On the determination of carbon and oxygen impurities in silicon by3He activation analysis

Carbon and oxygen impurities in silicon have been determined by 7.00 MeV³He activation analysis. The detection limits obtained for interference-free conditions are 0.1 ppb (wt) for carbon and 1.0 ppb (wt) for oxygen in silicon.     

Determination of oxygen in gallium arsenide by3He activation analysis using substoichiometric precipitation

Distillation of fluoride as fluorosilicic acid and substoichiometric precipitation as lanthanum fluoride was studied for the determination of oxygen in gallium arsenide by³He activation analysis. Fluoride could be separated substoichiometrically with a good reproducibility by two distillations and successive precipitation with lanthanum. The oxygen concentration in gallium arsenide prepared by the horizontal Bridgman technique was 10 to 36 ppb and increased a little along the front, middle and tail portions in the crystal.     

Trace determination of oxygen in gold-copper alloys and in high purity gold using3He and4He activation analysis

Trace amounts of oxygen in gold-copper alloys and high purity gold have been determined by³He and⁴He activation analysis. Interferences from the matrix have been identified and the factors which can have an effect upon the precision and the accuracy of the method have been investigated. Thus a destructive technique has been choosen. The¹⁸F produced was chemically separated by steam distillation and precipitated as PbClF. The values of the oxygen concentration were found to range between 0.2 and 2 μg·g⁻¹ depending on the copper concentration and the thermal treatment applied to the samples. A possible mechanism of internal oxidation is presented.     

3He activation analysis for S,Cl, K and Ca

Résumé On utilise trois radioisotopes facilement détectés³⁸Cl,^34mCl et³⁸K, produits à partir du soufre, du chlore, de la potasse et du calcium pour doser ces éléments par activation au³He. On a analysé un certain nombre d'échantillons de fa?on non-destructive en utilisant différentes réactions nucléaires pour examiner la précision de la méthode et l'étendue des interférences. On donne les fonctions d'excitation absolue pour les réactions nucléaires aux hélions 3.

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Work was performed under the auspices of the U. S. Atomic Energy Commission.     

The simultaneous determination of carbon and oxygen in semiconductor silicon by helium-3 activation analysis

A non-destructive method for the simultaneous determination of carbon and oxygen in silicon by helium-3 activation analysis is described. The determination is based on a simplified standardization method. The method was applied to samples containing 0.05–3 p.p.m. of carbon and 0.05–10 p.p.m. of oxygen. The determination limit of carbon varies from 30 to 300 p.p.b. depending on the oxygen concentration.     

Charged particle activation analysis for carbon,nitrogen and oxygen in semiconductor silicon

Convenient processes are described for the charged particle activation analysis for carbon, nitrogen, and oxygen in semiconductor silicon. Suitable activation reactions and incident particle energies were selected, and the interferences examined; the activation curves for the Si+³He→¹¹C and Si+³He→¹⁸F reactions, which may seriously interfere with³He activation analysis, were measured, and the interference caused by the fission of the matrix itself is discussed. A simple technique for the separation of¹¹C present in silicon is proposed. Reliable determination of as low as several parts per billion of the three elements has thus become possible. Semiconductor silicons of various origin were analyzed for C, N and O, and the behaviour of these elements during zone-melting is reported.     

Measurements of oxygen,nitrogen and carbon for in vivo photon activation analysis

When the human body is subjected to Bremsstrahlung radiation at selected maximum energies (13–25 MeV) in a betatron the radionuclides ¹⁵O (2.05 min), ¹³N (10.0 min) and ¹¹C (20.5 min) are formed from oxygen, nitrogen and carbon in the body. In the present study these activities were measured in phantoms consisting of beef tissue weighing about 150 g. In those samples oxygen, nitrogen and carbon could be determined at the following dose levels: oxygen, < 0.5 rad; nitrogen, ~ 5 rad; carbon, < 0.5 rad.     

Photon-activation analysis for carbon and oxygen

A method is described for the determination of carbon and oxygen in organic materials by means of the reactions (12)C(gamma, n)(11)C and (16)O(gamma, n)(15)O. Samples are irradiated with bremsstrahlung from a 32-MeV electron beam impinging on a tungsten target, and the active products are separated before the positron annihilation gamma rays are counted. Limits of detection of 0.003 mug of carbon and 0.1 mug of oxygen are obtained.     

