Kr Ions Research Articles

Enhanced Mobility in MoS2 Thin Film Transistors Through Kr Ion Beam-Generated Surface Defects

Enhanced Mobility in MoS2 Thin Film Transistors Through Kr Ion Beam-Generated Surface Defects

Temperature dependence of irradiation-induced amorphization in a high-entropy titanate pyrochlore

AbstractThe temperature dependence of amorphization in a high-entropy pyrochlore, (Yb0.2Tm0.2Lu0.2Ho0.2Er0.2)2Ti2O7, under irradiation with 600 keV Xe ions has been studied using in situ transmission electron microscopy (TEM). The critical amorphization dose increases with temperature, and the critical temperature for amorphization is 800 K. At room temperature, the critical amorphization dose is larger than that previously determined for this pyrochlore under bulk-like 4 MeV Au ion irradiation but is similar to the critical doses determined in two other high-entropy titanate pyrochlores under 800 keV Kr ion irradiation using in situ TEM, which is consistent with reported behavior in simple rare-earth titanate pyrochlores. Graphical abstract

Radiation Resistance of High-Entropy Alloys CoCrFeNi and CoCrFeMnNi, Sequentially Irradiated with Kr and He Ions.

This work studied the effect of sequential irradiation by krypton and helium ions at room temperature on the composition and structure of CoCrFeNi and CoCrFeMnNi high-entropy alloys (HEAs). Irradiation of the HEAs by 280 keV Kr14+ ions up to a fluence of 5 × 1015 cm-2 and 40 keV He2+ ions up to a fluence of 2 × 1017 cm-2 did not alter their elemental distribution and constituent phases. Blisters formed on the nickel surface after sequential irradiation, where large blisters had an average diameter of 3.8 μm. The lattice parameter of the (Co, Cr, Fe and Ni) and (Co, Cr, Fe, Mn and Ni) solid solutions increased by 0.17% and 0.37% after sequential irradiation, respectively. Irradiation by Kr ions led to a decrease in tensile macrostresses in the HEAs in the region of krypton ion implantation (Region I) and the formation of compressive macrostresses in the region behind the peak of implanted krypton (Region II). Sequential irradiation formed large compressive stresses in Ni and HEAs equal to -131.5 MPa, -300 MPa and -613.5 MPa in Ni, CoCrFeNi and CoCrFeMnNi, respectively, in the Region II. Irradiation by krypton ions decreased the dislocation density by 1.6-2.3 times, and irradiation with helium ions increased it by 11-15 times relative to unirradiated samples for CoCrFeNi and CoCrFeMnNi, respectively. Sequentially irradiated CoCrFeMnNi HEA had higher macrostresses and dislocation density than CoCrFeNi.

Comparison of collective acceleration of ions in a luce diode in residual atmospheres of air, argon and krypton

The paper compares the collective acceleration of ions in a Luce diode in residual atmospheres of air, argon and krypton at pressures of 6–156 mPa, evaluating the efficiency of capture of Ar and Kr ions into collective acceleration from their residual atmospheres. At a diode voltage of ∼232 kV, proton energies were 510 ± 38, 619 ± 62 and 567 ± 59 keV for air, argon, and krypton atmospheres, respectively, while the number of protons per shot was approximately 2 and 3 times higher in the argon and krypton residual atmosphere compared to the normal residual atmosphere. This increase in energy also led to a significant increase in the proportion of protons with energies greater than 3.02 MeV - to 1010 per shot on average. It was found that with increasing argon pressure, the diode current noticeably decreases, and with increasing krypton pressure, on the contrary, the diode current noticeably increases, which can be explained by the fact that argon is more neutral than krypton. The efficiency of capture of Ar and Kr ions into collective acceleration from their residual atmospheres was estimated as 0.06 % and 0.19 %, respectively.

