstellar grains. We have observed the yield enhancement of secondary hydrocarbon cluster ion emission from graphite irradiated by energetic cluster ions. As energetic cluster ions can bombard a very small (atomic size) area of a solid surface with many atoms simultaneously and release large kinetic energy in a very short time (from femto-to pico-second region), nonlinear effects or synergetic effects are caused. This effect enhances the secondary ion emission yields. Energetic cluster ion beams used for the study of secondary ion emission processes were pro-duced by the TIARA tandem accelerator at Takasaki Advanced Radiation Research Institute, JAEA. A time of flight (TOF) mass spectrometer combined with a pulsed cluster ion beam was used for a secondary ion measurement. In this report we present some results of positive and negative secondary ion emission from a highly oriented pyrolytic graphite (HOPG) target bombarded with 0.5 MeV/atom (˜ 42 keV/amu) C1+ ˜ C8+ ions. The total secondary ion yields except for yields of hydrogen ions (H+, H2+, H3+ or H-) from a HOPG target bombarded with carbon cluster ions are presented. The yields of negative secondary ions for all incident cluster ions Cn+ are about twice of positive ion yields and the super-linear relation can be seen. We will discuss about this enhancement of the yield of secondary emission.

Shibata, Hiromi; Saitoh, Yuichi; Chiba, Atsuya; Narumi, Kazumasa

184

Ion irradiation of inhomogeneous Schottky barriers on silicon carbide  

SciTech Connect

In this paper, the effects of ion irradiation on Schottky barriers formed on silicon carbide are discussed. After Si-ion irradiation at the near-interface region in Ti/4H-SiC contacts an increase of the Schottky barrier height from 1.05 to 1.21 eV was observed, accompanied by a lowering of the reverse leakage current. The combination of several methods allowed us to determine the physical properties of the Schottky barrier and to explain the mechanism responsible for the barrier height changes. In particular, the structural and electrical modifications of the interfacial region, both of Ti layer and SiC (i.e., different orientation of the Ti layer, irradiation-induced defects in the epilayer, dopant deactivation, and the consequent reduction of the surface electric field) are responsible for the increase of the Schottky barrier height and the reduction of the leakage current. The electrical characterization of the contacts at different temperatures also suggested that ion irradiation induced modifications in the inhomogeneous nature of the Ti Schottky barrier.

Roccaforte, F.; Libertino, S.; Giannazzo, F.; Bongiorno, C.; La Via, F.; Raineri, V. [Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Sezione di Catania, Stradale Primosole 50, I-95121 Catania (Italy)

2005-06-15

185

Kr ion irradiation study of the depleted-uranium alloys.  

SciTech Connect

Fuel development for the reduced enrichment research and test reactor (RERTR) program is tasked with the development of new low enrichment uranium nuclear fuels that can be employed to replace existing high enrichment uranium fuels currently used in some research reactors throughout the world. For dispersion type fuels, radiation stability of the fuel-cladding interaction product has a strong impact on fuel performance. Three depleted-uranium alloys are cast for the radiation stability studies of the fuel-cladding interaction product using Kr ion irradiation to investigate radiation damage from fission products. SEM analysis indicates the presence of the phases of interest: U(Al, Si){sub 3}, (U, Mo)(Al, Si){sub 3}, UMo{sub 2}Al{sub 20}, U{sub 6}Mo{sub 4}Al{sub 43} and UAl{sub 4}. Irradiations of TEM disc samples were conducted with 500 keV Kr ions at 200 C to ion doses up to 2.5 x 10{sup 19} ions/m{sup 2} ({approx}10 dpa) with an Kr ion flux of 10{sup 16} ions/m{sup 2}/s ({approx}4.0 x 10{sup -3} dpa/s). Microstructural evolution of the phases relevant to fuel-cladding interaction products was investigated using transmission electron microscopy.

Gan, J.; Keiser, D. D.; Miller, B. D.; Kirk, M. A.; Rest, J.; Allen, T. R.; Wachs, D. M. (Materials Science Division); (INL); (Univ. of Wisconsin)

2010-12-01

186

Kr Ion Irradiation Study of the Depleted-Uranium Alloys  

SciTech Connect

Fuel development for the Reduced Enrichment Research and Test Reactor program is tasked with the development of new low-enriched uranium nuclear fuels that can be employed to replace existing highly enriched uranium fuels currently used in some research reactors throughout the world. For dispersion-type fuels, radiation stability of the fuel/cladding interaction product has a strong impact on fuel performance. Three depleted uranium alloys are cast for the radiation stability studies of the fuel/cladding interaction product using Kr ion irradiation to investigate radiation damage from fission products. SEM analysis indicates the presence of the phases of interest: U(Si, Al)3, (U, Mo)(Si, Al)3, UMo2Al20, U6Mo4Al43, and UAl4. Irradiations of TEM disc samples were conducted with 500 keV Kr ions at 200ºC to ion doses up to 2.5 × 1015 ions/cm2 (~ 10 dpa) with an Kr ion flux of 1012 ions/cm2-sec (~ 4.0 × 10-3 dpa/sec). Microstructural evolution of the phases relevant to fuel-cladding interaction products was investigated using transmission electron microscopy.

J. Gan; D. Keiser; B. Miller; M. Kirk; J. Rest; T. Allen; D. Wachs

2010-12-01

187

Comparison of Deuterium Retention for Ion-irradiated and Neutron-irradiated Tungsten  

SciTech Connect

The behavior of D retention for Fe{sup 2+}-irradiated tungsten with a damage of 0.025-3 dpa was compared with that for neutron-irradiated tungsten with 0.025 dpa. The D{sub 2} thermal desorption spectroscopy (TDS) spectra for Fe{sup 2+}-irradiated tungsten consisted of two desorption stages at 450 and 550 K, while that for neutron-irradiated tungsten was composed of three stages and an addition desorption stage was found at 750 K. The desorption rate of the major desorption stage at 550K increased as the displacement damage increased due to Fe{sup 2+} irradiation increasing. In addition, the first desorption stage at 450K was found only for damaged samples. Therefore, the second stage would be based on intrinsic defects or vacancy produced by Fe{sup 2+} irradiation, and the first stage should be the accumulation of D in mono-vacancy and the activation energy would be relatively reduced, where the dislocation loop and vacancy is produced. The third one was found only for neutron irradiation, showing the D trapping by a void or vacancy cluster, and the diffusion effect is also contributed to by the high full-width at half-maximum of the TDS spectrum. Therefore, it can be said that the D{sub 2} TDS spectra for Fe{sup 2+}-irradiated tungsten cannot represent that for the neutron-irradiated one, indicating that the deuterium trapping and desorption mechanism for neutron-irradiated tungsten is different from that for the ion-irradiated one.

Yasuhisa Oya; Masashi Shimada; Makoto Kobayashi; Takuji Oda; Masanori Hara; Hideo Watanabe; Yuji Hatano; Pattrick Calderoni; Kenji Okuno

2011-12-01

188

Positive ion irradiation of CdS\\/Cu2S thin film solar cells  

Microsoft Academic Search

The effect of positive ion bombardment on unencapsulated CdS\\/Cu2S thin film solar cells has been studied using monoenergetic positive ions (of H, He, O, S, Cl, Ar, Cu, Kr, Cd or Xe) with energies in the range 10–50 keV. The current-voltage characteristics of the cells have been analysed in terms of a five parameter model. The cell degradations produced by

F. J. Bryant; R. W. Glew

1976-01-01

189

An infrared study of pure and ion irradiated frozen formamide  

NASA Astrophysics Data System (ADS)

Context.The chemical evolution of formamide (HCONH2), a molecule of astrobiological interest that has been tentatively identified in interstellar ices and in cometary coma, has been studied in laboratory under simulated astrophysical conditions such as ion irradiation at low temperature.Aims.To evaluate the abundances of formamide observed in space or in laboratory, the integrated absorbances for all the principal IR features of frozen amorphous pure formamide deposited at 20 K were measured. Further evidence that energetic processing of ices occurring in space is extremely relevant both to astrochemistry and to astrobiology has been found, showing that new molecular species are synthesized by ion irradiation at a low temperature.Methods.Pure formamide were deposited at 20 K and IR transmission spectra measured for different ice thicknesses. The ice thickness was derived by looking at the interference pattern (intensity versus time) of a He-Ne laser beam reflected at an angle of 45 deg by the vacuum-film and film-substrate interfaces. Samples of formamide ice were irradiated with 200 keV H+ ions and IR spectra recorded at different ion fluences.Results.New molecules were synthesized among which are CO, CO2, N2O, isocyanic acid (HNCO), and ammonium cyanate (NH4^+OCN^-). Some of these species remain stable after warming up to room temperature.

Brucato, J. R.; Baratta, G. A.; Strazzulla, G.

2006-08-01

190

Elastic wave from fast heavy ion irradiation on solids  

NASA Astrophysics Data System (ADS)

To study the time-dependent mechanical effects of fast heavy ion irradiations, we have irradiated various solids by a short-bunch beam of 95 MeV/u Ar ions and observed elastic waves generated in the bulk. The irradiated targets were square-shaped plates of poly-crystals of metals (Al and Cu), invar alloy, ceramic (Al 2O 3), fused silica (SiO 2) and single crystals of KC1 and LiF with a thickness of 10 mm. The beam was incident perpendicular to the surface and all ions were stopped in the target. Two piezo-electric ultrasonic sensors were attached to the surface of the target and detected the elastic waves. The elastic waveforms as well as the time structure and intensity of the beam bunch were recorded for each shot of a beam bunch. The sensor placed opposite to the beam spot recorded a clear waveform of the longitudinal wave across the material, except for the invar and fused silica targets. From its propagation time along with the sound velocity and the thickness of the target, the depth of the wave source was estimated. The result was compared with ion ranges calculated for these materials by TRIM code.

Kambara, T.; Kageyama, K.; Kanai, Y.; Kojima, T. M.; Nanai, Y.; Yoneda, A.; Yamazaki, Y.

2002-06-01

191

Late degeneration in rabbit tissues after irradiation by heavy ions  

NASA Technical Reports Server (NTRS)

Results are presented for investigations of the late effects of heavy-ion irradiation on rabbit tissues which were undertaken to assess the hazards associated with the long-term exposure of humans to heavy ions in space during such activities as the construction of solar power stations or voyages to Mars. White rabbits approximately six weeks old were exposed to various doses of collimated beams of 400-MeV/n Ne ions, 570 MeV/n Ar ions and Co-60 gamma rays directed through both eyes, and the responses of the various tissues (hair follicles, skin, cornea, lens, retina, Harderian glands, bone and forebrain) were examined. Proliferating tissues are found to exhibit high damage levels in the early and late periods following irradiation, while terminally differentiating tissues repond to radiation most intensely in the late period, years after irradiation, with no intermediate recovery. The results obtained from rabbits are used to predict the occurrence of late tissue degeneration in the central nervous system, terminally differentiating systems and stem cells of humans one or more decades following exposure to radiation levels anticipated during long-duration space flights. The studies also indicate that tissues may be prematurely aged in the sense that tissue life spans may be shortened without the development of malignancies.

Lett, J. T.; Cox, A. B.; Keng, P. C.; Lee, A. C.; Su, C. M.; Bergtold, D. S.

1980-01-01

192

Mechanical stresses induced in ceramic oxides by ion irradiation  

NASA Astrophysics Data System (ADS)

The damage and the residual stresses induced by 4 MeV Au ion irradiation in selected ceramic oxides (cubic zirconia and Gd 2(Ti 2-xZr x)O 7 pyrochlores with x = 1 and 2) were investigated by X-ray diffraction. The variations of the lattice parameter and of residual stresses upon irradiation were shown to depend on the compound. The highest compressive stresses, linked to the largest swelling, were found in amorphizable Gd 2TiZrO 7. A two-step process was observed in damage, swelling and stress build-ups for non-amorphizable oxides (zirconia and Gd 2Zr 2O 7).

Sattonnay, G.; Moll, S.; Herbst-Ghysel, M.; Legros, C.; Costantini, J.-M.; Thomé, L.

2008-06-01

193

Effect of irradiation spectrum on the microstructure of ion-irradiated Al{sub 2}O{sub 3}  

SciTech Connect

Polycrystalline samples of alpha-alumina have been irradiated with various ions ranging from 3.6 MeV Fe{sup +} to 1 MeV H{sup +} ions at 650 C. Cross-section transmission electron microscopy was used to investigate the depth-dependent microstructure of the irradiated specimens. The microstructure following irradiation was observed to be dependent on the irradiation spectrum. In particular, defect cluster nucleation was effectively suppressed in specimens irradiated with light ions such as 1 MeV H{sup +} ions. On the other hand, light ion irradiation tended to accelerate the growth rate of dislocation loops. The microstructural observations are discussed in terms of ionization enhanced diffusion processes.

Zinkle, S.J. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

1994-12-31

194

Ion-irradiation-induced amorphization of cobalt nanoparticles  

SciTech Connect

The amorphization of Co nanoparticles embedded in SiO{sub 2} has been investigated by measuring their structure and size, before and after ion irradiation, by x-ray absorption spectroscopy and small-angle x-ray scattering, respectively. Compared to bulk material, unirradiated crystalline nanoparticles exhibited increased structural disorder and a decreased average coordination number as a result of finite-size effects. Upon irradiation, there was no variation in nanoparticle size yet significant structural change. The coordination number decreased further while the mean value (bondlength), variance (Debye-Waller factor), and asymmetry (third cumulant) of the interatomic distance distribution all increased, as consistent with theoretical predictions for an amorphous elemental metal. Furthermore, the interatomic distance distribution for irradiated Co nanoparticles was in excellent agreement with our molecular dynamics simulations for bulk amorphous Co, and we have thus attributed the observed structural changes to the formation of an amorphous phase. Though such a crystalline-to-amorphous phase transformation is not readily achievable in bulk material by ion irradiation, we suggest that the perturbed structural state prior to irradiation and the amorphous surrounding matrix both contribute to nucleating and stabilizing the amorphous phase in irradiated Co nanoparticles. In addition to the structural properties, the vibrational properties of the amorphous phase were also probed, using temperature-dependent x-ray absorption spectroscopy measurements. The Einstein temperature of the unirradiated crystalline nanoparticles was lower than that of bulk material due to loosely bonded surface/interfacial atoms. In contrast, that of the irradiated amorphous nanoparticles was substantially higher than the bulk value. We attribute this apparent bond stiffening to the influence of the rigid surrounding matrix.

Sprouster, D. J.; Giulian, R.; Araujo, L. L.; Kluth, P.; Johannessen, B.; Kirby, N.; Nordlund, K.; Ridgway, M. C. [Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia); Australian Synchrotron, Clayton, Victoria 3168 (Australia); Department of Physics and Helsinki Institute of Physics, University of Helsinki, Helsinki (Finland); Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia)

2010-04-15

195

Magnetization and susceptibility of ion-irradiated granular magnetite films  

SciTech Connect

Porous granular films of magnetite (Fe{sub 3}O{sub 4}) with grains of {approx}3 nm in size were prepared using a state-of-the-art nanocluster deposition system. The films are initially superparamagnetic but become magnetized following Si{sup 2+} ion irradiation. A significant increase in the grain size and a dramatic change in the microstructure are observed. There are dipolar interactions between the nanoparticles in both the unirradiated and irradiated films. The in-phase alternating current magnetic susceptibility of the unirradiated film shows a blocking temperature of {approx}150 K, depending on frequency. A broadened Verwey transition for the irradiated film occurs at {approx}75 K, above which the susceptibility exhibits unusual behavior: a nearly linear decrease with decreasing temperature. There are irreversible domain rotations in the irradiated film during zero-field cooling and warming cycles between 10 and 300 K. The observed behavior of the irradiated granular films is quite distinct from that of metallic nanostructures after irradiation, and is due to the dramatic change in microstructures.

Jiang, W.; McCloy, J. S.; Lea, A. S.; Sundararajan, J. A.; Yao, Q.; Qiang, Y. [Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Physics Department, University of Idaho, Moscow, Idaho 83844 (United States)

2011-04-01

196

Magnetic properties of graphite irradiated with MeV ions  

SciTech Connect

We have studied the change in the magnetic properties produced on highly oriented pyrolytic graphite samples by irradiation of H, C, and N ions in the mega-electron-volt energy range. The use of specially made sample holders for the magnetic measurements provided high reproducibility allowing us to obtain directly the irradiation effects without any corrections or subtractions. Our results show that three magnetic phenomena are triggered by the defects produced by the irradiation, namely, Curie-type paramagnetism, ferromagnetism and an anomalous paramagnetic state that appears as precursor of the magnetic ordered state. Using SRIM simulations to estimate the amount of vacancies produced by the irradiation, the Curie-type paramagnetic response indicates an effective Bohr magneton number per nominally produced vacancy p=0.27+-0.02mu{sub B}. Direct measurements of the surface sample temperature during irradiation and the decrease in the (as-received) paramagnetic as well as ferromagnetic contributions after irradiation indicate that self-heating is one of the causes for small yield of ferromagnetism. Taking into account the hydrogen distribution in the virgin samples, the obtained results indicate that the induced ferromagnetism appears when the average vacancy distance is {approx}2 nm in the near surface region.

Ramos, M. A.; Munoz-Martin, A.; Climent-Font, A. [CMAM and Instituto de Ciencia de Materiales 'Nicolas Cabrera', Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Barzola-Quiquia, J.; Esquinazi, P. [Division of Superconductivity and Magnetism, Institut fuer Experimentelle Physik II, Universitaet Leipzig, Linnestrasse 5, D-04103 Leipzig (Germany); Garcia-Hernandez, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain)

2010-06-01

197

Ion Beams from Short Pulse Laser Irradiation for Fast Ignition  

NASA Astrophysics Data System (ADS)

The ePLAS implicit/hybrid code is being used to model fast ion generation for ignition in targets irradiated by short pulse lasers. The code calculates E&B-Fields by the implicit moment methodootnotetextR. J. Mason, JCP 71, 429 (1987) and R. J. Mason, PRL 96, 035001 (2006). and couples electrons to ions at corrected Spitzer rates with variable Z from the Sesame Tables. The moderate to low Z ions are modeled as either PIC particles or a fluid. Typical laser illumination is from 5 x 10^19 to 3 x 10^20W/cm^2 in 1-10 Picosecond pulses, 7 -- 40 ?m in diameter. We will discuss results for a variety of illumination schemes and tuning options to focus and collect the ions, including the use of multiple shells and beams.

Kirkpatrick, R. C.; Mason, R. J.; Faehl, R. J.

2011-11-01

198

Metastable hydronium ions in UV-irradiated ice  

NASA Astrophysics Data System (ADS)

We show that the irradiation of UV light (10-11 eV) onto an ice film produces metastable hydronium (H3O+) ions in the ice at low temperatures (53-140 K). Evidence of the presence of metastable hydronium ions was obtained by experiments involving adsorption of methylamine onto UV-irradiated ice films and hydrogen-deuterium (H/D) isotopic exchange reaction. The methylamine adsorption experiments showed that photogenerated H3O+ species transferred a proton to the methylamine arriving at the ice surface, thus producing the methyl ammonium ion, which was detected by low energy sputtering method. The H3O+ species induced the H/D exchange of water, which was monitored through the detection of water isotopomers on the surface by using the Cs+ reactive ion scattering method. Thermal and temporal stabilities of H3O+ and its proton migration activity were examined. The lifetime of the hydronium ions in the amorphized ice was greater than 1 h at ~53 K and decreased to ~5 min at 140 K. Interestingly, a small portion of hydronium ions survived for an extraordinarily long time in the ice, even at 140 K. The average migration distance of protons released from H3O+ in the ice was estimated to be about two water molecules at ~54 K and about six molecules at 100 K. These results indicate that UV-generated hydronium ions can be efficiently stabilized in low-temperature ice. Such metastable hydronium ions may play a significant role in the acid-base chemistry of ice particles in interstellar clouds.

Moon, Eui-Seong; Kang, Heon

2012-11-01

199

Mutagenic effects of heavy ion irradiation on rice seeds  

NASA Astrophysics Data System (ADS)

Three varieties of rice seeds were subjected to irradiation using low-energy and medium-energy ions. The damage and mutations induced by the ions were examined. In addition, genetic analysis and gene mapping of spotted leaf (spl) mutants were performed. Low-energy ions had no significant influence on germination, survival or seedling height, except for the survival of Nipponbare. Medium-energy ions had a significant influence on germination and survival but had no significant effect on seedling height. In the low-energy group, among 60,000 M2 plants, 2823 putative morphological mutants were found, and the mutation frequency was approximately 4.71%. In the medium-energy group, 3132 putative morphological mutants were found, and the mutation frequency was approximately 5.22%. Five spl mutants (spl29-spl33) were obtained by ion irradiation, and the heredity of the spl mutants was stable. The characteristics of the spl mutants were found, by genetic analysis and preliminary mapping, to be controlled by a single recessive gene, and spl30 and spl33 were found to be new lesion-mimic mutants.

Xu, Xue; Liu, Binmei; Zhang, Lili; Wu, Yuejin

2012-11-01

200

Spectroscopic studies of swift heavy ion irradiated nanophase mullite  

NASA Astrophysics Data System (ADS)

Photoluminescence (PL) studies of 100 MeV swift Ag 8+ ion bombarded combustion synthesized nanophase mullite has been studied at room temperature (RT) and the results are reported here. A pair of PL bands, one broad band centres at ˜550 nm and another sharp one at ˜690 nm are observed with excitation by a 442 nm laser beam. However, when the sample is excited with 326 nm laser beam, three bands with peaks at ˜460, 550 and a well resolved one with peak at 760 nm are observed. It is observed that the PL intensity increases up to 5 × 10 11 ions/cm 2 and thereafter it decreases with increase of ion fluence. The pristine as well as Ag 8+ ion irradiated mullites are characterized by infrared spectroscopy (IR) and X-ray diffraction (XRD) techniques. The decrease in PL intensity is attributed to Al-O and Si-O bonds present as the surface getting amorphized. The effects of Ag 8+ irradiation are compared to those obtained with Ni 8+ ions and the results are discussed.

Nagabhushana, H.; Lakshminarasappa, B. N.; Prashantha, S. C.; Nagabhushana, K. R.; Singh, Fouran

2006-03-01

201

Tunable nanometer electrode gaps by MeV ion irradiation  

SciTech Connect

We report the use of MeV ion-irradiation-induced plastic deformation of amorphous materials to fabricate electrodes with nanometer-sized gaps. Plastic deformation of the amorphous metal Pd{sub 80}Si{sub 20} is induced by 4.64 MeV O{sup 2+} ion irradiation, allowing the complete closing of a sub-micrometer gap. We measure the evolving gap size in situ by monitoring the field emission current-voltage (I-V) characteristics between electrodes. The I-V behavior is consistent with Fowler-Nordheim tunneling. We show that using feedback control on this signal permits gap size fabrication with atomic-scale precision. We expect this approach to nanogap fabrication will enable the practical realization of single molecule controlled devices and sensors.

Cheang-Wong, J.-C.; Narumi, K.; Schuermann, G. M. [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); Aziz, M. J. [School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States); Golovchenko, J. A. [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States)

2012-04-09

202

He ion irradiation damage to Al/Nb multilayers  

SciTech Connect

We investigated the evolution of microstructure and mechanical properties of sputter-deposited Al/Nb multilayers with individual layer thickness, h, of 1-200 nm, subjected to helium ion irradiations: 100 keV He{sup +} ions with a dose of 6 x 10{sup 16}/cm{sup 2}. Helium bubbles, 1-2 nm in diameter, were observed. When h is greater than 25 nm, hardnesses of irradiated multilayers barely change, whereas radiation hardening is more significant at smaller h. Transmission electron microscopy and scanning transmission electron microscopy studies reveal the formation of a thin layer of Nb{sub 3}Al intermetallic along the Al/Nb interface as a consequence of radiation induced intermixing. The dependence of radiation hardening on h is interpreted by using a composite model considering the formation of the hard Nb{sub 3}Al intermetallic layer.

Misra, Amit [Los Alamos National Laboratory; Li, Nan [TEXAS A& M; Martin, M S [TEXAS A& M; Anderoglu, Osman [TEXAS A& M; Shao, L [TEXAS A& M; Wang, H [TEXAS A& M; Zhang, X [TEXAS A& M

2009-01-01

203

He ion irradiation damage in Fe/W nanolayer films  

NASA Astrophysics Data System (ADS)

We report on the evolution of microstructure and mechanical properties of Fe/W multilayers subjected to helium ion irradiations. Sputtered Fe/W multilayers with individual layer thickness, varying from 1 to 200 nm, were subjected to He + ion irradiation with a peak displacement per atom value of 6 at ambient temperatures. Helium bubbles, 1-2 nm in diameter, were observed in Fe and W, and more so along layer interfaces. The magnitude of hardness variation after radiation depends on the individual layer thickness. Radiation hardening is observed in specimens with individual layer thickness of ?5 nm. At smaller layer thickness, the hardness barely changes. Analysis indicates that radiation hardening may originate mainly from dislocation loops and partially from He bubbles.

Li, Nan; Fu, E. G.; Wang, H.; Carter, J. J.; Shao, L.; Maloy, S. A.; Misra, A.; Zhang, X.

2009-06-01

204

Post-collision interaction effects following 4p-shell ionization of Xe  

Microsoft Academic Search

Yield spectra of multiply charged ions in coincidence with threshold electrons (Ekin<=0.03 eV) have been measured near the 4p-shell ionization region of Xe. The coincidence spectra of Xe3+ and Xe4+ ions as a function of photon energy exhibit characteristic profiles induced by post-collision interactions in Auger cascades following 4p-shell threshold ionization of Xe. Peaks of the profiles shift from the

T. Hayaishi; T. Matsui; H. Yoshii; A. Higurashi; E. Murakami; A. Yagishita; T. Aoto; T. Onuma; Y. Morioka

2002-01-01

205

Light-ion-irradiation-induced thermal spikes in nanoporous silica  

NASA Astrophysics Data System (ADS)

Improving mechanical properties of low-density nanoporous solids has been a long standing challenge. Here, we study how alpha particle bombardment and thermal annealing can be used to improve mechanical properties of nanoporous silica aerogels analysed by depth-sensing nanoindentation. Data suggest that light-ion irradiation creates non-melting thermal spikes in unconstrained nanoligaments of the aerogel, resulting in improved ligament connectivity.

Kucheyev, S. O.; Wang, Y. M.; Hamza, A. V.; Worsley, M. A.

2011-03-01

206

Distribution of DNA fragment sizes after irradiation with ions.  

PubMed

Ionizing radiation is responsible for production of double-strand breaks (DSBs) in a DNA structure. In contrast to sparsely ionizing radiation, densely ionizing radiation produces DSBs that are non-randomly distributed along the DNA molecule and can form clusters of various size. The paper discusses minimalistic models that describe observable patterns of fragment length in DNA segments irradiated with heavy ions and applies the formalism to interpret the recent experimental data collected by use of atomic force microscope (AFM). PMID:19823885

Gudowska-Nowak, E; Psonka-Anto?czyk, K; Weron, K; Elsässer, T; Taucher-Scholz, G

2009-11-01

207

Development of an ion beam alignment system for real-time scanning tunneling microscope observation of dopant-ion irradiation  

SciTech Connect

An ion beam alignment system has been developed in order to realize real-time scanning tunneling microscope (STM) observation of 'dopant-ion' irradiation that has been difficult due to the low emission intensity of the liquid-metal-ion-source (LMIS) containing dopant atoms. The alignment system is installed in our original ion gun and STM combined system (IG/STM) which is used for in situ STM observation during ion irradiation. By using an absorbed electron image unit and a dummy sample, ion beam alignment operation is drastically simplified and accurized. We demonstrate that sequential STM images during phosphorus-ion irradiation are successfully obtained for sample surfaces of Si(111)-7x7 at room temperature and a high temperature of 500 deg. C. The LMIS-IG/STM equipped with the developed ion beam alignment system would be a powerful tool for microscopic investigation of the dynamic processes of ion irradiation.

Kamioka, Takefumi [Faculty of Science and Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555 (Japan); Kagami Memorial Laboratory for Materials Science and Technology, Waseda University, 2-8-26 Nishiwaseda, Shinjuku-ku, Tokyo 169-0051 (Japan); Sato, Kou; Kazama, Yutaka [Faculty of Science and Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555 (Japan); Watanabe, Takanobu [Faculty of Science and Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555 (Japan); Institute for Nanoscience and Nanotechnology, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555 (Japan); Ohdomari, Iwao [Faculty of Science and Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555 (Japan); Kagami Memorial Laboratory for Materials Science and Technology, Waseda University, 2-8-26 Nishiwaseda, Shinjuku-ku, Tokyo 169-0051 (Japan); Institute for Nanoscience and Nanotechnology, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555 (Japan)

2008-07-15

208

A Raman study of ion irradiated icy mixtures  

NASA Astrophysics Data System (ADS)

In this paper we present a Raman study of pure CH4, H2O:CH4:N2 and CH3OH:N2 frozen films before and after ion irradiation at 12 K, 100 K and 300 K. By means of Raman spectroscopy, we monitor the structural evolution of each film, whose chemical and physical properties are deeply modified by the interaction with the ion beam. For the two methane containing samples, Raman spectra show that the initial ice is partially converted into a refractory residue, which under further irradiation evolves towards an amorphous carbon (AC) with a band near 1560 cm-1 (G line) and a shoulder at about 1360 cm-1 (D line). No evidence of the AC Raman band is seen in the spectra of the methanol-containing mixture. By means of Lorentzian fits, we have determined the specific parameters of the AC band (G and D line peak positions, widths and relative intensities) in our spectra after ion irradiation and we have compared them with the corresponding parameters of the band as observed in the spectra of 11 IDPs (Interplanetary Dust Particles). Here we present the experimental results and discuss their contribution to our knowledge of the origin and evolution of IDPs.

Ferini, G.; Baratta, G. A.; Palumbo, M. E.

2004-02-01

209

A Raman study of ion irradiated icy mixtures  

NASA Astrophysics Data System (ADS)

We present a Raman study of pure CH_4, H_2O:CH_4:N_2 and CH_3OH:N_2 frozen films before and after ion irradiation at low (12 K) and high (100 K or 300 K) temperature. By means of Raman spectroscopy, we monitor the structural evolution of each film, whose optical properties are deeply modified by the interaction with the ion beam. Raman spectra show that the sample is partially converted into a refractory residue, which under further irradiation evolves towards an amorphous carbon with a band near 1560 cm-1 (G line) and a shoulder at about 1360 cm-1 (D line). The specific parameters of this 'double-peaked' feature (peaks position, widths and relative intensities) can be used as diagnostic to classify different carbonaceous materials and infer information about their degree of order. We have compared these parameters for our samples (ion irradiated frozen films and residues), for different kinds of hydrogenated carbon grains and for some IDPs. We have found that IDPs have in general a narrower G line, which peaks at higher wavenumbers, than most of the laboratory samples here discussed. This implies that IDPs have a structure with a higher degree of order than that of our samples. Here we present the experimenal results and discuss their relevance to the study of the origin and evolution of IDPs.

