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Publikationen - Ionenstrahlbeschleuniger

Hier finden Sie aktuelle Veröffentlichungen, die aus Nutzerexperimenten und Kollaborationen mit unserer Gruppe entstanden sind.

Jahr ab 2020
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Temperature Effects of Nuclear and Electronic Stopping Power on Si and C Radiation Damage in 3C-SiC

Kucal, E.; Józwik, P.; Mieszczynski, C.; Heller, R.; Akhmadaliev, S.; Dufour, C.; Czerski, K.

Abstract

Silicon carbide has been considered a material for use in the construction of advanced hightemperature
nuclear reactors. However, one of the most important design issues for future reactors is
the development of structural defects in SiC under a strong irradiation field at high temperatures. To
understand how high temperatures affect radiation damage, SiC single crystals were irradiated at
room temperature and after being heated to 800 °C with carbon and silicon ions of energies ranging
between 0.5 and 21 MeV. The number of displaced atoms and the disorder parameters have been
estimated by using the channeling Rutherford backscattering spectrometry. The experimentally
determined depth profiles of induced defects at room temperature agree very well with theoretical
calculations assuming its proportionality to the electronic and nuclear-stopping power values. On
the other hand, a significant reduction in the number of crystal defects was observed for irradiations
performed at high temperatures or for samples annealed after irradiation. Additionally, indications
of saturation of the crystal defect concentration were observed for higher fluences and the irradiation
of previously defected samples.

Keywords: radiation damage; stopping power; Rutherford backscattering; ion channeling

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Permalink: https://www.hzdr.de/publications/Publ-40896


Microstructural Investigation of Au Ion-Irradiated Eu-Doped LaPO4 Ceramics and Single Crystals

Gilson, S.; Svitlyk, V.; Bukaemskiy, A. A.; Niessen, J.; Lender, T.; Murphy, G. L.; Henkes, M.; Lippold, H.; Marquardt, J.; Akhmadaliev, S.; Hennig, C.; Winkler, B.; Tonnesen, T.; Peters, L.; Fischer, C.; Huittinen, N. M.

Abstract

To mimic radiation damage by recoiling nuclei following alpha-decay, ceramics and single crystals of LaPO4 monazite doped with Eu(III) were irradiated with 14 MeV Au5+ ions at three different fluences. The crystallinity, local coordination environments, and topography of the samples were probed using numerous methods including grazing-incidence X-ray diffraction (GIXRD), vertical scanning interferometry (VSI), scanning electron microscopy (SEM), Raman, and luminescence spectroscopy. GIXRD data collected from the irradiated regions of the ceramics revealed fluence dependent amorphization. A similar level of amorphization was detected for samples irradiated with 5×1013 ions/cm2 (fluence, F1) and 1×1014 ions/cm2 (F2), while a slightly lower contribution to the scattering signal from the amorphous part was obtained for the sample irradiated with the highest fluence of 1×1015 ions/cm2 (F3). VSI showed clear swelling of entire grains at the highest ion fluence, while more localized damage to grain boundaries was detected for ceramic samples irradiated at the lowest fluence. Single crystal specimens showed no pronounced topography changes following irradiation. SEM backscattered electron images revealed that the ceramic irradiated at the highest fluence exhibited topological features indicative of grain surface melting or softening and displacement of grains. Finally, Raman and luminescence data showed a different degree of disorder in polycrystalline vs. single crystal samples. While changes to PO4 stretching and bending vibrations could be observed in the ceramics, these changes were more subtle or not present in the single crystals. The opposite was observed when probing the local Ln-O environment using Eu(III) luminescence, where the larger changes in terms of an elongation of the Eu-O (or La-O) bond and an increasing relative disorder with increasing fluence were observed only for the single crystals. The dissimilar trends observed in irradiated single crystals and ceramics indicate that grain boundary chemistry likely plays a significant role in the radiation response.

Keywords: ion irradiation; damage; monazite; Raman; luminescence; grazing incidence diffraction; vertical scanning interferometry; scanning electron microscopy

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Permalink: https://www.hzdr.de/publications/Publ-38869


Grazing incidence synchrotron radiation diffraction studies on irradiated Ce-doped and pristine Y-stabilized ZrO2 at the Rossendorf Beamline

Svitlyk, V.; Braga Ferreira Dos Santos, L.; Niessen, J.; Gilson, S.; Marquardt, J.; Findeisen, S.; Richter, S.; Akhmadaliev, S.; Huittinen, N. M.; Hennig, C.

