Nuclear Reaction 18O Research Articles

Comparison of gaseous contamination of thin tungsten and gold coatings deposited from ablated plasma generated by Intense Pulsed Ion Beams

The paper presents experimental results on C, N and O contamination in thin tungsten and gold coatings deposited on GaAs substrates from ablated plasma generated by intense pulsed ion beams accelerated in a magnetically insulated diode. The coating thickness was controlled by energy-dispersive X-Ray Fluorescence analysis. Depth profiles of C, N and O concentrations in the coatings were determined using quantitative Auger Electron Spectroscopy (AES) with ion sputtering. Non-destructive charged particle activation analysis via the nuclear reactions 12C(d,n)13N, 14N(d,n)15O and 16O(d,n)17F, induced by 3 MeV deuterons of extracted from a cyclotron was used to calibrate the AES determination of C, N and O. The gold coating was found to be devoid of detectable amounts of all gases, while carbon dominated by an order of magnitude over nitrogen and oxygen in tungsten coatings. Carbon contamination increased linearly with an increase in the number of ion shots applied. It was concluded that the main source of gas contamination is the residual atmosphere of the working chamber and the purest coatings can be obtained at the highest deposition rates per shot. A significant increase of oxygen admixture was found in the tungsten coatings after the samples were stored in the ambient atmosphere for 25 years. The storage did not affect the purity of the gold coating, but carbon seemed to diffuse from the Au/GaAs interface to the coating surface.

Installation of First Medium Energy Medical Cyclotron in Bangladesh at National Institute of Nuclear Medicine and Allied Sciences (NINMAS) for PET radiopharmaceuticals Production

PET-CT (positron emission tomography and computed tomography) is a gold-standard cancer imaging tool for diagnosis and management, as well as prognostic information based on treatment. Positron-emitting radionuclide 18F (Fluorine) is generated by accelerating particles to energies high enough to cause a certain nuclear reaction 18O(p,n)18F within the particle accelerator, the cyclotron. Mannose triflate is converted to 2-[18F] Fluoro-2-deox-D-yglucose ([18F]FDG) via nucleophilic reaction. Under the ownership of Bangladesh Atomic Energy Commission installed a medium energy (18/9 MeV, IBA) Cyclotron at National Institute of Nuclear Medicine and Allied Sciences (NINMAS). The facility was established in the oncology Building (Block F) of Bangabandhu Sheikh Mujib Medical University (BSMMU). Cyclotron vault and the Control room are located in the underground i.e. basement floor. Each wall of the cyclotron vault and ceiling is made of concrete with a density of 2.35 g/cm3 and a thickness sufficient to shield gamma and neutron radiation. On the ground floor, there are Synthesis room, Quality control laboratory, and the Decontamination room. PET-CT rooms are located on the first floor. Identification, Radionuclide purity (Gamma spectrum detection and half-life measurement), Radiochemical Purity, Chemical purity, Residual solvent measurement, pH measurement, Sterility, and bacterial endotoxins (LAL test) are performed to maintain the quality of the product. The current uses of the Cyclotron are mostly for the synthesis of 18F-FDG. Bangladesh J. Nuclear Med. 24(1&2): 48-50, 2021

Characterization of oxygen self-diffusion in TiO2 resistive-switching layers by nuclear reaction profiling

Oxygen self-diffusion was investigated in TiO2 layers employed for resistive-switching memories using resonant nuclear reaction profiling (NRP) and 18O labeling. The layers were grown using physical vapor deposition technique (sputtering) and were polycrystalline. The diffusivity was measured over the temperature range 600–800 °C and the activation energy for oxygen self-diffusion in sputter-deposited TiO2 films determined to be 1.09 ± 0.16 eV, a value consistent with results obtained by previous studies (Marmitt et al., 2017).

Study of diffusion processes in the oxide layer of zirconium alloys

Abstract In the active zone of a nuclear reactor where zirconium alloys are used as a coating material, this material is subject to various harmful impacts. During water decomposition reactions, hydrogen and oxygen are evolved that may diffuse through the oxidic layer either through zirconium dioxide (ZrO2) crystals or along ZrO2 grains. The diffusion mechanism can be studied using the Ion Beam Analysis (IBA) method where nuclear reaction 18O(p,α)15N is used. A tube made of zirconium alloy E110 (with 1 wt. % of Nb) was used for making samples that were pre-exposed in UJP PRAHA a.s. and subsequently exposed to isotopically cleansed environment of H2 18O medium in an autoclave. The samples were analysed with gravimetric methods and IBA methods performed at the electrostatic particle accelerator Tandetron 4130 MC in the Nucler Physics Institute of the CAS, Řež. With IBA methods, the overall thicknesses of corrosion layers on the samples, element composition of the alloy and distribution of oxygen isotope 18O in the corrosion layer and its penetration in the alloy were identified. The retrieved data shows at the oxygen diffusion along ZrO2 grains because there are two peaks of 18O isotope concentrations in the corrosion layer. These peaks occur at the environment-oxide and oxide-metal interface. The element analysis identified the presence of undesirable hafnium.