Baratta, G. A.; Ferini, G.; Palumbo, M. E.

2003-04-01

210

Manipulation of the graphene surface potential by ion irradiation  

SciTech Connect

We show that the work function of exfoliated single layer graphene can be modified by irradiation with swift (E{sub kin}=92 MeV) heavy ions under glancing angles of incidence. Upon ion impact individual surface tracks are created in graphene on silicon carbide. Due to the very localized energy deposition characteristic for ions in this energy range, the surface area which is structurally altered is limited to Almost-Equal-To 0.01 {mu}m{sup 2} per track. Kelvin probe force microscopy reveals that those surface tracks consist of electronically modified material and that a few tracks suffice to shift the surface potential of the whole single layer flake by Almost-Equal-To 400 meV. Thus, the irradiation turns the initially n-doped graphene into p-doped graphene with a hole density of 8.5 Multiplication-Sign 10{sup 12} holes/cm{sup 2}. This doping effect persists even after heating the irradiated samples to 500 Degree-Sign C. Therefore, this charge transfer is not due to adsorbates but must instead be attributed to implanted atoms. The method presented here opens up a way to efficiently manipulate the charge carrier concentration of graphene.

Ochedowski, O.; Kleine Bussmann, B.; Schleberger, M. [Fakultaet fuer Physik and CeNIDE, Universitaet Duisburg-Essen, D-47048 Duisburg (Germany)] [Fakultaet fuer Physik and CeNIDE, Universitaet Duisburg-Essen, D-47048 Duisburg (Germany); Ban d'Etat, B.; Lebius, H. [CIMAP (CEA-CNRS-ENSICAEN-UCBN), 14070 Caen Cedex 5 (France)] [CIMAP (CEA-CNRS-ENSICAEN-UCBN), 14070 Caen Cedex 5 (France)

2013-04-15

211

Defect production and accumulation under hydrogen and helium ion irradiation  

NASA Astrophysics Data System (ADS)

The 316L stainless steel (316L SS) is a candidate material for the first wall of a fusion reactor, which will be irradiated with 14 MeV neutrons and escaped ions. This will produce helium and hydrogen in the matrix, which come both from the transmutation production and escaped ions of the plasma. The synergistic action of high-energy cascades and helium induces important damage, such as swelling, blistering and helium embrittlement. The hydrogen combines with the radiation defects to produce dense tiny bubbles (or voids) and substitutes for gaseous impurities (such as soluted oxygen, nitrogen, sulfur and phosphorus) which react with other composites Fe, Cr, Ni and Mo to form new phases, such as Cr 2O 3, (CrFe) 2O 3, (Fe 5C 2)28N, (CrMo)N, (Fe 2Mo)12H and (FeNi) 9S 8. These induce mechanical property changes. The hydrogen combined with helium and high energy cascades will induce more serious damage than that of helium alone. To exhibit the synergistic action of helium and hydrogen, the 316L SS specimens were bombarded with helium, hydrogen and mixed ion beam with energy ranging from 27 to 38 keV to a dose of 10 17-8 × 10 18 ions/cm 2 at 573 K. The results indicate that (a) for the helium ion irradiation, the threshold dose for blistering in the energy range 27-100 keV is higher than that for the 1.0 MeV helium ion irradiation. The surface effects play an important role in the blistering. (b) When specimens bombarded with the mixed beam of helium and hydrogen ions of 27 keV reached the same helium dose (6.4 × 10 17 He +/cm 2), the diameter and density of bubble on surface increase at a ratio of the hydrogen to helium increase. The more hydrogen ions implanted, the easier and more serious the blister is. (c) When the kinetic energy of the mixed beam decreases in the range 10-30 keV, the action of hydrogen ions on the blistering appears more evident. It seems that the hydrogen plays an important role in bubble formation and growth.

Yu, Jinnan; Zhao, Xinjie; Zhang, Wen; Yang, Wen; Chu, Fengmin

1997-11-01

212

Synthesis of embedded Au nanostructures by ion irradiation: influence of ion induced viscous flow and sputtering  

PubMed Central

Summary The ion-irradiation induced synthesis of embedded Au nanoparticles (NPs) into glass from islands of Au on a glass substrate is studied in the context of recoiling atoms, sputtering and viscous flow. Cross sectional transmission electron microscopy studies revealed the formation of Au NPs embedded in the glass substrates by the 50 keV Si? ion irradiation of irregularly shaped Au nanostructures on the glass surfaces at a fluence of 3 × 1016 ions/cm2. The depth profiles of Au in the samples were obtained from high-resolution Rutherford backscattering spectrometry studies. The results from TRIDYN simulation reveal the role of various ion-induced processes during the synthesis of the embedded Au NPs, viz. sputtering and recoiling atoms. Simulation and experimental results suggest that the viscous flow is one of the major factors that are responsible for the embedding of Au nanoparticles into the glass substrate.

Agarwal, D C; Khan, S A; Mohapatra, S; Amekura, H; Datta, D P; Kumar, Ajay; Choudhury, R K; Chan, T K; Osipowicz, Thomas; Avasthi, D K

2014-01-01

213

Light ion irradiation for unfavorable soft tissue sarcoma  

SciTech Connect

Between 1978 and 1989, 32 patients with unfavorable soft tissue sarcoma underwent light ion (helium, neon) irradiation with curative intent at Lawrence Berkeley Laboratory. The tumors were located in the trunk in 22 patients and head and neck in 10. Macroscopic tumor was present in 22 at the time of irradiation. Two patients had tumors apparently induced by previous therapeutic irradiation. Follow-up times for surviving patients ranged from 4 to 121 months (median 27 months). The overall 3-year actuarial local control rate was 62%; the corresponding survival rate was 50%. The 3-year actuarial control rate for patients irradiated with macroscopic tumors was 48%, while none of the patients with microscopic disease developed local recurrence (100%). The corresponding 3-year actuarial survival rates were 40% (macroscopic) and 78% (microscopic). Patients with retroperitoneal sarcoma did notably well; the local control rate and survival rate were 64% and 62%, respectively. Complications were acceptable; there were no radiation related deaths, while two patients (6%) required operations to correct significant radiation-related injuries. These results appear promising compared to those achieved by low -LET irradiation, and suggest that this technique merits further investigation.

Linstadt, D.; Castro, J.R.; Phillips, T.L.; Petti, P.L.; Collier, J.M.; Daftari, I.; Schoethaler, R.; Rayner, A.

1990-09-01

214

Characterization of polymeric films subjected to lithium ion beam irradiation  

NASA Astrophysics Data System (ADS)

Two different polymeric materials that are candidate materials for use as binders for mixed uranium-plutonium oxide nuclear fuel pellets were subjected to Li ion beam irradiation, in order to simulate intense alpha irradiation. The materials (a polyethylene glycol 8000 and a microcrystalline wax) were then analyzed using a combination of mass spectrometry (MS) approaches and X-ray photoelectron spectroscopy (XPS). Samples of the irradiated PEG materials were dissolved in H2O and then analyzed using electrospray ionization-MS, which showed the formation of a series of small oligomers in addition to intact large PEG oligomers. The small oligomers were likely formed by radiation-induced homolytic scissions of the C-O and C-C bonds, which furnish radical intermediates that react by radical recombination with Hrad and OHrad . Surface analysis using SIMS revealed a heterogeneous surface that contained not only PEG-derived polymers, but also hydrocarbon-based entities that are likely surface contaminants. XPS of the irradiated PEG samples indicated the emergence of different carbon species, with peak shifts suggesting the presence of sp2 carbon atoms. Analysis of the paraffinic film using XPS showed the emergence of oxygen on the surface of the sample, and also a broadening and shifting of the C1s peak, demonstrating a change in the chemistry on the surface. The paraffinic film did not dissolve in either H2O or a H2O-methanol solution, and hence the bulk of the material could not be analyzed using electrospray. However a series of oligomers was leached from the bulk material that produced ion series in the ESI-MS analyses that were identified octylphenyl ethoxylate oligomers. Upon Li ion bombardment, these shifted to a lower average molecular weight, but more importantly showed the emergence of three new ion series that are being formed as a result of radiation damage. Surface analysis of the paraffinic polymers using SIMS produced spectra that were wholly dominated by hydrocarbon ion series, and no difference was observed between unirradiated and irradiated samples. The studies demonstrate that for the PEG-based polymers, direct evidence for radiolytic scission can be observed using ESI-MS, and suggests that both radiolytic pathways and efficiencies as a function of dose should be measurable by calibrating instrument response to the small oligomeric degradation products.

Groenewold, Gary S.; Cannon, W. Roger; Lessing, Paul A.; Avci, Recep; Deliorman, Muhammedin; Wolfenden, Mark; Akers, Doug W.; Jewell, J. Keith; Zuck, Larry D.

2013-02-01

215

Ion irradiation damage in ilmenite at 100 K  

USGS Publications Warehouse

A natural single crystal of ilmenite (FeTiO3) was irradiated at 100 K with 200 keV Ar2+. Rutherford backscattering spectroscopy and ion channeling with 2 MeV He+ ions were used to monitor damage accumulation in the surface region of the implanted crystal. At an irradiation fluence of 1 ?? 1015 Ar2+/cm2, considerable near-surface He+ ion dechanneling was observed, to the extent that ion yield from a portion of the aligned crystal spectrum reached the yield level of a random spectrum. This observation suggests that the near-surface region of the crystal was amorphized by the implantation. Cross-sectional transmission electron microscopy and electron diffraction on this sample confirmed the presence of a 150 nm thick amorphous layer. These results are compared to similar investigations on geikielite (MgTiO3) and spinel (MgAl2O4) to explore factors that may influence radiation damage response in oxides.

Mitchell, J. N.; Yu, N.; Devanathan, R.; Sickafus, K. E.; Nastasi, M. A.; Nord, Jr. , G. L.

1997-01-01

216

Ion irradiation damage in ilmenite under cryogenic conditions  

SciTech Connect

A natural single crystal of ilmenite was irradiated at 100 K with 200 keV Ar{sup 2+}. Rutherford backscattering spectroscopy and ion channeling with 2 MeV He{sup +} ions were used to monitor damage accumulation in the surface region of the implanted crystal. At an irradiation fluence of 1 {times} 10{sup 15} Ar{sup 2+} cm{sup {minus}2}, considerable near-surface He{sup +} ion dechanneling was observed, to the extent that ion yield from a portion of the aligned crystal spectrum reached the yield level of a random spectrum. This observation suggests that the near-surface region of the crystal was amorphized by the implantation. Cross-sectional transmission electron microscopy and electron diffraction on this sample confirmed the presence of a 150 mm thick amorphous layer. These results are compared to similar investigations on geikielite (MgTiO{sub 3}) and spinel (MgAl{sub 2}O{sub 4}) to explore factors that may influence radiation damage response in oxides.

Mitchell, J.N.; Yu, N.; Devanathan, R.; Sickafus, K.E.; Nastasi, M.A. [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.; Nord, G.L. Jr. [Geological Survey, Reston, VA (United States)

1996-11-01

217

Ion irradiation damage in ilmenite at 100 K  

SciTech Connect

A natural single crystal of ilmenite (FeTiO{sub 3}) was irradiated at 100 K with 200 keV Ar{sup 2+}. Rutherford backscattering spectroscopy and ion channeling with MeV He{sup +} ions were used to monitor damage accumulation in the surface region of the implanted crystal. At an irradiation fluence of 1 {times} 10{sup 15} Ar{sup 2+} cm{sup {minus}2}, considerable near-surface He{sup +} ion dechanneling was observed, to the extent that ion yield from a portion of the aligned crystal spectrum reached the yield level of a random spectrum. This observation suggests that the near-surface region of the crystal was amorphized by the implantation. Cross-sectional transmission electron microscopy and electron diffraction on this sample confirmed the presence of a 150 nm thick amorphous layer. These results are compared to similar investigations on geikielite (MgTiO{sub 3}) and spinel (MgAl{sub 2}O{sub 4}) to explore factors that may influence radiation damage response in oxides.

Mitchell, J.N.; Yu, N.; Devanathan, R.; Sickafus, K.E.; Nastasi, M.A. [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.; Nord, G.L. Jr. [Geological Survey, Reston, VA (United States)

1997-10-01

218

Low-energy D+ and H+ ion irradiation effects on highly oriented pyrolytic graphite  

NASA Astrophysics Data System (ADS)

We have investigated the low-energy (100 eV) D+ and H+ ion irradiation effects on the structural and chemical properties of highly oriented pyrolytic graphite (HOPG). Structural disorder due to the ion irradiation was identified by the Raman spectroscopy, the D+ irradiation giving rise to greater structural disorder than the H+ irradiation. Only sp2 bonding was identified in the X-ray photoemission spectroscopy of the D+-irradiated HOPG, indicating no change in the surface chemical structure. The H+ irradiation, on the other hand, gave rise to sp3 bonding and ? -? transition, the sp3 bonding increasing with increasing irradiation dose. It is thus shown that the chemical properties of the HOPG surface may be sensitively modified by the low-energy H+ ion irradiation, but not by the low-energy D+ ion irradiation.

Kue Park, Jun; Won Lee, Kyu; Hee Han, Jun; Jung Kweon, Jin; Kim, Dowan; Eui Lee, Cheol; Lim, Sun-Taek; Kim, Gon-Ho; Noh, S. J.; Kim, H. S.

2013-12-01

219

Origins of ion irradiation-induced Ga nanoparticle motion on GaAs surfaces  

SciTech Connect

We have examined the origins of ion irradiation-induced nanoparticle (NP) motion. Focused-ion-beam irradiation of GaAs surfaces induces random walks of Ga NPs, which are biased in the direction opposite to that of ion beam scanning. Although the instantaneous NP velocities are constant, the NP drift velocities are dependent on the off-normal irradiation angle, likely due to a difference in surface non-stoichiometry induced by the irradiation angle dependence of the sputtering yield. It is hypothesized that the random walks are initiated by ion irradiation-induced thermal fluctuations, with biasing driven by anisotropic mass transport.

Kang, M.; Wu, J. H.; Chen, H. Y.; Thornton, K.; Goldman, R. S. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)] [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Sofferman, D. L. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, Adelphi University, Garden City, New York 11530-0701 (United States); Beskin, I. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)] [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)

2013-08-12

220

Origins of ion irradiation-induced Ga nanoparticle motion on GaAs surfaces  

NASA Astrophysics Data System (ADS)

We have examined the origins of ion irradiation-induced nanoparticle (NP) motion. Focused-ion-beam irradiation of GaAs surfaces induces random walks of Ga NPs, which are biased in the direction opposite to that of ion beam scanning. Although the instantaneous NP velocities are constant, the NP drift velocities are dependent on the off-normal irradiation angle, likely due to a difference in surface non-stoichiometry induced by the irradiation angle dependence of the sputtering yield. It is hypothesized that the random walks are initiated by ion irradiation-induced thermal fluctuations, with biasing driven by anisotropic mass transport.

Kang, M.; Wu, J. H.; Sofferman, D. L.; Beskin, I.; Chen, H. Y.; Thornton, K.; Goldman, R. S.

2013-08-01

221

Radiation damage induced by swift heavy ions in TiO2 sol-gel films nanocrystallines  

NASA Astrophysics Data System (ADS)

TiO2 films prepared by sol-gel were irradiated with 25.8 MeV Cu and 90 MeV Xe ions at room temperature under normal incidence. The irradiation with Cu and Xe ions were performed respectively at iThemba labs, South Africa and GANIL, Caen, France. The properties of radiation defects induced in TiO2 nanostructures were investigated using grazing angle X-ray diffraction (GAXRD), atomic force microscopy (AFM) and UV-visible spectrophotometry. From GAXRD analysis, it is found that anatase (1 0 1) peak intensity decrease with increasing the fluence and disappear completely above a threshold ion fluence of 5 × 1012 ion/cm2. This indicates that the crystallinity of the TiO2 film is destroyed upon irradiation due to the amorphous track formation. The track radius estimated from the Poisson's law is about 2 and 4 nm after irradiation with 25.8 MeV Cu and 90 MeV Xe ions, respectively. According to the AFM analysis, the elaborated TiO2 films are composed of particles with a triangular shape of a size in the range of 200-500 nm. It is found that the particle size increases after irradiation with both Cu and Xe ions. In addition, the root-mean-square (RMS) surface roughness for 780 nm × 780 nm area scans decreases exponentially with increasing fluence up to 1013 ions/cm2 in the case of Xe irradiation, but increases drastically above 2.68 × 1011 ions/cm2 in the case of Cu ion irradiation and reaches a mean value of ˜3 nm. The absorption measurements reveal that the optical band gap is not affected by both Xe and Cu ions irradiation.

Hazem, R.; Izerrouken, M.; Sari, A.; Kermadi, S.; Msimanga, M.; Benyagoub, A.; Maaza, M.; Belgaid, M.; Boumaour, M.

2013-06-01

222

Swift heavy ion irradiation of Pt nanocrystals: I. shape transformation and dissolution  

SciTech Connect

We report on the effects of swift heavy ion irradiation of embedded Pt nanocrystals (NCs), which change from spheres to prolate spheroids to rods upon irradiation. Using a broad range of ion irradiation energies and NC mean sizes we demonstrate that the elongation and dissolution processes are energy and size dependent, attaining comparable levels of shape transformation and dissolution upon a given energy density deposited in the matrix. The NC shape transformation remains operative despite discontinuous ion tracks in the matrix and exhibits a constant threshold size for elongation. In contrast, for ion irradiations in which the ion tracks are continuous, the threshold size for elongation is clearly energy dependent.

Giulian, R.; Araujo, L.L.; Kluth, P.; Sprouster, D.J.; Schnohr, C.S.; Byrne, A.P.; Ridgway, M.C. (ANU)

2011-12-09

223

Electronic spectroscopy of I2-Xe complexes in solid Krypton  

NASA Astrophysics Data System (ADS)

In the present work, we have studied ion-pair states of matrix-isolated I2 with vacuum-UV absorption and UV-vis-NIR emission, where the matrix environment is systematically changed by mixing Kr with Xe, from pure Kr to a more polarizable Xe host. Particular emphasis is put on low doping levels of Xe that yield a binary complex I2-Xe, as verified by coherent anti-Stokes Raman scattering (CARS) measurements. Associated with interaction of I2 with Xe we can observe strong new absorption in vacuum-UV, redshifted 2400 cm-1 from the X --> D transition of I2. Observed redshift can be explained by symmetry breaking of ion-pair states within the I2-Xe complex. Systematic Xe doping of Kr matrices shows that at low doping levels, positions of I2 ion-pair emissions are not significantly affected by complexation with Xe, but simultaneous increase of emissions from doubly spin-excited states indicates non-radiative relaxation to valence states. At intermediate doping levels ion-pair emissions shift systematically to red due to change in the average polarizability of the environment. We have conducted spectrally resolved ultrafast pump-probe ion-pair emission studies with pure and Xe doped Kr matrices, in order to reveal the influence of Xe to I2 dynamics in solid Kr. Strikingly, relaxed emission from the ion-pair states shows no indication of complex presence. It further indicates that the complex escapes detection due to a non-radiative relaxation.

Hulkko, Eero; Ahokas, Jussi; Lindgren, Johan; Myllyperkiö, Pasi; Pettersson, Mika

2012-05-01

224

R&D Toward Future Liquid Xe Double Beta Detectors  

NASA Astrophysics Data System (ADS)

We report on several R&D projects aimed at possible future ton-scale Xe detectors for 0nuBB searches. A liquid Xe cell is being developed to measure material reflectivity for Xe scintillation light in liquid Xe, knowledge of which will be important for detector design and optimization. A vacuum test chamber, equipped with with cryogenic cooling and sources of VUV light, is being commissioned for candidate scintillation detectors. Finally, 136Cs, produced by 136Xe(p,n) at an accelerator, is being pursed as a source of Ba+ ions useful to ongoing R&D toward extraction and identification of the double beta decay daughter in ^136Xe.

Daniels, Tim; Bonatt, Joshua; Kumar, Krishna; Lodato, Mark; Mackeen, Cameron; Malone, Kelly; Pocar, Andrea; Wright, David

2012-10-01

225

Ion beam shaping of embedded metal nanoparticles by Si+ ion irradiation  

NASA Astrophysics Data System (ADS)

Fine Co and Pt nanoparticles are nucleated when a silica sample is implanted with 400 keV Co+ and 1370 keV Pt+ ions. At the implanted range, Co and Pt react to form small Co x Pt(1-x) nanoparticles during Si+ ion irradiation at 300 °C. Thermal annealing of the pre-implanted silica substrate at 1000 °C results in the formation of spherical nanoparticles of various sizes. When irradiated with Si+ ions at 300 °C, particles in the size range of 5-17 nm undergo rod-like shape transformation with an elongation in the direction of the incident ion beam, while those particles in the size range of 17-26 nm turn into elliptical shape. Moreover, it is suspected that very big nanoparticles (size >26 nm) decrease in size, while small nanoparticles (size <5 nm) do not undergo any transformation. During Si+ ion irradiation, the crystalline nature of the nanoparticles is preserved. The results are discussed in the light of the thermal spike model.

Balaji, S.; Panigrahi, B. K.; Saravanan, K.; David, C.; Amirthapandian, S.; Kalavathi, S.; Nair, K. G. M.; Hübner, René

2014-05-01

226

Production and irradiation of ionic liquid cluster ions  

NASA Astrophysics Data System (ADS)

We have developed a field-emission-type of cluster ion source using ionic liquids such as 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6). The current obtained was stable by placing a porous cap around the emitter. Time-of-flight (TOF) measurement showed that the peak mass number was approximately 5000 for positive and negative BMIM-PF6 ion beams. This indicated that BMIM-PF6 clusters with a size of a few tens of molecules were produced. With regard to the surface modification by BMIM-PF6 ion beams, positive and negative cluster ion beams were used to irradiate Si(1 0 0) and glass substrates. Scanning electron microscope (SEM) and atomic force microscope (AFM) observations showed that the surface roughness of substrates increased. Furthermore, X-ray photoelectron spectroscopy (XPS) measurement showed that the composition ratio of layers deposited by positive or negative cluster ion beams was similar to that of BMIM-PF6 solvent.

Takaoka, Gikan H.; Takeuchi, Mitsuaki; Ryuto, Hiromichi; Ueda, Ryo

2013-07-01

227

Compaction of microporous amorphous solid water by ion irradiation  

SciTech Connect

We have studied the compaction of vapor-deposited amorphous solid water by energetic ions at 40 K. The porosity was characterized by ultraviolet-visible spectroscopy, infrared spectroscopy, and methane adsorption/desorption. These three techniques provide different and complementary views of the structural changes in ice resulting from irradiation. We find that the decrease in internal surface area of the pores, signaled by infrared absorption by dangling bonds, precedes the decrease in the pore volume during irradiation. Our results imply that impacts from cosmic rays can cause compaction in the icy mantles of the interstellar grains, which can explain the absence of dangling bond features in the infrared spectrum of molecular clouds.

Raut, U.; Teolis, B. D.; Loeffler, M. J.; Vidal, R. A.; Fama, M.; Baragiola, R. A. [Laboratory of Atomic and Surface Physics (LASP), University of Virginia, Charlottesville, Virginia 22904 (United States)

2007-06-28

228

Formation of Ge nanocrystals from ion-irradiated GeO2 nanocrystals by swift Ni ion beam  

NASA Astrophysics Data System (ADS)

GeO2 nanocrystal (NC) thin films were deposited on Si substrate using a magnetron sputtering method and irradiated with swift heavy ions of 80 MeV Ni at various fluences ranging from 5 × 1012 to 1 × 1014 ions/cm2. Grazing incidence X-ray diffraction measurements indicate the decrease in average size of NCs with increase in fluence of ion irradiation. Micro-Raman spectroscopy studies show clearly the formation of Ge NCs with the increase of irradiation fluence. Field emission scanning electron microscopy was employed to study the morphology and modifications in NCs due to ion irradiation. Transmission electron microscopy measurement of the ion-irradiated sample at 1 × 1014 ions/cm2 confirmed the presence of few nm-sized Ge NCs, which were not observed in as-deposited sample. The overall results suggest that GeO2 NCs are reduced in size and few of them are converted into Ge NCs due to the effects of electronic energy deposition by the irradiating ions. This formation of Ge NCs in the ion-irradiated GeO2 NC thin films has been understood on the basis of irradiation-induced separation of oxygen from GeO2 NCs.

Saikiran, V.; Srinivasa Rao, N.; Devaraju, G.; Chang, G. S.; Pathak, A. P.

2013-10-01

229

High-energy ion tracks in polyimide: I. Properties of polyimide irradiated with high-energy ions  

SciTech Connect

Properties of polyimide irradiated with high-energy Ar and Kr ions (energies 40 and 210 Mev, respectively) are discussed. Irradiation resulted in the degradation of imide rings followed by the formation of amido groups and crosslinks. Circular dichroism of the polyimide IR absorption bands and the dependence of the chemical stability of the polymer on ion fluences were studied.

Vilenskii, A.I.; Oleinikov, V.A.; Mchedlishvili, B.V. [Shubnikov Institute of Crystallography, Moscow (Russian Federation)] [and others

1994-07-01

230

QUB Low Energy Ion-Ices Irradiation Experiment  

NASA Astrophysics Data System (ADS)

Ion processing plays an important role in the chemical and physical modification of ice surfaces in astrophysical environments. This experimental project supported by the LASSIE ITN, led by Dr Tom Field, will investigate irradiation of astrophysical ice analogues by singly and multiply charged ion analogues of cosmic rays. Singly or multiply charged ions of either gaseous or solid elements are produced by a compact permanent magnet Electron Cyclotron Resonance (ECR) ion source attached to a ''floating beamline'' accelerator. Charge (q) to mass analysed ion beams in the energy range from a few 100 eV to 5xq keV are directed into a dedicated experimental chamber containing a temperature controlled (6K - 300K) cryostatically cooled sample of an astrophysical ice analogue. Current diagnostics include a differentially pumped, high resolution, quadrupole mass spectrometer mounted in ''line of sight'' of the ion impact area of the ice sample In a preliminary collaborative experiment with the groups of Prof Nigel Mason (Open University, UK) and Prof Elisabetta Palumbo (INAF-Osservatorio Astrofisico di Catania. Italy) and using a cryostat and FTIR spectrometer provided by Prof Nigel Mason we studied the interaction of 4 keV C+ and C2+ ions with H2O ices at 30K AND 90K. The most significant species formed in these interactions was 13CO2, the yield of which, with singly charged ions, could be explained by the competition between a formation and a destruction mechanism. In the case of doubly charged ions, explanation of the CO2 yield required additional formation and destruction mechanisms which were considered to be a result of the additional potential energy possessed by the projectile ions. These results also showed the influence of sample temperature and morphology. It is clear that for both singly and doubly charged projectile ions, the yield of 13CO2 was greater at 30K than at 90K. This effect has been observed elsewhere and has been assigned to the greater porosity of the 30K ice which leads to increased surface area on which reactions may occur.

Muntean, A.; Field, T.; Hunniford, A.; McCullough, B.; Konanoff, J.; Millar, T.

2011-05-01

231

Ion beam irradiation induced fabrication of vertical coupling waveguides  

NASA Astrophysics Data System (ADS)

Vertically coupled waveguides have been fabricated on a silicon-on-insulator platform using a combination of reactive ion etching to pattern the device layer and high-energy proton beam irradiation followed by electrochemical etching to pattern the substrate. Infra-red light can be coupled from the lower rib waveguide within the substrate into the upper waveguide within the device layer. By varying the proton energy along the lower waveguide, we have fabricated a tapered profile which is thin at the coupling region for higher efficiency and thicker towards the outer ends for easier coupling of light. A typical coupling efficiency of 26% has been achieved.

Liang, H. D.; Kumar, V. S.; Wu, J. F.; Breese, M. B. H.

2013-04-01

232

Ion formation in laser-irradiated cesium vapor  

NASA Astrophysics Data System (ADS)

We study theoretically the formation of Cs and Cs2+ during cw laser radiation resonant with 6s-7p transition of Cs atomic vapor. This is done by numerically solving rate equations for the evolution of atomic state and electron populations. The results of calculations for the atomic and molecular ions density at different values of laser power clarified that the associative ionization and Penning ionization process play an important role for producing the Cs2+ and Cs, respectively, during the plasma formation. Also, the results showed that laser power of the order of 150 mW and 40 50 ns irradiation time are optimal in producing a fully ionized plasma.

Mahmoud, M. A.; Gamal, Y. E. E.; Abd El-Rahman, H. A.

2006-11-01

233

Behavior of nuclear materials irradiated with a dual ion beam  

NASA Astrophysics Data System (ADS)

Synergistic effects of nuclear (Sn) and electronic (Se) energy losses are investigated by comparing the damage accumulated in selected oxide (c-ZrO2, MgO, Gd2Ti2O7) and carbide (SiC) single crystals irradiated with single and dual low and high energy ion beams. Channeling results show that the Sn/Se synergy induces a strong decrease of the damage in MgO and SiC (where amorphization is prevented) and almost no effects in c-ZrO2 and Gd2Ti2O7. Raman and TEM results confirm this statement. The healing of defects generated by nuclear collisions in MgO and SiC is due to the electronic excitation produced in the wake of swift ions. These results present a strong interest for technological applications in the nuclear industry where expected cooperative Sn/Se effects may preserve the integrity of nuclear materials.

Thomé, Lionel; Veli?a, Gihan; Debelle, Aurélien; Miro, Sandrine; Garrido, Frédérico; Trocellier, Patrick; Serruys, Yves

2014-05-01

234

Helium release and amorphization resistance in ion irradiated nanochannel films  

NASA Astrophysics Data System (ADS)

Volumetric swelling, surface blistering, exfoliation and embrittlement partially induced by the aggregation of gas bubbles are serious problems for materials in nuclear reactors. This letter demonstrates that the “vein-like” nanochannel films possess greater He management capability and radiation tolerance. For a given fluence, the He bubble size in the nanochannel film decreases with increasing the nanochannel density. For a given nanochannel density, the bubble size increases with increasing fluence initially but levels off to a maximum value of 0.8 nm after the ion fluence reaches 2\\times10^{17}\\ \\text{ions/cm}^{2} , corresponding to He release ratio of 79% in the irradiated CrN RT films. The abundant surfaces in the nanochannel films are perfect defect sinks and thereby large sized He bubbles and supersaturated defects are less likely to be developed in these high radiation tolerant materials.