Abstract

Ce-doped yttria-stabilized zirconia (YSZ) and pure YSZ phases were subjected to irradiation with 14 MeV Au ions. The irradiation studies were performed to simulate long-term structural and microstructural damage due to self-irradiation in YSZ phases hosting alpha-active radioactive species. It was found that both the Ce-doped YSZ and YSZ phases were rather tolerant to irradiation at high ion fluences and the bulk crystallinity was well preserved. Nevertheless, local microstrain increased in all the studied compounds after the irradiation, with the Ce-doped phases being less affected than pure YSZ. Doping with cerium ions increased the microstructural stability of YSZ phases through a possible reduction in the mobility of oxygen atoms, which limits the formation of structural defects. Doping of YSZ with tetravalent actinide elements is expected to have a similar effect. Thus, YSZ phases are promising for the safe long-term storage of radioactive elements. Using synchrotron radiation diffraction, measurements of the thin irradiated layers of the Ce-YSZ and YSZ samples were performed in grazing incidence (GI) mode. A corresponding module for measurements in GI mode was developed at ROBL and relevant technical details of sample alignment and data collection are also presented.

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Permalink: https://www.hzdr.de/publications/Publ-37717


Microstructural characterization of reactor pressure vessel steels

Lai, L.; Chekhonin, P.; Akhmadaliev, S.; Brandenburg, J.-E.; Bergner, F.

Abstract

Ion irradiation is a promising tool to emulate neutron-irradiation effects on reactor pressure vessel (RPV) steels, especially in the situation of limited availability of suitable neu-tron-irradiated material. This approach requires the consideration of ion-neutron transferability issues, which are addressed in the present study by comparing the effect of ions with neu-tron-irradiation effects reported for the same materials. The first part of the study covers a com-prehensive characterization, based on dedicated electron microscopy techniques, of the selected unirradiated RPV materials, namely a base metal and a weld. The results obtained for the grain size, dislocation density and precipitates are put in context in terms of hardening contributions and sink strength. The second part is focused on the depth-dependent characterization of the dislocation loops formed in ion-irradiated samples. This work is based on scanning transmission electron microscopy applied to cross-sectional samples prepared by the focused ion beam tech-nique. A band-like arrangement of loops is observed in the depths range close to the peak of in-jected interstitials. Two levels of displacement damage, 0.1 and 1 dpa (displacements per atom), as well as post-irradiation annealed conditions are included for both RPV materials. Compared with neutron irradiation, ion irradiation creates a similar average size but a higher number density of loops presumably due to the higher dose rate during ion irradiation.

Keywords: reactor pressure vessel steels; microstructural characterization; ion irradiation; transmission electron microscope; dislocation loop

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Permalink: https://www.hzdr.de/publications/Publ-37302


Structural analyses of heavy-ion irradiated monazites

Huittinen, N. M.; Gilson, S.; Bukaemskiy, A.; Murphy, G. L.; Marquardt, J.; Lender, T.; Lippold, H.; Svitlyk, V.; Nießen, J.; Hennig, C.; Richter, S.; Akhmadaliev, S.; Poonoosamy, J.; Trautmann, C.

Abstract

Monazites are rare earth phosphates that are potential host matrices for the immobilization of actinides in high-level radioactive waste streams. This is due to their ability to incorporate various cations through different substitution mechanisms as well as their radiation resistance as observed in natural monazite mineral samples. In this study, LnPO4 monazite ceramics and single crystals doped with 500 ppm EuIII as a luminescent probe were irradiated with heavy ions to simulate the recoil of daughter products that occurs during alpha decay of the actinides. More specifically, irradiation experiments were conducted either with 14 MeV Au ions at fluences ranging from 5×1013 – 1×1015 ions/cm2 or with swift 1.7 GeV Au ions at fluences of 5×1011 – 2×1012 ions/cm2.
Irradiated monazite ceramics were analyzed with electron microscopy (SEM), vertical scanning interferometry (VSI), grazing incidence diffraction (GID), Raman spectroscopy, and luminescence spectroscopy to probe long and short range order of the monazite microstructure.
SEM micrographs and VSI data show clear damage of the irradiated regions of the ceramics, in the form of swollen grains and grain boundaries. GID images and powder patterns reveal diffuse scattering and amorphous contributions in irradiated samples. Solid solution compositions show larger damage than corresponding monazite endmembers, while polycrystalline and single crystal samples show similar level of amorphization. In the local coordination environments, Raman spectra of irradiated samples display a shoulder on the ν1 peak, indicating disruption in the vibrational modes of the phosphate tetrahedra. Confocal measurements of the swift heavy-ion irradiated monazites show full amorphization of the surface layers of the monazites samples, and increasing crystallinity with increasing sample depth. Luminescence data illustrate differences in the local LnO9 polyhedral environment in the monazites with irradiation. Integrated excitation spectra show a difference in the intensity and position of the excitation peak with irradiation. Especially single crystal data show a systematic decrease of the local site symmetry of the Eu3+ cation, and a general broadening of emission spectra, indicative for reduced local order following amorphization.

