MeV Proton Irradiation Research Articles

Radiation tolerance characterization of dual band InAs/GaSb type-II strain-layer superlattice pBp detectors using 63 MeV protons

The radiation tolerance characterization of dual band InAs/GaSb type-II strain-layer superlattice pBp detectors of varying size using 63 MeV proton irradiation is presented. The detectors' mid-wave infrared performance degraded with increasing proton fluence ΦP up to 3.75 × 1012 cm−2 or, equivalently, a total ionizing dose = 500 kRad (Si). At this ΦP, an ∼31% drop in quantum efficiency η, ∼2 order increase in dark current density JD, and consequently, >1 order drop in calculated detectivity D* were observed. Proton damage factors were determined for η and D*. Arrhenius-analysis of temperature-dependent JD measurements reflected significant changes in the activation energies following irradiation.

Cross sections from 800 MeV proton irradiation of terbium

A single terbium foil was irradiated with 800 MeV protons to ascertain the potential for production of lanthanide isotopes of interest in medical, astrophysical, and basic science research and to contribute to nuclear data repositories. Isotopes produced in the foil were quantified by gamma spectroscopy. Cross sections for 36 isotopes produced in the irradiation are reported and compared with predictions by the MCNP6 transport code using the CEM03.03, Bertini, and INCL+ABLA event generators. Our results indicate the need to accurately consider fission and fragmentation of relatively light target nuclei like terbium in the modeling of nuclear reactions at 800 MeV. The predictive power of the code was found to be different for each event generator tested but was satisfactory for most of the product yields in the mass region where spallation reactions dominate. However, none of the event generators' results are in complete agreement with measured data.

Prebiotic organic microstructures.

Micro- and sub-micrometer spheres, tubules and fiber-filament soft structures have been synthesized in our experiments conducted with 3 MeV proton irradiations of a mixture of simple inorganic constituents, CO, N2 and H2O. We analysed the irradiation products, with scanning electron microscopy (SEM) and atomic force microscopy (AFM). These laboratory organic structures produced a wide variety of proteinaceous and non-proteinaceous amino acids after HCl hydrolysis. The enantiomer analysis for D,L-alanine confirmed that the amino acids were abiotically synthesized during the laboratory experiment. We discuss the presence of CO2 and the production of H2 during exothermic processes of serpentinization and consequently we discuss the production of hydrothermal CO in a ferromagnesian silicate mineral environment. We also discuss the low intensity of the Earth’s magnetic field during the Paleoarchaean Era and consequently we conclude that excitation sources arising from cosmic radiation were much more abundant during this Era. We then show that our laboratory prebiotic microstructures might be synthesized during the Archaean Eon, as a product of the serpentinization process of the rocks and of their mineral contents.

225Ac and 223Ra production via 800 MeV proton irradiation of natural thorium targets

Cross sections for the formation of 225,227Ac, 223,225Ra, and 227Th via the proton bombardment of natural thorium targets were measured at a nominal proton energy of 800MeV. No earlier experimental cross section data for the production of 223,225Ra, 227Ac and 227Th by this method were found in the literature. A comparison of theoretical predictions with the experimental data shows agreement within a factor of two. Results indicate that accelerator-based production of 225Ac and 223Ra is a viable production method.

Proton irradiation energy dependence of dc and rf characteristics on InAlN/GaN high electron mobility transistors

The effects of proton irradiation energy on dc and rf characteristics of InAlN/GaN high electron mobility transistors (HEMTs) were investigated. A fixed proton dose of 5 × 1015 cm−2 with 5, 10, and 15 MeV irradiation energies was used in this study. For the dc characteristics, degradation was observed for sheet resistance, transfer resistance, contact resistivity, saturation drain current, maximum transconductance, reverse-bias gate leakage current, and sub-threshold drain leakage current for all the irradiated HEMTs; however, the degree of the degradation was decreased as the irradiation energy increased. Similar trends were obtained for the rf performance of the devices, with ∼10% degradation of the unity gain cut-off frequency (fT) and maximum oscillation frequency ( fmax) for the HEMTs irradiated with 15 MeV protons but 30% for 5 MeV proton irradiation. The carrier removal rate was in the range 0.66–1.24 cm−1 over the range of proton energies investigated.