Hong, Mengqing; Wang, Yongqiang; Ren, Feng; Zhang, Hongxiu; Fu, Dejun; Yang, Bing; Xiao, Xiangheng; Jiang, Changzhong

2014-04-01

235

Structure and mechanical properties of swift heavy ion irradiated tungsten-bearing delta-phase oxides Y6W1O12 and Yb6W1O12  

NASA Astrophysics Data System (ADS)

We report on the relationship between structure and mechanical properties of complex oxides whose structures are derivatives of fluorite, following irradiation with swift heavy ion (92 MeV Xe) which approximately simulates fission product irradiation, where the electronic energy loss dominates. The two compounds of interest in this paper are Y6W1O12 and Yb6W1O12. These compounds possess an ordered, fluorite derivative crystal structure known as the delta (?) phase, a rhombohedral structure belonging to space group R3¯. Structural changes induced by irradiation were examined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD investigations indicated an irradiation-induced amorphization in these compounds. This result is consistent with our previous study on Y6W1O12 under displacive radiation environment in which the nuclear energy loss is dominant. High resolution TEM also revealed that individual ion tracks was amorphized. The mechanical properties of both irradiated compounds, were determined by cross-sectional nano-indentation measurements as a function of ion penetration depth. The decreases in Young's modulus, E, and hardness, H (both by about 40% at the irradiated surface) suggest amorphization beyond simple defect accumulation occurs under this irradiation condition.

Tang, M.; Wynn, T. A.; Patel, M. K.; Won, J.; Monnet, I.; Pivin, J. C.; Mara, N. A.; Sickafus, K. E.

2012-06-01

236

The change of microstructure and thermal properties in ion irradiated carbon nanotube mats as a function of ion penetration depth  

SciTech Connect

A stack of three carbon nanotube (CNT) mats was irradiated with 3 MeV He ions. The change in structural and thermal properties of individual mats as a function of ion penetration depth was characterized using electron microscopy and laser flash techniques. Ion irradiation can enhance thermal conductivity of the mats by introducing inter-tube displacements, which improve phonon transport across adjacent nanotubes. The enhancement, however, is reduced at higher damage levels due to the increasing phonon-defect scattering within the tubes. This study demonstrates the feasibility of using ion irradiation to manipulate thermal transport in carbon nanotubes.

Aitkaliyeva, A. [Materials Science and Engineering Program, Texas A and M University, College Station, Texas 77843 (United States)] [Materials Science and Engineering Program, Texas A and M University, College Station, Texas 77843 (United States); Shao, L. [Materials Science and Engineering Program, Texas A and M University, College Station, Texas 77843 (United States) [Materials Science and Engineering Program, Texas A and M University, College Station, Texas 77843 (United States); Department of Nuclear Engineering, Texas A and M University, College Station, Texas 77843 (United States)

2013-02-11

237

Application of ion scattering spectroscopy to measurement of surface potential of MgO thin film under ion irradiation  

SciTech Connect

An experimental approach was proposed for the measurement of the surface potential (SP) induced on an insulator surface during ion irradiation by ion scattering spectroscopy (ISS). The resultant ISS spectra obtained for a MgO thin film of 600 nm thickness on a Si substrate under 950 eV He{sup +} irradiation revealed that the surface is positively charged by approximately 230 V. In addition, the onset energy of a secondary ion peak indicated a SP of approximately 205 V. The present results confirmed that ISS is an effective technique for measuring the SP during ion irradiation.

Nagatomi, T.; Kuwayama, T.; Takai, Y. [Department of Material and Life Science, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871 (Japan); Yoshino, K.; Morita, Y.; Kitagawa, M. [Panasonic AVC Networks Company, Matsushita Electric Industrial Co., Ltd., Ibaraki, Osaka 567-0026 (Japan); Nishitani, M. [Matsushita Electric Industrial Co., Ltd., Moriguchi, Osaka 570-8501 (Japan)

2008-02-25

238

Using HaXe  

Microsoft Academic Search

haXe is a high-level programming language for web development. It can be compiled into .js files for JavaScript developers\\u000a or into .swf files for Flash, and it also supports the Neko virtual machine. Before going into the details of haXe, I’ll explain\\u000a how it came to be and how it is related to the evolution of Flash, ActionScript, and some

Nicolas Cannasse

239

Multiple photoionization following 3d5\\/2-shell threshold ionization of Xe  

Microsoft Academic Search

Multiple photoionization of Xe near the 3d5\\/2-shell threshold photoionization region is studied by threshold electron-ion coincidence spectroscopy. The coincidence spectra of Xe3+ to Xe7+ ions exhibit characteristic profiles associated with multi-step post-collision interactions in Auger cascades following 3d5\\/2-shell threshold photoionization. The Auger cascade decay channels leading to the formation of multiply charged ions are deduced from the energies of the

T. Matsui; H. Yoshii; K. Tsukamoto; S. Kawakita; E. Murakami; J. Adachi; A. Yagishita; Y. Morioka; T. Hayaishi

2004-01-01

240

Radiation-induced luminescence of PET and PEN films under MeV ion and pulsed UV laser irradiation  

Microsoft Academic Search

Ion- and photo-induced luminescence of polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) films was investigated during irradiation by MeV H and He ions and an ultraviolet pulsed laser. At the beginning of ion irradiation, the PEN film emitted blue luminescence, whose intensity was an order of magnitude higher than that emitted by the PET film. Successive ion irradiation effectively reduced

S. Nagata; H. Katsui; K. Takahiro; B. Tsuchiya; T. Shikama

2010-01-01

241

Effects of argon ion irradiation on the microstructures and physical properties of carbon fibers [rapid communication  

NASA Astrophysics Data System (ADS)

Eight kinds of carbon fibers with different microstructures have been exposed to argon ion implantation at 175 MeV - 1 ?A for 399 min using AVF cyclotron, Takasaki Radiation Chemistry Research Establishment, JAERI. After ion irradiation changes in diameters and cross-sectional areas of carbon fibers were determined by scanning electron microscopy. Tensile properties were measured before and after ion irradiation. As a result, the diameter generally tended to decrease after ion irradiation, except for the carbon fiber with the dual microstructure that has two directions (radial and circumferential) of basal planes in the cross-section of the fiber. Tensile strength decreased after ion irradiation. The decrease in tensile strength suggests that changes in axial microstructures due to ion irradiation give an influence on the mechanical properties of the fibers.

Oku, T.; Kurumada, A.; Kawamata, K.; Inagaki, M.

2002-06-01

242

Application of heavy-ion microbeam system at Kyoto University: Energy response for imaging plate by single ion irradiation  

NASA Astrophysics Data System (ADS)

A heavy-ion microbeam system for cell irradiation has been developed using an accelerator at Kyoto University. We have successfully developed proton-, carbon-, fluorine- and silicon-beams in order to irradiate a micro-meter sized area with ion counting, especially single ion irradiation. In the heavy-ion microbeam system, an imaging plate (IP) was utilized for beam diagnostics on the irradiation. The IP is widely used for radiography studies in biology. However, there are a few studies on the low linear energy transfer (LET) by single ions, i.e., low-intensity exposure. Thus we have investigated the energy response for the IP, which can be utilized for microbeam diagnostics.

Tosaki, M.; Nakamura, M.; Hirose, M.; Matsumoto, H.

2011-12-01

243

Radioluminescence of alumina during proton and heavy ion irradiation  

NASA Astrophysics Data System (ADS)

Radioluminescence (RL) of sapphire and polycrystalline alumina (p-Al 2O 3) under 8 MeV proton (flux 2 × 10 12 proton/cm 2s), 150 MeV argon (4.3 × 10 8 ion/cm 2 s) and 253 MeV krypton (4.3 × 10 8 ion/cm 2 s) ion irradiation has been measured in the UV and visible ranges. The processes causing the changes of RL of sapphire with a dose differ from those of p-Al 2O 3. Radiation-induced annealing of oxygen vacancies in p-Al 2O 3 occurs with decreasing F +-band. Inhomogeneous distribution of traps associated with grain boundaries causes electrical charging of microscopic regions in p-Al 2O 3 and an increase of F-band of RL. The accumulation of charge carriers at traps increases excitation probability of F +-center and results in growth of F +-band of sapphire. A ratio of initial to saturation intensity of the F +-band increases with increasing the linear energy loss of incident particles.

Plaksin, O. A.; Stepanov, V. A.; Demenkov, P. V.; Stepanov, P. A.; Skuratov, V. A.; Kishimoto, N.

2003-05-01

244

Induction of Adaptive Response by High LET Heavy Ion Irradiations in Mice  

NASA Astrophysics Data System (ADS)

Characterization of radiation-induced adaptive response provides important scientific infor-mation contributing to mechanism research, radiation protection and practical application. In this study, induction of adaptive response by X-rays in combination with high LET irradiations from accelerated heavy ions including carbon, neon, silicon and iron particles was attempted in utero in fetal mice and in vivo in adult mice. In the in utero study, an adaptive response was induced by combination of priming X-irradiations with challenging heavy ion irradiations from carbon or silicon but iron particles; no adaptive response was observable for the combi-nation of priming heavy ion irradiations from carbon, silicon or iron particles with challenging X-irradiations. In the in vivo study, an adaptive response was demonstrated by combination of priming X-irradiations with challenging heavy ion irradiations from carbon or silicon but iron particles; an adaptive response was also observable in the combination of priming heavy ion irradiations from carbon (but neon or silicon) particles with challenging X-irradiations. These findings suggest that induction of adaptive response at whole body level in mice by X-rays in combination with high LET irradiations from accelerated heavy ions is possibly a radiation quality (LET or/and particle) dependent event.

Wang, Bing; Tanaka, Kaoru; Vares, Guillaume; Shang, Yi; Fujita, Kazuko; Ninomiya, Yasuharu; Nakajima, Tetsuo; Eguchi-Kasai, Kiyomi; Nenoi, Mitsuru

245

Surface pattern formation during MeV energy ion beam irradiation  

SciTech Connect

Surface patterning during high energy heavy ion irradiation is a relatively recent observation. We report in this paper the results of a study on the formation of self organized ripple patterns on silica surface irradiated with MeV energy gold ions.

Srivastava, S. K.; Nair, K. G. M.; Kannan, R. Kamala; Kamruddin, M.; Panigrahi, B. K.; Tyagi, A. K. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)

2012-06-05

246

Microchannel formation in polyimide by heavy ion irradiation. For the electric packaging board.  

National Technical Information Service (NTIS)

The relations between the formation of microchannels and the conditions of heavy ion irradiation and the etching have been examined for 35 (mu)m thick polyimide mounted on copper plate, which was irradiated over a mask by the heavy ions. A NaClO aqueous s...

Y. Matsumoto Y. Matsuura Y. Hibino K. Kawakami Y. Komaki

1993-01-01

247

Analysis of grain growth due to ion irradiation of thin films  

Microsoft Academic Search

It has been reported recently that ion irradiation of thin films can lead to grain growth. In this paper, an analysis of grain growth in ion-irradiated thin films is discussed. It is based on establishing an analogy with thermally-activated grain growth. Recently reported experimental results are used to test the validity of the analysis.

A. M. Ibrahim

1988-01-01

248

X-ray photoelectron spectroscopy analysis of organic materials irradiated with gas cluster ion beam  

SciTech Connect

Irradiation effect of gas cluster ion beams (GCIB) on organic materials were studied with X-ray photoelectron spectroscopy by comparison to that with Ar-monomer ions. In the case of polyimide, the intensity of both N-C = O and -C-O- bond decreased with 500 eV Ar monomer ion irradiation. On the other hand, there was no significant change in the XPS spectra after Ar-GCIB irradiation. From the size-selected GCIB irradiation study, the damages in polyimide decreased with increasing the cluster size owing to the reduction of energy per atoms.

Nakagiri, Motohiro; Toyoda, Noriaki; Yamada, Isao [Incubation center, Graduate school of engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo, 671-2280 (Japan)

2011-01-07

249

Energetic Ion and Electron Irradiation of the Icy Galilean Satellites  

NASA Technical Reports Server (NTRS)

Galileo Orbiter measurements of energetic ions (20 keV to 100 MeV) and electrons (20-700 keV) in Jupiter's magnetosphere are used, in conjunction with the JPL electron model (less than 40 MeV), to compute irradiation effects in the surface layers of Europa, Ganymede, and Callisto. Significant elemental modifications are produced on unshielded surfaces to approximately centimeter depths in times of less than or equal to 10(exp 6) years, whereas micrometer depths on Europa are fully processed in approximately 10 years. Most observations of surface composition are limited to optical depths of approximately 1 mm, which are indirect contact with the space environment. Incident flux modeling includes Stormer deflection by the Ganymede dipole magnetic field, likely variable over that satellite's irradiation history. Delivered energy flux of approximately 8 x 10(exp 10) keV/square cm-s at Europa is comparable to total internal heat flux in the same units from tidal and radiogenic sources, while exceeding that for solar UV energies (greater than 6 eV) relevant to ice chemistry. Particle energy fluxes to Ganymede's equator and Callisto are similar at approximately 2-3 x 10(exp 8) keV/square cm-s with 5 x 10(exp 9) at Ganymede's polar cap, the latter being comparable to radiogenic energy input. Rates of change in optical reflectance and molecular composition on Europa, and on Ganymede's polar cap, are strongly driven by energy from irradiation, even in relatively young regions. Irradiation of nonice materials can produce SO2 and CO2, detected on Callisto and Europa, and simple to complex hydrocarbons. Iogenic neutral atoms and meteoroids deliver negligible energy approximately 10(exp 4-5) keV/square cm-s but impacts of the latter are important for burial or removal of irradiation products. Downward transport of radiation produced oxidants and hydrocarbons could deliver significant chemical energy into the satellite interiors for astrobiological evolution in putative sub-surface oceans.

Cooper, John F.; Johnson, Robert E.; Mauk, Barry H.; Garrett, Henry B.; Gehrels, Neil

2001-01-01

250

Enhancement of the field emission of carbon nanotubes straightened by application of argon ion irradiation  

Microsoft Academic Search

The field emission properties of carbon nanotubes (CNTs) were enhanced by argon ion irradiation. Argon irradiation treatment led to an enhancement in the emission properties of CNTs which showed a decrease in turn-on field and an increase in total emission current after the treatment. The irradiation treatment permanently straightened as-grown curly CNTs, and, as a result, the local electric field

Do-Hyung Kim; Hoon-Sik Jang; Chang-Duk Kim; Dong-Soo Cho; Hee-Dong Kang; Hyeong-Rag Lee

2003-01-01

251

Modifications of the magnetic properties of ferrites by swift heavy ion irradiations  

NASA Astrophysics Data System (ADS)

Single crystal plates of ferrimagnetic yttrium iron garnet (111)-YIG:Si (Y3Fe4.94Si0.06O12) and barium hexaferrite (00.1)-BaM (BaFe12O19) or (00.1)-BaM:Co,Ti (BaFe9.1Co1.4Ti1.5O19) are irradiated with swift heavy ions (3.8 GeV 129Xe or 6.0 GeV 208Pb) in the electronic slowing down regime, above the threshold (~20 keV nm-1) of formation of continuous and homogeneous cylindrical amorphous tracks. The modifications of the magnetic properties are studied by 57Fe Mössbauer spectroscopy and ac magnetic permeability measurements versus ion fluence. In the doped crystals having a planar magnetic anisotropy (YIG:Si and BaM:Co,Ti), the room-temperature Mössbauer spectra show that the magnetization is flipped perpendicularly to the sample plane at a critical amorphous fraction around 30% in both compounds. This corresponds to a 90% drop of the measured in-plane magnetic permeability. No such effect is seen in the undoped BaM samples with the axial [00.1] anisotropy. These data are interpreted by a magnetomechanical effect generated by the stress field induced by the amorphous tracks in the sample plane which flips the magnetization along the track-axis direction when the stress-induced anisotropy constant surpasses the pristine crystal anisotropy constant at the critical amorphous fraction. In the case of YIG:Si single crystal, a track-induced anisotropy field around 0.1 T is deduced from the Mössbauer spectra under a magnetic field applied in the sample (111) plane which rotates the magnetization back to the easy <111> magnetization axis lying near the sample (111) plane in a reversible manner. The magnetic ordering of amorphous YIG:Si below 70 K is also studied by Mössbauer spectroscopy under high magnetic field (5 T). A two-dimensional Bruggeman model used for the calculation of the permeability of the crystal+amorphous track composites yields track-core radii larger by about 40% than the values previously obtained for both compounds by Mössbauer spectroscopy. We think that such discrepancies show that the samples cannot be treated like standard two-phase composites since the undamaged crystal undergoes a variable stress field depending on the damaged fraction.

Costantini, Jean-Marc; Studer, Francis; Peuzin, Jean-Claude

2001-07-01

252

Modifications of the magnetic properties of ferrites by swift heavy ion irradiations  

SciTech Connect

Single crystal plates of ferrimagnetic yttrium iron garnet (111)-YIG:Si (Y{sub 3}Fe{sub 4.94}Si{sub 0.06}O{sub 12}) and barium hexaferrite (00.1)-BaM (BaFe{sub 12}O{sub 19}) or (00.1)-BaM:Co,Ti (BaFe{sub 9.1}Co{sub 1.4}Ti{sub 1.5}O{sub 19}) are irradiated with swift heavy ions (3.8 GeV {sup 129}Xe or 6.0 GeV {sup 208}Pb) in the electronic slowing down regime, above the threshold ({approximately}20 keV nm{minus}1) of formation of continuous and homogeneous cylindrical amorphous tracks. The modifications of the magnetic properties are studied by {sup 57}Fe Moessbauer spectroscopy and ac magnetic permeability measurements versus ion fluence. In the doped crystals having a planar magnetic anisotropy (YIG:Si and BaM:Co,Ti), the room-temperature Moessbauer spectra show that the magnetization is flipped perpendicularly to the sample plane at a critical amorphous fraction around 30% in both compounds. This corresponds to a 90% drop of the measured in-plane magnetic permeability. No such effect is seen in the undoped BaM samples with the axial [00.1] anisotropy. These data are interpreted by a magnetomechanical effect generated by the stress field induced by the amorphous tracks in the sample plane which flips the magnetization along the track-axis direction when the stress-induced anisotropy constant surpasses the pristine crystal anisotropy constant at the critical amorphous fraction. In the case of YIG:Si single crystal, a track-induced anisotropy field around 0.1 T is deduced from the Moessbauer spectra under a magnetic field applied in the sample (111) plane which rotates the magnetization back to the easy {l_angle}111{r_angle} magnetization axis lying near the sample (111) plane in a reversible manner. The magnetic ordering of amorphous YIG:Si below 70 K is also studied by Moessbauer spectroscopy under high magnetic field (5 T). A two-dimensional Bruggeman model used for the calculation of the permeability of the crystal+amorphous track composites yields track-core radii larger by about 40% than the values previously obtained for both compounds by Moessbauer spectroscopy. We think that such discrepancies show that the samples cannot be treated like standard two-phase composites since the undamaged crystal undergoes a variable stress field depending on the damaged fraction. {copyright} 2001 American Institute of Physics.

Costantini, Jean-Marc; Studer, Francis; Peuzin, Jean-Claude

2001-07-01

253

Ion-chain interaction in keV ion-beam-irradiated polystyrene  

SciTech Connect

Molecular weight distribution has been measured in monodisperse polystyrene film (MW = 9 000 amu) after ion bombardment, in the ion fluence range 10/sup 11/--10/sup 13/ ions/cm/sup 2/. The chosen beams are 100 keV He, 200 keV Ne, and 400 keV Ar. The experimental data have been interpreted in terms of a simple statistical model for cross-links. The chemical yield is found to be very high and equal to 0.30, about a factor of 10 higher than the values given in the literature for gamma irradiation (M. Dole, in The Radiation Chemistry of Macromolecules (Academic, New York, 1973), Vol. 2, Chap. 5, p. 57).

Calcagno, L.; Foti, G.; Licciardello, A.; Puglisi, O.

1987-09-21

254

Magnetic strip patterns induced by focused ion beam irradiation  

SciTech Connect

Focused ion beam exposure was used to locally alter the magnetic properties of a continuous Co/Pd multilayer film with perpendicular magnetic anisotropy. The saturation magnetization, coercivity, and magnetic anisotropy of the films can be tuned by Ga irradiation depending on exposure dose. As a result, a periodic strip pattern consisting of 80 nm wide exposed strips which are magnetically soft, separated by 170 nm wide magnetically hard, unexposed areas was created. Due to strong magnetostatic coupling between the strips, a number of magnetic domain configurations could be stabilized and these have been observed by magnetic force microscopy and magneto-optic Kerr effect measurements. The magnetic domain configurations and their reversal behavior were investigated by micromagnetic simulations as a function of exposure dose and strip period.

Makarov, D.; Tibus, S. [Department of Physics, University of Konstanz, D-78457 Konstanz (Germany); Rettner, C. T. [IBM Almaden Research Center, 650 Harry Road, San Jose, California 95123 (United States); Thomson, T.; Terris, B. D. [San Jose Research Center, Hitachi Global Storage Technologies, 3403 Yerba Buena Road, San Jose, California 95135 (United States); Schrefl, T. [Department of Engineering Materials, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Albrecht, M. [Institute of Physics, Chemnitz University of Technology, D-09107 Chemnitz (Germany)

2008-03-15

255

Effect of 120 MeV Ag9+ ion irradiation of YCOB single crystals  

NASA Astrophysics Data System (ADS)

Single crystals of yttrium calcium oxy borate (YCOB) grown from boron-tri-oxide flux were subjected to swift heavy ion irradiation using silver Ag9+ ions from the 15 UD Pelletron facility at Inter University Accelerator Center, New Delhi. The crystals were irradiated at 1 × 1013, 5 × 1013 and 1 × 1014 ions/cm2 fluences at room temperature and with 5 × 1013 ions/cm2 fluence at liquid nitrogen temperature. The pristine and the irradiated samples were characterized by glancing angle X-ray diffraction, UV-Vis-NIR and photoluminescence studies. From the characterization studies performed on the samples, it is inferred that the crystals irradiated at liquid nitrogen temperature had fewer defects compared to the crystals irradiated at room temperature and the defects increased when the ion fluence was increased at room temperature.

Arun Kumar, R.; Dhanasekaran, R.

2012-09-01

256

Solid phase epitaxy of amorphous silicon carbide: Ion fluence dependence  

NASA Astrophysics Data System (ADS)

We have investigated the effect of radiation damage and impurity concentration on solid phase epitaxial growth of amorphous silicon carbide (SiC) as well as microstructures of recrystallized layer using transmission electron microscopy. Single crystals of 6H-SiC with (0001) orientation were irradiated with 150 keV Xe ions to fluences of 1015 and 1016 /cm2, followed by annealing at 890°C. Full epitaxial recrystallization took place in a specimen implanted with 1015 Xe ions, while retardation of recrystallization was observed in a specimen implanted with 1016 /cm2 Xe ions. Atomic pair-distribution function analyses and energy dispersive x-ray spectroscopy results suggested that the retardation of recrystallization of the 1016 Xe/cm2 implanted sample is attributed to the difference in amorphous structures between the 1015 and 1016 Xe/cm2 implanted samples, i.e., more chemically disordered atomistic structure and higher Xe impurity concentration in the 1016 Xe/cm2 implanted sample.

Bae, In-Tae; Ishimaru, Manabu; Hirotsu, Yoshihiko; Sickafus, Kurt E.

2004-08-01

257

Ray florets color and shape mutants induced by 12C 5+ ion beam irradiation in chrysanthemum  

Microsoft Academic Search

Ion beam irradiation is attracting attention in floriculture as a means of inducing mutations. We investigated the effect of ion beam irradiation on induction of ray florets color\\/shape mutants from two strains of chrysanthemum to create new flower cultivars. The ray florets and leaf explants of chrysanthemum cultivars, ‘Shiroyamate’ and ‘H13’, respectively, cultured on MS medium were irradiated with 12C5+

Atsushi Matsumura; Toshikazu Nomizu; Noriyuki Furutani; Ken Hayashi; Yasuhiro Minamiyama; Yoshihiro Hase

2010-01-01

258

Photoluminescence of Tris(8-hydroxyquinoline)aluminum Thin Films and Influence of Swift Heavy Ion Irradiation  

Microsoft Academic Search

The effect of swift heavy ion (SHI) irradiation on the optical properties of Tris-(8-hydraxyquinoline) aluminum (Alq3) thin films has been studied. It is confirmed that PL and lifetime of SHI irradiated Alq3 thin films irradiated both at room temperature and low temperature decrease for increasing ion fluences indicating the transfer of excitons energy to unstable cationic Alq3 species. It is

K. Thangaraju; R. Kumaran; K. Asokan; P. Ramamoorthy; D. Kanjilal; J. Kumar

2008-01-01

259

Comparison of swelling for structural materials on neutron and ion irradiation  

SciTech Connect

The swelling of V-base alloys, Type 316 stainless steel, Fe-25Ni-15Cr alloys, ferritic steels, Cu, Ni, Nb-1% Zr, and Mo on neutron irradiation is compared with the swelling for these materials on ion irradiation. The results of this comparison show that utilization of the ion-irradiation technique provides for a discriminative assessment of the potential for swelling of candidate materials for fusion reactors.

Loomis, B.A.

1986-03-01

260

Observation of grain growth in swift heavy ion irradiated NiO thin films  

Microsoft Academic Search

NiO thin films grown on Si(100) substrates by electron beam evaporation, were sintered at 500 °C and 700 °C. The films were\\u000a irradiated with 120 MeV Au9+ ions. Irradiation had different effects depending upon the initial microstructure of the films. Irradiation of the films\\u000a at a fluence of 3 × 1011 ions cm?2 leads to grain growth for the films

P. Mallick; Chandana Rath; J. K. Dash; R. Biswal; D. C. Agarwal; D. Behera; D. K. Avasthi; D. Kanjilal; P. V. Satyam; N. C. Mishra

2010-01-01

261

Effect of ion beam irradiation on interfacial structure in bilayers  

NASA Astrophysics Data System (ADS)

In the present thesis, we study the change in structural properties induced by ion beam irradiation of Ni/Fe and Co/Cu bilayers using various x-ray scattering techniques. These bilayers exhibit interesting GMR and magnetotransport properties. We show that an N-step model is useful in simulating any given electron density profile. We test four different interface profile functions in fitting the reflectivity and conclude that the error-function profile best describes our samples. Different types of interfaces are introduced, namely graded and rough interfaces, together with a discussion of their representation and their effect on both specular reflectivity and non-specular x-ray intensity. We develop a data acquisition and processing method in order to separate the specular and diffuse components of x-ray scattering and to obtain the normalized reflectivity. A computer program in C was developed to calculate the x-ray reflectivity (XRR) and diffuse scattering intensity and to fit the theoretical calculation to the experimental data using a non-linear least-squares fitting method. By fitting the XRR data of six bilayers of Ni/Fe and Cu/Co of different thicknesses and deposition sequence, the electron density profiles are constructed for different irradiation doses, ?. The intermixing at interfaces is found to increase with increasing ?. No change in the bulk materials electron density is observed upon irradiation of four single layers of these materials. A more detailed study is performed on Si/Ni(500A)/Fe(500A) bilayers. From diffuse-scan fits we find that as ? increases the interfaces become rougher, more jagged and the height-height correlation length of the roughness decreases. The intermixing can be approximated using the ballistic model of ion mixing. Using high-angle x-ray diffraction (XRD) measurements, the samples are found to be polycrystalline with a strong texture of fcc Ni(111) and bcc Fe(101) parallel to the substrate surface. Both plane-view and cross-sectional transmission electron microscopy (TEM, XTEM) images show that in-plane and out-of-plane grain sizes increase with ?, in good agreement with out-of-plane grain sizes calculated from Bragg peaks. The high-angle x-ray Bragg peak positions agree well with selected-area electron diffraction (SAED) rings. The iron oxide parameters obtained from XTEM and SAED patterns agree well with XRR results.

Abdouche, Randa Kamel

2001-11-01

262

Silver nanocluster formation in ion-exchanged glasses by annealing, ion beam and laser beam irradiation: An EXAFS study  

Microsoft Academic Search

Extended X-ray absorption fine structure analysis is used to determine the silver local environment in silicate glasses doped by the Ag-alkali ion-exchange process, followed by different treatments, namely, ion irradiation, thermal annealing in reducing atmosphere, laser irradiation. The obtained results indicate that metal nanocluster composites with different cluster structures may be formed with these multistep methodologies, pointing out the role

G. Battaglin; E. Cattaruzza; F. Gonella; R. Polloni; F. D’Acapito; S. Colonna; G. Mattei; C. Maurizio; P. Mazzoldi; S. Padovani; C. Sada; A. Quaranta; A. Longo

2003-01-01

263

Structural phase diagram for ZnS nanocrystalline thin films under swift heavy ion irradiation  

Microsoft Academic Search

The synthesis of nanocrystalline ZnS thin films by pulsed laser deposition and their modification by swift heavy ions are presented. The irradiations with 150MeV Ni ions at fluences of 1×1011, 1×1012 and 1×1013ions\\/cm2 have been used for these studies. Irradiation results in structural phase transformation and bandgap modification of these films are investigated by using X-ray diffraction and UV–visible absorption

Shiv P. Patel; S. A. Khan; A. K. Chawla; R. Chandra; J. C. Pivin; D. Kanjilal; Lokendra Kumar

2011-01-01

264

Magnetic reversal in ion-irradiated FePt thin films  

Microsoft Academic Search

Previous work on ion irradiation control of FePt thin film magnetic anisotropy is extended to ultrathin films (2-10 nm). The effects of 30 keV He ion irradiation on the magnetic properties are explored as a function of ion fluence and film thickness. Depending on their growth conditions, the thinnest films exhibit different magnetic properties. Although this affects their final magnetic

A. Mougin; J. Ferré; O. Plantevin; H. Cruguel; F. Fortuna; H. Bernas; A. Marty; C. Beigné; Y. Samson

2010-01-01

265

The Influence of Annealing and Heavy Ion Irradiation of Multiple Melting and Crystallization in PBT Films  

Microsoft Academic Search

The influence of heavy ion-irradiation (Ar 5.5 MeV amu-1, 51011 ion cm-2) on the melting and crystallization of two PBT films subjected to different modes of thermal treatment was investigated.\\u000a Differences were observed between the processes occurring in both initial films, due to differences in crystalline phase content.\\u000a The course of melting and crystallization in heavy ion-irradiated films during first

K. Cie?la

1999-01-01

266

Effect of swift heavy ion beam irradiation on the dielectric and ferroelectric properties of pure and cobalt doped TGS crystals  

Microsoft Academic Search

Effect of swift heavy ion (100MeV O7+ ion) beam irradiation on the temperature and frequency dependence of real (??) and imaginary (??) parts of dielectric permittivity in pure and Co2+ doped TGS crystals are analyzed. Irradiation with swift heavy ion beam changes the dielectric response considerably. Observed dielectric peak in irradiated crystals shifts towards lower temperature and broadens up; the

P. K. Bajpai; Deepak Shah; Ravi Kumar

267

Swift heavy ion irradiation acts as a size filter to Ag nanoparticles embedded in silica glass  

NASA Astrophysics Data System (ADS)

The swift heavy ion (SHI) irradiation using as a tool for the ion-beam-shaping technique has attracted much attention in recently years, which can transform spherical metal nanoparticles (Nps) to prolate spheroids, nanorods or nanowires, with the elongation along the beam direction. In the present paper, we show that SHI irradiation can also act as a size filter to Ag Nps embedded in silica glass. In experiment, Ag Nps were introduced into silica glass by Ag ion implantation. Subsequently, 73 MeV Ca ions were used to irradiate the samples contained Ag Nps to different fluences. The direction of incident ions is perpendicular to sample surface. The surface plasmon resonance (SPR) absorbance peak of Ag Nps shifts to short wavelength with increase of irradiation fluence, meanwhile, the full width at half maximum (FWHM) of SPR peak decreases with increase of irradiation fluence. The decrease of FWHM indicates the reduction of Ag Nps size dispersion. TEM results show that Ag Nps smaller than 2.0 nm dissolve during irradiation, only Ag Nps larger than 2.0 nm survive and distribute in a narrow region. High energy Ca ion irradiation seems to act as a size filter. From TEM micrographs the size dispersion of Ag Nps is reduced comparing with that before irradiation, which is consistent with optical results.