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  • Vortrag (Konferenzbeitrag)
    47th Scientific Basis for Nuclear Waste Management (SBNWM), 06.-10.11.2023, Cologne, Germany

Permalink: https://www.hzdr.de/publications/Publ-36880


Tailored engineering of crystalline surface enabled by ion-irradiation-assisted femtosecond laser ablation

Ren, Y.; Wang, C.; Cui, Z.; Liu, H.; Han, X.; Liu, P.; Akhmadaliev, S.; Zhou, S.; Cai, Y.

Abstract

Ion irradiation and femtosecond laser ablation (FLA) are powerful technologies for micro-/nano-machining of transparent materials. In this work, we demonstrate selective surface engineering of optical crystal surface via ion irradiation and subsequent FLA, namely ion-irradiation-assisted FLA. Based on the material modification effects in the ion-irradiated layers, different types of surface structuring characterized by grooves, nanogratings or sub-micron tracks are selectively induced by FLA. It is revealed that the ion-electron interaction induced localized lattice defects and related property modulation in target crystal play important roles in the formation and evolution of laser ablation regimes. Furthermore, the formation process of high-spatial-frequency nanograting is illustrated with the periodical enhancement of local field through the excitation of surface plasmon polaritons, which is experimentally supported through the measurements of transmission electron microscope and energy-dispersive spectroscopy. Our findings further clarify the ion- and laser-matter interactions and the correlation between these processes and surface modifications. The approach proposed in this work shows potential applications in the rapid fabrication of hybrid and versatile surface structures on crystalline materials.

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Permalink: https://www.hzdr.de/publications/Publ-35021


Tunable structural colors in all-dielectric photonic crystals using energetic ion beams

Li, J.; Zhang, K.; Pang, C.; Zhao, Y.; Zhou, H.; Chen, H.; Lu, G.; Liu, F.; Wu, A.; Du, G.; Akhmadaliev, S.; Zhou, S.; Chen, F.

Abstract

The modulation of structural color through various methods has attracted considerable attention. Herein, a new modulation method for the structural colors in all-dielectric photonic crystals (PCs) using energetic ion beams is proposed. One type of periodic PC and two different defective PCs were experimentally investigated. Under carbon-ion irradiation, the color variation primarily originated from the blue shift of the optical spectra. The varying degrees of both the reflection and transmission structural colors mainly depended on the carbon-ion fluences. Such nanostructures are promising for tunable color filters and double-sided chromatic displays based on PCs.

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Permalink: https://www.hzdr.de/publications/Publ-34809


Second harmonic generation from precise diamond blade diced ridge waveguides

Xu, H.; Li, Z.; Pang, C.; Li, R.; Li, G.; Akhmadaliev, S.; Zhou, S.; Lu, Q.; Jia, Y.; Chen, F.

Abstract

In this work, carbon ion irradiation and precise diamond blade dicing are applied for Nd:GdCOB ridge waveguide fabrication. The propagation properties of the fabricated Nd:GdCOB waveguides are investigated through experiments and theoretical analysis. The micro-Raman analysis reveals that the lattice of Nd:GdCOB crystal expands during the irradiation process. The micro-second harmonic spectroscopic analysis suggests that the original nonlinear properties of the Nd:GdCOB crystal are greatly enhanced within the waveguide volume. Under a pulsed 1064-nm laser pumping, second harmonic generation (SHG) at 532 nm have been achieved in the fabricated waveguides. The maximum SHG conversion efficiencies are determined to be ~8.32%W^-1 and ~22.36%W^-1 for planar and ridge waveguides, respectively.

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Permalink: https://www.hzdr.de/publications/Publ-34807


Data publication: Nanoindentation response of ion-irradiated Fe, Fe-Cr alloys and ferritic-martensitic steel Eurofer 97: The effect of ion energy

Das, A.; Altstadt, E.; Kaden, C.; Kapoor, G.; Akhmadaliev, S.; Bergner, F.

Abstract

The dataset consists of inputs from ion irradiation experiments, nanoindentation and empirical modeling results for Fe (G379), ferrritic Fe-9Cr (G385), martensitic Fe-9Cr (L252) and Eurofer 97 steel. The dataset also includes the basic characterization of microstructure.

Keywords: iron; Fe-Cr alloy; ferritic-martensitic steel; ion irradiation; displacement damage; nanoindentation; irradiation hardeníng; indentation size effect

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Permalink: https://www.hzdr.de/publications/Publ-33362


Nanoindentation response of ion-irradiated Fe, Fe-Cr alloys and ferritic-martensitic steel Eurofer 97: The effect of ion energy

Das, A.; Altstadt, E.; Kaden, C.; Kapoor, G.; Akhmadaliev, S.; Bergner, F.

