The use of charged particle bombardment for studying oxygen self-diffusion in oxides

The various nuclear techniques which have been used to study oxygen self-diffusion in oxides are discussed. Results are given for measurements using resonance capture in the¹⁸O(p, α)¹⁵N and¹⁸O(p, γ)¹⁹F reactions and the different techniques are compared.     

The development of nuclear microprobe techniques for the spatial determination of13C and13C/12C ratios

Sensitive and selective nuclear reaction methods have been sought for the nuclear microprobe measurement of the spatial distributions of¹³C and¹³C/¹²C ratios. The¹³C(α, n)¹⁶O reaction, with neutron detection, is the most selective for¹³C, and has a sensitivity of ca. 100 ppm. The reactions¹³C(d, p)¹⁴C and¹²C(d, p)¹³C, with proton detection, are the most sensitive for the simultaneous measurement of¹³C and¹²C, with detection limits of 30 and 2 ppm respectively. Less sensitive alternative reaction pairs are;¹³C(³He, p)¹⁵N and¹²C(³He, p)¹⁴N;¹³C(d, nγ)¹⁴N and¹²C(d, pγ)¹³C;¹³C(³He, pγ)¹⁵N and¹²C(³He, pγ)¹⁴N. The conditions governing their use, particularly light element interferences, are detailed.     

Light element profiling using nuclear reaction analysis on tapered corrosion sections

A scanned microbeam has been used to profile tapered corrosion sections of thickness up to 500 μm. The method of beam scanning and data collection is described and selected profiles are presented for the reactions D(³He, p)α,¹²C(d, p)¹³C,¹⁴N(p, α)¹²C and¹⁸O(p, α)¹⁵N. Finally the advantages and limitations of the technique are discussed.     

A study of thermally oxidized SiO2 surface layers by means of nuclear reactions

Conclusions The nuclear reaction from low-energy deuteron-bombardment has proved to be a valuable tool for surface oxide layer examination. Using the¹⁶O(d, p)¹⁷O and¹⁶O(d, α)¹⁴N reactions, some important properties of Si−SiO₂ structures, such as total number of oxygen nuclei and oxygen concentration profile, can be determined in one measurement with an accuracy of several percent, within one hour. Some effects of oxygen deficiency in SiO₂ layers of thicknesses exceeding 6000 ? have been found. A more detailed study of this effect will be the subject of forth-coming experiments.     

New method to measure oxygen isotopic concentration ratios18O/16O by gamma-activation analysis,especially in biological media

The photonuclear reactions used for this isotopic analysis are as follows:¹⁶O(γ, n)¹⁵O threshold energy 15.7 MeV;¹⁸O(γ, p)¹⁷N threshold energy 16.3 MeV.¹⁵O is a pure β⁺ emitter of half-life 2.03 minutes, whereas¹⁷N presents a 4.2 second neutron emission. The principle of the method is founded on the simultaneous measurement of the above characteristic radioactivities, the intensities of which are proportional to the respective quantities of¹⁶O and¹⁸O present in the irradiated sample. The potentialities of this new oxygen isotope analysis method, based on the use of an electron accelerator, are described. Detection limit of 0.1 μg¹⁸O is easily attainable. The equipment designed and built to industrialise this technique is described. It allows a hundred samples to be analysed automatically, the accelerator, detection instruments and pneumatic transfer circuits being controlled by a logic system linked to an electronic chronometer.     

A method for charged-particle activation analysis and its application to fluorine determination by the19F(p, αγ)16O reaction

A simple method for calculating the sensitivity for detecting a nuclide distributed uniformly in any given matrix through charged particle activation is described. This method takes into account the actual values of the reaction cross section at different energies as the beam traverses through a thick target and the corresponding stopping power values. The detection sensitivity for fluorine in a number of matrices through the¹⁹F(p, αγ)¹⁶O reaction have been calculated as a function of the energy from threshold to 4.16 MeV using this method and the sensitivity curves plotted. The sensitivity values (dps/ppm/μA) for a thick or thin target and even for a layer of known thickness at a particular depth within a sample can be directly read from these curves for known bombarding conditions. The comparator methods for charged particle activation analysis of RICCI¹ and of CHAUDHRI,² especially when the matrices of the sample and standard are different, have been compared in the case of F determination through the¹⁹F(p, αγ)¹⁶O reaction. It has been found that the errors are reduced by almost a factor of two when the latter method is used compared to the former one. The fluorine concentration in animal bones and teeth, apatite crystal, and rocks have been determined through the¹⁹F(p, αγ)¹⁶O reaction using the Melbourne University Pelletron.     

