1. M. Karlušić et al, Response of GaN to energetic ion irradiation: conditions for ion track formation, J Phys D Appl Phys 48 (2015) 325304 (12pp)
In the work “Response of the GaN to energetic ion irradiation: conditions for ion track formation” published in J. Phys. D: Appl. Phys. and featured on the journal cover page, results have been reported on investigations regarding swift heavy ion irradiation of wurzite GaN surface, and showed for the first time that GISAXS can be utilized for analysis of such irradiated surface. In contrast to previous works where nanohillocks were found within the surface ion track, morphology of 92 MeV Xe ion tracks consist of both nanohillocks and nanoholes. For lower energy irradiation using 23 MeV I, ion tracks consist only of nanoholes. In addition, TOF-ERDA measurements showed significant loss of nitrogen during irradiation and opens up the question of the composition of ion tracks.
2. O. Ochedowski et al, Nanostructuring graphene by dense electronic excitation, Nanotechnology 26 (2016) 465302
In the work “Nanostructuring graphene by dense electronic excitation”, published in Nanotechnology detailed investigation of graphene response to the swift heavy ion irradiation in a wide range of energies has been reported. It was demonstrated that medium scale accelerator facilities like the one at the RBI can be used successfully for nanostructuring graphene. By choosing appropriate ion beam irradiation parameters, not only graphene can be pierced, thus producing nanoscale pores within it, but also different kind of defects can be introduced into it in a controlled manner. The study was done as collaboration between scientists from Germany (Universities Duisburg-Essen, Ulm and Jena), France (GANIL ion accelerator facility in Caen) and RBI.
3. M. Erich et al, EBS/C proton spectra from a virgin diamond crystal, Nuclear Instruments and Methods in Physics Research B 381 (2016) 96-102
In case of diamond, elastic backscattering channeling spectra (EBS/c) of protons in a <100> diamond crystal were experimentally and theoretically studied. Proton incident energies for EBS/c spectra were in the energy range from 1.0 MeV to 1.9 MeV. The energy range was chosen in order to explore a distinct strong resonance of the 12C(p,p0)12C elastic scattering at 1737 keV. The observations confirm the physical interpretation of the fitting parameters used in theoretical analysis of spectra. Also, they constitute the basics for the further development of the model for the quantification of induced amorphization and depth profiling of implanted ions, which will be the second step of work. The work has been performed in collaboration between the Demokritos Research Center (Greece), Vinca Institute (Serbia) and RBI. The analysis of EBS/c virgin spectra have been published in NIM B.
4. Vittone et al, Charge collection efficiency degradation induced by MeV ions in semiconductor devices: Model and experiment, Nuclear Instruments and Methods in Physics Research B 372 (2016)128-142
Theoretical and experimental study of the charge collection efficiency (CCE) degradation in silicon diodes induced by energetic ions has also been studied. Ion Beam Induced Charge (IBIC) measurements carried out on n- and p-type silicon diodes which were previously irradiated with MeV He ions show evidence that the CCE degradation does not only depend on the mass, energy and fluence of the damaging ion, but also depends on the ion probe species and on the polarization state of the device. A general one dimensional model is derived, which accounts for the ion-induced defect distribution, the ionization profile of the probing ion and the charge induction mechanism. Using the ionizing and non-ionizing energy loss profiles resulting from simulations based on the binary collision approximation and on the electrostatic/transport parameters of the diode under study as input, the model is able to accurately reproduce the experimental CCE degradation curves without introducing any phenomenological additional term or formula. Although limited to low level of damage, the model is quite general, including the displacement damage approach as a special case and can be applied to any semiconductor device. It provides a method to measure the capture coefficients of the radiation induced recombination centres. They can be considered indexes, which can contribute to assessing the relative radiation hardness of semiconductor materials. The work has been performed in collaboration between University of Torino, ANSTO (Australia), National University of Singapore, CNA (Sevilla, Spain), University of Helsinki, ATOMKI (Debrecen), IAEA, Sandia National Labs (USA) and RBI.
5. V. Grilj et al, The evaluation of radiation damage parameter for CVD diamond, Nuclear Instruments and Methods in Physics Research B 372 (2016)161-164
The other study on diamond has been on evaluation of radiation damage paramater for CVD diamond. There are a few different phenomenological approaches that aim to track the dependence of signal height in irradiated solid state detectors on the fluence of damaging particles. However, none of them are capable to provide a unique radiation hardness parameter that would reflect solely the material capability to withstand high radiation environment. To extract such a parameter for chemical vapor deposited (CVD) diamond, two different diamond detectors were irradiated with proton beams in MeV energy range and subjected afterwards to ion beam induced charge (IBIC) analysis. The change in charge collection efficiency (CCE) due to defects produced was investigated in context of a theoretical model that was developed on the basis of the adjoint method for linearization of the continuity equations of electrons and holes. The work has been performed in collaboration between the Japan Atomic Energy Commission (Takasaki, Japan), Gunma University (Japan), CEA-LIST (Saclay, France) and RBI.