Abstract

Nanoindentation of ion-irradiated nuclear structural materials and model alloys has received considerable interest in the published literature. In the reported studies, the materials were typically exposed to irradiations using a single ion energy varying from study to study from below 1 MeV to above 10 MeV. However, systematic investigations into the effect of ion energy are still missing, meaning that the possibilities to gain insight from systematic energy variations are not yet exhausted. We have exposed pure Fe, ferritic Fe-9Cr, martensitic Fe-9Cr and the ferritic-martensitic reduced-activation steel Eurofer 97 to ion irradiations at 300 °C using 1 MeV, 2 MeV and 5 MeV Fe2+ ions as well as 8 MeV Fe3+ ions and applied nanoindentation, using a Berkovich diamond indenter, to characterize as-irradiated samples and unirradiated references. The effect of the ion energy on the measured nanoindentation response is discussed for each material. Two versions of a primary-damage-informed model are applied to fit the measured irradiation-induced hardening. The models are critically compared with the experimental results also taking into account reported microstructural evidence. Related ion-neutron transferability issues are addressed.

Keywords: iron; Fe-Cr alloy; ferritic-martensitic steel; ion irradiation; displacement damage; nanoindentation; irradiation hardeníng; indentation size effect

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Permalink: https://www.hzdr.de/publications/Publ-33324


Examining alkali silica reaction of radiation-damaged quartz and feldspar minerals

Roode-Gutzmer, Q. I.; Rößler, C.; Akhmadaliev, S.; Schymura, S.; Barkleit, A.; Stumpf, T.

Abstract

Quartz and feldspar in end-of-life biological shielding concrete in nuclear power plants exhibit a maximum volume expansion at a neutron fluence of 10⁹ n/cm² of 17.8 % and 7.7 % respectively. [1] To simulate neutron-radiation damage, shallow ion-penetration depths in the order of a few hundred nanometers are optimal for 2D examinations of radiation-induced structural changes in silicate minerals and subsequent hydraulic weathering under aqueous alkaline conditions.

Using vertical scanning interferometry (VSI) we observed an out-of-plane expansion for quartz within concrete equivalent to 18.8 vol. % using Si-ion radiation with a fluence of 5·10¹⁴ ions/cm² and an energy of 300 keV. This agrees well with results recently acquired by Luu et al. (2021), [2] who achieved 18.1 vol. % using a Si-ion fluence and beam energy each an order of magnitude higher (6·10¹⁵ ions/cm², 3000 keV). These irradiation conditions correspond to penetration depths calculated in SRIM [3] of respectively 430 nm and 2000 nm.

By virtue of the resistance to polishing exhibited by feldspars, it is difficult to reduce the inherent surface roughness down to submicron relief required for VSI and even finer for electron backscatter diffraction (EBSD). Furthermore, structural relaxation in feldspar begins further away from the surface than quartz. We polish mineral specimen surfaces using a low-energy and -incident Ar+ broad ion beam (Ar-BIB) prior to Si-ion irradiation. In addition to depth profile changes due to radiation-induced structural relaxation and subsequent aqueous alkaline dissolution using VSI, we examine structural changes using EBSD in conjunction with electron scanning microscopy (SEM).

[1] Le Pape et al. (2018) J. Adv. Conc. Technol. 16 191-209
[2] Luu et al. (2021) J. Nucl. Mat. 545 152734
[3] Ziegler et al. (2010) Nucl. Instrum. Methods Phys. Res. B268 1818-1823 (http://www.SRIM.org)

Keywords: alkali silica reaction; radiation damage; quartz; feldspar; biological shield concrete

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  • Vortrag (Konferenzbeitrag)
    20th International Conference on Environmental Degradation of Materials in Nuclear Power Systems -- Water Reactors, 17.-21.07.2022, Snowmass Village, Colorado, USA

Permalink: https://www.hzdr.de/publications/Publ-33229


Creation of Gold Nanoparticles in ZnO by Ion Implantation–DFT and Experimental Studies

Cajzl, J.; Jeníčková, K.; Nekvindová, P.; Michalcová, A.; Veselý, M.; Macková, A.; Malinský, P.; Jágerová, A.; Mikšová, R.; Akhmadaliev, S.

Abstract

Three different crystallographic orientations of the wurtzite ZnO structure (labeled as c-plane, a-plane and m-plane) were implanted with Au + ions using various energies and fluences to form gold nanoparticles (GNPs). The ion implantation process was followed by annealing at 600°C in an oxygen atmosphere to decrease the number of unwanted defects and improve luminescence properties. With regard to our previous publications, the paper provides a summary of theoretical and experimental results, i.e., both DFT and FLUX simulations, as well as experimental results from TEM, HRTEM, RBS, RBS/C, Raman spectroscopy and photoluminescence. From the results, it follows that in the ZnO structure, implanted gold atoms are located in random interstitial positions—experimentally, the amount of interstitial gold atoms increased with increasing ion implantation fluence. During ion implantation and subsequent annealing, the metal clusters and nanoparticles with sizes from 2 to 20 nm were formed. The crystal structure of the resulting gold was not cubic (confirmed by diffraction patterns), but it had a hexagonal close-packed (hcp) arrangement. The ion implantation of gold leads to the creation of Zn and O interstitial defects and extended defects with distinct character in various crystallographic cuts of ZnO, where significant O-sublattice disordering occurred in m-plane ZnO.