Investigation of water diffusion into quartz using ion beam analysis techniques

Diffusion of water into quartz was studied by measuring H and ¹⁸O concentration profiles in surface layers of quartz samples treated hydrothermally in the range of 125° C to 200° C. Sample surfaces were orientated normal to the c-axis. The measurements were performed using the nuclear reactions ¹H(¹⁵N,αγ)¹²C and ¹⁸O(p,α)¹⁵N. The diffusion profiles have widths of up to 500 nm. Diffusion rate constants derived from the profiles are in the range of 10^–15 cm²/s to 10^–18 cm²/s and show a distinct temperature dependence, yielding a rough estimate of about 60 kJ/mole for the activation energy. Received: 24 June 1996 / Revised: 20 January 1997 / Accepted: 22 January 1997     

Oxygen depth profiling by activation with the16O(3He,p,)18F reaction

A technique has been developed for oxygen depth profiling in a thickness range of 5 to about 100 mg cm⁻² by activation with the¹⁶O(³He, p)¹⁸F reaction. An apparatus was set up for the activation of oxygen with a uniform probability along the depth, and a method has been devised for step-wise etching of the activated sample. This technique has been applied to the study of oxygen behaviour in heat treatment of silicon under various conditions.     

Determination of oxygen with reactor neutrons

Oxygen in silicon was determined by the secondary nuclear reactions of⁶Li(n, α)T and¹⁶O(t, n)¹⁸F. Lithium fluoride was deposited in vacuum on fused quartz, covered with the sample and irradiated in a nuclear reactor. The depth profiles of¹⁸F in fused quartz and in silicon were observed, and enough depth to eliminate surface oxygen was estimated. On the basis of these results, oxygen was determined by the average cross-section method. Oxygen concentration in CZ silicon with various growing condition was 5–26 ppm and was consistent with those determined by the infrared absorption method. The detection limit of oxygen in silicon is 5 ppm.     

Depth profiling of oxygen in oxide films by 18O(p,α)15N nuclear reaction analysis

The paper describes the determination and depth profiling of oxygen in thin oxide films using ¹⁸O(p,??)¹⁵N nuclear reaction. The excitation function of ¹⁸O(p,??)¹⁵N nuclear reaction exhibits a resonance at 629?keV and a plateau at 730?keV with uniform cross-section. The resonance is used to determine the depth profile of oxygen in films while the plateau, to estimate its overall concentration. The resonance, characterized by a width of 2.1?keV enables high-depth resolution (~20?nm) measurements and has a probing depth of more than a micron. The paper presents depth profile measurements of oxygen in several metal oxide films (SiO₂, TiO₂ and HfO₂) using this resonance. Possible interferences arising from ¹⁵N(p,??)¹²C, ¹⁹F(p,??)¹⁶O and ¹¹B(p,??)2?? nuclear reactions are also discussed. It has been shown that it can serve as a suitable alternative to 3.05?MeV ¹⁶O(??,??)¹⁶O resonant scattering which is generally used for depth profiling oxygen. It is, in fact, more reliable and precise in materials that witness significant large angle multiple scattering. It can also be advantageously used to monitor ¹⁸O, when used as a tracer.     

The application of nuclear techniques to high temperature oxidation studies

The¹⁸O(p, α)¹⁵N reaction has been used to determine the¹⁸O distribution in the oxides of a number of alloys which have been oxidised sequentially in natural gas and¹⁸O-labelled gas. A significant feature of all the cases investigated is the penetration of¹⁸O into the oxide formed previously in the natural gas. This penetration may occur in various ways and would be difficult to study by other techniques. The evidence presented here shows that there are subtle differences in oxidation behaviour and confirms that penetration of oxygen is a feature in the oxidation of alloys in which the predominant mechanism is transport of cations. This may have implications in explanations given to account for oxidation kinetics and adhesion and buckling of scales.     

Fluorine concentration profile determination in MAGNOX reactor fuel canning material

The role of fluorine, as a corrosion inhibitant was investigated by determining fluorine concentration profiles in corroded MAGNOX reactor fuel cladding material. A nuclear convolution method was employed, based on the¹⁹F(p, αγ)¹⁶O resonant reaction and prompt gamma detection. The investigation was carried out for scale thicknesses of 3.5 and 4.5 μm as determined using 4.5 MeV protons and a broad resonance in¹⁶O(p, p)¹⁶O back-scattering cross-section. The results indicate the presence of thin fluorine concentration layers near to the scale surface on both etched and pre-oxidized magnesium alloy samples. Furthermore, an additional lower concentration distribution was also observed throughout the scale of the pre-oxidized sample.     

Helium-3 activation analysis of oxygen in silicon nitride films on silicon wafers

Oxygen in silicon nitride films on silicon wafers was analyzed by activation with the¹⁶O(³He, p)¹⁸F reaction. By³He bombardment of samples propertly arranged under consideration of the¹⁸F recoil effect, total oxygen was reliably determined and its predominant part was estimated to be located whether on film surface, in film interior, or on film-substrate interface. Sample films with 0.1 to 2 μm thicknesses were found to contain 0.2 to 2 μg/cm² of oxygen in locations varying with preparation conditions. This method has been compared with ESCA and other methods for surface analysis.     

The elemental and isotopic determination of lithium by the coincidence measurement of complementary particles

The coincident measurement of both nuclear products at their complementary angles was used to determine⁶Li by the reactions⁶Li(d, α)⁴He and⁶Li(p, α)³He, and⁷Li by the reaction⁷Li(p, α)⁴He. Elemental lithium was determined in natural samples or samples of known isotopic composition. Isotopic analyses could be carried out over the entire range from 0 to 100 atom% with a relative standard deviation of about 4%. The CMCP technique is highly specific and effectively eliminates interference and background.     