Quantum emitters in aluminum nitride induced by heavy ion irradiation

The integration of solid-state single-photon sources with foundry-compatible photonic platforms is crucial for practical and scalable quantum photonic applications. This study explores aluminum nitride (AlN) as a material with properties highly suitable for integrated on-chip photonics and the ability to host defect-center related single-photon emitters. We have conducted a comprehensive analysis of the creation of single-photon emitters in AlN, utilizing heavy ion irradiation and thermal annealing techniques. Subsequently, we have performed a detailed analysis of their photophysical properties. Guided by theoretical predictions, we assessed the potential of Zirconium (Zr) ions to create optically addressable spin defects and employed Krypton (Kr) ions as an alternative to target lattice defects without inducing chemical doping effects. With a 532 nm excitation wavelength, we found that single-photon emitters induced by ion irradiation were primarily associated with vacancy-type defects in the AlN lattice for both Zr and Kr ions. The density of these emitters increased with ion fluence, and there was an optimal value that resulted in a high density of emitters with low AlN background fluorescence. Under a shorter excitation wavelength of 405 nm, Zr-irradiated AlN exhibited isolated point-like emitters with fluorescence in the spectral range theoretically predicted for spin-defects. However, similar defects emitting in the same spectral range were also observed in AlN irradiated with Kr ions as well as in as-grown AlN with intrinsic defects. This result is supportive of the earlier theoretical predictions, but at the same time highlights the difficulties in identifying the sought-after quantum emitters with interesting properties related to the incorporation of Zr ions into the AlN lattice by fluorescence alone. The results of this study largely contribute to the field of creating quantum emitters in AlN by ion irradiation and direct future studies emphasizing the need for spatially localized Zr implantation and testing for specific spin properties.

Color Centers in BaFBr Crystals: Experimental Study and Theoretical Modeling.

This study presents theoretical and experimental investigations into the electron and hole color centers in BaFBr crystals, characterizing their electronic and optical properties. Stoichiometric BaFBr crystals grown by the Steber method were used in the experiments. Radiation defects in BaFBr crystals were created by irradiation with 147 MeV 84Kr ions with up to fluences of 1010-1014 ions/cm2. The formation of electron color centers (F(F-), F2(F-), F2(Br-)) and hole aggregates was experimentally established by optical absorption spectroscopy. Performed measurements are compared with theoretical calculations. It allows us to determine the electron transition mechanisms and investigate the processes involved in photoluminescence emission in Eu-doped BaFBr materials to enhance the understanding of the fundamental electronic structure and properties of electron and hole color centers formed in BaFBr crystals.

Insights into magnetism generation in pristine O-polar ZnO thin films through Kr ion implantation: experimental and theoretical study

Insights into magnetism generation in pristine O-polar ZnO thin films through Kr ion implantation: experimental and theoretical study

On the question whether surface roughness can explain the absence of a prominent single-collision peak in keV heavy-ion scattering off a polycrystalline Ru surface

In a joint experimental and modeling effort, we have studied 15 keV Ar2+, Kr2+, and Xe2+ projectiles scattering off a polycrystalline Ru surface to assess the possible role of surface roughness in the apparent near-absence of the single-collision (SC) peak for Xe, the heaviest of the ions. The surface roughness of the Ru sample was determined by atomic force microscopy (AFM). The AFM image is used as input to simulations by means of the ray tracing code SPRAY. The observed spectra display a significant SC peak in the energy distributions of reflected Ar and Kr ions, which is not the case for Xe. The energy spectrum produced by the reflection of Xe and recoiled Ru ions closely corresponds to the results obtained from our SPRAY simulations. It is evident that surface roughness plays a crucial role in the visibility of the SC peak. From simulations for different target roughnesses, it is clear that a concentrated distribution of inclination angles centered around 2° effectively reduces the intensity of the single-collision peak for Xe ion scattering. The presence of a distinct SC peak for Ar and Kr ions, unlike Xe ions, supports the notion that the absence of a prominent SC peak in Xe ion scattering is not primarily due to geometric blocking of trajectories by surface roughness. This suggests that for slow, heavy ions like Xe, scattering effects arising from the nearest neighbors to the binary collision partner are significant and should be carefully examined.