Keywords: gold; ZnO; nanoparticles; ion implantation; luminescence; DFT; RBS

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Permalink: https://www.hzdr.de/publications/Publ-31948


Depth distribution of irradiation-induced dislocation loops in an Fe-9Cr model alloy irradiated with Fe ions: The effect of ion energy

Vogel, K.; Chekhonin, P.; Kaden, C.; Hernández-Mayoral, M.; Akhmadaliev, S.; Bergner, F.

Abstract

It is generally accepted that the microstructure of ion-irradiated Fe-based alloys does not only depend on the local level of displacement damage and the initial microstructure. Other factors such as the vicinity of a surface and the injected ions also play a role and may give rise to peculiar depth dependencies of the irradiated microstructure. Some investigators reported a band-like appearance indicating depth ranges of relatively uniform microstructure clearly distinguished from other ranges. Clarification is important for at least two purposes: first, to identify a depth range suitable for gaining meaningful information about the behaviour of materials exposed to neutron irradiation and, second, to correctly interpret results obtained by methods, such as nanoindentation, that integrate over extended depth ranges. A variation of the ion energy is expected to gain additional insight. In this work, two samples of Fe-9%Cr were irradiated at 300 °C with Fe2+ ions, one sample using 1 MeV ions and another sample using 5 MeV ions. Calculations using the binary collision code SRIM indicate displacement damage peaks at depths of 0.3 and 1.3 µm for ion energies of 1 and 5 MeV, respectively. The depth distribution of irradiation-induced dislocation loops was studied by cross-sectional scanning transmission electron microscopy (STEM). Loops visible in the STEM images were found to be arranged within two bands with the positions of these bands depending on the profiles of displacement damage and injected interstitials. The first and second band exhibit noticeably different number densities and mean sizes of the loops. For the 5 MeV irradiation, an extended range between the sample surface and the first band was observed, where decoration of pre¬existing line dislocations with loops is dominant. This microstructure resembles cases reported for neutron irradiation. For the 1 MeV irradiation, such a range does not exist. Estimates characterizing the loop size and number density in the distinct depth ranges are provided.

Keywords: Fe-9Cr; Ion irradiation; Scanning TEM; Dislocation loops

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Permalink: https://www.hzdr.de/publications/Publ-31891


Structural and magnetic properties of swift heavy-ion irradiated SiC

Zhang, X.; Zhang, Z.; Akhmadaliev, S.; Zhou, S.; Wu, Y.; Guo, B.

Abstract

Ferromagnetism has been observed in ion and neutron irradiated SiC single crystals. In this paper, we present a structural and magnetic investigation on 6H–SiC irradiated by swift heavy ions. The co-exist of paramagnetism, superparamagnetism and ferromagnetism is revealed by using different magnetometry methods. The ferromagnetic component persists well above room temperature. This study confirms the general existence of defect-induced magnetism in SiC.

Keywords: Ferromagnetism Magnetometry; Heavy ions; Silicon carbide; Superparamagnetism; Ferromagnetic component; Induced magnetism; Neutron irradiated SiC single crystals; Structural and magnetic properties; Swift heavy ions; Silicon compounds

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Permalink: https://www.hzdr.de/publications/Publ-31777


The absence of metamictisation in natural monazite

Nasdala, L.; Akhmadaliev, S.; Burakov, B. E.; Chanmuang N, C.; Škoda, R.

Abstract

The actinide-containing mineral monazite–(Ce) is a common accessory rock component that bears petrogenetic information, is widely used in geochronology and thermochronology, and is considered as potential host material for immobilisation of radioactive waste. Natural samples of this mineral show merely moderate degrees of radiation damage, despite having sustained high self-irradiation induced by the decay of Th and U (for the sample studied herein 8.9 ± 0.3 × 1019 α/g). This is assigned to low damage-annealing temperature of monazite–(Ce) and “alpha-particle-assisted reconstitution”.
Here we show that the response of monazite–(Ce) to alpha radiation changes dramatically, depending on the damage state. Only in radiation-damaged monazite–(Ce), 4He ions cause gradual structural restoration. In contrast, its high-temperature annealed (i.e. well crystalline) analogue and synthetic CePO4 experience He-irradiation damage. Alpha-assisted annealing contributes to preventing irradiation-induced amorphisation (“metamictisation”) of monazite–(Ce); however, this process is only significant above a certain damage level.