6. M. Jakšić et al, In-air ion beam analysis with high spatial resolution proton microbeam, Nuclear Instruments and Methods in Physics Research B 371 (2016)185-188
High resolution in-air microbeam could be applied for IBIC (Ion Beam Induced Charge) tests of large detectors used in nuclear and high energy physics that otherwise cannot be tested in relatively small microbeam vacuum chambers. One of the possible ways to maintain the micrometre spatial resolution while performing ion beam analysis in the air is to increase the energy of ions. In order to explore capabilities and limitations of this approach, we have tested a range of proton beam energies (2–6 MeV) using in-air STIM (Scanning Ion Transmission Microscopy) setup. Measurements of the spatial resolution dependence on proton energy have been compared with SRIM simulation and modelling of proton multiple scattering by different approaches. Results were used to select experimental conditions in which 1 micrometre spatial resolution could be obtained.
7. Karlušić et al, Formation of swift heavy ion tracks on a rutile TiO2 (001) surface, Journal of Applied Crystallography 49 (2016) 1704
In this work the response of a rutile TiO2 (001) surface to grazing-incidence swift heavy ion irradiation is investigated. Surface ion tracks with the well known intermittent inner structure were successfully produced using 23 MeV I ions. Samples irradiated with different ion fluences were investigated using atomic force microscopy and grazing-incidence small-angle X-ray scattering. With these two complementary approaches, a detailed description of the swift heavy ion impact sites, i.e. the ion tracks on the surface, can be obtained even for the case of multiple ion track overlap. In addition to the structural investigation of surface ion tracks, the change in stoichiometry of the rutile TiO2 (001) surface during swift heavy ion irradiation was monitored using in situ time-of-flight elastic recoil detection analysis, and a preferential loss of oxygen was found.
8. Božičević Mihalić et al, Study of ion beam induced chemical effects in silicon with a downsized high resolution X-ray spectrometer for use with focused ion beams, Journal of Analytical Atomic Spectrometry 31 (2016) 2293
A downsized wavelength dispersive X-ray spectrometer, employing a flat crystal and a CCD detector for use with focused ion beams has been constructed and employed to study ion beam induced chemical effects in Si K X-ray spectra from silicon and its selected compounds. By using ADP, PET and LiF(110) diffraction crystals, the spectrometer can measure X-rays in the energy range between 1.2 and 8.4 keV making possible studies of secondary effects in the K X-ray spectra of light elements, L-shell spectra of medium Z elements and M-shell spectra from heavy elements. The K X-ray spectra of silicon and selected silicon compounds were measured after excitation with 2 MeV protons and 20 MeV carbon ions focused to micrometer size. The results obtained for peak relative intensities were analyzed to study their dependence on the silicon oxidation states and effective charge on Si. The results were compared with the existing data obtained by proton, electron and photon induced ionization mechanisms, and clear differences between the ionization sources were observed. Si Kα multiple ionization satellites were studied with 20 MeV carbon ions on Si, SiO2 and SiC.
9. Karlušić et al, Swift heavy ion track formation in SrTiO3 and TiO2 under random, channeling and near-channeling conditions, J. Phys. D: Appl. Phys. 50 (2017) 205302 (13pp)
In this work conditions for ion track formation in single crystal SrTiO3 and TiO2 (rutile) after irradiations using swift heavy ion beams with specific energies below 1 MeV/amu were investigated. Ion tracks in the bulk were measured by Rutherford backscattering spectroscopy in channeling mode, and those on the surfaces were measured by atomic force microscopy. Variations in the ion track sizes and respective thresholds were observed after irradiations under random, channeling and near-channeling conditions close to normal incidence. These variations are attributed to the specifics of the electronic stopping power of swift heavy ions under the investigated conditions. In the case of ion channeling, electronic stopping power is reduced and observed ion tracks are smaller. The opposite was found under the near-channeling conditions when lowering of the ion track formation threshold was observed. We attribute this finding to the oscillating electronic stopping power with large peak values. For both materials, thresholds for bulk and surface ion track formation were found to be surprisingly close, around 10 keV nm−1. Obtained results are compared with predictions of the analytical thermal spike model.
10. Vasquez et al, Creating nanoporous graphene with swift heavy ions, Carbon 114 (2017) 511
In this work swift heavy ion-induced defect production in suspended single layer graphene was studied using Raman spectroscopy and a two temperature molecular dynamics model that couples the ionic and electronic subsystems. Heavy ion irradiations were performed in GANIL (France) for higher energy ions (91 MeV Xe), and at the RBI Tandem Accelerator Facility and University of Helsinki for lower energy ions. The results indicate that swift heavy ions can create nanopores in graphene, and that their size can be tuned between 1 and 4 nm diameter by choosing a suitable stopping power.