Processing of hafnium oxide thin films by 2 MeV Kr ion beam for opto-electronic applications

The ion irradiation on 100 nm and 200 nm HfO2 films was performed using a 2 MeV Kr8+ beam at three different fluences viz. 1.5 × 1015 ions/cm2, 2 × 1015 ions/cm2 and 2.5 × 1015 ions/cm2 and various characterization techniques were employed to analyze the as-deposited and irradiated films. The AFM analysis showed that contrary to 200 nm films, the surface roughness of 100 nm films increases with increasing the ion fluence as also validated by FE-SEM. For 100 nm films, the phase analysis done by XRD indicated that the pristine films co-exist in dual phases of cubic and monoclinic; which also prevailed with post-irradiation. However, the pristine 200 nm films coexisted in dual monoclinic and orthorhombic phases and changed to sole orthorhombic phase with increasing ion fluences. The pristine 200 nm film showed more conductivity, which decreases with increasing ion fluences. Interestingly, the optical reflectivity of as-deposited 200 nm film was higher than that of 100 nm film and upon ion irradiation, both films showed inverse trend of reflectivity change; in 100 nm thin films, it decreases with increasing ion fluences. Thus, the ion irradiation seems to be a fascinating tool to tailor HfO2 thin films for their device applications.

The Effect of 147 MeV 84Kr and 24.5 MeV 14N Ions Irradiation on the Optical Absorption, Luminescence, Raman Spectra and Surface of BaFBr Crystals

Today, BaFBr crystals activated by europium ions are used as detectors that store absorbed energy in metastable centers. In these materials, the image created by X-ray irradiation remains stable in the dark for long periods at room temperature. As a result, memory image plates are created, and they are extended to other types of ionizing radiation as well. Despite significant progress towards X-ray storage and readout of information, the mechanisms of these processes have not been fully identified to date, which has hindered the efficiency of this class of phosphors. In this study, using photoluminescence (PL), optical absorption (OA), Raman spectroscopy (RS), and atomic force microscopy (AFM), the luminescence of oxygen vacancy defects to BaFBr crystals irradiated with 147 MeV 84Kr and 24.5 MeV 14N ions at 300 K to fluences (1010–1014) ion/cm2 was investigated. BaFBr crystals were grown by the Shteber method on a special device. Energy-dispersive X-ray spectroscopy (EDX) analysis revealed the presence of Ba, Br, F, and O. The effect of oxygen impurities present in the studied crystals was considered. The analysis of the complex PL band, depending on the fluence and type of ions, showed the formation of three types of oxygen vacancy defects. Macrodefects (tracks) and aggregates significantly influence the luminescence of oxygen vacancy defects. The creation of hillocks and tracks in BaFBr crystals irradiated with 147 MeV 84Kr ions is shown for the first time. Raman spectra analysis confirmed that BaFBr crystals were amorphized by 147 MeV 84Kr ions due to track overlap, in contrast to samples irradiated with 24.5 MeV 14N ions. Raman and absorption spectra demonstrated the formation of hole and electron aggregate centers upon swift heavy ions irradiation.

Argon admixture-driven enhanced ionization and performance of a 5 kW Hall thruster on krypton

Utilizing alternative propellants has been recognized as a strategy to reduce the total cost of propellants in electric propulsion-based missions. The aim of this study is to quantify the Hall effect thruster (HET) performance and operating characteristics using a Kr–Ar mixture to enable mission designers to evaluate the impact on mission and spacecraft design. We present the performance and plume plasma properties of the P5 5 kW-class HET operated with a Kr–Ar mixture with Ar volumetric flow rate fractions from 0 to 100%. The thruster is characterized at discharge power levels of 2.6 kW and 4.1 kW at constant discharge current and voltage over the range of Ar fractions. Despite higher ionization energy and lower mass of Ar, the thruster exhibited a similar level of thrust within 2% when comparing the pure Kr and 26%-Ar mixture cases. The derived ion energy distribution functions and analytical modeling suggest that the characteristic length for the ionization region is extended as the Ar fraction increases. The increased residence time of Kr at the extended ionization region and background energetic electrons from the ionized Ar neutrals are considered to cause this enhanced ionization of the injected Kr neutrals. This leads to a 6% higher Kr ion density at the 26%-Ar case even at the 16% less injected Kr neutral density than in the pure Kr case. The enhanced Kr ionization and generated Ar ions in the 26%-Ar case consequently led to a comparable thrust with that of the pure Kr case. The study indicates that mixing Ar with approximately 26% volumetrically with Kr can provide a similar or even higher thrust performance at the same discharge power. This will be particularly advantageous for various space missions that require high impulses by reducing the total cost of the propellant.