Yang, Yitao; Zhang, Chonghong; Song, Yin; Gou, Jie; Zhang, Liqing; Meng, Yancheng; Zhang, Hengqing; Ma, Yizhun

2013-08-01

268

Thermal stability of ion-irradiated InGaAs with subpicosecond carrier lifetime  

NASA Astrophysics Data System (ADS)

Due to its very short carrier lifetime and its absorption window in the 1550nm spectral range, ion-irradiated InGaAs is a material of choice for opto-electronic telecommunication systems. Ion irradiated-InGaAs is a well adapted material for realizing fast saturable absorbers and fast photoconductive antennas. However, to our knowledge, no detailed experimental study has been reported on the thermal stability of ion-irradiated InGaAs. Post-irradiation annealing of such a material is required to enhance opto-electrical response, and the thermal stability of irradiated devices. Moreover, the study of annealing kinetics provides useful information about the nature of defects and their initial distribution. The carrier lifetime, the mobility and the residual carrier concentration versus anneal in heavy(Au+) and light(H+) ion-irradiated InGaAs samples have been measured. The defect annealing kinetics observed in proton-irradiated samples is described well by a Frenkel pair recombination model, thereby indicating the dominance of isolated point defects. In contrast, the model is not adapted to describe the thermal behavior of Au+-irradiation-induced defects that are clusters of point defects as observed via Transmission Electronic Microscopy. A higher thermal stability for the components based on Au+-irradiated InGaAs than on H+-irradiated ones is then expected.

Mangeney, Juliette; Joulaud, Laurent; Lourtioz, Jean-Michel; Crozat, Paul; Patriarche, Gilles

2004-06-01

269

Nanohole pattern formation on germanium induced by focused ion beam and broad beam Ga{sup +} irradiation  

SciTech Connect

Hexagonally ordered nanohole patterns were produced on Ge(100) surfaces by focused Ga{sup +} ion beam and broad Ga{sup +} ion beam irradiations with 5 keV energy under normal incidence. Identical patterns were obtained by irradiations with a scanning focused ion beam under different irradiation conditions and with a broad Ga{sup +} beam without scanning and five orders of magnitude smaller ion flux. Thus, we could demonstrate that nanohole pattern formation is independent of ion flux over several orders of magnitude and scanning of a focused ion beam under appropriate conditions is identical to broad ion beam irradiation.

Fritzsche, Monika; Muecklich, Arndt; Facsko, Stefan [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden (Germany)

2012-05-28

270

Swift heavy ions induced irradiation effects in monolayer graphene and highly oriented pyrolytic graphite  

NASA Astrophysics Data System (ADS)

Monolayer graphene and highly oriented pyrolytic graphite (HOPG) were irradiated by swift heavy ions (209Bi and 112Sn) with the fluence between 1011 and 1014 ions/cm2. Both pristine and irradiated samples were investigated by Raman spectroscopy. It was found that D and D? peaks appear after irradiation, which indicated the ion irradiation introduced damage both in the graphene and graphite lattice. Due to the special single atomic layer structure of graphene, the irradiation fluence threshold ?th of the D band of graphene is significantly lower (<1 × 1011 ions/cm2) than that (2.5 × 1012 ions/cm2) of HOPG. The larger defect density in graphene than in HOPG indicates that the monolayer graphene is much easier to be damaged than bulk graphite by swift heavy ions. Moreover, different defect types in graphene and HOPG were detected by the different values of ID/ID?. For the irradiation with the same electronic energy loss, the velocity effect was found in HOPG. However, in this experiment, the velocity effect was not observed in graphene samples irradiated by swift heavy ions.

Zeng, J.; Yao, H. J.; Zhang, S. X.; Zhai, P. F.; Duan, J. L.; Sun, Y. M.; Li, G. P.; Liu, J.

2014-07-01

271

In situ TEM ion irradiation and implantation effects on Au nanoparticle morphologies.  

PubMed

Energetic heavy and light ion effects on gold nanoparticles were probed by irradiating 20 and 60 nm diameter nanoparticles with either 3 MeV Cu(3+) or 10 keV He(+) ions in situ inside of a transmission electron microscope. Both ion species caused sintering, agglomeration, and ablation of the nanoparticles via sputtering, although at different rates. PMID:24584417

Bufford, Daniel; Pratt, Sarah H; Boyle, Timothy J; Hattar, Khalid

2014-06-19

272

Surface patterning of SrTiO 3 by 30 keV ion irradiation  

Microsoft Academic Search

Strontium titanate single crystals are irradiated by using a focused ion beam microscope working with 30 keV gallium ions. Depending on the dose we found different stages of modification at the crystal surface. The topography of the exposed regions is investigated by atomic force microscopy. It is observed that the surface structure strongly depends on the dose of gallium ions.

J. Albrecht; S. Leonhardt; R. Spolenak; U. Taffner; H.-U. Habermeier; G. Schutz

2003-01-01

273

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

NASA Astrophysics Data System (ADS)

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

Potera, P.; Ubizskii, S.; Zhydachevskii, Y. A.; Sugak, D.; Solskii; Lukasiewicz, T.

274

Wettability and compositional analysis of hydroxyapatite films modified by low and high energy ion irradiation  

NASA Astrophysics Data System (ADS)

Hydroxyapatite-like thin films on silicon substrate were deposited using atomic layer deposition and were subjected to irradiation with Ar ions accelerated through 0.6-1.2 kV as well as 2 MeV 16O + ions. After low energy Ar irradiation a significant reduction in contact angle was observed. However, the Ca/P atomic ratio remained unchanged. No reduction in contact angle was seen for high energy 16O + irradiation. Atomic force microscopy showed the enhancement of floral-like pattern after low energy Ar bombardment while high energy oxygen irradiation lead to raised islands on as-deposited films.

Ananda Sagari, A. R.; Rahkila, Paavo; Väisänen, Markku; Lehto, Roope; Sajavaara, Timo; Gorelick, Sergey; Laitinen, Mikko; Putkonen, Matti; Sangyuenyongpipat, Somjai; Timonen, Jussi; Cheng, Sulin; Whitlow, Harry J.

2008-05-01

275

Microstructure and thermal desorption of deuterium in heavy-ion-irradiated pure tungsten  

NASA Astrophysics Data System (ADS)

To understand the fundamental processes of deuterium retention and desorption of irradiated plasma facing materials, thermal desorption of deuterium in pure W with and without ion irradiation up to 2 dpa by 2.4 MeV Cu2+ have been investigated. After the ion irradiation at room temperature, high density of small interstitial typed dislocation loops and also nano-voids due to cascade collisions were detected by TEM observation. Thermal desorption of spectra of D showed that fine vacancy clusters are formed even at low fluence and at room temperature irradiation, these defects act as the strong trapping center of deuterium in the temperature range of 660-900 K.

Watanabe, Hideo; Futagami, Naoki; Naitou, Shiori; Yoshida, Naoaki

2014-12-01

276

Ion irradiation-induced bimodal surface morphology changes in InSb.  

PubMed

High-energy ion irradiation of InSb results in the formation of bimodal surface structures, namely microscale hillock-like structures fully composed of nanoscale fibers. Analysis of the surface structures by a wide range of electron microscopy techniques reveals correlations between the irradiation conditions, such as the ion energy and fluence, and changes in the surface morphology. Sputtering effects play a key role in the integrity of the surface layer with increasing ion fluence. Possible mechanisms responsible for the morphological transformation are discussed, including both irradiation-induced and mechanical effects. PMID:20639585

Perez-Bergquist, Alejandro G; Li, Kundar; Zhang, Yanwen; Wang, Lumin

2010-08-13

277

n-Selective Single Capture Following Xe{sup 18+} And Xe{sup 54+} Impact On Na(3s) And Na*(3p)  

SciTech Connect

State selective single charge exchange n-level cross sections are calculated for collisions of Xe18+ and Xe54+ ions with Na(3s) and Na*(3p) over the energy range of 0.1 to 10.0 keV/amu. The CTMC method is used which includes all two-body interactions. Experimental state-selective cross sections and their corresponding transverse momentum spectra for Xe18+ are found to be in reasonable accord with the calculations.

Otranto, S. [CONICET and Dto. de Fisica, Universidad Nacional del Sur, 8000 Bahia Blanca (Argentina); Olson, R. E. [Physics Department, Missouri University of Science and Technology, Rolla, MO 65401 (United States); Hasan, V. G.; Hoekstra, R. [KVI-Atomic and Molecular Physics, University of Groeningen (Netherlands)

2011-06-01

278

Creation of surface nanostructures in Al2O3 by slow highly charged ions  

NASA Astrophysics Data System (ADS)

Al2O3 single crystals were irradiated with slow highly charged Xe ions of various charge states from an EBIT (Electron Beam Ion Trap) source at the Dresden two source facility. The irradiations were performed at room temperature and under normal incidence. Scanning force microscopy (SFM) was utilized to investigate the topography of the irradiated surfaces. The measurements showed that above a potential energy threshold, each ion creates a nanohillock protruding from the surface. These structures are compared to those created by swift heavy ions (SHI). The results are discussed in terms of potential energy deposition of highly charged ions (HCI) and electronic energy loss of SHI.

El-Said, A. S.; Wilhelm, R. A.; Heller, R.; Akhmadaliev, Sh.; Facsko, S.

2013-12-01

279

Application of Amberlite XE270 resin to purification of neptunium  

Microsoft Academic Search

Amberlite XE-270, a macroreticular weak-base ion-exchange resin, was ; used successfully over an 8-month period in the Hanford Purex plant to purify ~8 ; kg of ²³⁷Np. For routine purification of ²³⁷Np, the Amberlite XE-270 ; resin provides four important advantages over conventional microreticular strong-; base resins used heretofore: greatly improved thorium decontamination ; performance, a much sharper neptunium elution

Schulz

1974-01-01

280

Effects of energetic heavy ion irradiation on hardness of Al-Mg-Si alloys  

NASA Astrophysics Data System (ADS)

Al-Mg-Si alloys were irradiated with 5.4 MeV Al ions, 7.3 MeV Fe ions, 10 MeV I ions, and 16 MeV Au ions at room temperature and the Vickers microhardness was measured. The hardness of Al-Mg-Si alloys increases with increasing the ion fluence. In a viewpoint of ion fluence, hardness change of the Al alloys is different by the kind of irradiating ions. But, in a viewpoint of the density of elastically deposited energy, the effect of the four kinds of them on hardness is almost the same. This result means that the effect of irradiation on hardness of Al-Mg-Si alloys is dominated by the elastically deposited energy. The microstructure of the ion-irradiated specimens were investigated by means of three-dimensional atom probe (3DAP). The experimental result was compared with the microstructure and the hardness for thermally aged specimens. We also discuss the difference in ion-irradiation induced change in hardness between Al-Mg-Si alloys and Al-Cu-Mg alloys (duralumin).

Ueyama, D.; Saitoh, Y.; Hori, F.; Kaneno, Y.; Nishida, K.; Dohi, K.; Soneda, N.; Semboshi, S.; Iwase, A.

2013-11-01

281

Effect of ion irradiation on the surface, structural and mechanical properties of brass  

NASA Astrophysics Data System (ADS)

Modifications to the surface, structural and mechanical properties of brass after ion irradiation have been investigated. Brass targets were bombarded by carbon ions of 2 MeV energy from a Pelletron linear accelerator for various fluences ranging from 56 × 1012 to 26 × 1013 ions/cm2. A scanning electron microscope and X-ray diffractometer were utilized to analyze the surface morphology and crystallographic structure respectively. To explore the mechanical properties e.g., yield stress, ultimate tensile strength and microhardness of irradiated brass, an universal tensile testing machine and Vickers microhardness tester were used. Scanning electron microscopy results revealed an irregular and randomly distributed sputter morphology for a lower ion fluence. With increasing ion fluence, the incoherently shaped structures were transformed into dendritic structures. Nano/micro sized craters and voids, along with the appearance of pits, were observed at the maximum ion fluence. From X-ray diffraction results, no new phases were observed to be formed in the brass upon irradiation. However, a change in the peak intensity and higher and lower angle shifting were observed, which represents the generation of ion-induced defects and stresses. Analyses confirmed modifications in the mechanical properties of irradiated brass. The yield stress, ultimate tensile strength and hardness initially decreased and then increased with increasing ion fluence. The changes in the mechanical properties of irradiated brass are well correlated with surface and crystallographic modifications and are attributed to the generation, augmentation, recombination and annihilation of the ion-induced defects.

Ahmad, Shahbaz; Bashir, Shazia; Ali, Nisar; Umm-i-Kalsoom; Yousaf, Daniel; Faizan-ul-Haq; Naeem, Athar; Ahmad, Riaz; Khlaeeq-ur-Rahman, M.

2014-04-01

282

Comparison of UV and high-energy ion irradiation of methanol:ammonia ice  

NASA Astrophysics Data System (ADS)

Aims: The main goal of this work is to compare the effects induced in ices of astrophysical relevance by high-energy ions, simulating cosmic rays, and by vacuum ultraviolet (UV) photons. Methods: This comparison relies on in situ infrared spectroscopy of irradiated CH3OH:NH3 ice. Swift heavy ions were provided by the GANIL accelerator. The source of UV was a microwave-stimulated hydrogen flow discharge lamp. The deposited energy doses were similar for ion beams and UV photons to allow a direct comparison. Results: A variety of organic species was detected during irradiation and later during ice warm-up. These products are common to ion and UV irradiation for doses up to a few tens of eV per molecule. Only the relative abundance of the CO product, after ice irradiation, was clearly higher in the ion irradiation experiments. Conclusions: For some ice mixture compositions, the irradiation products formed depend only weakly on the type of irradiation, swift heavy ions, or UV photons. This simplifies the chemical modeling of energetic ice processing in space.

Muñoz Caro, G. M.; Dartois, E.; Boduch, P.; Rothard, H.; Domaracka, A.; Jiménez-Escobar, A.

2014-06-01

283

Incoherent twin boundary migration induced by ion irradiation in Cu  

SciTech Connect

Grain boundaries can act as sinks for radiation-induced point defects. The sink capability is dependent on the atomic structures and varies with the type of point defects. Using high-resolution transmission electron microscopy, we observed that {Sigma}3{l_brace}112{r_brace} incoherent twin boundary (ITB) in Cu films migrates under Cu{sup 3+} ion irradiation. Using atomistic modeling, we found that {Sigma}3{l_brace}112{r_brace} ITB has the preferred sites for adsorbing interstitials and the preferential diffusion channels along the Shockley partial dislocations. Coupling with the high mobility of grain boundary Shockley dislocations within {Sigma}3{l_brace}112{r_brace} ITB, we infer that {Sigma}3{l_brace}112{r_brace} ITB migrates through the collective glide of grain boundary Shockley dislocations, driven by a concurrent reduction in the density of radiation-induced defects, which is demonstrated by the distribution of nearby radiation-induced defects.

Li, N.; Misra, A. [Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Wang, J.; Wang, Y. Q. [Materials Science and Technology Division, MST-8, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Serruys, Y. [CEA, DEN, Service de Recherches de Metallurgie Physique, Laboratoire JANNUS, F-91191 Gif-sur-Yvette (France); Nastasi, M. [Nebraska Center for Energy Sciences Research, University of Nebraska, Lincoln, Nebraska 68588 (United States)

2013-01-14

284

Investigations of structural, dielectric and optical properties on silicon ion irradiated glycine monophosphate single crystals  

NASA Astrophysics Data System (ADS)

The 50 MeV silicon ion irradiation induced modifications on structural, optical and dielectric properties of solution grown glycine monophosphate (GMP) crystals were studied. The high-resolution X-ray diffraction study shows the unaltered value of integrated intensity on irradiation. The dielectric constant as a function of frequency and temperature was studied. UV-visible studies reveal the decrease in bandgap values on irradiation and presence of F-centers. The fluorescence spectrum shows the existence of some energy levels, which remains unaffected after irradiation. The scanning electron micrographs reveal the defects formed on irradiation.

Kanagasekaran, T.; Mythili, P.; Bhagavannarayana, G.; Kanjilal, D.; Gopalakrishnan, R.

2009-08-01

285

Nano structuring of GaAs(100) surface using low energy ion irradiation  

SciTech Connect

Nanostructuring of semi insulating GaAs (100) has been observed after irradiation of 50 keV Ar{sup +} ion beam in a wide angular range of 0 deg. to 60 deg. with respect to surface normal. Atomic Force Microscopy (AFM) analysis shows the formation of nano dots at smaller angle of irradiation. At higher angle of irradiation, self organized ripples were developed on the surface. The rms roughness estimated from the AFM analysis shows exponential growth with angle of irradiation. In the high frequency regime, PSD analysis suggests that surface morphology of the irradiated samples is governed by the surface diffusion and mass transport dominated processes.

Kumar, Tanuj; Khan, S. A.; Verma, S.; Kanjilal, D. [Inter-university Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110067 (India)

2012-06-05

286

Investigation of the effect of low energy ion beam irradiation on mono-layer graphene  

SciTech Connect

In this paper, the effect of low energy irradiation on mono-layer graphene was studied. Mono-layer graphene films were irradiated with B, N and F ions at different energy and fluence. X-ray photoelectron spectroscopy indicates that foreign ions implanted at ion energies below 35 eV could dope into the graphene lattice and form new chemical bonds with carbon atoms. The results of Raman measurement indicate that ion beam irradiation causes defects and disorder to the graphene crystal structure, and the level of defects increases with increasing of ion energy and fluence. Surface morphology images also prove that ion beam irradiation creates damages to graphene film. The experiment results suggest that low-energy irradiation with energies of about 30 eV and fluences up to 5·10{sup 14} cm{sup ?2} could realize small amount of doping, while introducing weak damage to graphene. Low energy ion beam irradiation, provides a promising approach for controlled doping of graphene.

Xu, Yijun [College of Physics science and technology, Soochow University, Suzhou215006 (China) [College of Physics science and technology, Soochow University, Suzhou215006 (China); II. Physikalisches Institut, Universität Göttingen, Friedrich- Hund- Platz 1, 37077 Göttingen (Germany); State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050 (China); Zhang, Kun; Brüsewitz, Christoph; Hofsäss, Hans Christian [II. Physikalisches Institut, Universität Göttingen, Friedrich- Hund- Platz 1, 37077 Göttingen (Germany)] [II. Physikalisches Institut, Universität Göttingen, Friedrich- Hund- Platz 1, 37077 Göttingen (Germany); Wu, Xuemei [College of Physics science and technology, Soochow University, Suzhou215006 (China) [College of Physics science and technology, Soochow University, Suzhou215006 (China); State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050 (China)

2013-07-15

287

Performance Measurement: XE6  

NSDL National Science Digital Library

The purpose of this guide is to suggest how to monitor the runtime behaviour of the user application and hence to obtain better information to apply performance-tuning optimisations on the XE6 machine. This process is called performance measurement, and profiling tools (alternatively called performance measurement tools) are available on HECToR to help users identify the bottlenecks of their code. This guide covers what and how to measure.

288

Positron annihilation spectroscopy and specific heat study of Neon ion irradiated MgB 2  

NASA Astrophysics Data System (ADS)

Specific heat studies under magnetic field and positron annihilation spectroscopy were carried out on 160 MeV Ne ion irradiated polycrystalline MgB 2 samples. There is an unusual decrease in positron lifetime in the irradiated sample which may be due to neon ion implantation. This was also indicated by change in cell volume. Coincidence Doppler Broadening Spectra of Mg, B, irradiated and unirradiated MgB 2 show that positrons primarily annihilate in boron sublattice in the unirradiated sample whereas there is some similarity of the spectrum of the irradiated sample with that of Mg. There is Mg deficiency in the unirradiated sample whereas predominantly boron vacancies exist in Ne ion irradiated MgB 2 sample. Specific heat measurements show that there is a small increase in electronic part of the specific heat and electron-phonon coupling constant.

Talapatra, A.; Bandyopadhyay, S. K.; Nambissan, P. M. G.; Sen, Pintu; Ganesan, V.

2008-02-01

289

Nanoscale surface pattern formation kinetics on germanium irradiated by Kr+ ions  

NASA Astrophysics Data System (ADS)

Nanoscale surface topography evolution on Ge surfaces irradiated by 1 keV Kr+ ions is examined in both directions perpendicular and parallel to the projection of the ion beam on the surface. Grazing incidence small angle x-ray scattering is used to measure in situ the evolution of surface morphology via the linear dispersion relation. A transition from smoothing (stability) to pattern-forming instability is observed at a critical ion incidence angle of approximately 62° with respect to the surface normal. The linear theory quadratic coefficients which determine the surface stability/instability are determined as a function of bombardment angle. The Ge surface evolution during Kr+ irradiation is qualitatively similar to that observed for Ar+ irradiation of Si. However, in contrast to the case of Si under Ar+ irradiation, the critical angle separating stability and instability for Ge under Kr+ irradiation cannot be quantitatively reproduced by the simple Carter-Vishnyakov mass redistribution model.

Anzenberg, Eitan; Perkinson, Joy C.; Madi, Charbel S.; Aziz, Michael J.; Ludwig, Karl F., Jr.

2012-12-01

290

Recrystallization of ion-irradiated germanium due to intense electronic excitation  

Microsoft Academic Search

Germanium single crystals were irradiated at room temperature by 1.5 MeV energy germanium ions and high energy silver ions of 100 MeV. Based on the transmission and high-resolution electron microscopic investigations, we present the experimental evidence of complete recrystallization of the amorphized germanium layer, formed by the self-ion-implantation, due to intense electronic excitations generated by the swift Ag ions. This

T. Som; J. Ghatak; O. P. Sinha; R. Sivakumar; D. Kanjilal

2008-01-01

291

Effect of 100MeV oxygen ion irradiation on silicon NPN power transistor  

SciTech Connect

The radiation response of npn Bipolar junction transistor (BJT) has been examined for 100 MeV O{sup 7+} ion. Key electrical properties like Gummel characteristics, dc current gain and capacitance-voltage of 100MeV O{sup 7+} ion irradiated transistor were studied before and after irradiation. The device was decapped and the electrical characterizations were performed at room temperature. Base current is observed to be more sensitive than collector current and gain appears to be degraded with ion fluence, also considerable degradation in C-V characteristics is observed and doping concentration is found to be increased along with the increase in ion fluence.

Kumar, M. Vinay; Krishnakumar, K. S.; Dinesh, C. M.; Krishnaveni, S.; Ramani [Department of studies in Physics, University of Mysore, Mysore (India); Department of Physics, APS College, Bengaluru (India); Department of Physics, DCE, Govt. First Grade College, Mangalore (India); Department of studies in Physics, University of Mysore, Mysore (India); Department of Physics, Bangalore University, Bengaluru (India)

2012-06-05

292

Nano-porosity in GaSb induced by swift heavy ion irradiation  

NASA Astrophysics Data System (ADS)

Nano-porous structures form in GaSb after ion irradiation with 185 MeV Au ions. The porous layer formation is governed by the dominant electronic energy loss at this energy regime. The porous layer morphology differs significantly from that previously reported for low-energy, ion-irradiated GaSb. Prior to the onset of porosity, positron annihilation lifetime spectroscopy indicates the formation of small vacancy clusters in single ion impacts, while transmission electron microscopy reveals fragmentation of the GaSb into nanocrystallites embedded in an amorphous matrix. Following this fragmentation process, macroscopic porosity forms, presumably within the amorphous phase.

Kluth, P.; Sullivan, J.; Li, W.; Weed, R.; Schnohr, C. S.; Giulian, R.; Araujo, L. L.; Lei, W.; Rodriguez, M. D.; Afra, B.; Bierschenk, T.; Ewing, R. C.; Ridgway, M. C.

2014-01-01

293

Grain growth and size distribution in ion-irradiated chemical vapor deposited amorphous silicon  

SciTech Connect

The amorphous to polycrystal transition in chemical vapor deposited (CVD) amorphous silicon has been studied at 450 /degree/C under Kr ion beam irradiation. The average grain size increases linearly with the ion dose, and the grain size distribution is very narrow compared to thermally grown grains. These results are consistent with the presence of crystal seeds in CVD material. All these seeds can grow simultaneously under ion beam irradiation. For layers completely preamorphized by Ge/sup +/ implantation, no ion beam induced nucleation is observed.

Spinella, C.; Lombardo, S.; Campisano, S. U.

1989-07-10

294

Study of low energy Ar+ ion irradiated 57Fe/Pt multilayers  

NASA Astrophysics Data System (ADS)

This paper reports a study on the effects of Ar+ ion irradiation in 57Fe/Pt multilayers having the structure Si (substrate)/[57Fe(19 Å)/Pt(25 Å)] × 10. The as-deposited multilayers were irradiated with 90 keV Ar+ ions at a fluence of 2 × 1016 ions cm-2 at different temperatures. X-ray reflectivity, x-ray diffraction and conversion electron Mossbauer spectroscopy were used for the characterization of the irradiated samples. Using x-ray reflectivity it was observed that irradiation results in mixing across the interfaces and deterioration of the multilayer structure. The mixing results in the formation of fcc FePt phase and no L10 ordering is observed in the samples. The results are discussed in terms of recoil displacements induced, energy transfers from ions supporting the observations of Bernas et al, using kinetic Monto Carlo simulations.

Raghavendra Reddy, V.; Kavita, S.; Amirthapandian, S.; Gupta, Ajay; Panigrahi, B. K.

2006-07-01

295

Electrical and optical isolation of GaN by high energy ion irradiation  

NASA Astrophysics Data System (ADS)

Unintentionally doped n-type gallium nitride (GaN) epitaxial layers grown by MOCVD technique on sapphire substrates have been subjected to 70 MeV nitrogen ion irradiation for various fluences. The sheet resistivity of GaN layer increases by 7 orders of magnitude for high fluence irradiation while its mobility and carrier concentration decrease as a function of ion fluence. The increase in sheet resistivity of GaN layer is explained with grain boundary controlled transport mechanism and the mobility degradation due to radiation induced charged scattering centers. Using deep level transient spectroscopy technique, a new deep level trap at 0.135 eV below the conduction band has been identified as a result of nitrogen ion irradiation. The photoluminescence emission of GaN layer decreases with increase in ion fluence and is completely quenched for high fluence irradiation.

Senthil Kumar, M.; Sonia, G.; Kanjilal, D.; Dhanasekaran, R.; Kumar, J.

2003-07-01

296

Effect of Swift Heavy Ion Irradiation on Lithium Zinc Silicate Glasses: A Photoluminescence Study  

SciTech Connect

Lithium zinc silicate glasses with and without copper were prepared by melt-quench method and their luminescence characteristics after swift heavy ion irradiation has been investigated. Based on these studies it is established that both these glasses contain colour centres and the luminescence from such centres get significantly quenched once these samples get irradiated with 100 MeV swift heavy Ag{sup +} ions with a fluence of 10{sup 13} ions/cm{sup 2} at room temperature. Trapping of the charge carriers by the increased defect concentration brought about by irradiation is responsible for the decrease in the luminescence intensity from the irradiated samples. Copper in these glasses mainly exists as Cu{sup +} ions as revealed by the broad emission around 500 nm.

Jogad, M. S. [Sharanabasaveshwar College of Science, Gulbarga 585 103 (India); Jogad, R. M. [Department of Physics, Gulburga University, Gulbarga 585106 (India); Sudarsan, V. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Krishna, P. S. R. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Kothiyal, G. P. [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

2011-07-15

297

Real structure of columnar pinning centers in heavy-ion-irradiated cuprate superconductors.  

National Technical Information Service (NTIS)

There has been considerable recent interest in the use of columnar defects produced by irradiation with energetic heavy ions to raise the irreversibility line and improve the critical current density of cuprate superconductors. In the interpretation and t...

D. O. Welch Y. Zhu R. C. Budhani

1995-01-01

298

Investigation of Current Spike Phenomena During Heavy Ion Irradiation of NAND Flash Memories  

NASA Technical Reports Server (NTRS)

A series of heavy ion and laser irradiations were performed to investigate previously reported current spikes in flash memories. High current events were observed, however, none matches the previously reported spikes. Plausible mechanisms are discussed.

Oldham, Timothy R.; Berg, Melanie; Friendlich, Mark; Wilcox, Ted; Seidleck, Christina; LaBel, Kenneth A.; Irom, Farokh; Buchner, Steven P.; McMorrow, Dale; Mavis, David G.; Eaton, Paul H.; Castillo, James

2011-01-01

299

Precipitate evolution in ion-irradiated HCM12A  

NASA Astrophysics Data System (ADS)

Precipitate evolution in HCM12A following proton irradiations to 3, 7 and 10 dpa at 400 °C, or following Fe++ irradiations to 100 and 500 dpa at 500 °C was studied. Ni/Si/Mn-rich precipitates were irradiation-induced and their nucleation was closely related to the local enrichment of Ni, Si and Mn at sinks such as dislocations due to radiation induced segregation. The composition of Ni/Si/Mn-rich precipitates evolved with irradiation dose and was different from that of the G-phase reported in irradiated ferritic-martensitic alloys. Nucleation of Cu-rich precipitates saturated after 3 dpa at 400 °C and coarsened at higher dose. Irradiation enhanced the precipitation of Cu-rich precipitates at 400 °C but suppressed the nucleation at 500 °C. Partial dissolution of Cu-rich precipitates must have occurred at 500 dpa at 500 °C as the volume fraction was smaller at 500 dpa than that at 100 dpa. Cr-rich precipitates were irradiation enhanced and were observed under irradiation at 400 °C but not observed at 500 °C due to the increase in Cr solubility with temperature. The evolution of Cr-rich precipitates with irradiation dose was likely related to the complex redistribution of Cr among chromium carbides, grain boundaries and matrix under irradiation. Radiation-induced Cr-rich carbides were observed following Fe++ irradiation to 500 dpa at 500 °C.