Damage recovery in the oxygen sublattice of ZnO by post-implantation annealing

Hydrothermally grown zinc oxide bulk samples were implanted with 200 keV-Co ions with a fluence of 4.5 × 10 16 cm −2 and then annealed in air during 30 min at different temperatures up to 900 °C. After the implantation and each annealing step, the samples were analyzed using the nuclear reaction 16O(α,α) 16O at 3.045 MeV He in random and channeling directions to follow the annealing of the disorder profile in the O sublattice. For comparison, the disorder in the Zn sublattice was also observed by Rutherford backscattering spectrometry (RBS) in random and channeling directions. The results reveal that the disorder created during the Co implantation is slightly higher in the O sublattice than in the Zn sublattice. The disorder recovery induced by the thermal treatments, starts at 500 °C in the O sublattice and at 700 °C in the Zn sublattice. Although, the most part of the disorder recovery occurs between 700 and 800 °C in both sublattices.

Polarization characteristics of nuclear quasi-free (p, dπ+) reaction

Nuclear reaction 16O(p, dπ+)15N is considered theoretically as a prototype of a specific class of nuclear quasi-free processes where deuteron, α-particle, 3H- or 3He-cluster are produced together with pion or η-meson in proton-nucleus interactions in the intermediate energy region.

Selective fluorination of m-tyrosine by OF 2

Fluorine-18 labeled aromatic amino acids are routinely used as tracers in positron emission tomography (PET) to study in vivo metabolic processes. The most versatile method for the production of such radiotracers is electrophilic fluorination of the aromatic amino acid with [ 18F]F 2, which is most commonly produced by the gas-phase nuclear reaction 18O(p, n) 18F. Although [ 18F]F 2 is the major product, considerable amounts of [ 18F]OF 2 (up to 20%) are also produced. Electrophilic fluorination reactions of l-phenylalanine, 3-nitro- l-tyrosine, 4-nitro- dl-phenylalanine, 3,4-dihydroxyphenyl- l-alanine ( l-DOPA), 3- O-methyl- l-DOPA, 3,4-dimethoxy- l-phenylalanine, p-tyrosine and o-tyrosine in H 2O and of m-tyrosine in anhydrous HF (aHF), CF 3SO 3H, CF 3COOH, CH 3COOH, HCOOH and H 2O using OF 2 were investigated. Although F 2 is an efficient fluorinating agent in aHF, electrophilic fluorination reactions using OF 2 were shown to be most efficient in less acidic media such as H 2O. In addition, and contrary to reports that OF 2 and F 2 have similar reactivities, m-tyrosine was the only aromatic system studied that was fluorinated by OF 2 and this was optimum in H 2O for the fluorinated m-tyrosine isomers (total yield, 4.35 ± 0.04%). The presence of [ 18F]OF 2 byproduct has no significant impact on the fluorination of aromatic amino acids investigated in this study and the subsequent production of their corresponding 18F-labeled radiotracers for patient use.

Investigation of the structural features of high-temperature superconducting crystals by the method of channelization and resonant nuclear reactions

The structural features of the oxygen sublattice in the YBa2Cu3O7 crystals are analyzed based on a comparison of the calculated angular dependence of the yield of resonant nuclear reaction 16O(α, α)16O with the available experimental results obtained for ions with energies of 3.055, 3.06, and 7.6 MeV. It is established that in crystal films there are vacancies in oxygen chains at room temperature, and oxygen atoms are considerably displaced from the equilibrium positions in directions perpendicular to the axis. In thick crystals at temperatures close to the temperature of phase transition into the superconducting state, no large thermal and/or static displacements of oxygen atoms from the equilibrium positions are observed.