Microstructural evolution of ion-irradiated commercially pure titanium

Radiation-induced dislocation loop evolution in ion-irradiated commercially pure (CP) Ti was investigated through both ex situ 4 MeV Ar beams and by in situ TEM irradiation with 1 MeV Kr ion beams at different temperatures. The dominant mechanism for dislocation loop growth was loop coalescence. Both <a>- and c-component loops exhibited an increase in size and density with increased irradiation dose and temperature. C-component loops were observed only after reaching a threshold incubation dose (TID). In CP Ti, these loops initiated at lower doses compared to previous observations in Zr, and the TID decreased with increasing temperature.

Evolutions of microstructural defects in high-entropy carbide ceramics under ion irradiations at room temperature

This work studied and compared the evolutions of irradiation-induced microstructural defects in five high-entropy carbide ceramics (HECCs) at room temperature to reveal the irradiation resistances of HECCs and corresponding underlying mechanisms. The five HECCs exhibit high phase stabilities and no amorphization is observed up to 40 dpa. In-situ 800 keV Kr ion irradiation reveals similar evolutions of irradiation-induced defects. The densities of dislocation loops show non-monotonic variations, which reach the maximum at ∼ 2 dpa and then decrease due to the interactions with each other. In contrast, the sizes of dislocation loops increase monotonically with dose. (NbTaZrW)C exhibits the lowest defect densities and highest defect sizes, which is probably due to the high lattice distortion and its induced high defect recombination efficiencies. Based on the characterization results, it is deduced that the species of constituent elements play more important role in the defect behaviors than the number of constituent elements.

Temperature and density dependence of Kr L-shell spectrum in hot dense plasmas

Kr L-shell spectroscopy modeling results are discussed in this paper, focusing on the n = 4 to n = 2 line transitions of Be- and Li-like Kr ions. Collisional radiative atomic kinetic and Stark-broadened spectral line shape calculations show electron temperature Te and density ne sensitivity in the spectrum. The combination of the Te dependence due to the relative intensity of Be-like to Li-like line emissions in the range from 1.5 to 3 keV and the ne sensitivity from the Stark broadening effect on the line shapes in the range from 5×1023 to 2×1024/ cc results in a spectrum that can be employed to diagnose Te and ne. Two different collisional radiative atomic kinetic models i.e., Prismspect [J. J. MacFarlane, et al., Int. Fusion Sci. Appl. Conf. Proc. 457 (2003)] and ABAKO [Florido, et al., PRE, 80, 056402 (2009)] produce similar results in level populations and spectra. In x-ray spectroscopy of implosion cores, this Kr L-shell spectrum may prove useful in an intermediate Te range in which Ar is too ionized for its K-shell to be of diagnostic value and Kr is not ionized enough for its K-shell emission to be useful.

Changes in the hydrophilicity of the surface of PADC under ionizing radiations: Anomalous increase of the contact angle of water droplets under protons

The contact angle of water droplets decreases above certain absorbed doses in the case of heavy ions (He, C and Kr ions). Similarly, monotonic decreases are seen due to exposures to corona discharge and UV lights. The present trends indicate that the hydrophilicity of PADC surface increases by the contribution of hydroxyl groups.In comparison, the contact angle increases due to proton irradiations up to 1.3×105 Gy. Then it begins to decrease monotonically with increasing the absorbed dose. The present anomalous trend is discussed based on the combination of the track overlapping model and the Young’s formula.