Jiao, Z.; Was, G. S.

2012-06-01

300

Application of WAXS diffraction in studies of crystallinity changes in heavy-ion-irradiated polyester films  

Microsoft Academic Search

WAXS diffraction was applied in studies of the effect of heavy ion irradiation on the content of crystalline phase in poly(ethyleneterephthalate) (PET) and poly(butyleneterephthalate)(PBT) films. A decrease of the crystalline phase content in PET and PBT films under the effect of heavy ions irradiation was discovered. The phenomenon was observed in the biaxially oriented 19 (mu) m thick PET film

Krystyna Ciesla

2000-01-01

301

Mass dependent surface interface modification of Ag\\/Co films under controlled ion beam irradiation  

Microsoft Academic Search

Modification difference of surface and interfaces, due to Ar+ and Kr+ irradiation under identical conditions of an immiscible bilayer thin film, Ag\\/Co (?25nm), deposited sequentially on Si(001) substrate by magnetron sputtering, is studied by X-ray reflectivity measurements and atomic force microscopy. Irradiations are done by150keV ion beams with fluences of 1×1014–5×1014ions\\/cm2. X-ray reflectivity data are collected with monochromatized Cuk?1 X-ray

S. Kundu

2006-01-01

302

Effect of Swift heavy ion irradiation on Tris(8-hydroxyquinoline) aluminum thin films  

Microsoft Academic Search

Tris-(8-hydroxyquinoline)aluminum (Alq3) is the most widely used light-emitting and electron transport materials in organic electroluminescent (EL) devices to date. Alq3 thin films have been deposited on glass substrates by thermal evaporation process. The deposited Alq3 thin films have been irradiated with Swift heavy ion (SHI) of Li3+ 40 MeV with various ion fluences. The effect of SHI irradiation on Alq3

K. Thangaraju; D. Kanjilal; J. Kumar

303

Heavy ion irradiation-induced phase transformation in polycrystalline Dy2O3  

Microsoft Academic Search

Radiation damage effects in polycrystalline pellets of the rare earth sesquioxide Dy2O3 irradiated with 300?keV Kr2+ ions were studied by combining grazing incidence X-ray diffraction (GIXRD) with transmission electron microscopy (TEM). Radiation damage was introduced using 300?keV Kr2+ ions to fluences up to 1?×?1020?Kr?m-2 at cryogenic temperature. GIXRD and cross-sectional TEM observations revealed that the crystal structure of the irradiated

M. Tang; P. Lu; J. A. Valdez; K. E. Sickafus

2006-01-01

304

Spatial ordering of nano-dislocation loops in ion-irradiated materials  

NASA Astrophysics Data System (ADS)

Defect microstructures formed in ion-irradiated metals, for example iron or tungsten, often exhibit patterns of spatially ordered nano-scale dislocation loops. We show that such ordered dislocation loop structures may form spontaneously as a result of Brownian motion of loops, biased by the angular-dependent elastic interaction between the loops. Patterns of spatially ordered loops form once the local density of loops produced by ion irradiation exceeds a critical threshold value.

Dudarev, S. L.; Arakawa, K.; Yi, X.; Yao, Z.; Jenkins, M. L.; Gilbert, M. R.; Derlet, P. M.

2014-12-01

305

Electrical and optical properties of ion-irradiated organic polymer Kapton H  

Microsoft Academic Search

An organic polymer Kapton H film was irradiated with high-energy (?MeV) N+2 ions. The specific resistivity of the film irradiated to a dose ?1017 N\\/cm2 was estimated to be ?10?2 ? cm, which is about 20 orders of magnitude smaller than that of the unirradiated film. With increase of dose, the irradiated region of the film became grayish silver with

Tatsumi Hioki; Shoji Noda; Masahiro Sugiura; Mitsutaka Kakeno; Kenichi Yamada; Junichi Kawamoto

1983-01-01

306

Biophysical characteristics of HIMAC clinical irradiation system for heavy-ion radiation therapy  

Microsoft Academic Search

Purpose: The irradiation system and biophysical characteristics of carbon beams are examined regarding radiation therapy.Methods and Materials: An irradiation system was developed for heavy-ion radiotherapy. Wobbler magnets and a scatterer were used for flattening the radiation field. A patient-positioning system using X ray and image intensifiers was also installed in the irradiation system. The depth-dose distributions of the carbon beams

Tatsuaki Kanai; Masahiro Endo; Shinichi Minohara; Nobuyuki Miyahara; Hiroko Koyama-ito; Hiromi Tomura; Naruhiro Matsufuji; Yasuyuki Futami; Akifumi Fukumura; Takeshi Hiraoka; Yoshiya Furusawa; Koichi Ando; Masao Suzuki; Fuminori Soga; Kiyomitsu Kawachi

1999-01-01

307

Structural and photoluminescence properties of swift heavy ion irradiated CdS thin films  

Microsoft Academic Search

This paper reports the results on structural and photoluminescence (PL) properties of thermally evaporated CdS thin films subjected to 100MeV Ag+7 ion irradiation. The structure of the pristine and irradiated films was found to be polycrystalline with preferred orientation along the (002) diffraction line of the CdS hexagonal phase. The films retain their crystallinity upon irradiation indicating structural stability against

R. Sathyamoorthy; S. Chandramohan; P. Sudhagar; D. Kanjilal; D. Kabiraj; K. Asokan

2006-01-01

308

Application of ion beam irradiated ePTFE to repair small vessel injuries  

NASA Astrophysics Data System (ADS)

In surgery, bleeding from small injured vessels often requires prompt hemostasis without occlusion. This study evaluated the usefulness of 0.06 mm thick ion beam irradiated ePTFE sheets to repair small holes in vessels. Both surfaces of ePTFE sheets were irradiated with a 150 keV-Ar + beam with fluences of 5 × 10 14 ions/cm 2. A small hole up to 2 mm in diameter was created in the common carotid artery of a rabbit. The defect was wrapped with an ion beam irradiated or non-irradiated ePTFE sheet. Fibrin glue was used to fix the ePTFE sheets to the common carotid artery. Hemostasis was instantly obtained with ion beam irradiated ePTFE but was rather difficult when using a non-irradiated ePTFE sheet. Three weeks after implantation, no occlusion was observed. Histological examination showed that the ePTFE sheets functioned as a scaffold for vessel wall regeneration. Thin ion beam irradiated ePTFE would be useful in vascular surgery.

Takahashi, N.; Suzuki, Y.; Ujiie, H.; Hori, T.; Iwaki, M.; Yamada, T.

2007-04-01

309

Oxide shell reduction and magnetic property changes in core-shell Fe nanoclusters under ion irradiation  

NASA Astrophysics Data System (ADS)

Ion irradiation effects are studied on the Fe-based core-shell nanocluster (NC) films with core as Fe and shell as Fe3O4/Fe3N. These NC films were deposited on Si substrates to thickness of ˜0.5 ?m using a NC deposition system. The films were irradiated at room temperature with 5.5 MeV Si2+ ions to ion fluences of 1015 and 1016 ions/cm2. It is found that the irradiation induces grain growth, Fe valence reduction in the shell, and crystallization or growth of Fe3N. The film retained its Fe-core and its ferromagnetic properties after irradiation. The nature and mechanism of oxide shell reduction and composition dependence after irradiation were studied by synthesizing additional NC films of Fe3O4 and FeO + Fe3N and irradiating them under the same conditions. The presence of nanocrystalline Fe is found to be a major factor for the oxide shell reduction. The surface morphologies of these films show dramatic changes in the microstructures due to cluster growth and agglomeration as a result of ion irradiation.

Sundararajan, Jennifer A.; Kaur, Maninder; Jiang, Weilin; McCloy, John S.; Qiang, You

2014-05-01

310

Ion dose dependence of the sputtering yield: Ar(sup +), Ne(sup +), and Xe(sup +) bombardment of Ru(0001) and Al(111).  

National Technical Information Service (NTIS)

The sputtering yield from clean metal surfaces has long been considered to be insensitive to primary ion dose at moderate ion fluences (< 10(sup 18) ions/cm(sup 2)). Using carefully cleaned and well-characterized targets, the ion dose dependence of the sp...

J. W. Burnett M. J. Pellin J. E. Whitten D. M. Gruen J. T. Yates

1994-01-01

311

Enhancement of electric double layer capacitance of carbon nanotubes by gallium ion irradiation  

SciTech Connect

Irradiation by 30 keV Ga{sup +} ions was used to create defects in multiwalled carbon nanotubes. Damage to the graphitic structure of the nanotube wall resulting from ion irradiation was observed by a transmission electron microscope which was accompanied by corresponding changes in Raman spectra. It was found that ion irradiation at 2 x 10{sup 13} ions/cm{sup 2} cumulative dose increases the electric double layer capacitance of a multiwalled carbon nanotube electrode by a factor of 2.3, followed by a decrease and saturation at higher (2 x 10{sup 14} and 4 x 10{sup 14} ions/cm{sup 2}) doses. This might be a trade-off between the enhancement caused by the tip opening and lowering of the capacitance due to amorphization of carbon nanotubes.

Rai, Padmnabh; Pandey, Srikrishna; Menemparabath, Minimol; Sug Kim, Young; Nikolaev, Pavel; Arepalli, Sivaram [Department of Energy Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Lee, Il Ha [Sungkyunkwan Advanced Institute of Nanotechnology, Suwon 440-746 (Korea, Republic of)

2011-02-15

312

Low-energy D{sup +} and H{sup +} ion irradiation effects on highly oriented pyrolytic graphite  

SciTech Connect

We have investigated the low-energy (100 eV) D{sup +} and H{sup +} ion irradiation effects on the structural and chemical properties of highly oriented pyrolytic graphite (HOPG). Structural disorder due to the ion irradiation was identified by the Raman spectroscopy, the D{sup +} irradiation giving rise to greater structural disorder than the H{sup +} irradiation. Only sp{sup 2} bonding was identified in the X-ray photoemission spectroscopy of the D{sup +}-irradiated HOPG, indicating no change in the surface chemical structure. The H{sup +} irradiation, on the other hand, gave rise to sp{sup 3} bonding and ???{sup *} transition, the sp{sup 3} bonding increasing with increasing irradiation dose. It is thus shown that the chemical properties of the HOPG surface may be sensitively modified by the low-energy H{sup +} ion irradiation, but not by the low-energy D{sup +} ion irradiation.

Kue Park, Jun; Won Lee, Kyu; Hee Han, Jun; Jung Kweon, Jin; Kim, Dowan; Eui Lee, Cheol [Department of Physics and Institute for Nano Science, Korea University, Seoul 136-713 (Korea, Republic of)] [Department of Physics and Institute for Nano Science, Korea University, Seoul 136-713 (Korea, Republic of); Lim, Sun-Taek; Kim, Gon-Ho [Department of Nuclear Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of)] [Department of Nuclear Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Noh, S. J.; Kim, H. S. [Department of Applied Physics, Dankook University, Yongin 448-701 (Korea, Republic of)] [Department of Applied Physics, Dankook University, Yongin 448-701 (Korea, Republic of)

2013-12-07

313

Anisotropic dislocation loop nucleation in ion-irradiated MgAl sub 2 O sub 4  

SciTech Connect

Polycrystalline disks of stoichiometric magnesium aluminate spinel (MgAl{sub 2}O{sub 4}) were irradiated with 2 MeV Al{sup +} ions at 650{degrees}C and subsequently analyzed in cross-section using transmission electron microscopy (TEM). Interstitial dislocation loops were observed on 110 and 11 habit planes. The population of loops on both sets of habit planes was strongly dependent on their orientation with respect to the ion beam direction. The density of loops with habit plane normals nearly perpendicular to the ion beam direction much higher than loops with habit plane normals nearly parallel to the ion beam direction. On the other hand, the loop size was nearly independent of habit plane orientation. This anisotropic loop nucleation does not occur in ion-irradiated metals such as copper. An additional anomaly associated with ion-irradiated spinel is that the loops on 111 planes were partially unfaulted with a Burgers vector of b = a/4<110>. Previous neutron irradiation studies have never reported unfaulted loops in stoichiometric spinel. Possible cause of the unusual response of spinel to ion irradiation are discussed. 12 refs., 14 figs.

Zinkle, S.J.

1991-01-01

314

Enhancement of band gap and photoconductivity in gamma indium selenide due to swift heavy ion irradiation  

SciTech Connect

{gamma}-In{sub 2}Se{sub 3} thin films prepared at different annealing temperatures ranging from 100 to 400 deg. C were irradiated using 90 MeV Si ions with a fluence of 2x10{sup 13} ions/cm{sup 2}. X-ray diffraction analysis proved that there is no considerable variation in structural properties of the films due to the swift heavy ion irradiation. However, photosensitivity and sheet resistance of the samples increased due to irradiation. It was observed that the sample, which had negative photoconductivity, exhibited positive photoconductivity, after irradiation. The negative photoconductivity was due to the combined effect of trapping of photoexcited electrons, at traps 1.42 and 1.26 eV, above the valence band along with destruction of the minority carriers, created during illumination, through recombination. Photoluminescence study revealed that the emission was due to the transition to a recombination center, which was 180 meV above the valence band. Optical absorption study proved that the defects present at 1.42 and 1.26 eV were annealed out by the ion beam irradiation. This allowed photoexcited carriers to reach conduction band, which resulted in positive photoconductivity. Optical absorption study also revealed that the band gap of the material could be increased by ion beam irradiation. The sample prepared at 400 deg. C had a band gap of 2 eV and this increased to 2.8 eV, after irradiation. The increase in optical band gap was attributed to the annihilation of localized defect bands, near the conduction and valence band edges, on irradiation. Thus, by ion beam irradiation, one could enhance photosensitivity as well as the optical band gap of {gamma}-In{sub 2}Se{sub 3}, making the material suitable for applications such as window layer in solar cells.

Sreekumar, R.; Jayakrishnan, R.; Sudha Kartha, C.; Vijayakumar, K. P.; Khan, S. A.; Avasthi, D. K. [Department of Physics, Cochin University of Science and Technology, Cochin 682022 (India); Material Science Division, Inter University Accelerator Centre, New Delhi 110 067 (India)

2008-01-15

315

Xe isotopic fractionation in a cathodeless glow discharge. [for carbonaceous meteoritic composition studies  

NASA Technical Reports Server (NTRS)

Results are reported on the isotopic composition of Xe processed in cathodeless glow discharges in rarefied air at pressures of 20-40 microns Hg, in the presence of activated charcoal and in empty pyrex containers. Residual gas phase Xe and trapped Xe were found to be fractionated, with the trapped Xe fractionated up to 1 percent per amu. A model is presented for the fractionating process in which Xe ions are simultaneously implanted and sputtered from substrate material, with a mass dependence favoring retention of the heavy isotopes in the substrate. Results of the investigation show that plasma synthesis of carbonaceous material is unnecessary for producing Xe fractionations, and that the fractionations observed in previous synthesis experiments are probably due to implantation of ions into the synthesized material.

Bernatowicz, T. J.; Fahey, A. J.

1986-01-01

316

Kr-86 ion-beam irradiation of hydrated DNA: free radical and unaltered base yields.  

PubMed

This work reports an ESR and product analysis investigation of Kr-86 ion-beam irradiation of hydrated DNA at 77 K. The irradiation results in the formation and trapping of both base radicals and sugar phosphate radicals (DNA backbone radicals). The absolute yields (G, ?mol/J) of the base radicals are smaller than the yields found in similarly prepared ?-irradiated DNA samples, and the relative yields of backbone radicals relative to base radicals are much higher than that found in ?-irradiated samples. From these results, we have elaborated our radiation chemical model of the track structure for ion-beam irradiated DNA as it applies to krypton ion-beams. The base radicals, which are trapped as ion radicals or reversibly protonated or deprotonated ion radicals, are formed almost entirely in the track penumbra, a region in which radiation chemical effects are similar to those found in ?-irradiated samples. By comparing the yields of base radicals in ion-beam samples to the yields of the same radicals in ?-irradiated samples, the partition of energy between the low-LET region (penumbra) and the core is experimentally determined. The neutral sugar and other backbone radicals, which are not as susceptible to recombination as are ion radicals, are formed largely in the track core. The backbone radicals show a linear dose response up to very high doses. Unaltered base release yields in Kr-86 irradiated hydrated DNA are equal to sugar radical yields within experimental error limits, consistent with radiation-chemical processes in which all base release originates with sugar radicals. Two phosphorus-centered radicals from fragmentation of the DNA backbone are found in low yields. PMID:23106211

Becker, David; Adhikary, Amitava; Tetteh, Smedley T; Bull, Arthur W; Sevilla, Michael D

2012-12-01

317

Kr-86 Ion-Beam Irradiation of Hydrated DNA: Free Radical and Unaltered Base Yields  

PubMed Central

This work reports an ESR and product analysis investigation of Kr-86 ion-beam irradiation of hydrated DNA at 77 K. The irradiation results in the formation and trapping of both base radicals and sugar phosphate radicals (DNA backbone radicals). The absolute yields (G, ?mol/J) of the base radicals are smaller than the yields found in similarly prepared ?-irradiated DNA samples, and the relative yields of backbone radicals relative to base radicals are much higher than that found in ?-irradiated samples. From these results, we have elaborated our radiation chemical model of the track structure for ion-beam irradiated DNA as it applies to krypton ion-beams. The base radicals, which are trapped as ion radicals or reversibly protonated or deprotonated ion radicals, are formed almost entirely in the track penumbra, a region in which radiation chemical effects are similar to those found in ?-irradiated samples. By comparing the yields of base radicals in ion-beam samples to the yields of the same radicals in ?-irradiated samples, the partition of energy between the low-LET region (penumbra) and the core is experimentally determined. The neutral sugar and other backbone radicals, which are not as susceptible to recombination as are ion radicals, are formed largely in the track core. The backbone radicals show a linear dose response up to very high doses. Unaltered base release yields in Kr-86 irradiated hydrated DNA are equal to sugar radical yields within experimental error limits, consistent with radiation-chemical processes in which all base release originates with sugar radicals. Two phosphorus-centered radicals from fragmentation of the DNA backbone are found in low yields.

Becker, David; Adhikary, Amitava; Tetteh, Smedley T.; Bull, Arthur W.; Sevilla, Michael D.

2012-01-01

318

Determination of the emission probability of the principal gamma ray of 135Xe  

NASA Astrophysics Data System (ADS)

The gamma ray emission probability is one of the most important characteristics used in quantifying radionuclides. This article describes in detail the principles and processes involved in the determination of the 135Xe gamma ray emission probability. Gaseous samples of 135Xe were generated by irradiating enriched 134Xe with a thermal neutron flux. The principal gamma ray emission probability of 135Xe was then determined to be 0.896±0.016 (k=1) by measuring the absolute activity using length-compensated internal gas proportional counters and ?-ray intensity using a high-purity germanium (HPGe) detector.

Li, Qi; Wang, Shilian; Jia, Huaimao; Fan, Yuanqing; Zhang, Xinjun; Chen, Zhanying; Zhao, Yungang; Chang, Yinzhong; Liu, Shujiang

2013-03-01

319

Controlled optical and magnetic properties of ZnO nanorods by Ar ion irradiation  

SciTech Connect

Herein we report a controlled defect-related emission and magnetization properties of zinc oxide nanorods using low energy (2-5 keV) Ar ion irradiation. The ratio of the defect related emission to the excitonic emission decreases by an order magnitude due to the ion bombardment. The hysteresis loops of pristine and irradiated nanorods show ferromagnetic behavior at room temperature. A sharp decrease in the value of magnetization is due to an enhancement of irradiation time and energy. Combining with x-ray photoelectron spectroscopy results, a direct link between the magnetization and defect-emission of ZnO nanorods is established.

Panigrahy, Bharati; Bahadur, D. [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai 400 076 (India); Aslam, M. [Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400 076 (India)

2011-05-02

320

DNA-PKcs Inhibition Sensitizes Cancer Cells to Carbon-Ion Irradiation via Telomere Capping Disruption  

PubMed Central

Heavy-ion irradiation induces a higher frequency of DNA double strand breaks (DSBs) which must be properly repaired. Critical shortening of telomeres can trigger DNA damage responses such as DSBs. Telomeres are very sensitive to oxidative stress such as ionizing radiation. The DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is the central component in the non-homologous end joining (NHEJ) repair complex and participates in telomere maintenance. Therefore, it is expected to enhance the cell killing effect of heavy-ion irradiation via DNA-PKcs inhibition. To test this hypothesis, cellular radiosensitivity was measured by the clonal genetic assay. DNA damage repair was relatively quantified by long PCR. Apoptosis was quantified by flow-cytometric analysis of annexin V/PI double staining, and senescence was analyzed by galactosidase activity. Telomere length was semi-quantified by real-time PCR. P53 and p21 expression was determined by western blotting. Our data demonstrated that MCF-7 and HeLa cells with DNA-PKcs inhibition were more susceptible to carbon-ion irradiation than Those without DNA-PKcs inhibition. Even though NHEJ was inhibited by the DNA-PKcs specific inhibitor, NU7026, most DNA damage induced by carbon-ion irradiation was repaired within 24 hours after irradiation in both cell lines. However, potential lethal damage repair (PLDR) could not restore cellular inactivation in DNA-PKcs inhibited cells. MCF-7 cells showed extensive senescence and accelerated telomere length reduction, while HeLa cells underwent significant apoptosis after irradiation with NU7026 incubation. In addition, both cell lines with shorter telomere were more susceptible to carbon-ion radiation. Our current data suggested that DNA-PKcs inhibition could enhance cellular sensitivity to carbon-ion radiation via disturbing its functional role in telomere end protection. The combination of DNA-PKcs inhibition and carbon-ion irradiation may be an efficient method of heavy-ion therapy.

Zhou, Xin; Zhang, Xin; Xie, Yi; Tanaka, Kaoru; Wang, Bing; Zhang, Hong

2013-01-01

321

The effect of He and swift heavy ions on nanocrystalline zirconium nitride  

NASA Astrophysics Data System (ADS)

Recent studies have shown that swift heavy ion irradiation may significantly modulate hydrogen and helium behaviour in some materials. This phenomenon is of considerable practical interest for ceramics in general and also for candidate materials for use as inert matrix fuel hosts. These materials will accumulate helium via (n, ?) reactions and will also be subjected to irradiation by fission fragments. Cross-sectional transmission electron microscopy and scanning electron microscopy was used to study nanocrystalline ZrN irradiated with 30 keV He to fluences between 1016 and 5 × 1016 cm?2, 167 MeV Xe to fluences between 5 × 1013 and 1014 cm?2 and also 695 MeV Bi to a fluence of 1.5 × 1013 cm?2. He/Bi and He/Xe irradiated samples were annealed at temperatures between 600 and 1000 °C and were analysed using SEM, XTEM and selected area diffraction. The results indicated that post irradiation heat treatment induces exfoliation at a depth that corresponds to the end-of-range of 30 keV He ions. SEM and XTEM analysis of He/Xe irradiated samples revealed that electronic excitation effects, due to Xe ions, suppress helium blister formation and consequently the exfoliation processes. He/Bi samples however do not show the same effects. This suggests that nanocrystalline ZrN is prone to the formation of He blisters which may ultimately lead material failure. These effects may however be mitigated by electronic excitation effects from certain SHIs.

Janse van Vuuren, A.; Neethling, J. H.; Skuratov, V. A.; Uglov, V. V.; Petrovich, S.

2014-05-01

322

Silver nanocluster formation in ion-exchanged glasses by annealing, ion beam and laser beam irradiation: An EXAFS study  

NASA Astrophysics Data System (ADS)

Extended X-ray absorption fine structure analysis is used to determine the silver local environment in silicate glasses doped by the Ag-alkali ion-exchange process, followed by different treatments, namely, ion irradiation, thermal annealing in reducing atmosphere, laser irradiation. The obtained results indicate that metal nanocluster composites with different cluster structures may be formed with these multistep methodologies, pointing out the role of the preparation parameters in giving rise to different features. Lattice parameters and cluster diameter were determined by grazing incidence X-ray diffraction.

Battaglin, G.; Cattaruzza, E.; Gonella, F.; Polloni, R.; D'Acapito, F.; Colonna, S.; Mattei, G.; Maurizio, C.; Mazzoldi, P.; Padovani, S.; Sada, C.; Quaranta, A.; Longo, A.

2003-01-01

323

Hydrogenated carbon layers produced by ion beam irradiation of PMMA and polystyrene films  

Microsoft Academic Search

The dissociation of the polymeric structure, which results from ion beam irradiation, leads to the formation of hydrogenated carbon layers exhibiting new optical and conducting properties at high fluence. The properties of these hydrogenated carbon layers have been compared to the properties of diamond-like carbon films prepared by plasma techniques: we discuss the modifications induced by ion beams in PMMA,

J. Davenas; P. Thevenard; G. Boiteux; M. Fallavier; X. L. Lu

1990-01-01

324

Optimization of the Properties of Carbon Nanotube-Based Structures by Electron and Ion Beam Irradiation  

Microsoft Academic Search

There is considerable interest in building new nanostructures for electronic devices and incorporating nanostructured fibers and particles into composites. Here, classical molecular dynamics simulations are used to study the production of new carbon nanotube junctions or cross-links through electron irradiation, in addition to the chemical modification of carbon nanotube-based structures and composites through ion and polyatomic ion beam deposition. In

Susan Sinnott

2005-01-01

325

Dislocation loops in spinel crystals irradiated successively with deep and shallow ion implants  

SciTech Connect

This study examines the influence of microstructural defects on irradiation damage accumulation in the oxide spinel. Single crystals of the compound MgAl{sub 2}O{sub 4} with surface normal [111] were irradiated under cryogenic temperature (100K) either with 50 keV Ne ions (fluence 5.0 {times} 10{sup 12}/cm{sup 2}), 400 keV Ne ions (fluence 6.7 {times} 10{sup 13}/cm{sup 2}) or successively with 400 keV Ne ions followed by 50 keV Ne ions. The projected range of 50 keV Ne ions in spinel is {approximately}50 mn (``shallow``) while the projected range of 400 keV Ne ions is {approximately}500 mn (``deep``). Transmission electron microscopy (TEM) was used to examine dislocation loops/defect clusters formed by the implantation process. Measurements of the dislocation loop size were made using weak-beam imaging technique on cross-sectional TEM ion-implanted specimens. Defect clusters were observed in both deep and shallow implanted specimens, while dislocation loops were observed in the shallow implanted sample that was previously irradiated by 400 keV Ne ions. Cluster size was seen to increase for shallow implants in crystals irradiated with a deep implant (size {approximately}8.5 nm) as compared to crystals treated only to a shallow implant (size {approximately}3.1 nm).

Ai, R.X.; Cooper, E.A.; Sickafus, K.E.; Nastasi, M. [Los Alamos National Lab., NM (United States); Bordes, N.; Ewing, R.C. [New Mexico Univ., Albuquerque, NM (United States)

1993-12-31

326

Properties of TL Dosemeters after Irradiation with Heavy Ions at High Doses.  

National Technical Information Service (NTIS)

The thermoluminescent phosphors LiF:Mg,Ti and CaF sub 2 :Mn were irradiated at different JINR accelerators with 630 MeV protons and with exp 12 C exp 6+ ions (73 MeV) and exp 18 O exp 8+ ions (75 MeV). For LiF luminophors (used in the thermoluminescent do...

K. Huebner

1981-01-01

327

Atomic transport in metal\\/ceramic interfaces under heavy ion irradiation  

Microsoft Academic Search

Ion beam mixing is a useful tool to modify the physical properties of interfaces in different materials. Metal\\/metal systems were extensively studied in the last decade. In the last few years research has been focused on the technologically more important metal\\/ceramic systems. In these systems, however, there is only limited knowledge on stability and diffusion processes under heavy ion irradiation.

R. Nagel; A. G Balogh

1999-01-01

328

Influence of irradiation spectrum and implanted ions on the amorphization of ceramics  

SciTech Connect

Polycrystalline Al2O3, magnesium aluminate spinel (MgAl2O4), MgO, Si3N4, and SiC were irradiated with various ions at 200-450 K, and microstructures were examined following irradiation using cross-section TEM. Amorphization was not observed in any of the irradiated oxide ceramics, despsite damage energy densities up to {similar_to}7 keV/atom (70 displacements per atom). On the other hand, SiC readily amorphized after damage levels of {similar_to}0.4 dpa at room temperature (RT). Si3N4 exhibited intermediate behavior; irradiation with Fe{sup 2+} ions at RT produced amorphization in the implanted ion region after damage levels of {similar_to}1 dpa. However, irradiated regions outside the implanted ion region did not amorphize even after damage levels > 5 dpa. The amorphous layer in the Fe-implanted region of Si3N4 did not appear if the specimen was simultaneoulsy irradiated with 1-MeV He{sup +} ions at RT. By comparison with published results, it is concluded that the implantation of certain chemical species has a pronounced effect on the amorphization threshold dose of all five materials. Intense ionizing radiation inhibits amorphization in Si3N4, but does not appear to significantly influence the amorphization of SiC.

Zinkle, S.J.; Snead, L.L.

1995-12-31

329

Damage and microstructure evolution in GaN under Au ion irradiation  

NASA Astrophysics Data System (ADS)

Damage and microstructure evolution in gallium nitride (GaN) under Au+ ion irradiation has been investigated using complementary electron microscopy, secondary ion mass spectrometry and ion-beam analysis techniques. Epitaxially-grown GaN layers (2 µm thick) have been irradiated by 2.0 MeV Au ions to 1.0 × 1015 and 1.4 × 1015 cm-2 at 155 K and to 7.3 × 1015 cm-2 at 200 K. The irradiation-induced damage has been analysed by Rutherford backscattering spectroscopy in a channelling direction (RBS/C). For a better determination of the ion-induced disorder profile, an iterative procedure and a Monte Carlo code (McChasy) are combined to analyse the ion channelling spectra. With increasing irradiation dose, separated amorphous layers develop from the sample surface and near the damage peak region. Formation of large nitrogen bubbles with sizes up to 70 nm is observed in the buried amorphous layer, while the surface layer contains small bubbles with a diameter of a few nanometres due to significant nitrogen loss from the surface. Volume expansion from 3% to 25% in the irradiated region is suggested by cross-sectional transmission electron microscope and RBS/C measurement. The anomalous shape of the Au distributions under three irradiations indicates out-diffusion of Au towards the sample surface. The results from the complementary techniques suggest that nitrogen is retained in the damaged GaN where the crystallinity is preserved. Once the amorphous state is reached in the surface region, GaN starts to decompose and nitrogen escapes from the surface. Furthermore, experimental results show considerable errors in both the disorder profile and the ion range predicted by the Stopping and Range of Ions in Matter code, indicating a significant overestimation of electronic stopping powers of Au ions in GaN.