Combined NRA, channeling-RBS and FTIR ellipsometry analyses for the determination of the interface and bonding state of thin SiOx and SiNxOy layers

The molecular ions O⁺₂ and NO⁺ are im- planted at room temperature into single-crystal silicon with an energy of E=6 keV/atom at fluences ranging from 2.5×10¹⁶ to 3.5×10¹⁷ at/cm². The samples are processed by electron beam rapid thermal annealing at 1100^°C for 15 s. The depth distributions of the implanted specimens (¹⁸O) are determined by nuclear reaction analyses using the reaction ¹⁸O(p,)¹⁵N. Channeling-RBS measurements are performed to obtain the interface structure between the implanted layer and the single-crystal Si substrate. The chemical bonding state of as-implanted and implanted-annealed specimens is observed by FTIR ellipsometry measurements.     

Recent developments in the analytical application of prompt spectrometry

A survey of the possibilities of analysis by alpha-induced prompt gamma-ray spectrometry is reported for 57 elements at a bombarding energy of 5 MeV. Additional data obtained at 11 and 16 MeV are given. Interference-free sensitivities are presented. The use of the position sensitive detector is introduced to overcome problems such as occur in prompt alpha spectrometry from (p, α) reactions. The technique is illustrated by studies on the reaction¹⁹F(p, α)¹⁶O and severely tested for boron analysis using the reaction¹¹B(p, α)⁸Be and measuring the α₀ and α₁ groups.     

Voltammetric response and electrochemical properties of the O2/O 2 •− couple in acetone

Voltammetric responses of the O₂/O ₂ ^•− couple as a function of aprotic solvents are investigated. The results show that acetone is a suitable solvent for examining the electrode reaction of the O₂/O ₂ ^•− couple. Studying the electrochemical behavior of the O₂/O ₂ ^•− couple at different electrodes in acetone by cyclic voltammetry suggests that the reversibility of the O₂/O ₂ ^•− couple and the redox peak currents at glassy carbon are better than those at gold and platinum. The kinetic parameters (electron transfer rate constant k ₀ and cathodic transfer coefficient α) of the oxygen reduction to superoxide ion (O ₂ ^•− ) are evaluated using normal-pulse voltammetry. The obtained values of k ₀ (cm/s) and α are (1.95 ± 0.05) × 10⁻⁴ and 0.34 ± 0.01, respectively. The scavenging activities of ascorbic acid and bilirubin are tested and the experimental results confirm that ascorbic acid is a better scavenger toward O ₂ ^•− . Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 2, pp. 188–194. The text was submitted by the authors in English.     

Fluorine profiles in Antarctic meteorites by nuclear reaction analysis (NRA)

Terrestrial fluorine enrichment on Antarctic meteorites can be measured by detection of γ-rays from the nuclear reaction ¹⁹F(p,αγ)¹⁶O, which is induced by a scanning proton beam. The technique (Nuclear Reaction Analysis by Proton Induced Gamma Emission: PIGME-NRA) allows simultaneous measurement of distribution and concentration without any chemical sample treatment and is not destructive. By using two detectors (HPGe and NaI) and taking into account the background contribution of the main interfering elements, the detection limit is below 10 μg/g. The information obtained allows to estimate the maximum exposure duration of meteorites on the Antarctic ice surface. Received: 15 July 1997 / Accepted: 11 December 1997     

Yields and average cross sections of recoil charged particle induced reactions on11B,12C,13C,14N,16O and18O

The yield and average cross section for the reactions¹¹B(p, n)¹¹C,¹²C(p, )¹³N,¹³C(p, n)¹³N, ₁₂ ¹² C(d, n)¹³N,¹⁴N(p, )¹¹C,¹⁶O(p, )¹³N,¹⁶O(d, n)¹⁷F,¹⁶O(t, n)¹⁸F, and¹⁸O(p, n)¹⁸F have been measured in different compounds. The charged particles were created in the samples themselves either through recoil by scattering of 14 MeV neutrons off hydrogen and deuterium, or by the (n, t) reaction on⁶Li using thermal neutrons. The yields of reactions¹²C(d, n);¹⁶O(p, );¹⁶O(t, n) and¹⁸O(p, n) have been measured using proton, deuteron and triton spectra generated by 14 MeV neutrons in the reactions D(n, p)2n;⁶Li(n, d);⁷Li(n, d) and¹⁰B(n, d);⁷Li(n, t) and¹⁰B(n, t), respectively.     

Die Bestimmung des Sauerstoffgehaltes in Silizium nach Ionenimplantation durch eine SiO2-Deckschicht mit Hilfe der Reaktion18O(p, α)15N

The recoil implantation yield of oxygen atoms recoiled from¹⁸O-enriched SiO₂ layers into silicon substrates has been studied using the¹⁸O(p, α)¹⁵N nuclear reaction. The method to determine the number of oxygen atoms in silicon is described in detail and the results are compared to the theoretical predictions.