Degradation of dc characteristics of InAlN/GaN high electron mobility transistors by 5 MeV proton irradiation

The dc characteristics of InAlN/GaN high electron mobility transistors were measured before and after irradiation with 5 MeV protons at doses up to 2 × 1015 cm−2. The on/off ratio degraded by two orders of magnitude for the highest dose, while the subthreshold slope increased from 77 to 122 mV/decade under these conditions. There was little change in transconductance or gate or drain currents for doses up to 2 × 1013 cm−2, but for the highest dose the drain current and transconductance decreased by ∼40% while the reverse gate current increased by a factor of ∼6. The minority carrier diffusion length was around 1 μm independent of proton dose. The InAlN/GaN heterostructure is at least as radiation hard as its AlGaN/GaN counterpart.

Reducing structural change in aluminum coated polyethylene naphthalate foils during MeV proton irradiation

Structural change in polyethylene naphthalate (PEN) foil during MeV proton beam irradiation was investigated by ion beam induced luminescence (IBIL). An aluminum thin film (thickness: 20 nm) was sputter-deposited on the upper surface of 4 μm thick PEN foil to evaluate how Al coating effects structural change. IBIL analysis reveals that the Al coating clearly reduces damage induced by ion beam irradiation, probably due to the enhancement of electrical conductivity of the foil.

Influence of random point defects introduced by proton irradiation on critical current density and vortex dynamics of Ba(Fe0.925Co0.075)2As2single crystals

In this work we analyze the influence of random point defects introduced by 3 MeV proton irradiation on the critical current density (${J}_{c}$) and vortex dynamics of a Ba(Fe${}_{0.925}$Co${}_{0.075}$)${}_{2}$As${}_{2}$ single crystal. The results show that at low temperatures ($T$) the irradiation produces an enhancement of ${J}_{c}$ of up to 2.6 times. However the ${J}_{c}$ ($T$) retention at different magnetic fields ($H$) in the elastic regime, estimated by the $n$ exponent in ${J}_{c}$ vs ${(1\ensuremath{-}{(T/{T}_{c})}^{2})}^{n}$, is poorer after the irradiations due to the thermal softening of the pinning by the random point defects. We found that the elastic-to-plastic crossover and melting lines are only affected by the reduction of the superconducting critical temperature (${T}_{c}$); they are exactly the same after rescaling the phase diagram by $T$/${T}_{c}$. The pinning mechanisms in the single crystals can be associated with a mixed pinning landscape that produces a modulation in $S$($H$, $T$) as a consequence of a fishtail or second peak in the magnetization.

Effects of 3 MeV proton irradiations on AlGaN/GaN high electron mobility transistors

AlGaN/GaN high electron mobility transistors (HEMT) are exposed to 3 MeV protons irradiation. The drain saturation current decreases 20% and the maximum transconductance decreases 5% at a fluence of 1× 1015 protons/cm2. As fluence increases, the thread voltage is shifted toward more positive values. After proton irradiation, the gate leakage current increases. The degradation caused by 1.8 MeV proton is significantly higher than by 3 MeV proton irradiation at the same fluence. The radiation damage area and the density of vacancies at a given depth are obtained from software SRIM. As the energy of the incident proton increases, the non-ionizing energy transferred to the crystal lattice decreases. It is concluded that vacancies introduced by proton irradiation may be the primary reason for the degradations of electrical characteristics of AlGaN/GaN HEMT.