Zhang, Yanwen; Ishimaru, Manabu; Jagielski, Jacek; Zhang, Weiming; Zhu, Zihua; Saraf, Laxmikant V.; Jiang, Weilin; Thome, Lionel; Weber, William J.

2010-03-01

330

Damage and Microstructure Evolution in GaN under Au Ion Irradiation  

SciTech Connect

Damage and microstructure evolution in gallium nitride (GaN) under Au+ ion irradiation has been investigated using complementary electron microscopy, secondary ion mass spectrometry and ion beam analysis techniques. Epitaxially-grown GaN layers (2-um-thick) have been irradiated by 2.0 MeV Au ions to 1.0 × 1015 and 1.4 × 1015 cm-2 at 155 K and 7.3 × 1015 cm-2 at 200 K. The irradiation-induced damage has been analyzed by Rutherford backscattering spectroscopy in a channeling direction (RBS/C). For a better determination of ion-induced disorder profile, an iterative procedure and a Monte Carlo code (McChasy) are combined to analyze the ion channeling spectra. With increasing irradiation dose, separated amorphous layers develop from the sample surface and near the damage peak region. Formation of large nitrogen bubbles with sizes up to 70 nm is observed in the buried amorphous layer, while the surface layer contains small bubbles with diameter of a few nanometers due to significant nitrogen loss from the surface. Volume expansion from 3% to 25% in the irradiated region is suggested by cross sectional transmission electron microscope and RBS/C measurement. The anomalous shape of the Au distributions under three irradiations indicates out-diffusion of Au toward sample surface. The results from the complementary techniques suggest that nitrogen is retained in the damaged GaN where the crystallinity is preserved. Once the amorphous state is reached in the surface region, GaN starts to decompose and nitrogen escapes from the surface. Furthermore, experimental results show considerable errors in both disorder profile and ion range predicted by the Stopping and Range of Ions in Matter code, indicating a significant overestimation of electronic stopping powers of Au ions in GaN.

Zhang, Yanwen; Ishimaru, Manabu; Jagielski, Jacek; Zhang, Weiming; Zhu, Zihua; Saraf, Laxmikant V.; Jiang, Weilin; Thome, Lionel; Weber, William J.

2010-02-11

331

Evaluation of cell behavior on modified polypropylene with swift heavy ion irradiation  

NASA Astrophysics Data System (ADS)

Ion beam irradiation is a well known means to change the physico-chemical properties of polymers, and induced bio and citocompatibility in controlled conditions and in selected areas of surface. However, the enhancement of cell adhesion on a modified substrate does not mean that the surface is adequate for functional cells. The purpose of the present work is to study proliferation, changes in cytoskeleton and cell morphology on substrates as a function of irradiation parameters. We irradiated polypropylene with sulfur (S) ion-beam at energies of 110 MeV with fluences between 1 × 10 6 and 2 × 10 10 ions cm -2. NIH 3T3 cells were cultured on each sample. Cell morphology was observed using phase contrast microscopy and cytoskeleton proteins with fluorescence microscopy. The analysis show different cellular responses as a functions of irradiation parameter, strongly suggests that different underlying substratum can result in distinct types of cytoskeleton reorganization.

Arbeitman, Claudia R.; Ibañez, Irene L.; García Bermúdez, Gerardo; Durán, Hebe; del Grosso, Mariela F.; Salguero, Noelia; Mazzei, Rubén

2012-02-01

332

Ion microbeam irradiation for radiobiology and radical chemistry: status and prospect  

NASA Astrophysics Data System (ADS)

Ion microbeams are commonly used to study local irradiation effects in living cells, as it has been established that ion beam irradiations can lead to deleterious changes in cells that are not struck directly by the microbeam. Such changes, which take place over distances long compared to the size of the irradiation spot and for times long compared to the time of irradiation, are collectively termed radiation-induced bystander effect or RIBE. Free-radical chemistry is frequently invoked to explain the RIBE but no unified model is available at present. Ion microbeams when coupled with advanced methods for observing free radicals are the tools of choice for investigating the chemistry and biological processes governing RIBE.

Khodja, H.

2011-01-01

333

Radiation damage and deuterium trapping in deuterium-ion-irradiated Fe-9Cr alloy  

NASA Astrophysics Data System (ADS)

Thermal desorption of deuterium (D2) from deuterium-ion (D2+)-irradiated Fe-9Cr was correlated with the microstructural evolution of the alloy during irradiation with 8-keV D2+ ions following annealing to determine the retention and desorption behavior of the implanted deuterium and to identify effective traps for them, particularly at high temperature. After irradiation at 573 K, a new desorption stage formed between 650 and 1100 K at higher fluences, and cavities were observed using transmission electron microscopy. The total amount of trapped deuterium following irradiation with a fluence of 3.0 × 1022 ions/m2 was 6.8 × 1017 D2/m2, or approximately 0.007%. These results indicate that the deuterium atoms recombined to form D2 molecules at the surfaces of the cavities.

Iwakir, Hirotomo; Tani, Munechika; Watanabe, Yoshiyuki; Yoshida, Naoaki

2014-01-01

334

Defects in 700 keV oxygen ion irradiated ZnO  

NASA Astrophysics Data System (ADS)

It is well known that energetic oxygen ions induce heavy crystalline disorder in ZnO, however, systematic study on this regard is very much limited. Here, we present photoluminescence (PL), optical absorption and sheet resistance measurements on poly and single crystalline ZnO samples irradiated with 700 keV O ions. Results have been compared with the effects of 1.2 MeV Ar irradiation on similar ZnO target. Colour change of the samples with increasing O irradiation fluence has also been noted. Non-monotonic variation of room temperature sheet resistance with the increase of fluence has been observed for polycrystalline ZnO. Such an outcome has been understood as point defects transforming to bigger size clusters. Near band edge (NBE) PL emission is largely reduced due to O ion irradiation. However, at 10 K NBE emission can be observed for irradiated polycrystalline samples. Irradiated ZnO single crystal does not show any band to band transition even at 10 K. It is evident that dynamic recovery of defects is more effective in polycrystalline samples. Ultraviolet-visible absorption spectrum of the irradiated ZnO crystal show pronounced sub-band gap absorption. Oxygen irradiation generated new absorption band in ZnO is at 3.05 eV. In the light of earlier reports, this particular band can be ascribed to absorption by neutral oxygen vacancy defects.

Pal, S.; Sarkar, A.; Chattopadhyay, S.; Chakrabarti, Mahuya; Sanyal, D.; Kumar, P.; Kanjilal, D.; Rakshit, T.; Ray, S. K.; Jana, D.

2013-09-01

335

Study on depth profile of heavy ion irradiation effects in poly(tetrafluoroethylene-co-ethylene)  

NASA Astrophysics Data System (ADS)

High linear energy transfer (LET) heavy ion beams were used to irradiate poly(tetrafluoroethylene-co-ethylene) (ETFE) under vacuum and in air. The irradiation effects in ETFE as a function of the depth were precisely evaluated by analyzing each of the films of the irradiated samples, which were made of stacked ETFE films. It was indicated that conjugated double bonds were generated by heavy ion beam irradiation, and their amounts showed the Bragg-curve-like distributions. Also, it was suggested that higher LET beams would induce radical formation in high density and longer conjugated C=C double bonds could be generated by the second-order reactions. Moreover, for samples irradiated in air, C=O was produced correlating to the yield of oxygen molecules diffusing from the sample surface.

Gowa, Tomoko; Shiotsu, Tomoyuki; Urakawa, Tatsuya; Oka, Toshitaka; Murakami, Takeshi; Oshima, Akihiro; Hama, Yoshimasa; Washio, Masakazu

2011-02-01

336

Genetics Home Reference: Fragile XE syndrome  

MedlinePLUS

... Testing Registry Genetic testing PubMed Recent literature OMIM Genetic disorder catalog Conditions > Fragile XE syndrome On this page: ... fragile XE syndrome? Fragile XE syndrome is a genetic disorder that impairs thinking ability and cognitive functioning. Most ...

337

Effects of laser irradiation on nanoparticle evolution in SiO 2 implanted with Cu ions  

NASA Astrophysics Data System (ADS)

Metal nanoparticle composites were fabricated by implantation of 60 keV Cu - ions into silica glass (a-SiO 2) and subsequently were irradiated with nanosecond laser pulses (energy density of 0.2 J/cm 2-pulse). Optical properties of the nanocomposites changed with variation of wavelength and total deposited energy of laser radiation. Laser irradiation at 532 nm resulted in dissolution of Cu nanoparticles with increasing the exposure time, whereas precipitation of Cu atoms was enhanced with increasing the time of laser irradiation at 355 nm. The controlled laser irradiation is promising for controlling precipitation or dissolution of nanoparticles, i.e. laser lithography.

Masuo, K.; Plaksin, O. A.; Fudamoto, Y.; Okubo, N.; Takeda, Y.; Kishimoto, N.

2006-06-01

338

Correlation between phase formation and magnetic properties of heavy ion irradiated Co/Pt bilayers  

SciTech Connect

In this letter, the authors report the correlation between the magnetic and the structural properties of 200 keV Kr and 50 keV Ar ion irradiated Co/Pt bilayer samples at different temperatures and fluences. They observe irradiation induced formation of stable Co-Pt phases, which appears to be more prominent at higher irradiation temperatures. A large shape anisotropy in the hysteresis loop is also observed when irradiated at higher temperatures, which could be indicative of a magnetization reversal. A CoPt ordered/disordered phase formation leads to the enhancement in the coercivity. The sequence of phase formations is predicted by the heat of formation rule.

Ghosh, Sanjukta; Maeder, M.; Groetzschel, R.; Gupta, A.; Som, T. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751 005 (India); Forschungszentrum Rossendorf, P.O. Box 510119, D-01314 Dresden (Germany); UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452 017 (India); Institute of Physics, Sachivalaya Marg, Bhubaneswar 751 005 (India)

2006-09-04

339

Enhancement of impact-induced mechanoluminescence by swift heavy ion irradiation  

SciTech Connect

In this Letter, we report a strategy using swift heavy ion (SHI) irradiation to enhance the impact-induced mechanoluminescence (ML) in ML materials. The impact-induced ML intensity of CaSrAl{sub 2}Si{sub 2}O{sub 8}:Eu{sup 2+} was enhanced by about one order of magnitude by using SHI irradiation. Furthermore, the enhancement was found to depend on electronic stopping power and irradiation fluence. The density of traps of a type suitable for impact-induced ML is considered to be increased by the SHI irradiation, resulting in the impact-induced ML enhancement.

Zhan, T. Z.; Terasawa, Y. [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Xu, C. N. [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); National Institute of Advanced Industrial Science and Technology, Kyushu, 807-1 Shuku, Tosu, Saga 841-0052 (Japan); CREST, Japan Science and Technology Agency, 4 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Yamada, H. [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); National Institute of Advanced Industrial Science and Technology, Kyushu, 807-1 Shuku, Tosu, Saga 841-0052 (Japan); Zhang, L. [National Institute of Advanced Industrial Science and Technology, Kyushu, 807-1 Shuku, Tosu, Saga 841-0052 (Japan); Iwase, H.; Kawai, M. [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

2012-01-02

340

Formation and evolution of ripples on ion-irradiated semiconductor surfaces  

NASA Astrophysics Data System (ADS)

We have examined the formation and evolution of ripples on focused-ion-beam (FIB) irradiated compound semiconductor surfaces. Using initially normal-incidence Ga+ FIB irradiation of InSb, we tuned the local beam incidence angle (?eff) by varying the pitch and/or dwell time. For single-pass FIB irradiation, increasing ?eff induces morphological evolution from pits and islands to ripples to featureless surfaces. Multiple-pass FIB irradiation of the rippled surfaces at a fixed ?eff leads to island formation on the ripple crests, followed by nanorod (NR) growth. This ripple-NR transition provides an alternative approach for achieving dense arrays of NRs.

Kang, M.; Wu, J. H.; Ye, W.; Jiang, Y.; Robb, E. A.; Chen, C.; Goldman, R. S.

2014-02-01

341

Enhancement of impact-induced mechanoluminescence by swift heavy ion irradiation  

NASA Astrophysics Data System (ADS)

In this Letter, we report a strategy using swift heavy ion (SHI) irradiation to enhance the impact-induced mechanoluminescence (ML) in ML materials. The impact-induced ML intensity of CaSrAl2Si2O8:Eu2+ was enhanced by about one order of magnitude by using SHI irradiation. Furthermore, the enhancement was found to depend on electronic stopping power and irradiation fluence. The density of traps of a type suitable for impact-induced ML is considered to be increased by the SHI irradiation, resulting in the impact-induced ML enhancement.

Zhan, T. Z.; Xu, C. N.; Yamada, H.; Terasawa, Y.; Zhang, L.; Iwase, H.; Kawai, M.

2012-01-01

342

Irradiation effects induced in silicon carbide by low and high energy ions  

NASA Astrophysics Data System (ADS)

Silicon carbide exhibits different behaviours in response to ion beam irradiation depending on the ion energy. At room temperature, this material is well known to be easily amorphized by low energy (i.e. a few hundred keV) ions. On the other hand, recent studies revealed that high energy (i.e. several hundred MeV) ions do not produce damage in crystalline silicon carbide. More interestingly, they instead induce at room temperature an epitaxial recrystallization in pre-damaged material by low energy ion irradiation. These swift heavy ion induced effects can both be interpreted in term of the thermal spike model where it is demonstrated that the amorphous phase does effectively attain the liquid state in contrast to the case of the crystalline structure.

Benyagoub, A.

2008-06-01

343

Ion dose dependence of the sputtering yield: Ar{sup +}, Ne{sup +}, and Xe{sup +} bombardment of Ru(0001) and Al(111)  

SciTech Connect

The sputtering yield from clean metal surfaces has long been considered to be insensitive to primary ion dose at moderate ion fluences (< 10{sup 18} ions/cm{sup 2}). Using carefully cleaned and well-characterized targets, the ion dose dependence of the sputtering yield of Ru(0001) and Al(111) has been investigated. The sputtering yield of Ru(0001) is found to decrease substantially following primary ion bombardment at low fluences, while the sputtering yield of Al(111) exhibits no fluence dependence at low primary ion dose. Using secondary neutral mass spectrometry (SNMS), the sputtering yield of ruthenium was observed to decrease following ion bombardment by argon, xenon, and neon. High-detection-efficiency time-of-flight mass spectrometry was coupled with nonresonant laser ionization to allow real-time sputtering yield measurements and to minimize target damage during data collection. The experiments show that the sputtering yield of Ru(0001) decreases by 50%, following a primary ion fluence of, less than 10{sup 16} ions/cm{sup 2} for sputtering by either argon or neon ions and by 25%, following primary ion fluences of less than 10{sup 14} ions/cm{sup 2} for sputtering by xenon. The small size of the experimentally determined damage cross section suggests that microscopic changes in the surface structure cause the observed sputtering yield depression. In contrast to the ruthenium results, the sputtering yield of Al(111) appears to be insensitive to primary ion fluence at low fluences. Calculations using the TRansport of Ions in Matter (TRIM) Monte Carlo sputtering simulation were carried out to investigate the effect of primary ion implantation upon the sputtering yield of ruthenium as well as the effect of a reduced surface binding energy of ruthenium surface atoms. The TRIM results indicate that neither of these mechanisms can explain the experimentally observed fluence dependence of the sputtering yield of ruthenium.

Burnett, J.W.; Pellin, M.J.; Whitten, J.E.; Gruen, D.M. [Argonne National Lab., IL (United States); Yates, J.T. Jr. [Univ. of Pittsburgh, PA (United States)

1994-04-01

344

SIMULTANEOUS IRRADIATION EFFECTS OF HEAVY IONS AND PHOTONS ON RADIATION DAMAGE IN INSULATING MATERIALS  

Microsoft Academic Search

Plasma-facing materials in fusion reactors are subjected to not only neutron\\/ion bombardment but also intense photon irradiation emitted from the burning plasma. Simultaneous irradiation effects of photons and heavy ions have been studied to explore fundamental processes in insulators. Photons of a sub-gap energy (2.3 eV) and Cu ions of 3 MeV were applied to a-SiO2 (KU-1) and MgO· 2.4(Al2O3).

N. KISHIMOTO; N. OKUBO; C. G. LEE; Y. TAKEDA

345

Investigation of swift heavy ion irradiation effects in CdTe crystals  

NASA Astrophysics Data System (ADS)

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

Veeramani, P.; Haris, M.; Kanjilal, D.; Asokan, K.; Moorthy Babu, S.

2006-07-01

346

Effects of ion beam-irradiated Si on atomic force microscope local oxidation  

NASA Astrophysics Data System (ADS)

Atomic force microscope oxidation lithography was used to study the effects of low-energy ion beams on a silicon substrate. The oxygen containing layer formed by H+ ion beam irradiation was characterized by Kelvin probe force microscopy. Giant oxide features with heights over 100 nm were fabricated by cathodic oxidation. The growth rate of the oxide features increased on the H+ ion-irradiated substrate and the etching selectivity was observed for individual oxide features. The density and oxygen concentration of the oxide features were affected by the chemical etching process. The mechanism of cathodic oxidation by Ohmic current was proposed.

Kim, H.; Kim, S.-K.; Lee, M.-K.; Yun, S.; Song, Y.; Kim, K.-R.; Shin, H.; Lee, H.

2013-04-01

347

Chemi-luminescence measurements of hyperthermal Xe{sup +}/Xe{sup 2+}+ NH{sub 3} reactions  

SciTech Connect

Luminescence spectra are recorded for the reactions of Xe{sup +}+ NH{sub 3} and Xe{sup 2+}+ NH{sub 3} at energies ranging from 11.5 to 206 eV in the center-of-mass (E{sub cm}) frame. Intense features of the luminescence spectra are attributed to the NH (A {sup 3}{Pi}{sub i}-X {sup 3}{Sigma}{sup -}), hydrogen Balmer series, and Xe I emission observable for both primary ions. Evidence for charge transfer products is only found through Xe I emission for both primary ions and NH{sup +} emission for Xe{sup 2+} primary ions. For both primary ions, the absolute NH (A-X) cross section increases with collision energy before leveling off at a constant value, approximately 9 x 10{sup -18} cm{sup 2}, at about 50 eV while H-{alpha} emission increases linearly with collision energy. The nascent NH (A) populations derived from the spectral analysis are found to be independent of collision energy and have a constant rotational temperature of 4200 K.

Prince, Benjamin D.; Steiner, Colby P. [Air Force Research Laboratory, Space Vehicles Directorate, Kirtland AFB, New Mexico 87117 (United States); Chiu, Yu-Hui [Busek Co. Inc, Natick, Massachusetts 01760 (United States)

2012-04-14

348

Enhancement of SPHK1 in vitro by carbon ion irradiation in oral squamous cell carcinoma  

SciTech Connect

Purpose The purpose of this study was to assess the gene expression changes in oral squamous cell carcinoma (OSCC) cells after carbon ion irradiation. Methods and Materials Three OSCC cell lines (HSC2, Ca9-22, and HSC3) were irradiated with accelerated carbon ion beams or X-rays using three different doses. The cellular sensitivities were determined by clonogenic survival assay. To identify genes the expression of which is influenced by carbon ion irradiation in a dose-dependent manner, we performed Affymetrix GeneChip analysis with HG-U133 plus 2.0 arrays containing 54,675 probe sets. The identified genes were analyzed using the Ingenuity Pathway Analysis Tool to investigate the functional network and gene ontology. Changes in mRNA expression in the genes were assessed by real-time reverse transcriptase-polymerase chain reaction. Results We identified 98 genes with expression levels that were altered significantly at least twofold in each of the three carbon-irradiated OSCC cell lines at all dose points compared with nonirradiated control cells. Among these, SPHK1, the expression of which was significantly upregulated by carbon ion irradiation, was modulated little by X-rays. The function of SPHK1 related to cellular growth and proliferation had the highest p value (p = 9.25e-7 to 2.19e-2). Real-time reverse transcriptase-polymerase chain reaction analysis showed significantly elevated SPHK1 expression levels after carbon ion irradiation (p < 0.05), consistent with microarray data. Clonogenic survival assay indicated that carbon ion irradiation could induce cell death in Ca9-22 cells more effectively than X-rays. Conclusions Our findings suggest that SPHK1 helps to elucidate the molecular mechanisms and processes underlying the biologic response to carbon ion beams in OSCC.

Higo, Morihiro [Department of Clinical Molecular Biology, Graduate School of Medicine, Chiba University, Chiba (Japan); Uzawa, Katsuhiro [Department of Clinical Molecular Biology, Graduate School of Medicine, Chiba University, Chiba (Japan) and Division of Dentistry and Oral-Maxillofacial Surgery, Chiba University Hospital, Chiba (Japan)]. E-mail: uzawak@faculty.chiba-u.jp; Kawata, Tetsuya [Department of Radiology, Graduate School of Medicine, Chiba University, Chiba (Japan); Kato, Yoshikuni [Department of Clinical Molecular Biology, Graduate School of Medicine, Chiba University, Chiba (Japan); Kouzu, Yukinao [Department of Clinical Molecular Biology, Graduate School of Medicine, Chiba University, Chiba (Japan); Yamamoto, Nobuharu [Department of Oral and Maxillo-Facial Surgery, Tokyo Dental College, Chiba (Japan); Shibahara, Takahiko [Department of Oral and Maxillo-Facial Surgery, Tokyo Dental College, Chiba (Japan); Mizoe, Jun-etsu [Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba (Japan); Ito, Hisao [Department of Radiology, Graduate School of Medicine, Chiba University, Chiba (Japan); Tsujii, Hirohiko [Center of Excellence (COE) Program in the 21st Century, Graduate School of Medicine, Chiba University, Chiba (Japan); Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba (Japan); Tanzawa, Hideki [Department of Clinical Molecular Biology, Graduate School of Medicine, Chiba University, Chiba (Japan); Division of Dentistry and Oral-Maxillofacial Surgery, Chiba University Hospital, Chiba (Japan); Center of Excellence (COE) Program in the 21st Century, Graduate School of Medicine, Chiba University, Chiba (Japan)

2006-07-01

349

Pattern-induced magnetic anisotropy in FePt thin films by ion irradiation  

SciTech Connect

The magnetic properties of FePt thin films have been modified by exposing the samples to irradiation of 4 MeV Cl{sup 2+} ions. Patterned magnetic films, without modified topographical profile, were fabricated by irradiating the films through a shadowing micrometric mask. The structural changes, ascribed to the ion-beam-induced amorphization of the thin films, promote the modification of the magnetic anisotropy. In particular, the out-of-plane component of the magnetization decreases simultaneously with an enhancement of in-plane anisotropy by increasing ion fluence. Moreover, the nonirradiated regions present unexpected anisotropic behavior owing to the stray field of the irradiated regions. The control of this effect, which can have unwished consequences for the patterning of magnetic properties by ion bombardment, needs to be suitably addressed.

Jaafar, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, ES-28049 Madrid (Spain); Dpto. Fisica de la Materia Condensada, UAM, ES-28049 Madrid (Spain); Sanz, R. [Instituto de Ciencia de Materiales de Madrid, CSIC, ES-28049 Madrid (Spain); Nanoate SL, Poeta Rafael Morales 2, ES-28702 San Sebastian de los Reyes, Madrid (Spain); McCord, J. [Institute of Ion Beam Physics and Materials Research, FZD, D-01314 Dresden (Germany); Jensen, J. [Thin Film Physics, Department of Physics, Chemistry and Biology, Linkoeping University, SE-581 83 Linkoeping (Sweden); Schaefer, R. [Leibniz Institute for Solid State and Materials Research, IFW, Helmholtzstrasse 20, D-01069 Dresden (Germany); Vazquez, M.; Asenjo, A. [Instituto de Ciencia de Materiales de Madrid, CSIC, ES-28049 Madrid (Spain)

2011-03-01

350

Producing metastable nanophase with sharp interface by means of focused ion beam irradiation  

SciTech Connect

Amorphous carbon/nickel double layers were irradiated by 30 keV Ga{sup +} ions via focused ion beam. The effect of irradiation on the concentration distribution of all constituents was studied by Auger electron spectroscopy depth profiling and cross sectional transmission electron microscopy, while the morphology change of the sample was determined by atomic force microscopy. The Ga{sup +} ion irradiation results in the formation of metastable Ni{sub 3}C layer with a uniform thickness. The C/Ni{sub 3}C and Ni{sub 3}C/Ni interfaces were found to be sharp up to a fluence of 200 Ga{sup +} ions/nm{sup 2}.

Barna, Arpad; Kotis, Laszlo; Labar, Janos; Osvath, Zoltan; Toth, Attila L.; Menyhard, Miklos [Research Institute for Technical Physics and Materials Science, P.O. Box 49, Budapest H-1525 (Hungary); Zalar, Anton; Panjan, Peter [Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia)

2009-02-15

351

Etch-free formation of porous silicon by high-energy ion irradiation  

SciTech Connect

In this study, porous silicon was fabricated without any chemical etching by self-ion implantation of crystalline Si performed at high temperature and at high fluences. The irradiated silicon samples, which remained crystalline under high temperature ion irradiation, exhibited an increased porous fraction with increasing sample temperature at a given fluence, up to the maximum tested temperature of 650 C. Extremely high ion fluences of at least 2 1018 ions/cm2 were necessary to produce significant void growth. Comparisons between the porous silicon structures and irradiation-induced porous networks in Ge, GaSb, and InSb are made, and differences in the formation conditions for these porous networks are discussed.

Perez-Bergquist, Dr. Alejandro G. [Los Alamos National Laboratory (LANL); Naab, Fabian U. [University of Michigan; Zhang, Yanwen [ORNL; Wang, Prof. Lumin [University of Michigan

2011-01-01

352

Etch-free Formation of Porous Silicon by High-energy Ion Irradiation  

SciTech Connect

In this study, porous silicon was fabricated without any chemical etching by self-ion implantation of crystalline Si performed at high temperature and at high fluences. The irradiated silicon samples, which remained crystalline under high temperature ion irradiation, exhibited an increased porous fraction with increasing sample temperature at a given fluence, up to the maximum tested temperature of 650º C. Extremely high ion fluences of at least 2 x 10¹? ions/cm² were necessary to produce significant void growth. Comparisons between the porous silicon structures and irradiation-induced porous networks in Ge, GaSb, and InSb are made, and differences in the formation conditions for these porous networks are discussed.

Perez-Bergquist, Alejandro G.; Naab, Fabian U.; Zhang, Yanwen; Wang, Lumin M.

2011-03-15

353

Swift ion irradiation effects on L-threonine amino acid single crystals  

Microsoft Academic Search

Single crystals of L-threonine were subjected to 50 MeV Li3+ ion irradiation at various ion fluences. Radiation induced changes in the structural, electrical, thermal and optical properties of the crystals have been studied in detail. The ion fluence dependence on these properties has also been discussed. Surface modifications in the crystals have been explored through atomic force microscopy. It has

G. Ramesh Kumar; S. Gokul Raj; V. Mathivanan; M. Kovendhan; R. Mohan; Thenneti Raghavalu; D. Kanjilal; K. Asokan; A. Tripathi; I. Sulania; Pawan K. Kulriya

2007-01-01

354

Some Structural Modifications At The Nanometric Scale Induced By Swift Heavy Ion Irradiation  

NASA Astrophysics Data System (ADS)

The effects of thermal spikes occurring in the wake of swift heavy ions on the structure of oxides, oxide-metal composites and carbon based targets are reported. Linear strings of metal nanoparticles are formed along the ion tracks in silicate glasses but nanowires of amorphous carbon in fullerenes or polymers. Changes of the size, shape or stress state of the particles induced by swift heavy ion irradiation in composites affect their optical and magnetic properties.

Pivin, J. C.; Singh, F.; Kumar, A.; Patel, M. K.; Avasthi, D. K.; Dimova-Malinovska, D.

355

Temperature dependence of ion irradiation induced amorphization of zirconolite  

SciTech Connect

Zirconolite is one of the major host phases for actinides in various wasteforms for immobilizing high level radioactive waste (HLW). Over time, zirconolite's crystalline matrix is damaged by {alpha}-particles and energetic recoil nuclei recoil resulting from {alpha}-decay events. The cumulative damage caused by these particles results in amorphization. Data from natural zirconolites suggest that radiation damage anneals over geologic time and is dependant on the thermal history of the material. Proposed HLW containment strategies rely on both a suitable wasteform and geologic isolation. Depending on the waste loading, depth of burial, and the repository-specific geothermal gradient, burial could result in a wasteform being exposed to temperatures of between 100--450 C. Consequently, it is important to assess the effect of temperature on radiation damage in synthetic zirconolite. Zirconolite containing wasteforms are likely to be hot pressed at or below 1,473 K (1,200 C) and/or sintered at or below 1,623 K (1,350 C). Zirconolite fabricated at temperatures below 1,523 K (1,250 C) contains many stacking faults. As there have been various attempts to link radiation resistance to structure, the authors decided it was also pertinent to assess the role of stacking faults in radiation resistance. In this study, they simulate {alpha}-decay damage in two zirconolite samples by irradiating them with 1.5 MeV Kr{sup +} ions using the High Voltage Electron Microscope-Tandem User Facility (HTUF) at Argonne National Laboratory (ANL) and measure the critical dose for amorphization (D{sub c}) at several temperatures between 20 and 773 K. One of the samples has a high degree of crystallographic perfection, the other contains many stacking faults on the unit cell scale. Previous authors proposed a model for estimating the activation energy of self annealing in zirconolite and for predicting the critical dose for amorphization at any temperature. The authors discuss their results and earlier published data in relation to that model.

Smith, K. L.; Blackford, M. G.; Lumpkin, G. R.; Zaluzec, N. J.