11. Karlušić et al, On the threshold for ion track formation in CaF2, New Journal of Physics 19 (2017) 023023
This work contributes to the debate related to the mechanism of swift heavy ion (SHI) track formation in CaF2. The study aims to shed light on this important topic using a range of complementary experimental techniques. Evidence of the threshold for ion track formation being below 3 keV nm−1 is provided by both transmission electron microscopy (TEM) and Rutherford backscattering spectroscopy in the channelling mode, which has direct consequences for the validity of models describing the response of CaF2 to SHI irradiation. Furthermore, information about the elemental composition within the ion tracks is obtained using scanning TEM, electron energy loss spectroscopy, and with respect to the stoichiometry of the materials surface by in-situ time of flight elastic recoil detection analysis. Advances in the analyses of the experimental data presented here pave the way for a better understanding of the ion track formation.
12. Lessmann et al., The effects of ion irradiation on the micromechanical fracture strength and hardness of a self-passivating tungsten alloy, Journal of Nuclear Materials 486 (2017) 34-43.
An ultra-fine grained self-passivating tungsten alloy (W88-Cr10-Ti2 in wt.%) has been implanted with iodine ions to average doses of 0.7 and 7 dpa, as well as with helium ions to an average concentration of 650 appm. Pile-up corrected Berkovich nanoindentation reveals significant irradiation hardening, with a maximum hardening of 1.9 GPa (17.5%) observed. The brittle fracture strength of the material in all implantation conditions was measured through un-notched cantilever bending at the microscopic scale. All cantilever beams failed catastrophically in an intergranular fashion. A statistically confirmed small decrease in strength is observed after low dose implantation, whilst the high dose implantation results in a significant increase in fracture strength, further increased by additional helium implantation. The use of iodine ions as the implantation ion type is justified through a comparison of the hardening behaviour of pure tungsten under tungsten and iodine implantation.
13. Sudić et al, Channeling STIM analysis of radiation damage in single crystal diamond membrane, Nuclear Instruments and Methods in Physics Research B 404 (2017) 96–99
The use of focused ion beam transmission channeling patterns to monitor the damage creation process in thin diamond single crystal membrane is described. A 0.8 MeV proton beam from the Ruder Bošković Institute nuclear microprobe was used to perform Channeling Scanning Transmission Ion Microscopy (CSTIM) measurements. CSTIM was used instead of RBS channeling because of (several orders of magnitude) lower damage done to the sample during the measurements. Damage was introduced in selected areas by 15 MeV carbon beam in range of fluences 31015–21017 ions/cm2. Contrary to Ion Beam Induced Charge (IBIC), CSTIM is shown to be sensitive to the large fluences of ion beam radiation. Complementary studies of both IBIC and CSTIM are presented to show that very high fluence range can be covered by these two microprobe techniques, providing much wider information about the diamond radiation hardness. In addition micro Raman measurements were performed and the height of the GR 1 peak was correlated to the ion beam fluence.
14. M. Karlušić et al, Monitoring Ion Track Formation Using In Situ RBS/c,ToF-ERDA, and HR-PIXE, Materials 10 (2017) 1041.
Feasibility of ion beam analysis techniques for monitoring swift heavy ion track formation was investigated. First, the use of the in situ Rutherford backscattering spectrometry in channeling mode to observe damage build-up in quartz SiO2 after MeV heavy ion irradiation was demonstrated. Second, new results of the in situ grazing incidence time-of-flight elastic recoil detection analysis used for monitoring the surface elemental composition during ion tracks formation in various materials were presented. Ion tracks were found on SrTiO3, quartz SiO2, a-SiO2, and muscovite mica surfaces by atomic force microscopy, but in contrast to our previous studies on GaN and TiO2, surface stoichiometry remained unchanged. Third, the usability of high resolution particle induced X-ray spectroscopy for observation of electronic dynamics during early stages of ion track formation was discussed.
15. M. Karlušić et al, Infrared spectroscopy of ion tracks in amorphous SiO2 and comparison to gamma irradiation induced changes, Journal of Nuclear Materials, accepted 6 November 2018, available online /doi.org/10.1016/j.jnucmat.2018.11.010
In the paper [14] ion beam analysis techniques for monitoring swift heavy ion track formation in crystalline and amorphous SiO2 was investigated. In this work ion track formation in amorphous SiO2 was investigated using complementary techniques, i.e. FTIR. For comparison, one set of samples was also irradiated using 1.25MeV gamma rays. An increase of 1044 cm−1 peak and decrease of 1078 cm−1 peak was observed in all cases. Experimental results were analysed using an analytical thermal spike model and non-standard model parameters were found. This finding is attributed to the amorphous structure of the material.