High Total-Dose Proton Radiation Tolerance in TiN/HfO2/TiN ReRAM Devices

ABSTRACTThe resistive switching properties of CMOS compatible TiN/HfO2/TiN resistive-random-access-memory (ReRAM) devices have been investigated after exposure to 1 MeV proton radiation. The HfO2-based ReRAM devices were found to have high total-ionizing-dose (TID) radiation tolerance up to 5 Grad(Si). TiN/HfO2/TiN ReRAM performance parameters include high-resistance state (HRS) resistance, low-resistance state (LRS) resistance, set and reset voltages. HfO2-based ReRAM devices exhibited no degradation in these performance parameters following proton irradiation exposure with TID from 105 to 109 rad(Si). Furthermore, the HfO2-based ReRAM devices exhibited more uniform resistive switching behavior with increased TID. Based on this radiation response it is proposed that the resistive switching mechanism in TiN/HfO2/TiN – trap-assisted tunneling associated with Hf-rich conducting filament formation – may be reinforced through proton exposure which acts to stabilize the formation/rupture of Hf-rich filaments. The high radiation tolerance of HfO2-based ReRAM devices suggests such devices may be potentially attractive for aerospace and nuclear applications.

Study of the proton irradiation damage on Capsule type polarization-maintaining optical fibers made in China

A spacecraft running in the space environment would be irradiated by the proton, and the irradiation effects on the most important parts of the optical fiber gyroscope in the spacecraft -the optical fiber ring is the most. In order to investigate the irradiation damage induced by proton irradiation on the Capsule type polarization-maintaining optical fibers made in china, the variation of the transportation power at 1310 nm wavelength is measured by means of situ measurement for the 5 MeV and 10 MeV environments protons irradiation on the Capsule type polarization-maintaining optical fibers made in china. The irradiation induced loss is calculated by us. The Stopping and Range of Ions in Matter (SRIM) software was used to simulate the ionic and displacement damage of 5 MeV and 10 MeV energy protons irradiation on the optical fibers. The O 1s and Si 2p analytic spectrum of the before and after irradiation were obtained by means of X ray photoelectron spectroscopy (XPS). Using the Fourier transform infrared spectrometer (FTIR), we analyzed the before and after irradiation spectrum. The results show that at the 1310 nm wavelength, the rradiation induced loss of the of optical fibers increase with the increasing of the protons fluence due to the increase of the SiOH concentration in optical fiber core. The 5 MeV proton irradiation induced loss is worse than that of the 10 MeV mainly because the more worse displacement and the ironic damage induced by 5 MeV proton at the position of the optical fiber core than that of 10 MeV, i.e., the more amount of SiOH generation.

8 MeV Proton Irradiation Damage and Its Recovery by Annealing on Single-Crystalline Zinc Oxide Crystals

ABSTRACTII-VI compound semiconductor ZnO has a potential for high radiation hardness since large threshold displacement energy of constituent atoms can be expected due to the small unit-cell volume and large bandgap energy of 3.37 eV. In order to study the radiation hardness, singlecrystalline c-axis-oriented O-polar ZnO films with and without two-dimensional electron gas, a Zn-polar ZnO bulk crystal, and a Ga-polar GaN bulk crystal for comparison, were irradiated by an 8 MeV proton beam using a tandem-type accelerator. The radiation damage increased the electrical resistance and decreased the photoluminescence (PL) intensity of these samples with the increase of proton fluence over specific threshold values. In agreement with the expectation, ZnO samples were revealed to have superior radiation hardness; the threshold fluences for the deterioration of PL intensity were 3×1013 p/cm2 for the GaN bulk crystal, 2×1014 p/cm2 for the ZnO bulk crystal, and 5×1014 p/cm2 for the two ZnO films, in accordance with the order of the threshold fluences for the electrical resistance increase. The effect of post-irradiation annealing was also studied for these damaged bulk crystals; both electrical and optical properties of the ZnO bulk crystal were almost recovered to the pre-irradiation values, however, only the electrical properties of the GaN bulk crystal were recovered, by the annealing up to 700°C. Such a rapid recovery of the ZnO bulk crystal indicates the easy annihilation of Zn vacancy complexes acting as non-radiative centers by the recombination with interstitial Zn atoms. Since the migration barrier height energy of interstitial Zn atoms is known to be so small that it might occur even at room temperature, we ascribed the superior radiation hardness of ZnO crystals to the restoration of damage-induced defects by a self-annealing effect during irradiation.