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Permalink: https://www.hzdr.de/publications/Publ-31530


Efficient Modulation of Photonic Bandgap and Defect Modes in All-Dielectric Photonic Crystals by Energetic Ion Beams

Du, G.; Zhou, X.; Pang, C.; Zhang, K.; Zhao, Y.; Lu, G.; Liu, F.; Wu, A.; Akhmadaliev, S.; Zhou, S.; Chen, F.

Abstract

The photonic bandgap and localization in photonic crystals can be effectively modulated by energetic ion beams owing to the induced modification of the thickness and refractive indices of the materials. In this work, the modulation of photonic bandgap and defect modes in 1D all-dielectric photonic crystals is investigated theoretically and experimentally by using carbon (C5+) ion irradiation. It is found that the photonic bandgap and defect mode have a remarkable hypsochromic shift under the C5+ ion irradiation. The degree of the blueshift mainly depends on the reduction of the material thickness that is nearly proportional to the fluences of C5+ ions. The blueshift of the band edges and defect modes shows a step-like behavior from transparency to opacification (near-zero transmittance or high reflectance) or a converse trend. The work paves a new way to tailor the photonic crystals toward the development of novel devices with tunable specific wavelengths and wavebands.

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Permalink: https://www.hzdr.de/publications/Publ-31481


Heavy ion irradiation damage in Zr3(Al0.9Si0.1)C2 MAX phase

Qarra, H. H.; Knowles, K. M.; Vickers, M. E.; Zapata-Solvas, E.; Akhmadaliev, S.

Abstract

A Zr3(Al0.9Si0.1)C2 MAX phase-based ceramic with 22 wt.% ZrC and 10 wt.% Zr5Si3 has been irradiated with 52 MeV I9+ ions at room temperature, achieving a maximum dose of 8 displacements per atom (dpa). The response of this MAX phase-rich material to irradiation has been studied using scanning electron microscopy, transmission electron microscopy and X-ray diffraction techniques. Post-irradiation examination of the material revealed a number of crystalline changes to the MAX phase. At low doses, Zr3(Al0.9Si0.1)C2 maintained a high degree of crystallinity, while at the highest doses, its degree of crystallinity was reduced significantly. A number of radiation-induced phase transformations were observed, including the decomposition of Zr3(Al0.9Si0.1)C2 into ZrC and other phases, and the formation of β-Zr3(Al,Si)C2, a MAX phase with a rearranged stacking sequence. Microstructural examination revealed that the majority of the extended defects in Zr3(Al0.9Si0.1)C2 lie in the (0001) basal planes. Analysis of X-ray diffraction profiles after heat treating the 8 dpa-irradiated material for 1 h at 300 °C and at 600 °C showed that there were only subtle changes to the profiles relative to that of the 8 dpa-irradiated material which had not been heat treated. Overall, the experimental results of this study show that the Zr3(Al0.9Si0.1)C2 MAX phase responds less well to irradiation relative to other MAX phases irradiated with high energy heavy ions at room temperature.

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Permalink: https://www.hzdr.de/publications/Publ-31304


Para-ferroelectric phase transition driven by swift heavy-ion irradiation in KTN crystal

He, S.; Yang, Q.; Li, X.; Liu, H.; Cao, L.; Akhmadaliev, S.; Wang, X.; Ren, Y.; Zhou, S.; Wu, P.

Abstract

We report a novel approach of using swift O5+ ion irradiation to implement para-ferroelectric phase transition in a relaxor ferroelectric KTa0.62Nb0.38O3 (KTN) single crystal. With 15-MeV swift O5+ ion irradiation, a well-defined two-layer structure has been formed in the KTN sample due to the interaction between the O ions and KTN via electronic stopping and the nuclear stopping, respectively. The microstructures in these two layers are characterized by using a micro-Raman (μ-Raman) spectral technique. The significant changes of both spectral intensities and locations in three characteristic Raman peaks suggest that the top layer of the KTN sample due to electronic stopping exists a single-domain-ferroelectric state with a uniform and enhanced polarization orientation along [0 0 1]c direction. More importantly, we observe the irradiated region can effectively confine the light propagation in the ferroelectric layer, which can be further controlled by external fields. The results are promising for designing new integrated photonic devices.

Keywords: Phase transition; Swift heavy ion irradiation; Relaxor ferroeletrics

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Permalink: https://www.hzdr.de/publications/Publ-31070


Hybrid graphene-based material promising target in laser matter interaction

Cutroneo, M.; Torrisi, L.; Badziak, J.; Rosinski, M.; Torrisi, A.; Fazio, M.; Sofer, Z. E.; Böttger, R.; Akhmadaliev, S.

