Xe Ion Irradiation Research Articles

Anisotropic nanocrystallization of a Zr-based metallic glass induced by Xe ion irradiation

Structural modification in a Zr-based metallic glass caused by irradiation with 7 MeV Xe26+ ions was investigated. Needle-like nanocrystalline structures, formed under ion irradiation, consist of Cu10Zr7 phase (primary) and/or minor (NixCu1−x)10Zr7 phase. The formation of needle-like nanocrystals suggested an anisotropic atomic diffusion caused by ion irradiation.

TiO2 films photocatalytic activity improvements by swift heavy ions irradiation

TiO2 thin films synthesized by sol–gel on glass substrates are irradiated by 90MeV 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 5×1012ions/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 1013Xe/cm2 exhibit the highest photoactivity; 69% of chromate (10ppm) is reduced at pH ~3 after 4h of exposure to sunlight (1120mWcm−2) with a quantum yield of 0.06%.

Ion-induced phase transformations in nanostructural TiZrAlN films

(Ti,Zr)1−xAlxNy thin films (300nm) with Ti:Zr ratio of ~1:1 and Al content in metal sublattice up to x=0.312 were deposited at Ts=270°C using reactive unbalanced magnetron co-sputtering in Ar+N2 plasma discharges. The nitrogen content, y, was understoichiometric when x≥0.102, despite constancy of N2 partial pressure used during growth. The influence of Xe ion irradiation (180keV, 1×1015−1×1017cm−2) on the structure, phase formation and mechanical properties of the films was investigated. The increase in Al content resulted in gradual evolution of the microstructure from single-phase, nanocrystalline cubic (c) solid solution (x≤0.072) to dual-phase nanocomposite (x=0.102–0.200) and then to amorphous (x=0.312) one. Nanocrystalline and amorphous films were stable under irradiation, while crystallization occurred in nanocomposite films for a typical ion fluence of 1×1016cm−2. This phase transformation is associated with the reduction of compressive stress and eventually leads to the development of a net tensile stress inside crystallites. For all films, a decrease of the nanoindentation hardness was observed after an ion fluence of 5×1016cm−2, likely related to the incorporation of Xe impurities, as revealed by RBS data.

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

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

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

The implantation-synthesized Cu nanoparticles (NPs) in silica were irradiated with 500keV 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 8.5nm, and especially, Cu NPs with a diameter of 11–14nm 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.

Direct characterization of ion implanted pyrolytic carbon coatings deposited from natural gas

Isotropic pyrolytic carbon (IPyC) prepared at 1300°C by chemical vapor deposition was implanted with 129Xe26+ ions to obtain a wide range of information and understanding about the coating materials in nuclear energy field. Microstructure of the pristine and ion-implanted IPyC on nuclear graphite substrate was firstly investigated using polarized light microscopy, scanning and transmission electron microscopy, X-ray diffraction, Raman spectroscopy, nanoindentation, and X-ray photoemission spectroscopy. It was demonstrated that the Xe ion irradiation resulted in concurrent changes in both physical and chemical structures of our standard polycrystalline sample. Influences of the thermal annealing temperature on the properties of the implanted IPyC at 500 and 1000°C were also studied. Ion-irradiation gave rise to the formation of structural deterioration along a and c axis, accompanying with the appearance of widespread clastic morphology among the irradiated zone of IPyC. There was a dose window that could be used to tune the mechanical properties of IPyC: the nanohardness and Young’s modulus increased after an irradiation, but decreased as the amorphization was reached.

Propagation of ripple patterns on Si during ion bombardment

The lateral propagation of surface ripples on Si, generated by Xe ion irradiation with and without codeposition of Fe surfactant atoms, was investigated by scanning electron microscopy with the help of micron-sized marker structures prepared by focused ion beam milling. For 10-keV Xe ion irradiation of Si at oblique incidence between 62 and 70\ifmmode^\circ\else\textdegree\fi{}, we determine lateral ripple propagation velocities varying from \ensuremath{-}1.9 to $+$2.9 nm per 10${}^{15}$ Xe ions/cm${}^{2}$. The propagation direction changes from opposite to the projected direction of the incident ion beam to along the projected beam direction within a narrow angular regime. At 67\ifmmode^\circ\else\textdegree\fi{}, the pattern is almost static. The result is in good agreement with predictions from the theoretical model of Bradley and Harper. For perpendicular incident 5-keV Xe ions and oblique codeposition of Fe surfactant atoms, we find that ripple patterns propagate across the surface with a negative ripple propagation velocity of about \ensuremath{-}0.7 nm per 10${}^{15}$ Xe ions/cm${}^{2}$, i.e., opposite to the projected deposition direction of Fe surfactant atoms. The novel experimental method to determine the lateral ripple propagation based on markers set with a focused ion beam system does not require an in situ analysis and can therefore be applied in general to analyze the dynamics of ion beam-induced patterns.