The effects of proton irradiation on the electrical properties of NbAlO/AlGaN/GaN MIS-HEMT

AlGaN/GaN metal-insulator-semiconductor high electron-mobility transistors (MIS-HEMTs) with atomic layer deposited (ALD) NbAlO gate dielectric were investigated using 3 MeV proton irradiation at a fluence of 1015 p/cm2. It was found that the proton irradiation damage caused degradation in DC performance and a flatband voltage shift in the capacitance-voltage curve. Gate-drain conductance measurements indicated that new traps were introduced in GaN from the irradiation, and the trap densities increased from 1.18×1012 cm−2·eV−1 to 1.82×1012 cm−2·eV-1 in MIS-HEMTs after irradiation. However, these increases in trap densities caused by irradiation in MIS-HEMT are less than those in HEMT, which can be attributed to the protection of the AlGaN surface by the NbAlO dielectric layer.

Prebiotic Organic Microstructures

AbstractMicro- and sub-micrometer spheres, tubules and fiber-filament soft structures have been synthesized in our experiments conducted with 3 MeV proton irradiations of a mixture of simple inorganic constituents, CO, N2 and H2O. We analysed the irradiation products, with scanning electron microscopy (SEM) and atomic force microscopy (AFM). These laboratory organic structures produced wide variety of proteinous and non-proteinous amino acids after HCl hydrolysis. The enantiomer analysis for D-, L- alanine confirmed that the amino acids were abiotically synthesized during the laboratory experiment. Considering hydrothermal activity, the presence of CO2 and H2, of a ferromagnesian silicate mineral environment, of an Earth magnetic field which was much less intense during Archean times than nowadays and consequently of a proton excitation source which was much more abundant, we propose that our laboratory organic microstructures might be synthesized during Archean times. We show similarities in morphology and in formation with some terrestrial Archean microstructures and we suggest that some of the observed Archean carbon spherical and filamentous microstructures might be composed of abiogenic organic molecules. We further propose a search for such prebiotic organic signatures on Mars. This article has been posted on Nature precedings on 21 July 2010 [1]. Extinct radionuclides as source of excitation have been replaced by cosmic radiations which were much more intense 3.5 Ga ago because of a much less intense Earth magnetic field. The new version of the article has been presented at the ORIGINS conference in Montpellier in july 2011 [2] and has since been published in Origins of Life and Evolution of Biospheres 42 (4) 307-316, 2012.DOI: 10.1007/s11084-012-9290-5

Application of a Pelletron accelerator to study total dose radiation effects on 50 GHz SiGe HBTs

We have investigated the effects of 50 MeV lithium ion irradiation on the DC electrical characteristics of first-generation silicon–germanium heterojunction bipolar transistors (50 GHz SiGe HBTs) in the dose range of 600 krad to 100 Mrad. The results of 50 MeV Li 3+ ion irradiation on the SiGe HBTs are compared with 63 MeV proton and Co-60 gamma irradiation results in the same dose range in order to understand the damage induced by different LET species. The radiation response of emitter–base (EB) spacer oxide and shallow trench isolation (STI) oxide to different irradiation types are discussed in this paper. We have also focused on the efficacy in the application of a Pelletron accelerator to study total dose irradiation studies in SiGe HBTs.