Investigation of copper patinas using ion beam analysis and scanning electron microscopy

AbstractIon beam analysis (IBA) techniques were applied successfully to the investigation of non‐corroded and artificially corroded patina layers grown on copper substrates in order to explore their potential use in the study of degradation phenomena of copper and copper alloys subjected to chemical treatment and exposed to selected environmental conditions. Rutherford backscattering spectroscopy (RBS) with deuterons as projectiles and the nuclear reactions 16O(d,p)17O and 32S(p,p′γ)32S were applied to the investigation of the depth distribution of oxygen and sulphur in near‐surface layers of synthetic patina consisting of mineral phases corresponding to chalcanthite as well as to cuprite + chalcanthite and antlerite + brochantite + chalcanthite. Electrochemical techniques (potentiodynamic polarization and cyclic voltammetry in 0.5 M Na2SO4) were used for artificial acceleration and study of the corrosion processes, and scanning electron microscopy (SEM/EDS) was used for examination of the surface morphology of the samples. A patinated roof sample from the Vienna Hofburg also was investigated using the same techniques. The measurement showed that IBA can provide valuable information for the study of patina near‐surface layers of thickness up to a few micrometres and indicated that cuprite was the mineral phase primarily formed on the copper substrates and the main component of the interface between the patina layer and the metallic substrate. The investigated copper patinas looked rather heterogeneous and were characterized by high porosity. Mixed patinas exhibited considerable stability to further corrosive attack. Copyright © 2005 John Wiley & Sons, Ltd.

Fully automated synthesis module for preparation of S-(2-[ 18F]fluoroethyl)-L-methionine by direct nucleophilic exchange on a quaternary 4-aminopyridinium resin

A fully automated preparation of S-(2-[ 18F]fluoroethyl)-L-methionine (FEMET), an amino acid tracer for tumor imaging with positron emission tomography, is described. [ 18F]F - was produced via nuclear reaction 18O(p,n) [ 18F] at PETtrace Cyclotron. Direction nucleophilic fluorination reaction of [ 18F]fluoride with 1,2-di(4-methylphenylsulfonyloxy)ethane on a quaternary 4-(4-methylpiperidinyl)pyridinium functionalized polystyrene anion exchange resin gave 2-[ 18F]-1-(4-methylphenyl-sulfonyloxy)ethane, and then [ 18F]fluoroalkylation of L-homocysteine thiolactone with 2-[ 18F]-1-(4-methylphenylsulfonyloxy)ethane yielded FEMET. The overall radiochemical yield with no decay correction was about 10%, the whole synthesis time was about 52 min, and the radiochemical purity was above 95%.

Oxygen analysis using energetic ion beams

Using a thin amorphous layer of SiO 2 (5.2 μg/cm 2) on Si, cross sections for the nuclear reactions 16O(d,p 1) 17O, 16O(d,α) 14N and 16O(α,α) 16O at a laboratory angle of 150° are determined over energies ranging from 0.701 to 1.057 MeV for D + ions and from 2.949 to 3.049 MeV for He + ions. The results are plotted and tabulated as a function of ion energy, with typical uncertainties of 4% for the cross section data and of ±5 keV for the resonance energy. An example for the analysis of atomic displacements on the O sublattice in a Au 2+-irradiated SrTiO 3 single crystal is given.

Influence of the Native Oxide Layer on the Silicon Surface During Initial Stages of Nitridation

Thin SiO2 layers were produced by thermal oxidation of Si wafer material. To study the effect of nitridation on the oxide layers, the specimens were nitrided in a furnace at high temperature. Non-destructive ion beam analysis was performed to determine changes in the elemental concentrations and depth profiles of the major components. In particular, N and O concentrations were measured using the non-resonant nuclear reactions 14N(d, α)12C and 16O(d, p)17O, respectively. To obtain depth profiles of the as-prepared and nitrided specimens, the samples were measured with RBS and heavy ion elastic recoil detection analysis. The ion beam analyses revealed an increase in thickness of the SiO2 layers with temperature. The specimens nitrided at 1200 °C were almost free of N. Surface topology investigations with scanning electron microscopy revealed concentric annular artificial patterns at the surfaces. In the centre of the pattern, only silicon was measured. Additionally, a band consisting of Si, O, and N surrounding the pattern was discovered. The findings are in agreement with specimens prepared at higher temperatures.