Enhanced Sputtering Yields from Single-Ion Impacts on Gold Nanorods

Sputtering yields, enhanced by more than an order of magnitude, have been observed for 80keV Xe ion irradiation of monocrystalline Au nanorods. Yields are in the range 100-1900 atoms/ion compared with values for a flat surface of ≈50. This enhancement results in part from the proximity of collision cascades and ensuing thermal spikes to the nanorod surfaces. Molecular dynamic modeling reveals that the range of incident angles occurring for irradiation of nanorods and the larger number of atoms in "explosively ejected" atomic clusters make a significant contribution to the enhanced yield.

Comparison of radiation and quenching rate effects on the structure of a sodium borosilicate glass

The effects of quenching rate and irradiation on the structure of a sodium borosilicate glass were compared using 29Si, 11B, and 23Na nuclear magnetic resonance and Raman spectroscopy. Quenching rate ranging from 0.1 to 3×104Kmin−1 was studied. Various irradiation conditions were performed, i.e. gold-ion irradiation in a multi-energy mode (from 1 to 6.75MeV), and Kr and Xe ion irradiations with energy of 74 and 92MeV, respectively. In pile irradiation with thermal neutron flux was performed as well, to study the effect of alpha radiation from the nuclear reaction 10B(n,α)7Li.Both irradiation and high quenching rate induce similar local order modification of the glass structure, mainly a decrease of the mean boron coordination and an increase of Q3 units. Nevertheless, the variations observed under irradiation are more pronounced than the ones induced by the quenching rate. Moreover, some important modifications of the glass medium range order, i.e. the emergence of the D2 band associated to three members silica rings and a modification of the Si–O–Si angle distribution were only noticed after irradiation. These results suggest that the irradiated structure is certainly not exactly the one obtained by a rapidly quenched equilibrated melt, but rather a more disordered structure that was weakly relaxed during the very rapid quenching phase following the energy deposition step.Raman spectroscopy showed a similar irradiated structure whereas the glass evolutions were controlled by the electronic energy loss in the ion track formation regime for Kr-ion irradiation or by the nuclear energy loss for Au and OSIRIS irradiation. The similar irradiated structure despite different irradiation routes, suggests that the final structural state of this sodium borosilicate glass is mainly controlled by the glass reconstruction after the energy deposition step.

Radiation stability of the ODS alloys against swift heavy ion impact

The microstructure of Cr16 ferritic steel reinforced with yttrium oxide particles and KP4 ODS alloy irradiated with 167MeV xenon and 700MeV bismuth ions at 300K has been studied using high resolution transmission electron microscopy. Amorphous latent tracks were identified in (Cr,W)23C6, Y2Ti2O7 and Y2TiO5 nanoparticles in Cr16 at a Bi ion fluence of 1.5×1012cm−2. It was found that multiple track overlapping leads to complete amorphization of carbide and (Y,Ti) oxide particles in Cr16 specimens. No latent tracks have been observed in Y4Al2O9 particles in KP4 irradiated with Bi ions. Small oxide particles (∼5nm), in KP4 alloy, remain crystalline at Bi ion fluences up to 1.5×1013cm−2, while subsurface regions in large (∼20nm) particles were amorphized. Xe ion irradiation at fluences of 1×1014cm−2 and 1.5×1015cm−2 resulted in amorphization of small Y4Al2O9 oxide particles while the amorphous bodies of large particles were found to contain small crystalline inclusions.

Radiation damage in multiphase ceramics

Four-phase ceramic composites containing 3mol% Y2O3 stabilized ZrO2 (3Y-TZP), Al2O3, MgAl2O4, and LaPO4 were synthesized as model materials representing inert matrix fuel with enhanced thermal conductivity and decreased radiation-induced microstructural damage with respect to single-phase UO2. This multi-phase concept, if successful, could be applied to design advanced nuclear fuels which could then be irradiated to higher burn-ups. 3Y-TZP in the composite represents a host (fuel) phase with the lowest thermal conductivity and Al2O3 is the high thermal conductivity phase. The role of MgAl2O4 and LaPO4 was to stabilize the structure under irradiation. The radiation response was evaluated by ion irradiation at 500°C with 10MeV Au ions and at 800°C with 92MeV Xe ions, to simulate damage due to primary knock-on atoms and fission fragments, respectively. Radiation damage and microstructural changes were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy and computational modeling. Al2O3, Y2O3 stabilized ZrO2 and MgAl2O4 phases exhibit high amorphization resistance and remain stable when irradiated with both Au and Xe ions. A monoclinic-to-tetragonal phase transformation, however, is promoted by Xe and Au ion irradiation in 3Y-TZP. The LaPO4 monazite phase appears to melt, dewet the other phases, and recrystallize under Au irradiation, but does not change under Xe irradiation.