Effect of irradiation on the microstructure and mechanical behavior of nanocrystalline nickel

The effect of 4.0 MeV proton irradiation on the microstructure and mechanical properties of nanocrystalline (nc) nickel was investigated. The irradiation damage induced in the sample was of the order of 0.004 dpa. Transmission electron microscopy of irradiated samples indicated the presence of dislocation loops within the grains. An increase in hardness and strain-rate sensitivity (m) of nc-Ni with irradiation was noted. The rate-controlling deformation mechanism in irradiated nc-Ni was identified to be interaction of dislocations with irradiation-induced defects. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

High fluence 1.8 MeV proton irradiation effects on n-type MOS capacitors

MOS capacitors with 7 nm SiO 2 dielectrics and n-doped Si substrate were irradiated by 1.8 MeV protons with fluences ranging from 10 12 to 5 × 10 13 cm −2 which correspond to the typical LHC fluence range. No significant increase in gate oxide leakage current was detected. A decrease of the capacitance was observed in the accumulation regime. This effect is explained by an increase of the substrate resistivity caused by displacement damage.

Radiolysis of sulfuric acid, sulfuric acid monohydrate, and sulfuric acid tetrahydrate and its relevance to Europa

We report laboratory studies on the 0.8 MeV proton irradiation of ices composed of sulfuric acid (H 2SO 4), sulfuric acid monohydrate (H 2SO 4·H 2O), and sulfuric acid tetrahydrate (H 2SO 4·4H 2O) between 10 and 180 K. Using infrared spectroscopy, we identify the main radiation products as H 2O, SO 2, (S 2O 3) x , H 3O +, HSO 4 - , and SO 4 2 - . At high radiation doses, we find that H 2SO 4 molecules are destroyed completely and that H 2SO 4·H 2O is formed on subsequent warming. This hydrate is significantly more stable to radiolytic destruction than pure H 2SO 4, falling to an equilibrium relative abundance of 50% of its original value on prolonged irradiation. Unlike either pure H 2SO 4 or H 2SO 4·H 2O, the loss of H 2SO 4·4H 2O exhibits a strong temperature dependence, as the tetrahydrate is essentially unchanged at the highest irradiation temperatures and completely destroyed at the lowest ones, which we speculate is due to a combination of radiolytic destruction and amorphization. Furthermore, at the lower temperatures it is clear that irradiation causes the tetrahydrate spectrum to transition to one that closely resembles the monohydrate spectrum. Extrapolating our results to Europa’s surface, we speculate that the variations in SO 2 concentrations observed in the chaotic terrains are a result of radiation processing of lower hydration states of sulfuric acid and that the monohydrate will remain stable on the surface over geological times, while the tetrahydrate will remain stable in the warmer regions but be destroyed in the colder regions, unless it can be reformed by other processes, such as thermal reactions induced by diurnal cycling.

H+ irradiation effect in Co-doped BaFe2As2 single crystals

We report the suppression of the critical temperature Tc in single crystalline Ba(Fe1−xCox)2As2 at under-, optimal-, and over-doping levels by 3MeV proton irradiation. Tc decreases and residual resistivity increases monotonically with increasing the dose. The low-temperature resistivity does not show the upturn in contrast with the α-particle irradiated NdFeAs(O,F), which suggests that proton irradiation introduces nonmagnetic scattering centers. Critical scattering rates for all samples obtained by three different ways are much higher than that expected in s±-pairing scenario based on inter-band scattering due to antiferro-magnetic spin fluctuations.

Deep level transient spectroscopy (DLTS) study of defects introduced in antimony doped Ge by 2 MeV proton irradiation

Deep level transient spectroscopy (DLTS) and Laplace-DLTS have been used to investigate the defects created in Sb doped Ge after irradiation with 2 MeV protons having a fluence of 1×10 13 protons/cm 2. The results show that proton irradiation resulted in primary hole traps at E V +0.15 and E V +0.30 eV and electron traps at E C −0.38, E C −0.32, E C −0.31, E C −0.22, E C −0.20, E C −0.17, E C −0.15 and E C −0.04 eV. Defects observed in this study are compared with those introduced in similar samples after MeV electron irradiation reported earlier. E C −0.31, E C −0.17 and E C −0.04, and E V +0.15 eV were not observed previously in similar samples after high energy irradiation. Results from this study suggest that although similar defects are introduced by electron and proton irradiation, traps introduced by the latter are dose dependent.