Oxygen diffusion studies in oxide scales thermally grown or deposited on mechanically loaded metallic surfaces (MS-P2)

The high temperature growth of oxides on metallic surfaces mechanically in loading is not well understood yet. The knowledge of the growth of oxides on static surfaces and of the mechanical behavior of the metal/oxide system does not give account of the synergetic effects between the load and the growth of the oxide. The formation of cracks on the oxide scales, their healing and the role of the load on the oxygen diffusion processes have been studied on pure nickel and zirconium samples in creep. The use of oxygen-18 to study the oxygen diffusion and the determination of local oxygen-18 diffusion profiles with use of the nuclear reaction 18O(p, α) 15N show a sharp influence of the load. The application of the load induces an increase of the oxygen diffusion coefficients until two orders of magnitude (typically from around 10 −15 cm 2 s −1 to around 10 −13 cm 2 s −1 in NiO thermally grown on nickel monocrystals). However, this enhancement decreases with the increase of the load. As the oxide scales are multilayered and as spalling and regrowth may occur, RBS mapping of the local thickness of the oxide stripes is also performed. This technique helps in understanding the formation of the microstructure and of the damaging process during the mechanical loading.

Study of tasin diffusion barrier

Due to its resistance to oxidation, TaSiN is a promising candidate as an electrically conductive barrier layer for integration of high permittivity oxides in advanced high-density memory devices. In this study we report on the properties and the resistance to oxidation of TaSiN thin films deposited by reactive magnetron sputtering and processed by rapid thermal annealing (RTA) in 18O2 at 650°C. In order to determine the composition, RBS (Rutherford Backscattering Spectroscopy) and NRA (Nuclear Reaction Analysis) techniques have been used. 18O depth profile concentrations were measured after RTA using the narrow (fwhm=100eV) resonance at 151 keV of the nuclear reaction 18O(p,α)15N.

Oxidation Resistance of TaSiN Diffusion Barriers for Stacked Capacitors

AbstractDue to its resistance to oxidation, TaSiN is a promising candidate as an electrically conductive barrier layer for integration of high permittivity oxides in advanced memory devices. In this study we report on the properties and the resistance to oxidation of TaSiN thin films deposited by reactive magnetron sputtering and processed by rapid thermal annealing (RTA) in 18O2 at 650°C. In order to determine the composition, RBS (Rutherford Backscattering Spectroscopy) and NRA (Nuclear Reaction Analysis) techniques have been used. 18O depth profile concentrations were measured after RTA using the narrow (fwhm=100eV) resonance at 151 keV in the nuclear reaction 18O(p,α)15N.

Oxidation of MoSi2/SiC nanolayered composite

The oxidation behavior of a nanolayered MoSi2/SiC composite material was determined at the temperature range of 400–900 °C in wet oxidation conditions. The samples were produced in the form of thin films using a sputtering technique from two different sources, and a rotating substrate holder, onto silicon single crystals and low carbon steel. For comparison, the oxidations of both constituents, MoSi2 and SiC, produced with the same sputtering technique, were measured separately. The microstructure of the MoSi2/SiC samples was determined with high resolution transmission electron microscopy (HRTEM), and the composition of the sputtered samples was measured using backscattering (BS) of protons. For quantitative determination of oxidation, the nuclear reaction 16O(d, p)17O was utilized. Oxide layers were also analyzed using a secondary ion mass spectrometry (SIMS) and the appearance of the oxidized surface with a scanning electron microscopy (SEM). As expected, the SiC films had both the lowest initial oxidation and steady state oxidation rate. The results show that the oxidation behavior of the MoSi2/SiC nanolayered composite material differs from that of both its constituents and involves a degradation mechanism of its own, resulting in the highest oxidation during the initial phase of the oxidation. A steady-state oxidation rate was observed after the initial transient phase to be the highest for the metastable C40 structure of the single MoSi2 layer. The oxidation rate of the nanolayered structure was retarded by the SiC layers. No signs of pest disintegration were observed on either of the MoSi2 containing coatings during the steady-state phase of the oxidation at 500 °C up to 40 h. Our results show that the oxidation of nanolayered structures can be only in part explained by the oxidation behavior of the constituents and that during the steady-state oxidation of the nanolayered structure the oxidation rate is largely determined by the constituent with the lowest oxidation rate and by the layered structure.