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

We have studied the effect of 200MeV 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.

Phase transformations in Y2O3 thin films under swift Xe ions irradiation

Yttrium oxide (Y2O3) thin films deposited on silicon (Si) by an ion beam sputtering technique have been irradiated by 92MeV 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.

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

TiO2 films prepared by sol–gel were irradiated with 25.8MeV Cu and 90MeV 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 (101) peak intensity decrease with increasing the fluence and disappear completely above a threshold ion fluence of 5×1012ion/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 4nm after irradiation with 25.8MeV Cu and 90MeV 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 200–500nm. 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 780nm×780nm area scans decreases exponentially with increasing fluence up to 1013ions/cm2 in the case of Xe irradiation, but increases drastically above 2.68×1011ions/cm2 in the case of Cu ion irradiation and reaches a mean value of ∼3nm. The absorption measurements reveal that the optical band gap is not affected by both Xe and Cu ions irradiation.

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

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.

Effect of swift heavy ion irradiation on transformations of oxide nanoclusters in ODS alloys

AbstractMicrostructure of Cr16 ferritic steel reinforced with yttrium oxide particles and KP4 oxide dispersion strengthened (ODS) alloy irradiated with 167 MeV xenon and 700 MeV bismuth ions at 300 K has been studied using high resolution transmission electron microscopy. It was found that Bi ion irradiation at fluences more than 1013 cm‐2 leads to complete amorphization of oxide particles in Cr16 samples, while central regions of large (∼20 nm) particles and small oxides (∼5 nm) in KP4 steel remain crystalline. The Xe ion irradiation effect consists in polycrystallization of single crystalline oxide particles. Small oxide particles at 1.5×1015 Xe×cm‐2 are fragmented to quasi‐amorphous state. No dissolution of nanoparticles has been revealed in all studied samples. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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

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. 300keV and 400keV 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 4×1016ions/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.

Electrophysical and Optical Properties of 4H-SiC Irradiated with Xe Ions

A comparative research of the cathodoluminescence and electrical characteristics of the samples 4H-SiC irradiated with high energy Xe ions (167 MeV) in wide range fluencies 4x109 –1x1011 cm-2 at temperatures 250C and 5000C are presented. After irradiation these samples were thermal annealed at 5000C for 30 min. Far-action effect at a depth of more than one order of magnitude of stopping distance was observed under Xe ions irradiation in 4H-SiC. An increase of the ion Xe fluencies increased the concentration of radiation-induced defects that resulted in rise of the compensation effect of conductivity in samples. Irradiation of 4H-SiC by Xe ions at 5000C was accompanied with "dynamic annealing" some low-temperature radiation-induced defects, which led to a partial recovery of the electrical characteristics of devices. The thermal annealing of irradiated samples led to additional partial annealing of radiation defects, which increases the radiation resource of devices based on 4H-SiC.

Sharp transition from ripple patterns to a flat surface for ion beam erosion of Si with simultaneous co-deposition of iron

We investigate pattern formation on Si by sputter erosion under simultaneous co-deposition of Fe atoms, both at off-normal incidence, as function of the Fe surface coverage. The patterns obtained for 5 keV Xe ion irradiation at 30° incidence angle are analyzed with atomic force microscopy. Rutherford backscattering spectroscopy of the local steady state Fe content of the Fe-Si surface layer allows a quantitative correlation between pattern type and Fe coverage. With increasing Fe coverage the patterns change, starting from a flat surface at low coverage (< 2×1015 Fe/cm2) over dot patterns (2-8×1015 Fe/cm2), ripples patterns (8-17×1015 Fe/cm2), pill bug structures (1.8×1016 Fe/cm2) and a rather flat surface with randomly distributed weak pits at high Fe coverage (>1.8×1016 Fe/cm2). Our results confirm the observations by Macko et al. for 2 keV Kr ion irradiation of Si with Fe co-deposition. In particular, we also find a sharp transition from pronounced ripple patterns with large amplitude (rms roughness ∼ 18 nm) to a rather flat surface (rms roughness ∼ 0.5 nm). Within this transition regime, we also observe the formation of pill bug structures, i.e. individual small hillocks with a rippled structure on an otherwise rather flat surface. The transition occurs within a very narrow regime of the steady state Fe surface coverage between 1.7 and 1.8×1016 Fe/cm2, where the composition of the mixed Fe-Si surface layer of about 10 nm thickness reaches the stoichiometry of FeSi2. Phase separation towards amorphous iron silicide is assumed as the major contribution for the pattern formation at lower Fe coverage and the sharp transition from ripple patterns to a flat surface.

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

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.