Internal structural changes in crystals induced by GeV heavy ion beam irradiation of LiF

&lt;sec&gt;When an incident high-energy heavy ion beam enters into solid material, the energy deposition density along the ion flight path can change the temperature and pressure of macroscopic target, and new material defects can be created under the high-pressure and high-density conditions. To accurately control the extreme state in material generated by heavy ion beam, it is necessary to conduct in-depth research on the energy deposition density of ions and ascertain the new potential defects in matter. Reported in this work is the new experiment conducted on the HIRFL-CSR at Lanzhou, with the extracted 264 MeV/u Xe&lt;sup&gt;36+&lt;/sup&gt; ion beams irradiating an LiF crystal target. The emission spectrum of the LiF is measured &lt;i&gt;in-situ&lt;/i&gt;. Moreover, the crystal color is observed to vary along the ion path, and X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are used to observe the potential new phases at different positions of crystal through the target dissociation method.&lt;/sec&gt;&lt;sec&gt;It is apparent that in No. 3-front a new phase around 52.6° is found in XRD result, which is believed to be LiF&lt;sub&gt;3&lt;/sub&gt; (LiF+F&lt;sub&gt;2&lt;/sub&gt;) structural phase and appears in the Bragg peak region of Xe ions in LiF. Furthermore, to verify this result, a similar experiment is done by using a 430 MeV/u &lt;sup&gt;84&lt;/sup&gt;Kr&lt;sup&gt;26+&lt;/sup&gt; ion beam, and the stacked layered LiF target is analyzed after the irradiation. The XPS result shows more complex defects aggregating in the Bragg peak region of Kr ions in LiF at room temperature. In previous study, such complex defects were all created under high temperature conditions. We find that these complex defects can be produced around the Bragg peak region of ions in LiF at room temperature, resulting in a temporally high temperature and high pressure condition. This paper can provide some experimental evidences and references for the target material modification in heavy ion beam driven high-energy density physics research.&lt;/sec&gt;

Paticularities of radiation defect formation in ceramic barium cerate

The results of the investigations are presented on the effect of irradiation with electrons, ions of inert gases (Ne, Ar, Kr) and oxygen on the structure and properties of Nd-doped barium cerate by the methods of X-ray diffraction analysis, scanning electron and atomic force microscopy, thermal desorption spectroscopy. It is shown that the low-energy irradiation with Ne and Ar ions stimulates the blistering processes on the surface, whereas the high energy ion irradiation by Ne, Ar, Kr ions the cerate surface undergoes the following stages of the spherulite growth - nucleation, growth (view of cauliflower), formation of spherulitic crust, correspondingly. The similar structures were not observed in the case of irradiation with high-energy oxygen ions. It is noticed that the irradiation of cerates with electrons leads to the formation of nano-sized acicular structures on the surface. The radiation of lowenergy ions of inert gases led to the conversion of most of the neodymium into a tetravalent state, as has been shown, accompanied by an increase in oxygen release and a decrease in water compared to non-irradiated cerate, as well as the independence of the amount of gases from the type of ions. Based on the data on thermal desorption of water and oxygen molecules from the irradiated barium cerate it was assumed that the irradiation stimulates the oxidation to Nd4+.