Study of diamond-like carbon films for protective coatings

Interest in investigating thin films of diamond-like carbon (DLC, a-C:H) has been motivated by the unique properties of this material and the demand of modern technologies. The development of low-temperature methods T3 s < 200 °C) for producing DLC films used as protective layers is of practical interest. In this work, a-C:H films were prepared by low-temperature deposition by using three methods: magnetron-sputtering of a graphite target in argon (80%)-hydrogen (20%) atmosphere, magnetron sputtering of graphite target combined with plasma-stimulated, gas-phase deposition from a mixture of gases (10% CH 4 + 90% Ar) and rf decomposition of a mixtures of gases (10% CH 4 + 90% Ar). A comprehensive investigation of the composition, structure, optical and electrical properties of a-C:H films was performed from the standpoint of the requirements that protective coatings for electrophotograhic information carriers and stable protector for Ag-based optics must meet. The investigation of the composition and structure was performed by elastic recoil detection (ERD), resonance nuclear reaction 16O (α, α) 16O and Raman spectroscopy. The optical properties (the transparency over a wide spectral range and the refractive index) were determined by means of IR-spectroscopy and ellipsometric measurements. It was shown that solid, diamond-like a-C:H films (DLC) can be obtained with low-temperature deposition. It was shown that a protective DLC coating increases the storage time in the air and the strength properties of the a-Se (or a-Se alloy) electrophotographic information carriers. It was determined that a protective DLC coating is an effective and stable protector for Ag-based optics from an attack of active sulfide.

Characterization of SiO xN yH z and SiN yH z using RBS, ERDA and NRA In memoriam Priv.-Doz. Dr. Rainer P.H. Garten

Rutherford backscattering (RBS) measurements, elastic recoil detection analysis (ERDA) and nuclear reaction analysis (NRA) were applied to determine the composition, the thickness and the density of plasma-deposited SiO x N y H z and SiN y H z layers on silicon substrate. RBS-measurements were carried out with 2.3 MeV 4He-ions in random and channeling geometry to determine the atomic ratios of N Si in the surface layers, and the layer thicknesses. Depth profiling for hydrogen in the samples was performed by means of α-ERDA using 2.3 or 2.9 MeV 4He-ions. In order to determine the atomic ratios of H N , heavy ion elastic recoil detection (HIERDA) using 32 MeV 28Si 7+-ions was applied. The oxygen contents were measured using the nuclear reaction 16O(d,p) 17O. Depth profiling for nitrogen was also performed by means of NRA using the reaction 14N(d,α) 12C. In addition, ellipsometric measurements of the layer thicknesses were utilized to determine the densities in absolute units (atoms/m 3 or kg/m 3).

Direct radiofluorination of dopamine: 18F-labeled 6-fluorodopamine for imaging cardiac sympathetic innervation in humans using positron emission tomography

Fluorine-18 labeled fluorodopamine (FDA) was synthesized by the direct fluorination with [ 18F]F 2 [produced by the nuclear reaction 18O(p,n) 18F] of dopamine in anhydrous hydrogen fluoride containing boron trifluoride at −65 °C. Reverse-phase high-performance liquid chromatography (HPLC) was used to separate [ 18F]6-FDA from the reaction mixture containing 18F-labeled 2- and 5-FDA. The radiochemical yield of [ 18F]6-FDA, with respect to [ 18F]F 2, was 10 ± 2% at the end of the 120-min synthesis from E0B1. The specific activity of [ 18F]6-FDA at the end of synthesis, 10 ± 1.5 Ci/mmol, is sufficiently high that the amount of 6-FDA associated with the infusion of a dose of 5 mCi of [ 18F]6-FDA over 3 min into a 50-kg human (0.5–0.7 μg/kg/min) is considerably lower than therapeutic doses (2–10 μg/kg/min) of dopamine.

Crystallization and oxidation behavior of Mo-Si-N coatings

Mo-Si-N coatings with different nitrogen concentrations were produced by nitrogen alloying simultaneously during sputter deposition from a planar magnetron MoSi 2 target with nitrogen plasma onto steel substrates. The ratio of molybdenum and silicon concentrations was 0.5. The nitrogen concentrations of the samples were 20, 35, and 50 at.% and the concentration profile was uniform througout the film thickness. The initial microstructure at all nitrogen concentrations involved was amorphous and the crystallization temperature was strongly dependent on nitrogen concentration. The sample with 50 at.% N was still amorphous after annealing at 1000°C whereas the sample with 35 at.% N was crystallized at 740-760°C and the sample with 20 at.% N at 660-680°C. Even this was higher than the crystallization temperature of a pure MoSi 2 coating, about 500°C. The oxidation behavior of the Mo-Si-N coatings with 50 at.% N was determined in wet oxidation conditions from 400 to 1000°C by measuring oxygen concentration on the surface using a nuclear reaction 16O(d,p) 17O or non-Rutherford scattering of He +. The excellent oxidation resistance of this coating on low carbon steel was confirmed up to 800°C, above which diffusion of nitrogen occurred, resulting in crystallization and degrading of the beneficial properties. The oxidation behavior of the Mo-Si-N coating can be explained in terms of amorphous microstructure and silicon-nitrogen interaction.