1999-12-22

356

Influence of 100 MeV oxygen ion irradiation on Ni/n-Si (100) Schottky barrier characteristics  

SciTech Connect

The influences of high energy ion irradiation on the Ni/n-Si Schottky barrier are discussed as a function of irradiation fluence. The variations in Schottky diode parameters are studied by using in situ current-voltage characterization in a fluence range between 1x10{sup 9} and 1x10{sup 13} ions/cm{sup 2}. The ion irradiation results in an increase of Schottky barrier height from a value of 0.59 eV for unirradiated diode to 0.68 eV after irradiation at a fluence of 1x10{sup 13} ions/cm{sup 2}. A decrease of the leakage current by about two orders of magnitude was observed after ion irradiation. These results are interpreted in terms of the ion irradiation induced defects inside the materials.

Kumar, Sandeep; Katharria, Y. S.; Kanjilal, D. [Inter-University Accelerator Centre, P.O. Box-10502, New Delhi, 110 067 (India)

2008-02-15

357

Microdosimetric Monte-Carlo Simulations and Measurements of Heavy Ion Irradiation of a TEPC  

NASA Astrophysics Data System (ADS)

Microdosimetric methods are well suited for systematic study and quantification of the absorbed energy spatial and temporal distribution in irradiated matter A standard instrument used to measure the energy dissipated in microscopic sites by individual ionizing events is the Tissue Equivalent Proportional Counter TEPC The main focus of this work is to examine interactions of heavy ions with tissue using both experimental and numerical methods Measurements with a TEPC instrument were carried out recently in heavy ion radiation fields at the Heavy Ion Medical Accelerator HIMAC facility in Chiba which belongs to the National Institute of Radiological Sciences NIRS in Japan The instrument has been exposed to two kinds of heavy ions under different irradiation geometries and beam parameters The heavy ions used were Oxygen with energy of 400 MeV u and Iron of 300 MeV u For the simulation of the irradiation experiments two Monte Carlo codes are used namely FLUKA and GEANT4 Both codes are widely used for basic research and applications in radiation protection and dosimetry radiobiology radiotherapy and space Besides scoring average quantities both Monte Carlo codes have the capability to score energy deposition on an event by event basis Thus together with the total energy deposition a simulation of microdosimetric spectra is possible The comparison of measured and simulated lineal energy distribution show a satisfactory agreement both for irradiation with Oxygen ions of 400 MeV u and for Iron ions of 300 MeV u We will discuss in detail the

Rollet, S.; Beck, P.; Bock, F.; Ferrari, A.; Latocha, M.; Uchihori, Y.; Wind, M.

358

In-situ Fe+ Ion Irradiation of an Oxide Dispersion Strengthened Steel  

NASA Astrophysics Data System (ADS)

Oxide Dispersion Strengthened (ODS) reduced activation ferritic steels are promising candidate materials for structural components of both nuclear fission and fusion reactors. However, when irradiated with energetic particles, they may suffer changes on their microstructures that degrade their mechanical performance. In-situ transmission electron microscopy studies on ion-irradiated ODS steels can give remarkable insights into fundamental aspects of radiation damage allowing dynamic observations of defect formation, mobilities, and interactions during irradiation. In this investigation, a commercially available PM2000 ODS steel was in-situ irradiated with 150 KeV Fe+ at room temperature and 700°C. These experiments showed that the oxide nanoparticles in these steels remain stable up to the higher irradiation dose (~ 1.5 dpa), and that these particles seem to be effective sinks for irradiation induced defects.

de Castro, V.; Briceno, M.; Jenkins, M. L.; Kirk, M.; Lozano-Perez, S.; Roberts, S. G.

2014-06-01

359

Morphological and biochemical responses of Oryza sativa L. (cultivar MR219) to ion beam irradiation*  

PubMed Central

Objective: Heavy ion beam, which has emerged as a new mutagen in the mutation breeding of crops and ornamental plants, is expected to result in the induction of novel mutations. This study investigates the morphological and biochemical responses of Oryza sativa toward different doses of carbon ion beam irradiation. Methods: In this study, the dry seeds of O. sativa were irradiated at 0, 20, 40, 60, 80, 100, and 120 Gy, followed by in-vitro germination under controlled conditions. Morphological and biochemical studies were conducted to investigate the morphological and physiological responses of O. sativa towards ion beam irradiation. Results: The study demonstrated that low doses (10 Gy) of ion beam have a stimulating effect on the height, root length, and fresh weight of the plantlets but not on the number of leaves. Meanwhile, doses higher than 10 Gy caused reductions in all the morphological parameters studied as compared to the control samples. The highest total soluble protein content [(2.11±0.47) mg/g FW] was observed in plantlets irradiated at 20 Gy. All irradiated plantlets were found to have 0.85% to 58.32% higher specific activity of peroxidase as compared to the control samples. The present study also revealed that low doses of ion beam (10 and 20 Gy) had negligible effect on the total chlorophyll content of O. sativa plantlets while 40 Gy had a stimulating effect on the chlorophyll content. Plantlets irradiated between 40 to 120 Gy were shown to be 0.38% to 9.98% higher in total soluble nitrogen content which, however, was not significantly different from the control samples. Conclusions: Carbon ion beam irradiation administered at low to moderate doses of 10 to 40 Gy may induce O. sativa mutants with superior characteristics.

Ling, Anna Pick Kiong; Ung, Ying Chian; Hussein, Sobri; Harun, Abdul Rahim; Tanaka, Atsushi; Yoshihiro, Hase

2013-01-01

360

Order-disorder phase transformation in ion-irradiated rare earth sesquioxides  

NASA Astrophysics Data System (ADS)

An order-to-disorder (OD) transformation induced by ion irradiation in rare earth (RE) sesquioxides, Dy2O3, Er2O3, and Lu2O3, was studied using grazing incidence x-ray diffraction and transmission electron microscopy. These sesquioxides are characterized by a cubic C-type RE structure known as bixbyite. They were irradiated with heavy Kr++ ions (300 keV) and light Ne+ ions (150 keV) at cryogenic temperature (~120 K). In each oxide, following a relatively low ion irradiation dose of ~2.5 displacements per atom, the ordered bixbyite structure was transformed to a disordered, anion-deficient fluorite structure. This OD transformation was found in all three RE sesquioxides (RE=Dy, Er, and Lu) regardless of the ion type used in the irradiation. The authors discuss the irradiation-induced OD transformation process in terms of anion disordering, i.e., destruction of the oxygen order associated with the bixbyite structure.

Tang, M.; Valdez, J. A.; Sickafus, K. E.; Lu, P.

2007-04-01

361

Quantitative control of magnetic ordering in FeRh thin films using 30 keV Ga ion irradiation from a focused ion beam system  

SciTech Connect

We investigated a low-energy ion-beam irradiation process for the magnetic modification of FeRh thin films using a focused ion beam system. Low-energy ion-beam irradiation induced ferromagnetic states in the FeRh thin films at low temperatures, that originally exhibited antiferromagnetism, as effectively as high-energy ion-beam irradiation. Because the energy deposited by the elastic collisions caused by the irradiation determined the magnetic properties of the samples, the magnetic state of the FeRh thin films could be quantitatively controlled. The low-energy ion-beam irradiation using a focused ion beam system is a potential technique to modify the magnetic properties of materials on the nano- and micro-scales, which may lead to a variety of novel spin devices and applications.

Aikoh, K.; Kosugi, S.; Matsui, T.; Iwase, A. [Graduate School of Engineering, Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan)

2011-04-01

362

Effect of irradiation parameters on defect aggregation during thermal annealing of LiF irradiated with swift ions and electrons  

SciTech Connect

Absorption spectroscopy were performed to study the effects of thermal annealing on the aggregation of color centers in LiF crystals irradiated with different ions between carbon and uranium of megaelectron volt-gigaelectron volt energy. The beam parameters such as energy, energy loss, and fluence have a pronounced influence on the initial defect composition and concentration as well as their evolution upon thermal annealing. A distinct phenomenon was observed, viz., the enhancement of F{sub n} centers for annealing temperatures between 500 and 700 K, followed by Li colloid formation above 700 K. The phenomenon requires specific irradiation conditions whereas the formation of Mg colloids from Mg impurities occurs in all irradiated crystals. The mechanisms of annealing and colloid formation are discussed.

Schwartz, K.; Neumann, R.; Trautmann, C. [GSI Helmholtzzentrum fuer Schwerionenforschung, Planckstr. 1, 64291 Darmstadt (Germany); Volkov, A. E.; Sorokin, M. V. [Russian Research Center 'Kurchatov Institute', Kurchatov Square 1, 123182 Moscow (Russian Federation)

2010-10-01

363

Biodamage via shock waves initiated by irradiation with ions  

PubMed Central

Radiation damage following the ionising radiation of tissue has different scenarios and mechanisms depending on the projectiles or radiation modality. We investigate the radiation damage effects due to shock waves produced by ions. We analyse the strength of the shock wave capable of directly producing DNA strand breaks and, depending on the ion's linear energy transfer, estimate the radius from the ion's path, within which DNA damage by the shock wave mechanism is dominant. At much smaller values of linear energy transfer, the shock waves turn out to be instrumental in propagating reactive species formed close to the ion's path to large distances, successfully competing with diffusion.

Surdutovich, Eugene; Yakubovich, Alexander V.; Solov'yov, Andrey V.

2013-01-01

364

Space Plasma Ion Processing of Ilmenite in the Lunar Soil: Insights from In-Situ TEM Ion Irradiation Experiments  

NASA Technical Reports Server (NTRS)

Space weathering on the moon and asteroids results largely from the alteration of the outer surfaces of regolith grains by the combined effects of solar ion irradiation and other processes that include deposition of impact or sputter-derived vapors. Although no longer considered the sole driver of space weathering, solar ion irradiation remains a key part of the space weathering puzzle, and quantitative data on its effects on regolith minerals are still in short supply. For the lunar regolith, previous transmission electron microscope (TEM) studies performed by ourselves and others have uncovered altered rims on ilmenite (FeTiO3) grains that point to this phase as a unique "witness plate" for unraveling nanoscale space weathering processes. Most notably, the radiation processed portions of these ilmenite rims consistently have a crystalline structure, in contrast to radiation damaged rims on regolith silicates that are characteristically amorphous. While this has tended to support informal designation of ilmenite as a "radiation resistant" regolith mineral, there are to date no experimental data that directly and quantitatively compare ilmenite s response to ion radiation relative to lunar silicates. Such data are needed because the radiation processed rims on ilmenite grains, although crystalline, are microstructurally and chemically complex, and exhibit changes linked to the formation of nanophase Fe metal, a key space weathering process. We report here the first ion radiation processing study of ilmenite performed by in-situ means using the Intermediate Voltage Electron Microscope- Tandem Irradiation facility (IVEM-Tandem) at Argonne National Laboratory. The capability of this facility for performing real time TEM observations of samples concurrent with ion irradiation makes it uniquely suited for studying the dose-dependence of amorphization and other changes in irradiated samples.

Christoffersen, R.; Keller, L. P.

2007-01-01

365

Electronic excitation effects on radiation damage in insulators under ion irradiation  

NASA Astrophysics Data System (ADS)

To extract electronic excitation effects from the synergistic damage processes, we have studied photon-irradiation effects on insulators under heavy ion irradiation. Copper ions (Cu 2+) of 3 MeV energy at an ion flux of 2 ?A/cm 2 and 2.3 eV photons at 0.2 J/cm 2pulse were used to amorphous SiO 2 (KU-1) and spinel MgO·2.4(Al 2O 3), either sequentially or simultaneously to fluences up to 5 × 10 17 ions/cm 2. Atomic force microscopy and cross-sectional TEM were conducted to study the surface morphology and internal microstructure, respectively. The simultaneous photon irradiation at high photon densities significantly enhanced surface damage for the insulators, but alleviated bulk defects. The electronic excitation gave rise to significant reduction in dislocation loops in MgO·2.4(Al 2O 3), whereas single ion irradiation produced copious dislocation loops. The results demonstrate that intense electronic excitation, coexistent with heavy ions, excite transient sub-gap states and the absorbed energy results in enhancement of atomic migration, either damaging the surface or annealing the internal defects.

Kishimoto, N.; Okubo, N.; Plaksin, O. A.; Takeda, Y.

2004-08-01

366

Irradiation effect of gas-hydrate cluster ions on solid surfaces  

NASA Astrophysics Data System (ADS)

In our newly developed gas-hydrate cluster ion source, a vapor of water bubbling with carbon dioxide (CO2) gas was ejected through a nozzle into a vacuum region, and mixed beams of water clusters and carbon dioxide-hydrate clusters were produced by adiabatic expansion. According to time-of-flight measurements, the largest water clusters consisted of approximately 2800 molecules at a vapor pressure of 0.3 MPa. Also, the largest mixed clusters contained approximately 2000 molecules. Copper and silicon substrates were irradiated by the water cluster ions as well as carbon dioxide-hydrate cluster ions. X-ray photoelectron spectroscopy measurements showed that carbon was included in the Cu and Si substrates irradiated by the carbon dioxide-hydrate cluster ions, and a chemical shift owing to the formation of carboxyl radicals occurred on the Cu surface. Furthermore, the Cu surface was sputtered, and the sputtering depth was larger than the distance penetrated by the water cluster ion irradiation. Therefore, the formation of carboxyl radicals played an important role in the sputtering of the Cu surface, which occurred effectively in carbon dioxide-hydrate cluster ion irradiation.

Takaoka, Gikan H.; Ryuto, Hiromichi; Takeuchi, Mitsuaki; Kobayashi, Hiroki

2014-05-01

367

Anisotropic evolution of Frank loops in ion-irradiated silicon carbide  

NASA Astrophysics Data System (ADS)

Frank loop evolution in highly damaged polycrystalline cubic silicon carbide irradiated with 5.1 MeV Si 2+ ions at 1673 K was studied by transmission electron microscopy (TEM). Individual TEM images of Frank loops formed on each {1 1 1} plane revealed that their population strongly depended upon their orientation with respect to the incident beam direction. However, no significant difference in loop growth rates was observed between each habit plane. The anisotropic loop evolution has not been reported for neutron-irradiated SiC. Our examination shows that a grain, containing {1 1 1} planes nearly parallel to the irradiated surface, was largely strained toward the free surface by the preferential formation of Frank loops on the plane. Compressive stress following the anisotropic swelling in ion-irradiated specimen may affect the loop evolution. The possible mechanism of the anisotropic loop evolution observed here is accounted for by the stress induced preferential nucleation of Frank loops.

Kondo, S.; Kohyama, A.; Hinoki, T.

2007-08-01

368

Surface reformation and electro-optical characteristics of liquid crystal alignment layers using ion beam irradiation  

SciTech Connect

The surface modification characteristics of liquid crystal (LC) alignment layers irradiated with various argon (Ar) ion beam (IB) energies were investigated as a substitute for rubbing technology. Various pretilt angles were created on the IB-irradiated polyimide (PI) surfaces after IB irradiation, but the Ar ions did not alter the morphology on the PI surface, indicating that the pretilt angle was not due to microgrooves. The chemical bonding states of the IB-irradiated PI surfaces were analyzed in detail by x-ray photoelectron spectroscopy to verify the compositional behavior for the LC alignment. Chemical structure analysis showed that the alignment ability of LCs was due to the preferential reorientation of the carbon network due to the breaking of C=O double bonds in the imide ring parallel to the incident IB direction. The potential of applying nonrubbing technology to display devices was further supported by the superior electro-optical characteristics compared to rubbed PI.

Oh, Byeong-Yun; Lee, Kang-Min; Kim, Byoung-Yong; Kim, Young-Hwan; Han, Jin-Woo; Han, Jeong-Min; Lee, Sang-Keuk; Seo, Dae-Shik [Information Display Device Laboratory, Department of Electrical and Electronic Engineering, Yonsei University, 262 Seongsanno, Seodaemun-gu, Seoul 120-749 (Korea, Republic of)

2008-09-15

369

Hyperpolarized (131)Xe NMR spectroscopy.  

PubMed

Hyperpolarized (hp) (131)Xe with up to 2.2% spin polarization (i.e., 5000-fold signal enhancement at 9.4 T) was obtained after separation from the rubidium vapor of the spin-exchange optical pumping (SEOP) process. The SEOP was applied for several minutes in a stopped-flow mode, and the fast, quadrupolar-driven T(1) relaxation of this spin I = 3/2 noble gas isotope required a rapid subsequent rubidium removal and swift transfer into the high magnetic field region for NMR detection. Because of the xenon density dependent (131)Xe quadrupolar relaxation in the gas phase, the SEOP polarization build-up exhibits an even more pronounced dependence on xenon partial pressure than that observed in (129)Xe SEOP. (131)Xe is the only stable noble gas isotope with a positive gyromagnetic ratio and shows therefore a different relative phase between hp signal and thermal signal compared to all other noble gases. The gas phase (131)Xe NMR spectrum displays a surface and magnetic field dependent quadrupolar splitting that was found to have additional gas pressure and gas composition dependence. The splitting was reduced by the presence of water vapor that presumably influences xenon-surface interactions. The hp (131)Xe spectrum shows differential line broadening, suggesting the presence of strong adsorption sites. Beyond hp (131)Xe NMR spectroscopy studies, a general equation for the high temperature, thermal spin polarization, P, for spin I ? 1/2 nuclei is presented. PMID:21051249

Stupic, Karl F; Cleveland, Zackary I; Pavlovskaya, Galina E; Meersmann, Thomas

2011-01-01

370

Hyperpolarized 131Xe NMR spectroscopy  

PubMed Central

Hyperpolarized (hp) 131Xe with up to 2.2% spin polarization (i.e., 5000-fold signal enhancement at 9.4 T) was obtained after separation from the rubidium vapor of the spin-exchange optical pumping (SEOP) process. The SEOP was applied for several minutes in a stopped-flow mode, and the fast, quadrupolar-driven T1 relaxation of this spin I = 3/2 noble gas isotope required a rapid subsequent rubidium removal and swift transfer into the high magnetic field region for NMR detection. Because of the xenon density dependent 131Xe quadrupolar relaxation in the gas phase, the SEOP polarization build-up exhibits an even more pronounced dependence on xenon partial pressure than that observed in 129Xe SEOP. 131Xe is the only stable noble gas isotope with a positive gyromagnetic ratio and shows therefore a different relative phase between hp signal and thermal signal compared to all other noble gases. The gas phase 131Xe NMR spectrum displays a surface and magnetic field dependent quadrupolar splitting that was found to have additional gas pressure and gas composition dependence. The splitting was reduced by the presence of water vapor that presumably influences xenon-surface interactions. The hp 131Xe spectrum shows differential line broadening, suggesting the presence of strong adsorption sites. Beyond hp 131Xe NMR spectroscopy studies, a general equation for the high temperature, thermal spin polarization, P, for spin I?1/2 nuclei is presented.

Stupic, Karl F.; Cleveland, Zackary I.; Pavlovskaya, Galina E.; Meersmann, Thomas

2011-01-01

371

Swelling of SiO(sub 2) quartz induced by energetic heavy ions.  

National Technical Information Service (NTIS)

A pronounced swelling effect occurs when irradiating SiO(sub 2) quartz with heavy ions (F, S, Cu, Kr, Xe, Ta, and Pb) in the electronic energy loss regime. Using a profilometer, the out-of-plane swelling was measured by scanning over the border line betwe...

C. Trautmann K. Schwartz J. M. Costantini A. Meftah J. P. Stoquert

1997-01-01

372

Highly charged heavy ion generation by pulsed laser irradiation  

NASA Astrophysics Data System (ADS)

At the Laboratorio Nazionale del Sud of the National Institute of Nuclear Physics (INFN-LNS) of Catania, different ion sources of multi-charged ions are available, including electron cyclotron resonance ion sources (ECRIS) and a laser ion source, based on a high energy infra-red pulsed laser working in single shot or pulsed mode with repetition rate of 30 Hz. A hybrid ion source based on laser source (Nd:Yag pulsed laser at 10 10 W/cm 2) coupled to ECRIS is under construction to generate intense heavy ion beams at very high charge states. This source will use the ECR plasma to enhance the ion charge state from 5 +-10 + to about 30 +-40 +. The description of this equipment will be shown along with some results of the preliminary experiments. Additional studies were carried out at Prague Asterix Laser Source (PALS) by means of a iodine pulsed laser at 10 15 W/cm 2, which produces a high density-high temperature plasma. The description of the ablation effects of metals and the study of the film deposition on different substrates will be presented. Preliminary investigations on heavy ions implantation will be also outlined.

Gammino, S.; Torrisi, L.; Ciavola, G.; Andò, L.; Wolowski, J.; Laska, L.; Krasa, J.; Picciotto, A.

2003-08-01

373

Microstructure evolution during silicon oxidation at room temperature under composite ion beam irradiation  

NASA Astrophysics Data System (ADS)

In this work, we studied the silicon microstructure evolution during its oxidation under composite beam ion irradiation at room temperature. It was found that when the composite ion beam was formed by hydrogen and dry oxygen mixture at low doses (˜1018 cm?2), a porous silicon layer was formed. During irradiation, the pore size gradually reduced and at a dose of ˜1020 cm?2 pores disappear completely, and an uniform layer of silicon oxide was formed. If residual gases and hydrogen are used to generate a composite ion beam, the formation of porous silicon is not found. The final thickness of irradiation-induced silicon oxide corresponded to the projected range of protons at a given energy in both cases.

Prikhodko, K. E.; Gurovich, B. A.; Komarov, D. A.; Goncharova, D. A.; Kutuzov, L. V.

2014-05-01

374

First tests of the ion irradiation and implantation beamline at the CMAM  

NASA Astrophysics Data System (ADS)

The implantation and irradiation beamline of the Tandem ion accelerator of the Centro de Micro Análisis de Materiales (CMAM), in Madrid, has been recently completed with a beam sweep and monitoring system, and a cryostat/furnace. These new implementations convert the beamline into a versatile tool to implant ions, between H and Au2, in different materials with precise control of the sample temperature, which may be varied between -180 °C and 600 °C. The size of the swept area on target may be as large as 10 × 10 cm2. The implantation chamber also allows carrying out in situ or/and on line analyses during the irradiations by means of advanced optical measurements, as well as ion beam analyses (IBA). These advancements can be employed in novel applications such as the fabrication of optical waveguides and irradiation tests of structural and functional materials for future fusion reactors. The results of beam tests and first experiments are shown.

Jiménez-Rey, D.; Benedicto, M.; Muñoz-Martín, A.; Bachiller-Perea, D.; Olivares, J.; Climent-Font, A.; Gómez-Ferrer, B.; Rodríguez, A.; Narros, J.; Maira, A.; Álvarez, J.; Nakbi, A.; Zucchiatti, A.; de Aragón, F.; García, J. M.; Vila, R.

2014-07-01

375

Cooperative effect of electronic and nuclear stopping on ion irradiation damage in silica  

NASA Astrophysics Data System (ADS)

Radiation damage by ions is conventionally believed to be produced either by displacement cascades or electronic energy deposition acting separately. There is, however, a range of ion energies where both processes are significant and can contribute to irradiation damage. The combination of two computational methods, namely binary collision approximation and molecular dynamics, the latter with input from the inelastic thermal spike model, makes it possible to examine the simultaneous contribution of both energy deposition mechanisms on the structural damage in the irradiated structure. We study the effect in amorphous SiO2 irradiated by Au ions with energies ranging between 0.6 and 76.5 MeV. We find that in the intermediate energy regime, the local heating due to electronic excitations gives a significant contribution to the displacement cascade damage.

Backman, M.; Djurabekova, F.; Pakarinen, O. H.; Nordlund, K.; Zhang, Y.; Toulemonde, M.; Weber, W. J.

2012-12-01

376

Microstructural evolution of P92 ferritic\\/martensitic steel under argon ion irradiation  

Microsoft Academic Search

Microstructural evolution of P92 ferritic\\/martensitic steel irradiated by Ar+ ion beams at doses from 0.6 to 230 displacements per atom (dpa) at room temperature was investigated with conventional transmission electron microscope technique. Selected-area electron diffraction combined with bright-field and dark-field contrast image indicated that carbide\\/matrix interfaces were more easily damaged. The carbide peripheries became partly amorphous at irradiation dose of

S. X. Jin; L. P. Guo; Z. Yang; D. J. Fu; C. S. Liu; R. Tang; F. H. Liu; Y. X. Qiao; H. D. Zhang

2011-01-01

377

Superconductivity and structure of ion irradiated LaSrCuO thin films  

Microsoft Academic Search

Superconducting LaSrCuO thin films yielding zero resistance values above 20 K have been deposited by sputtering from single compound targets. The films have been irradiated at low temperature (5 K, 77 K) with 300 keV protons and He+ ions. The irradiation induced Tc-depression are strongly dependent on the initial material quality and for best films comparable to results obtained for

J. Remmel; J. Geerk; G. Linker; O. Meyer; R. Smithey; B. Strehlau; G. C. Xiong

1990-01-01

378

Post-irradiation effect of Deuterium ion beam onto Rh/W/Cu multilayer thin film  

NASA Astrophysics Data System (ADS)

The fabrication of mirror like multilayer Rh/W/Cu thin films via Pulsed Laser Deposition technique is reported in this paper. These multilayer thin film mirrors were irradiated to 10, 20 and 30 keV energy of Deuterium ion beam. The post-irradiation effects onto the quality of these thin films were investigated by subjecting them to X-ray Diffractometer, Scanning Electron Microscope, Atomic Force Microscope, Ultraviolet (UV)-Visible and Far Infrared (FIR) spectrometer.

Mostako, A. T. T.; Khare, Alika; Rao, C. V. S.; Vala, Sudhirsinh; Basu, T. K.; Raole, Prakash M.; Makwana, Rajinikant

2014-03-01

379

Optical properties of swift ion beam irradiated CdTe thin films  

Microsoft Academic Search

This paper reports the effect of swift (80 MeV) oxygen (O+6) ion irradiation on the optical properties of CdTe thin films grown by conventional thermal evaporation on glass substrates. The films are found to be slightly Te-rich in composition and irradiation results no change in the elemental composition. The optical constants such as refractive index (n), absorption coefficient (?) and the

S. Chandramohan; R. Sathyamoorthy; P. Sudhagar; D. Kanjilal; D. Kabiraj; K. Asokan

2008-01-01

380

Nanoindentation creep study on an ion beam irradiated oxide dispersion strengthened alloy  

NASA Astrophysics Data System (ADS)

Oxide dispersion strengthened (ODS) alloys are considered advanced structural materials for nuclear application due to their radiation tolerance and creep resistance. Ion beam irradiation is used to study the property changes due to displacement damage. In this work 1 dpa displacement damage in an ODS was produced followed by a nanoindentation creep study at temperatures up to 600 °C to evaluate the changes in mechanical properties due to irradiation. Converted yield strength (YS) and creep related parameters are reported.

Huang, Zijing; Harris, Adrian; Maloy, Stuart A.; Hosemann, Peter

2014-08-01

381

Effects induced by keV low-energy ion irradiation in the nematode Caenorhabditis elegans  

Microsoft Academic Search

The nematode Caenorhabditis elegans is an excellent model organism with which to study the biological effects and mechanisms of ionizing irradiation. In this\\u000a study, using C. elegans as a model, the effects of keV low-energy argon ion irradiation were investigated, by examining cuticle damage, worm survival,\\u000a brood size, life span, and germ cell death. The surface etching of worm cuticle

Xuelan Liu; Kezhou Cai; Huiyun Feng; Hang Yuan; Mingguang Kong; Lijun Wu; Yuejin Wu; Zengliang Yu

2007-01-01

382

Heavy ion irradiation effects in the rare-earth sesquioxide Dy2O3  

Microsoft Academic Search

Polycrystalline pellets of the rare-earth sesquioxide Dy2O3 with cubic C-type rare-earth structure were irradiated with 300 keV Kr2+ ions at fluences up to 5 × 1020 Kr\\/m2 at cryogenic temperature. Irradiation-induced microstructural evolution is characterized using grazing incidence X-ray diffraction (GIXRD) and transmission electron microscopy (TEM). In previous work, we found a phase transformation from a cubic, C-type (Ia3¯) to

M. Tang; P. Lu; J. A. Valdez; K. E. Sickafus

2006-01-01

383

Swift heavy ion irradiation and fish tail magnetization in NBCO films - the cause and effect  

NASA Astrophysics Data System (ADS)

NBCO films, prepared by pulsed laser ablation, were irradiated by 200 MeV Au ions. The magnetization curve shows a shoulder/fish tail peak effect (FTPE) in the irradiated film while the pristine or as-grown film does not have any such signature. The absence of FTPE in the preirradiated film and its appearance in the postirradiated film are explained in the context of compositional variation of spatial density of defects and the concomitant vortex mobility .

Khatua, Sanghamitra; Mishra, P. K.; Kulkarni, D. G.; Kumar, Ravi; John, J.; Sahni, V. C.; Pinto, R.

2000-03-01

384

Nanoscale density fluctuations in swift heavy ion irradiated amorphous SiO2  

NASA Astrophysics Data System (ADS)

We report on the observation of nanoscale density fluctuations in 2 ?m thick amorphous SiO2 layers irradiated with 185 MeV Au ions. At high fluences, in excess of approximately 5 × 1012 ions/cm2, where the surface is completely covered by ion tracks, synchrotron small angle x-ray scattering measurements reveal the existence of a steady state of density fluctuations. In agreement with molecular dynamics simulations, this steady state is consistent with an ion track ``annihilation'' process, where high-density regions generated in the periphery of new tracks fill in low-density regions located at the center of existing tracks.

Kluth, P.; Pakarinen, O. H.; Djurabekova, F.; Giulian, R.; Ridgway, M. C.; Byrne, A. P.; Nordlund, K.

2011-12-01

385

The ion beam analysis of laser-irradiated borosilicate glass  

NASA Astrophysics Data System (ADS)

The chemical effects of carbon dioxide laser irradiation on some borosilicate glasses have been investigated. Specimens of Tempax and BK7 glass were analysed before and after laser irradiation and were found to have undergone subtle changes in chemical composition. These were thought to have been caused by surface heating. This paper describes the application of Rutherford backscattering spectrometry and nuclear reaction analysis using the 11B(p,?) 8Be and 16O(d,p) 17O reactions to the study of these glasses.

Lane, D. W.