Surface Activated Si-Si Wafer Bonding Using Different Ion Species

Surface activated bonding (SAB) on wafer level is enabled by the EVG ComBond® system for irradiation with different ion species. In this process, the native oxide of 200 mm Si wafers is sputter-removed, and an amorphous layer is generated. After ion treatment, the wafers are bonded in ultra-high vacuum (UHV) at room temperature. The impact of Ar, Kr and Xe ion irradiation on the amorphous layer thickness (ALT) was investigated with the goal of optimizing the bonding process. This was i.a. motivated by the fact, that the presence of an amorphous layer reduces the electrical conductivity across the wafer interface [1].The ALT of unbonded wafers was evaluated via spectroscopic ellipsometry (SE) for varying ion species, ion energies and angles of incidence. The results show that heavier ions generate a thinner amorphous layer than light ions (see Fig. 1). This is most likely due to the higher scattering cross section of heavy ions resulting in a lower penetration depth. For each ion type there is a minimum in the ALT as a function of the ion energy which can be attributed to sputter-implantation dynamics. Furthermore, the ALT is decreasing with the angle of incidence as the incoming ions are projected into the material.Transmission electron microscopy (TEM) measurements were conducted on bonded wafer pairs and confirm the trend of heavy ions generating a thinner amorphous layer. Moreover, the TEM measurements show that post-bond annealing at 450°C for 5 h reduces the ALT due to recrystallization near the bonding interface.To ensure mechanical stability for further wafer processing and for the final device, bonding energy measurements were conducted via the Maszara method [2]. Although maximum bonding energy can be achieved for specific parameters with each ion species, Xe irradiated samples tend to have a higher overall bonding energy.[1] P.A. Stolk et al., “Contribution of defects to electronic, structural, and thermodynamic properties of amorphous silicon”, in Journal of Applied Physics, vol. 75, no. 11, pp. 7266-7286 (1994).[2] W.P. Maszara et al., “Bonding of silicon wafers for silicon-on-insulator”, in Journal of Applied Physics, vol. 64, no. 10, pp. 4943-4950 (1988). Figure 1

Application of polyimide films as a nuclear track detector (1): A systematic study of track registration sensitivity

This paper reports the variation of track registration sensitivity as a function of the stopping power of heavy ions in UPILEX-S® films, which is known as the most radiation tolerant polyimide (PI). The detection thresholds in the stopping power for etch pit formation are determined as 4,000, 4,100, 4,800, and 5600 keV/μm for 40Ar, 84Kr, 132Xe and 238U ions, respectively. Furthermore, we investigate the latent track structure in two kinds of PI films (UPILEX-S® and Kapton) by means of FT-IR spectroscopy. At the similar stopping power value, the radiation chemical yields (G value) for heavier ions are lower than those of lighter ions. This is due to the difference of the radial dose distribution for low and high velocity ions.

Study of Electron Impact Excitation of Na-like Kr Ion for Impurity Seeding Experiment in Large Helical Device

In this work, a krypton gas impurity seeding experiment was conducted in a Large Helical Device. Emission lines from the Na-like Kr ion in the extreme ultraviolet wavelength region, such as 22.00 nm, 17.89 nm, 16.51 nm, 15.99 nm, and 14.08 nm, respective to 2p63p(2P1/2o)−2p63s(2S1/2), 2p63p(2P3/2o)−2p63s(2S1/2), 2p63d(2D3/2)−2p63p(2P3/2o), 2p63d(2D5/2)−2p63p(2P3/2o), and 2p63d(2D3/2)−2p63p(2P1/2o) transitions, are observed. In order to generate a theoretical synthetic spectrum, an extensive calculation concerning the excitation of the Kr25+ ion through electron impact was performed for the development of a suitable plasma model. For this, the relativistic multiconfiguration Dirac–Hartree–Fock method was employed along with its extension to the relativistic configuration interaction method to compute the relativistic bound-state wave functions and excitation energies of the fine structure levels using the General Relativistic Atomic Structure Package-2018. In addition, another set of calculations was carried out utilizing the relativistic many-body perturbation theory and relativistic configuration interaction methods integrated within the Flexible Atomic Code. To investigate the reliability of our findings, the results of excitation energies, transition probabilities, and weighted oscillator strengths of different dipole-allowed transitions obtained from these different methods are presented and compared with the available data. Further, the detailed electron impact excitation cross-sections and their respective rate coefficients are obtained for various fine structure resolved transitions using the fully relativistic distorted wave method. Rate coefficients, calculated using the Flexible Atomic Code for population and de-population kinetic processes, are integrated into the collisional-radiative plasma model to generate a theoretical spectrum. Further, the emission lines observed from the Kr25+ ion in the impurity seeding experiment were compared with the present plasma model spectrum, demonstrating a noteworthy overall agreement between the measurement and the theoretical synthetic spectrum.