Abstract

Graphene oxide foils implanted with copper ions at low energy and high dose, have been proposed as hybrid graphene-based materials suitable to be laser irradiated in vacuum to produce hot plasmas. The special lattice structure of the graphene oxide foil can improve the propagation of the laser accelerated electrons inside the foil and to enhance the electron density emerging from the rear foil surface. In such conditions the electric field developed in the non-equilibrium plasma increases and consequently in the forward ion acceleration. The foils have been optimized in thickness and they were irradiated with optimized laser parameters in order to produce high energy and quasi-monoenergetic proton beams by the femtosecond laser at the Institute of Plasma Physics and Laser Microfusion in Warsaw, Poland. Gaf chromic film and silicon carbide detectors were used to monitor the plasma properties and to measure the velocity of the emitted protons and carbon ions from plasma.

Keywords: Data analysis; Lasers

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Permalink: https://www.hzdr.de/publications/Publ-30937


Radiation damage tolerance of a novel metastable refractory high entropy alloy V2.5Cr1.2WMoCo0.04

Patel, D.; Richardson, M. D.; Jim, B.; Akhmadaliev, S.; Goodall, R.; Gandy, A. S.

Abstract

A novel multicomponent alloy, V2.5Cr1.2WMoCo0.04, produced from elements expected to favour a BCC crystal structure, and to be suitable for high temperature environments, was fabricated by arc melting and found to exhibit a multiphase dendritic microstructure with W-rich dendrites and V-Cr segregated to the inter-dendritic cores. The as-cast alloy displayed an apparent single-phase XRD pattern. Following heat treatment at 1187 °C for 500 h the alloy transformed into three different distinct phases - BCC, orthorhombic, and tetragonal in crystal structure. This attests to the BCC crystal structure observed in the as-cast state being metastable. The radiation damage response was investigated through room temperature 5 MeV Au+ ion irradiation studies. Metastable as-cast V2.5Cr1.2WMoCo0.04 shows good resistance to radiation induced damage up to 40 displacements per atom (dpa). 96 wt% of the as-cast single-phase BCC crystal structure remained intact, as exhibited by grazing incidence X-ray diffraction (GI-XRD) patterns, whilst the remainder of the alloy transformed into an additional BCC crystal structure with a similar lattice parameter. The exceptional phase stability seen here is attributed to a combination of self-healing processes and the BCC structure, rather than a high configurational entropy, as has been suggested for some of these multicomponent "High Entropy Alloy" types. The importance of the stability of metastable high entropy alloy phases for behaviour under irradiation is for the first time highlighted and the findings thus challenge the current understanding of phase stability after irradiation of systems like the HEAs.

Keywords: High entropy alloy (HEA); Structural materials; Ion implantation; Radiation damage; Metastability

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Permalink: https://www.hzdr.de/publications/Publ-30936


Diamond-blade diced trapezoidal ridge waveguides in YCOB crystal for second harmonic generation

Chen, C.; Lu, Q.; Akhmadaliev, S.; Zhou, S.

Abstract

Trapezoidal ridge waveguides have been fabricated in YCOB nonlinear optical crystals by carbon ion irradiation and precise diamond-blade dicing. The diced ridges with smooth side-walls allow for near-infrared (1064 nm) light guiding with propagation losses around 1 dB/cm. Refractive index profile of a waveguide has been reconstructed in a reasonable manner. Green second harmonic light have been generated at room temperature via type I birefringent phase matching. Under the pump of continuous and pulsed lasers, conversion efficiencies for guided-wave frequency doubling can be up to ~1.10% Wsup-1 and ~6.22%, respectively.

Keywords: Trapezoidal ridge waveguides; YCOB crystal; SHG

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Permalink: https://www.hzdr.de/publications/Publ-30935


Tuning Tailored Single-Walled Carbon Nanotubes by Highly Energetic Heavy Ions

El-Said, A. S.; Rao, S.; Akhmadaliev, S.; Facsko, S.

Abstract

Carbon-based nanomaterials have attracted a lot of interest lately due to their highly promising applications. Here, we report on the modifications of single-walled carbon nanotubes (SWCNTs) induced by swift (highly energetic) heavy ions. Using scanning force microscopy and Raman spec- troscopy, we observed a dramatic change in the structure of the irradiated SWCNTs, accompanied by an increase of the adhesion force as a function of ion fluence and electronic energy loss. With increasing ion fluence the SWCNTs exhibit a partial transformation from metallic to more semicon- ducting. Moreover, at high fluence they break into segments of 10–20 nm length.

Keywords: Swift Heavy Ion; Ion Irradiation; Carbon Nanotubes

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Permalink: https://www.hzdr.de/publications/Publ-30908


Relationships between depth-resolved primary radiation damage, irradiation-induced nanostructure and nanoindentation response of ion-irradiated Fe-Cr and ODS Fe-Cr alloys

Vogel, K.; Heintze, C.; Chekhonin, P.; Akhmadaliev, S.; Altstadt, E.; Bergner, F.