1992-02-01

386

Application of 6 MeV\\/n heavy-ion beams to biophysical experiments  

Microsoft Academic Search

A new accelerator facility and two irradiation methods using 6 MeV\\/n heavy-ion beams are described along with preliminary results concerning their applications to biophysical investigations. The beams are obtained from the injector linac installed at the Heavy Ion Medical Accelerator in Chiba. Various ion species (He–Xe) having different charge states are accelerated to the same velocity, which is suitable for

Y. Sato; A. Tanaka; Y. Furusawa; S. Matsumoto; T. Murakami; F. Soga; K. Takeo; Y. Fujita

1996-01-01

387

Issues to consider using nano indentation on shallow ion beam irradiated materials  

NASA Astrophysics Data System (ADS)

Ion beam irradiation is a widely used method to cause radiation damage in materials in order to study materials degradation under radiation in a laboratory setting. Nanoindentation has become an often used tool to measure the mechanical property changes due to ion beam irradiation. While the combination of ion beam irradiation and nanoindentation is a powerful tool, difficulties arise and need to be discussed in detail. This work intends to draw attention to the potential issues one might face if nanoindentation is used to evaluate radiation induced hardening, especially if compared to other mechanical tests such as yield strength from tensile tests on irradiated materials and others. In this work we focus on issues associated with size and dose effects associated with quasi static nanoindentation on shallow irradiated Cu [1 0 0] single crystal material. It is shown that on 1 ?m deep irradiated material it is not possible to correlate a single dose to a specific hardness value, rather a dose range has to be considered. However, deeper indents will always sample contributions of the unirradiated material. Moreover, the correlation between the indentation hardness and macroscopic properties is not straight forward.

Hosemann, Peter; Kiener, Daniel; Wang, Yongqiang; Maloy, Stuart A.

2012-06-01

388

Microstructural evolution in Cu-A125 alloy under 300 keV Cu + ion irradiation  

NASA Astrophysics Data System (ADS)

Dispersion strengthened (DS) Cu-Al25 alloy containing small Al 2O 3 particles (˜4 nm in diameter) was irradiated by 300 keV Cu + ion to doses of 10 dpa and 30 dpa with a displacement rate of 3.7×10 -2 dpa/s at room temperature, which simulates the effects of high energy primary knock-on atoms (PKA) produced by 14 MeV neutrons. Microstructural evolution was investigated by transmission electron microscopy (TEM). Selected area diffraction (SAD) was used to study the phase stability of alumina under irradiation. The defect cluster structure formed by irradiation was investigated by dynamic two-beam techniques. Small particles of Al 2O 3 were dissolved under ion irradiation with increasing fluences. A large number of small Frank vacancy and interstitial dislocation loops (˜5 nm in diameter) with different Burgers vectors of a/3 <1 1 1> are produced by ion irradiation. At the region adjacent to the irradiation surface the number of vacancy loops was greater than that of interstitial ones. This result is in good agreement with the computer simulation results.

Li, Jing; Xu, Hui; Yu, Jinnan; Wu, Baoli; He, Qingfu

1998-10-01

389

Microstructure evolution of metallic nanocrystalline thin-films under ion-beam irradiation  

NASA Astrophysics Data System (ADS)

The microstructural evolution of nanocrystalline metallic thin-films under ion irradiation, especially grain growth and second-phase precipitation, was studied with detailed in situ experiments, and a theoretical model was developed to explain the results of grain-growth. Free-standing Zr, Pt, Cu and Au, Cu-Fe, and Zr-Fe nanocrystalline thin films prepared by sputter deposition were irradiated in-situ at the Intermediate Voltage Electron Microscope (IVEM) at Argonne National Laboratory with Ar and Kr ions to fluences in excess of 1016 ion/cm2 at temperatures ranging from 20 to 773 K. The microstructural evolution of the thin-films was followed in situ by systematically recording bright field images and diffraction patterns at successive ion-irradiation doses. Grain growth was observed as a result of irradiation in all samples at all irradiation temperatures. The results suggest the existence of three regimes with increasing irradiating temperature: a low temperature regime (below about 0.15 to 0.22 Tm) where grain-growth does not depend on the irradiation temperature, a thermally assisted regime where both the grain-growth rate and the final grain size increase with increasing irradiation temperature, and a thermal regime where thermal effects dominate ion beam effects. Similarly to thermal grain growth, the ion-irradiation induced grain growth curves could be best fitted with curves of the type: Dn-Dn0=KF with n˜3 in the low temperature regime. The effect of solute addition on grain-growth was investigated using Zr(Fe) and Cu(Fe) supersaturated solid-solutions. In the case of Zr-Fe, Zr2Fe precipitates formed during irradiation (with the dose-to-precipitation of Zr2Fe decreasing with increasing irradiation temperature), whereas Cu-Fe remained as a solid-solution. The grain-growth rate and final size decreased in both alloys with respect to the pure metallic films as a result of second-phase particle pinning (Zener drag) (Zr-Fe), and solute drag (Cu-Fe). The grain-growth rate was found to depend on material and on irradiation conditions. In particular, neither grain-growth nor precipitation occurred under 1 MeV electron irradiation. Combined with rate-theory calculations, this shows that long range diffusion does not play a role in the process. A model of grain-growth under ion irradiation in the temperature-independent regime was developed, based on direct impact of irradiation-induced thermal spikes on grain-boundaries. Grain-boundary migration occurs by atomic jumps within the thermal spike biased by the grain-boundary curvature driving force. The model incorporates cascade structure features such as subcascade formation, and the probability of subcascades occurring at grain-boundaries. This results in a power law expression relating the average grain-size with the ion dose, where the exponent is 3 in agreement with the experimental data. In the thermally assisted regime, the increased grain-growth is explained within the framework of the same model, by the increased thermal spike size with higher substrate temperature. At the highest temperatures, other effects such as subcascade overlap and point defect migration to sinks may also enhance the process.

Kaoumi, Djamel

390

Monte Carlo study of molecular weight distribution changes induced by degradation of ion beam irradiated polymers  

NASA Astrophysics Data System (ADS)

In this work we study a polymeric material that degrades upon irradiation due to the energy inhomogeneously deposited by heavy ion beams. Ion beam irradiation of polymers generates rather different effects than those induced by "classical" low ionizing particles such as electrons or gamma rays. This is due to the high electronic stopping power and the inhomogeneous distribution of deposited energy. This energy is transferred to the material within a small volume along the ion path forming the so called "nuclear track" or "latent track". The track size primarily depends on the ion velocity, and it is determined by the secondary electrons (delta rays) generated along the ion trajectory. By means of Monte Carlo simulations we first obtained equilibrated polymer configurations using a coarse-grained model, and then investigated the spatially inhomogeneous chain scission process due to the passage of the ions. The number average molecular weight, weight average molecular weight and the polydispersity were calculated as a function of track radius, scission probability within the ion track and irradiation fluence. Finally we compared our results with a numerical implementation of a model for random homogeneous degradation.

Chappa, V. C.; Pastorino, C.; del Grosso, M. F.; Arbeitman, C. R.; Müller, M.; García Bermúdez, G.

2010-10-01

391

Differential cross-section measurements of multiply charged xenon ions produced in 10-28keV eXe collisions  

Microsoft Academic Search

Partial single-differential ionization cross sections (PSDICSs) of a multiply ionized xenon atom ( Xen+ , n=1-7 ) are measured for impact of 10-28keV electrons with xenon by performing coincidences between the produced recoil ions and the electrons of indiscriminated energies detected at 90° with respect to the incident electron beam direction. Values of relative PSDICSs for doubly charged ions are

S. Mondal; R. Shanker

2005-01-01

392

Fabricating high-density magnetic storage elements by low-dose ion beam irradiation  

SciTech Connect

We fabricate magnetic storage elements by irradiating an antiferromagnetically coupled ferromagnetic/nonmagnetic/ferromagnetic trilayer by a low-dose ion beam. The irradiated areas become ferromagnetically coupled and are capable of storing information if their size is small enough. We employ Fe/Cr/Fe trilayers and a 30 keV focused Ga{sup +}-ion beam to demonstrate the working principle for a storage array with a bit density of 7 Gbit/in.{sup 2}. Micromagnetic simulations suggest that bit densities of at least two magnitudes of order larger should be possible.

Neb, R.; Sebastian, T.; Pirro, P.; Hillebrands, B. [Fachbereich Physik and Research Center Optimas, Technische Universitaet Kaiserslautern, Erwin-Schroedinger-Strasse 56, 67663 Kaiserslautern (Germany); Pofahl, S.; Schaefer, R. [Leibniz-Institut fuer Festkoerper- und Werkstoffforschung Dresden, IFW Dresden, Helmholtzstrasse 20, 01069 Dresden (Germany); Reuscher, B. [Institut fuer Oberflaechen-und Schichtanalytik, IFOS, Trippstadter Strasse 120, 67663 Kaiserslautern (Germany)

2012-09-10

393

Tunable electronically anisotropic materials with ion-irradiated polysilanes on semiconductor  

NASA Astrophysics Data System (ADS)

Studies on tunable electronically anisotropic material on semiconductor, “TEAMS”, with a polysilane layer spin-coated onto a silicon wafer and then contacted on both top and rear sides, are reported in the present paper. This structure was irradiated with swift heavy ions, and its electrical characteristics were studied both during and after irradiation. It was found that the current/voltage characteristics depend on the ion fluence, the time of voltage application, the gating voltage, the ambient pressure, light, and the post-annealing temperature of the samples. Under specific conditions, a negative differential resistance was also exhibited. The observations are indicative of a peculiar conduction mechanism.

Fink, D.; Chandra, A.; Opitz-Coutureau, J.; Fahrner, W. R.; Hoppe, K.; Papaleo, R. M.

2007-03-01

394

Evaluation of Surface Damage of Organic Films due to Irradiation with Energetic Ion Beams  

SciTech Connect

The surface of L-leucine films irradiated with an Ar{sub 5000} cluster ion beam (5 keV) was characterized by using the X-ray reflective (XRR) measurement method, atomic force microscopy (AFM) and ellipsometry. No significant damage was detected on the surface of the L-leucine films irradiated with the Ar cluster ion beam. Therefore, the large cluster-low-energy (about 1 eV/atom) beam would be suitable for low-damage etching of organic materials.

Hada, Masaki; Hontani, Yusaku; Ichiki, Kazuya; Seki, Toshio [Department of Nuclear Engineering, Kyoto University, Sakyo, Kyoto, 606-8501 (Japan); Ibuki, Sachi; Ninomiya, Satoshi; Matsuo, Jiro [Quantum Science and Engineering Center, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Aoki, Takaaki [Department of Electronic Science and Engineering, Kyoto University, Nishigyo, Kyoto, 615-8530 (Japan)

2011-01-07

395

Grain growth kinetics during ion beam irradiation of chemical vapor deposited amorphous silicon  

SciTech Connect

The amorphous to polycrystal transition during Kr ion beam irradiation of chemical vapor deposited silicon layers has been studied in the temperature range 320--480 {degree}C. At each irradiation temperature the average grain diameter increases linearly with the Kr dose, while the grain density remains constant within the experimental accuracy. The growth rate follows a complex behavior which can be described by dynamic defect generation and annihilation. The absolute value of the grain growth rate is equal to that of the ion-assisted epitaxial layer by layer crystallization in the silicon (111) orientation. This result can be related to the crystal grain structure and morphology.

Spinella, C.; Lombardo, S. (Istituto di Metodologie e Tecnologie per la Microelettronica, CNR, corso Italia 57, I 95129 Catania (Italy)); Campisano, S.U. (Dipartimento di Fisica dell'Universita, corso Italia 57, I 95129 Catania (Italy))

1990-08-06

396

Enhancement of ferromagnetism in Pd nanoparticle by swift heavy ion irradiation  

SciTech Connect

In this study, the effect of swift heavy ion irradiation on the magnetic properties of the Pd nanoparticles has been investigated. Structural investigations along with superconducting quantum interface device measurements show that ferromagnetic properties of the Pd nanoparticles are due to the deviation of their electronic structure from that of bulk. The electronic structure is further modified due to the creation of defects on ion irradiation, which results in 20 times increase in the saturation magnetization. The present study establishes that the defect induced modification of Pd 4d electronic structure is responsible for the ferromagnetic properties of the Pd nanoparticles.

Kulriya, P. K. [Department of Physics, Thin Film Laboratory, Indian Institute of Technology, New Delhi 110 016 (India); Inter-University Accelerator Centre, Aruna Asaf Ali Road, New Delhi 110067 (India); Mehta, B. R. [Department of Physics, Thin Film Laboratory, Indian Institute of Technology, New Delhi 110 016 (India); Avasthi, D. K.; Agarwal, D. C. [Inter-University Accelerator Centre, Aruna Asaf Ali Road, New Delhi 110067 (India); Thakur, P.; Brookes, N. B. [European Synchrotron Radiation Facility (ESRF), BP 220, F-38043 Grenoble Cedex (France); Chawla, A. K.; Chandra, R. [Nanoscience Laboratory, Institute Instrumentation Centre, Indian Institute of Technology Roorkee, Roorkee 247667 (India)

2010-02-01

397

Application of WAXS diffraction in studies of crystallinity changes in heavy-ion-irradiated polyester films  

NASA Astrophysics Data System (ADS)

WAXS diffraction was applied in studies of the effect of heavy ion irradiation on the content of crystalline phase in poly(ethyleneterephthalate) (PET) and poly(butyleneterephthalate)(PBT) films. A decrease of the crystalline phase content in PET and PBT films under the effect of heavy ions irradiation was discovered. The phenomenon was observed in the biaxially oriented 19 (mu) m thick PET film as well as in the non-oriented 90-100 (mu) m thick PET and PBT films. The amorphization of the films was confirmed by SAXS, DSC, and FTIR methods as well as by density measurements.

Ciesla, Krystyna

2000-09-01

398

Impacts of Ion Irradiation on Hafnium oxide-based Resistive Random Access Memory Devices  

NASA Astrophysics Data System (ADS)

The impacts of ion irradiation on so-called vacancy-change mechanism (VCM) and electrochemical-metallization mechanism (ECM) ReRAM devices based on HfO2 are investigated using various ion sources: H + (1 MeV), He+ (1 MeV), N+ (1 MeV), Ne+ (1.6 MeV) and Ar+ (2.75 MeV) over a range of total doses (105 -- 1011 rad(Si)) and fluences (1012 -- 1015 cm-2). VCM-ReRAM devices show robust resistive switching function after all irradiation experiments. VCM resistive switching parameters including set voltage (V set), reset voltage (Vreset), on-state resistance (R on) and off-state resistance (Roff) exhibited, in most cases, modest changes after irradiation. Decreases in forming voltage (Vf) and initial resistance (Rfresh) of fresh devices were observed after all irradiation experiments on VCM-ReRAM devices with the exception of Ar+ irradiation at the highest fluence (10 15 cm-2). In that case Rfresh increased by an order of magnitude. For VCM-ReRAM devices it was also observed that irradiation beyond a dose threshold of approximately 5 Grad(Si) could induce off-to-on state transition events. This behavior could lead to errors in a VCM-ReRAM memory system. ECM-ReRAM devices (based on HfO2) were also subjected to ion irradiation. Under proton irradiation ECM-ReRAM devices remained functional, but with relatively large positive variations (20-40%) in Vset, Vreset and Ron and large negative variations (˜ -60%) in Roff. In contrast to VCM HfO2-ReRAMs, ECM-based devices exhibited increased V f after irradiation, and no off-to-on transitions were observed. Interestingly, for ECM-ReRAM devices, high-fluence Ar irradiation resulted in a transition of the electrical conduction mechanism associated with the conductive filament forming process from a Poole-Frenkel conduction mechanism (pre-irradiation) to ionic conduction (post-Ar irradiation). ECM-ReRAM devices irradiated with lighter ions did not exhibit this effect. The different ion irradiation responses of the two types of HfO2-ReRAMs studied originate from their distinct switching mechanisms -- vacancy filament switching for VCM-ReRAMs and metal filament switching for ECM-ReRAMs -- which respond differently to the irradiation-induced changes in the vacancy/defect densities and crystallite structures in HfO2. SRIM (Stopping and Range of Ions in Matter) modeling was used to roughly estimate the density of irradiation-induced vacancies. These model results correlated well with experimental observations in terms of vacancy defect density thresholds sufficient to impact ReRAM switching behavior. Physical characterization of pre- and post-irradiation ReRAM devices using techniques including XRD, AES, SEM, EDS, and SIMS were also employed to support the modeling and electrical measurements. This work suggests that HfO2-based ReRAM devices are a promising candidate for space and nuclear applications requiring a 'radiation-hard' memory technology.

He, Xiaoli

399

Incorporation of the effect of the composite electric fields of molecular ions as a simulation tool for biological damage due to heavy ion irradiation II  

SciTech Connect

This paper presents a theoretical study of the DNA damage due to the effect of the composite electric fields of H{sub 2}O{sup +} ions produced from the irradiation of a heavy ion onto a cell. It is found that a much larger number of electrons, which are produced from electron impact ionization, is trapped near the track of an incident ion in the case of C{sup 6+} ion irradiation with the energy of 3 MeV/u than that of proton irradiation. Therefore, the irradiation of carbon ions may produce a larger number of cluster DNA damage than that in the irradiation of protons. This may lead to the understanding of relative biological effectiveness (RBE).

Moribayashi, Kengo [Quantum Beam Science Directorate, Japan Atomic Energy Agency, 8-1-7, Umemidai, Kizugawa-city, 619-0215 (Japan) and Faculty of Life and Medical Sciences, Doshisha University, 1-3 Tatara Miyakodani, Kyotanabe City, 610-0394 (Japan)

2012-07-11

400

Magnetic anisotropy and domain patterning of amorphous films by He-ion irradiation  

SciTech Connect

The magnetic anisotropy in amorphous soft magnetic FeCoSiB films was modified by He-ion irradiation. A rotation of uniaxial anisotropy depending on the applied field direction in the irradiated areas is observed by magnetometry and complementary domain observation by Kerr microscopy. No significant degradation in magnetic properties relative to the as-deposited state is found from the magnetization loops on nonpatterned films. Using irradiation together with photolithography, the films were treated locally, resulting in 'anisotropy patterned' structures. Complicated periodic domain patterns form due to the locally varying anisotropy distribution. Overall magnetic properties and domain patterns are adjusted.

McCord, Jeffrey; Gemming, Thomas; Schultz, Ludwig; Fassbender, Juergen; Liedke, Maciej Oskar; Frommberger, Michael; Quandt, Eckhard [Leibniz Institute for Solid State and Materials Research IFW Dresden, Helmholtzstrasse 20, 01069 Dresden (Germany); Institut fuer Ionenstrahlphysik und Materialforschung, Forschungszentrum Rossendorf, Bautzner Landstrasse 128, 01328 Dresden (Germany); Research Center CAESAR, Ludwig-Erhard-Allee 2, 53175 Bonn (Germany)

2005-04-18

401

Ion irradiation induced enhancement of out-of-plane magnetic anisotropy in ultrathin Co films  

SciTech Connect

Ga{sup +} or He{sup +} irradiated MBE grown ultrathin films of sapphire/Pt/Co(d{sub Co})/Pt(d{sub Pt}) were studied using polar Kerr effect in wide ranges of both cobalt d{sub Co} and platinum d{sub Pt} thicknesses as well as ion fluences F. Two branches of increased magnetic anisotropy and enhanced Kerr rotation angle induced by Ga{sup +} or He{sup +} irradiation are clearly visible in two-dimensional (d{sub Co}, LogF) diagrams. Only Ga{sup +} irradiation induces two branches of out-of-plane magnetization state.

Mazalski, P.; Kurant, Z.; Maziewski, A. [Faculty of Physics, University of Bialystok, Bialystok (Poland); Liedke, M. O.; Fassbender, J. [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Baczewski, L. T.; Wawro, A. [Institute of Physics, Polish Academy of Science, Warszawa (Poland)

2013-05-07

402

Effect of titanium ion irradiation on the surface and defect centre formation in sapphire  

NASA Astrophysics Data System (ADS)

Swift titanium ion irradiation was carried out on sapphire (Al 2O 3: Fe, Ti, Cr) to study optical properties of defect centers and surface topography of modified sapphire using UV-visible absorption spectroscopy, photoluminescence (PL) and atomic force microscopy (AFM) techniques. Single crystals of sapphire were irradiated at room temperature with different fluence of 100 MeV Ti ions. The PL spectra showed three emission bands centred at 2.56 (480 nm), 2.45 (504 nm) and 2.31 eV (535 nm) assigned to F + centre, F 2 centre and F 22+ defect centre, respectively. The intensity of these bands was found to change with fluence. R lines of Cr 3+ ion impurity, though weak in pristine sample, grew tremendously on ion irradiation. The changes in the intensity of R lines are correlated with the Cr 3+-defect centre pair formation. Both bands and lines showed downward trend at higher fluence but at a different fluence value. Results are interpreted in terms of creation of defect centres, aggregation/cluster formation, diffusion or radiation induced annihilation of the defects. The defect centres (F 2+ and F 22+) and R-line of Cr 3+ ions were observed in optical spectra and their behaviour upon irradiation is also discussed in terms of dense ionization. The behaviour of bands corresponding to the electronic transitions of Fe 2+/Ti 4+ ions in the presence of oxygen vacancies, observed in optical spectra, are discussed in terms of dense ionization. The hillocks like structures were developed on the surface of irradiated sapphires. Their concentration, height and area are correlated with the ion beam fluence.

Jheeta, K. S.; Jain, D. C.; Ravi Kumar; Garg, K. B.

2007-12-01

403

Activated Ion Electron Capture Dissociation (AI ECD) of Proteins: Synchronization of Infrared and Electron Irradiation with Ion Magnetron Motion  

PubMed Central

Here, we show that to perform activated ion electron capture dissociation (AI-ECD) in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer equipped with a CO2 laser, it is necessary to synchronize both infrared irradiation and electron capture dissociation with ion magnetron motion. This requirement is essential for instruments in which the infrared laser is angled off-axis, such as the Thermo Finnigan LTQ FT. Generally, the electron irradiation time required for proteins is much shorter (ms) than that required for peptides (tens of ms), and the modulation of ECD, AI ECD, and infrared multiphoton dissociation (IRMPD) with ion magnetron motion is more pronounced. We have optimized AI ECD for ubiquitin, cytochrome c, and myoglobin; however the results can be extended to other proteins. We demonstrate that pre-ECD and post-ECD activation are physically different and display different kinetics. We also demonstrate how, by use of appropriate AI ECD time sequences and normalization, the kinetics of protein gas-phase refolding can be deconvoluted from the diffusion of the ion cloud and measured on the time scale longer than the period of ion magnetron motion.

Mikhailov, Victor A.; Cooper, Helen J.

2009-01-01

404

Evaluation of surface damage on organic materials irradiated with Ar cluster ion beam  

NASA Astrophysics Data System (ADS)

The sputtering yields of organic materials under large cluster ion bombardment are much higher than those under conventional monomer ion bombardment. The sputtering rate of arginine remains constant with fluence for an Ar cluster ion beam, but decreases with fluence for Ar monomer. Additionally, because Ar cluster etching induces little damage, Ar cluster ion can be used to achieve molecular depth profiling of organic materials. In this study, we evaluated the damage to poly methyl methacrylate (PMMA) and arginine samples irradiated with Ar atomic and Ar cluster ion beams. Arginine samples were analyzed by secondary ion mass spectrometry (SIMS) and PMMA samples were analyzed by X-ray photoelectron spectroscopy (XPS). The chemical structure of organic materials remained unchanged after Ar cluster irradiation, but was seriously damaged. These results indicated that bombardment with Ar cluster ions induced less surface damage than bombardment with Ar atomic ion. The damage layer thickness with 5 keV Ar cluster ion bombardment was less than 1 nm.

Yamamoto, Y.; Ichiki, K.; Ninomiya, S.; Seki, T.; Aoki, T.; Matsuo, J.

2011-01-01

405

Damage Profiles and Ion Distribution in Pt-irradiated SiC  

SciTech Connect

Single crystalline 6H-SiC samples were irradiated at 150 K with 2 MeV Pt ions. The local volume swelling was determined by electron energy loss spectroscopy (EELS), and a nearly sigmoidal dependence on irradiation dose is observed. The disorder profiles and ion distribution were determined by Rutherford backscattering spectrometry (RBS), transmission electron microscopy, and secondary ion mass spectrometry. Since the volume swelling reaches 12% over the damage region at high ion fluence, the effect of lattice expansion is considered and corrected for in the analysis of RBS spectra to obtain depth profiles. Projectile and damage profiles are estimated by SRIM (Stopping and Range of Ions in Matter).When compared with the measured profiles, the SRIM code predictions of ion distribution and the damage profiles are underestimated due to significant overestimation of the electronic stopping power for the slow heavy Pt ions. By utilizing the reciprocity method, which is based on the invariance of the inelastic energy loss in ion-solid collisions against interchange of projectile and target atom, a much lower electronic stopping power is deduced. A simple approach, based on reducing the density of SiC target in SRIM simulation, is proposed to compensate the overestimated SRIM electronic stopping power values, which results in improved agreement between predicted and measured damage profiles and ion ranges.

Xue, Haizhou; Zhang, Yanwen; Zhu, Zihua; Zhang, Weiming; Bae, In-Tae; Weber, William J.

2012-09-01

406

Damage Profiles and Ion Distribution in Pt-irradiated SiC  

SciTech Connect

Single crystalline 6H-SiC samples were irradiated at 150 K using 2MeV Pt ions. Local volume swelling is determined by electron energy loss spectroscopy (EELS), a nearly sigmoidal dependence with irradiation dose is observed. The disorder profiles and ion distribution are determined by Rutherford backscattering spectrometry (RBS), transmission electron microscopy and secondary ion mass spectrum. Since the volume swelling reaches 12% over the damage region under high ion fluence, lattice expansion is considered and corrected during the data analysis of RBS spectra to obtain depth profiles. Projectile and damage profiles are estimated by SRIM (Stopping and Range of Ions in Matter). Comparing with the measured profiles, SRIM code significantly overestimates the electronic stopping power for the slow heavy Pt ions, and large derivations are observed in the predicted ion distribution and the damage profiles. Utilizing the reciprocity method that is based on the invariance of the inelastic excitation in ion atom collisions against interchange of projectile and target, much lower electronic stopping is deduced. A simple approach based on reducing the density of SiC target in SRIM simulation is proposed to compensate the overestimated SRIM electronic stopping power values. Better damage profile and ion range are predicted.

Xue, Haizhou [University of Tennessee, Knoxville (UTK); Zhang, Yanwen [ORNL; Zhu, Zihua [Pacific Northwest National Laboratory (PNNL); Zhang, Weiming [Peking University; Bae, Dr. In-Tae [State University of New York, Binghamton; Weber, William J [ORNL

2012-01-01

407

75 MeV boron ion irradiation studies on Si PIN photodiodes  

NASA Astrophysics Data System (ADS)

The highly sensitive silicon PIN photodiodes were fabricated to use in radiation environments. The Si PIN photodiodes are coated with 150 nm silicon dioxide (SiO2) as anti-reflective (AR) coating. The presence of AR coating on the performance of irradiated PIN photodiodes is studied up to a total dose of 10 Mrad. The effects of 75 MeV boron (B5+) ions and 60Co gamma radiation on the I-V, C-V and spectral responses of PIN photodiodes were studied systematically to understand the radiation tolerance of the devices. The 75 MeV B5+ irradiation results are compared with 60Co gamma irradiated results in the same dose range for 1 mm × 1 mm and 10 mm × 10 mm active area PIN photodiodes. The irradiation results show that the ion irradiated PIN photodiodes show more degradation when compared 60Co gamma irradiated devices. The irradiation results are presented in this paper and the possible mechanism behind the degradation of photodiodes is also discussed in the paper.

Prabhakara Rao, Y. P.; Praveen, K. C.; Rejeena Rani, Y.; Tripathi, Ambuj; Gnana Prakash, A. P.

2013-12-01

408

Irradiation of ionic liquid ion beams on silicon and glass substrates  

NASA Astrophysics Data System (ADS)

Irradiation of an ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6) ion beam on borosilicate glass and single crystalline Si(100) surface was demonstrated by using an ionic liquid ion source we developed. Surface smoothing on the glass substrates was produced by the irradiations at an acceleration voltage of 4 kV with both positive and negative ion beams, which include cation-anion pairs attached to a single ion of either polarity. Water contact angle measurements and X-ray photoelectron spectroscopy indicated that the surface smoothing was probably caused by surface modification involving nano-ordered chemical etching by Si-F reaction, implantation and deposition of P, N and C.

Takeuchi, Mitsuaki; Hamaguchi, Takuya; Ryuto, Hiromichi; Takaoka, Gikan H.

2013-11-01

409

The effect of solutes on defect distributions in ion-irradiated model LWR pressure vessel steels  

SciTech Connect

A series of nine model LWR pressure vessel steels were ion irradiated at 300 C using 2.5-MeV He ions, to a dose of 1.4x10{sup 17} ion/cm{sup 2}, corresponding to about 0.1 dpa at a depth of 2 {mu}m and about 3.5 dpa at the peak damage region which occurs at about 4 {mu}m deep. Resultant changes in hardness vs depth were measured using a Nanoindenter {reg_sign}. TEM was used to investigate the defect distributions. Effects of various solutes, Cu and N in particular, but Mn and Ti as well, on change of hardness and defect distribution due to ion irradiation are discussed.

Rice, P.M.; Stoller, R.E.

1996-10-01

410

Graphitic nanostripes in silicon carbide surfaces created by swift heavy ion irradiation.  

PubMed

The controlled creation of defects in silicon carbide represents a major challenge. A well-known and efficient tool for defect creation in dielectric materials is the irradiation with swift (Ekin?500?keV/amu) heavy ions, which deposit a significant amount of their kinetic energy into the electronic system. However, in the case of silicon carbide, a significant defect creation by individual ions could hitherto not be achieved. Here we present experimental evidence that silicon carbide surfaces can be modified by individual swift heavy ions with an energy well below the proposed threshold if the irradiation takes place under oblique angles. Depending on the angle of incidence, these grooves can span several hundreds of nanometres. We show that our experimental data are fully compatible with the assumption that each ion induces the sublimation of silicon atoms along its trajectory, resulting in narrow graphitic grooves in the silicon carbide matrix. PMID:24905053

Ochedowski, Oliver; Osmani, Orkhan; Schade, Martin; Bussmann, Benedict Kleine; Ban-d'Etat, Brigitte; Lebius, Henning; Schleberger, Marika

2014-01-01

411

Understanding the role of heavy ion-irradiation induced surface columnar nanostructures through FESEM imaging  

Microsoft Academic Search

In this paper we report on the effects of “surface columnar defects” (blind holes) generated by heavy ion irradiation by performing Field Emission Scanning Electron Microscopy (FESEM) imaging of the columns created across a selected set of specimens, ranging from YBa2Cu3O7?x melt-textured bulks and Bi2Sr2Ca2Cu3Ox monofilamentary tapes to YBa2Cu3O7?x single crystals. Different ion fluences, resulting into modifying the superconducting properties,

Angelica Chiodoni; Francesco Laviano; Roberto Gerbaldo; Gianluca Ghigo; Laura Gozzelino; Enrica Mezzetti; Bruno Minetti; Wai K. Kwok

2010-01-01

412