16. M. Erich et al, Channeling implantation of high energy carbon ions in a diamond crystal: Determination of the induced crystal amorphization, Nuclear Instruments and Methods in Physics Research B 416 (2018) 89
Induced diamond crystal amorphization by 4 MeV carbon ions implanted in the 〈100〉 oriented crystal was studied and its characterisation by application of RBS/C and EBS/C techniques. The spectra from the implanted samples were measured by 1.2, 1.5, 1.75 and 1.9 MeV protons. For the two latter ones the strong resonance of the nuclear elastic scattering 12C(p,p0)12C at 1.737 MeV was explored. The backscattering channeling spectra were successfully fitted and the ion beam induced crystal amorphization depth profile was determined using a phenomenological approach, which is based on the properly defined Gompertz type dechanneling functions for protons in the 〈100〉 diamond crystal channels and the introduction of the concept of ion beam amorphization, which is implemented through our newly developed computer code CSIM.
17. I. Božičević Mihalić et al, High resolution K X-ray spectra of selected silicates induced by MeV proton and carbon micro-beams, Nuclear Instruments and Methods in Physics Research B 417 (2018) 70
Recently we developed a high resolution wavelength dispersive X-ray spectrometer based on the flat diffraction crystals for use with focused ion beams and used it to study chemical effects in ion beam induced Si K X-ray spectra of silicon and its selected binary compounds [8]. In this work we extended the study to selected silicates. We measured high resolution Si Kα and Kβ X-ray spectra of three silicates: feldspar, kyanite and tourmaline. The spectra have been measured with 2 MeV protons (Kα and Kβ regions) and 20 MeV carbon ions (only Kα region). The results obtained for peak relative intensities were analysed and compared with the related relative intensities obtained from Si, SiC and SiO2.
18. C.M. Heirwegh at al, Multiple ionization X-ray satellites of magnesium, aluminum and silicon in alpha particle PIXE, Nuclear Instruments and Methods in Physics Research B 428 (2018) 9-16
Wavelength-dispersive spectroscopy was used to study the multiple ionization satellites in the K X ray spectra of magnesium, aluminum and silicon bombarded by alpha particles having energies of 3, 4 and 5 MeV. The measured energy shifts and intensities relative to the diagram lines of the groups with one, two and three L-shell vacancies were extracted from the spectra. These results compare well with the values in an interim database which was recently assembled from the limited existing literature. The present work is the first step in refining this database so that it may be used to improve the accuracy of PIXE analysis using alpha particle beams, including the PIXE mode of the Mars alpha particle X-ray spectrometers. The effects of oxide bonding are also determined and compared to those observed when excitation is effected by photons and by electrons.
19. M. Axiotis et al, A benchmarking procedure for PIGE related differential cross-sections, Nuclear Instruments and Methods in Physics Research B 423 (2018) 92-96
The application of standard-less PIGE requires the a priori knowledge of the differential cross section of the reaction used for the quantification of each detected light element. Towards this end, a lot of datasets have been published the last few years from several laboratories around the world. The discrepancies often found between different measured cross sections can be resolved by applying a rigorous benchmarking procedure through the measurement of thick target yields. Such a procedure is proposed in the present paper and is applied in the case of the 19F(p,p′γ)19F reaction.
20. W. Kada et al, Evaluation of scintillation properties of α- and β-SiAlON phosphors under focused microbeam irradiation using ion-beam-induced luminescence analysis, Nuclear Instruments and Methods in Physics Research, accepted 6 November 2018, available online /doi.org/10.1016/j.nimb.2018.09.002
Two different types of SiAlON phosphors, namely, α-SiAlON:Eu and β-SiAlON:Eu, that have been developed as scintillators are evaluated for their luminescent properties by ion-beam-induced luminescence (IBIL) analysis under 2–3 MeV H+ microbeam irradiation. The IBIL spectra show that both α-SiAlON:Eu and β-SiAlON:Eu have bright luminescence similar to that of ZnS:Ag scintillators. The α-SiAlON:Eu and β-SiAlON:Eu IBIL spectra have peaks at wavelengths of 605 and 540 nm, respectively, which lie in the preferred range of general optical sensors. As the irradiation progresses, the IBIL intensity of conventional ZnS:Ag scintillators decreases sharply, whereas that of the two SiAlONs remains largely unchanged. Moreover, the thermal resistivity of β-SiAlON:Eu is measured by IBIL under temperature control. The IBIL intensity retains half of its original value at the highest temperature of 773 K. The present experimental results reveal the two different types of SiAlON to be potential candidates for a scintillation monitoring tool for harsh environments in which intense beam irradiation at high temperature can be expected.