Abstract

Ion irradiations are indispensable for exploring radiation effects on materials, for example, radiation hardening. However, the extraction of radiation hardening as function of displacement damage from the nanoindentation (NI) response of self-ion-irradiated metallic alloys is a challenge. In particular, recent attempts suffer from interference with contributions arising from injected self-interstitial atoms. Moreover, instances of available microstructural evidence and NI results reported for the same material and same irradiation are rare. In order to tackle these issues, the depth-dependent irradiated microstructure and the NI response were analyzed for Fe-9Cr and oxide dispersion strengthened Fe-Cr alloys irradiated with 5 MeV iron ions. Cross-sectional transmission electron microscopy indicated the appearance of irradiation-induced dislocation loops but no other types of visible microstructural changes. NI indicated maxima of the radiation hardening as function of contact depth. Links between the depth-resolved primary radiation damage, the observed depth-dependent characteristics of loops and the measured hardening are considered. As a key point, the link between loops and hardening requires the integration of the local hardening contributions over the indentation plastic zone. Calculations and measurements are compared with respect to both the depth position of maximum hardening and the substrate effect. The role of the model assumptions is discussed with special emphasis on the plastic zone size and the superposition of hardening contributions. The latter is found to be material-specific. The model also allows hardening contributions arising from displacement damage and injected interstitials to be separated.

Keywords: Fe-alloys; ion irradiation; TEM; nanoindentation; irradiation hardening

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Permalink: https://www.hzdr.de/publications/Publ-30720


Impact of low energy ion beams on the properties of rr-P3HT films

Kislyuk, V.; Kotrechko, S.; Trachevskij, V.; Melnyk, A.; Pud, A.; Ogurtsov, N.; Noskov, Y.; Osiponok, M.; Lytvyn, P.; Dzyazko, Y.; Nierobisch, F.; Schneider, A.; Ludewig, F.; Akhmadaliev, S.; Aniol, R.; Kentsch, U.; Krause, M.; Facsko, S.

Abstract

Two types of ions (fluorine and titanium) are implanted into films of regio-regular poly(3-hexylthiophene-2,5-diyl) (rr-P3HT) spin-coated on glass substrates with subsequent annealing in argon atmosphere to modify their electrical properties and structure. The ion energy and fluence were within 0.2–40 keV and 10¹³–10¹⁵ cm⁻² respectively. The dc resistance enhances after the intensive ion beam treatment while the ac impedance decreases. Ti ion implantation with 40 keV energy and 10¹⁴ cm⁻² fluence induces decrease of the ac impedance by almost two orders of magnitude and appearance of the molecular hydrogen features in ¹H NMR spectrum. The UV–VIS spectra of the films are blue shifted after their exposal to the ion beams, which correlates with the presence of oxygen. The ratio of the oxygen to carbon peak intensities (O1s/C1s) in the XPS spectra is proposed as a measure for the local partial disturbance of the film. EPR spectra demonstrate formation of the paramagnetic states with g factor <2, which is accompanied with the down-field shift of the NMR spectrum. The ion beams are found to have no significant etching effect as per results of the film thickness measurements and AFM images.

Keywords: Ion implantation; rr-P3HT; Doping; Resistance; Ac impedance; Organic electronics

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Permalink: https://www.hzdr.de/publications/Publ-30504


High-current caesium sputter ion source with planar ionizer for accelerator mass spectrometry

Yordanov, D.; Hofsäss, H.; Rugel, G.; Akhmadaliev, S.; Borany, J.; Facsko, S.; Feige, J.

Abstract

A new caesium sputter negative ion source with planar ionizer for Accelerator Mass Spectrometry (AMS) is being built, regarding quantifying the ratios of long-lived cosmogenic radionuclides in micrometeorites.
The focus of the ion source is on an optimal ion-optics design, together with a realization of new concepts for the construction and function of the ionizer, with the possibility of the precise in-situ adjustment of the ion-optical components, and optimization of the caesium ion beam and ion transport. In addition, the source is designed for operation with higher cathode voltage (up to 20 kV), which aims to increase the sputter rate of the sample, and in turn to increase the extracted negative current. Higher ion currents and better ion yields mean shorter measuring times, higher precision due to higher counting statistics and/or higher throughput of samples in an AMS runs.
The authors would like to thank the Federal Ministry of Education and Research of Germany for its financial support (project 05K2016), and the HZDR’s Ion Beam Center for its essential contribution to the realization of this project.

Keywords: New Mass Spectrometric Methods and Technical Developments

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Permalink: https://www.hzdr.de/publications/Publ-30125