Charged-particle activation analysis studies on carbon,nitrogen and oxygen mainly in semiconductor silicon

High utility value of charged-particle activation analysis is exemplified by the study on carbon, nitrogen and oxygen in semiconductor silicon. A summary of the present authors' works is shown, and the equilibrium of carbon and oxygen in a silicon melt with ambient carbon monoxide is discussed. Also, a note is given about the chemical separation of¹⁸F for the³He activation analysis of various matrices.     

The routine determination of boron,carbon, nitrogen and oxygen by charged-particle activation analysis

Normalized parameters for the determination of boron, carbon, nitrogen and oxygen are given. The irradiations are performed with 9 MeV protons or 7.5 MeV deutons. The beam current is measured with a Faraday cup and beam current fluctuations are corrected for by a computer calculation. The samples are automatically counted on a time schedule based upon the half-lives. Counting data are evaluated by means of computerized least squares decay analysis. Absolute sensitivity factors with the dimension dpm⁻¹ μA⁻¹(g/cm²)⁻¹ are determined.     

The determination of oxygen in silicon by alpha and helium-3 activation analysis

A non-destructive analytical method for oxygen in silicon by both helium-3 and α-particle activation analysis was applied to different samples, containing 0.05–10 p.p.m. of oxygen. The accuracy and precision of the method were studied. For concentrations above 1 p.p.m., the average coefficient of variation is about 6% for α-activation and 13% for helium-3 activation. For concentrations of about 60 p.p.b., the corresponding figure is about 20%. The results of both methods, which agree within 8%, are compared to infrared analysis. The determination limit of the method is 4 p.p.b. for helium-3 activation and 22 p.p.b. for α-activation.     

Determination of boron, carbon, nitrogen and oxygen in nickel by charged particle activation analysis

Summary The determination of boron, carbon, nitrogen and oxygen in nickel by charged particle activation using the reactions ¹⁰B(d, n)¹¹C, ¹²C(d, n)¹³N, ¹⁴N(p, )¹¹C and ¹⁶O(³He, p)¹⁸F is studied. The interference of ¹¹B(p, n)¹¹C with the ¹⁴N(p, )¹¹C reaction is taken into account. ¹¹C, ¹³N and ¹⁸F are separated by oxygen combustion followed by trapping of ¹¹CO₂ in NaOH and by steam distillation of ¹³NH₃ and of H₂Si¹⁸F₆, respectively. The results obtained were 0.129±0.035 g g^–1 for boron, 86.4±8.3 g g^–1 for carbon, 1.077±0.037 g g^–1 for nitrogen and 8.91±1.00 g g^–1 for oxygen. The results for nitrogen and oxygen agreed satisfactorily with those of other analytical methods.Grateful acknowledgement is made to Prof. J. Hoste for his interest shown in this work, to J. Pauwels (B.C.M.N., Geel) for providing the samples, to B. F. Schmitt (Bundesanstalt für Materialprüfung, Berlin) for helpful information concerning the radiochemical separation of ¹¹C and to the NFWO and the IIKW for financial support.     

Accurate fast neutron activation analysis for oxygen in geological materials

Sources of error in the fast neutron activation analysis determination of oxygen have been investigated and minimised. The oxygen contents of eighteen international rock standards and a sulphide ore standard have been determined, and compared with the values calculated by difference using the reported full analyses. Accuracies of 0.3% average deviation and reproducibilities of ±0.2% standard deviation have been obtained, where oxygen contents exceeded 1.0 g.     

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.     

Corrections for carbon and oxygen interference in the 14-MeV neutron activation determination of nitrogen

Reactions in the carbon and oxygen atoms of sample matrix can lead to errors in the 14 MeV neutron activation determination of nitrogen based on the¹⁴N(n, 2n) reaction, particularly as a consequence of proton-induced reactions leading to¹³N formation in samples of an organic nature. In this study, the extent of such interferences have been evaluated by measuring the apparent N contribution when a series of alcohols and a water sample were irradiated with 14 MeV neutrons from a Texas-Nuclear neutron generator under the same conditions used for trace N determination and contributions amounting to from 0.1 to 1% apparent N content observed (and corrected for). Owing to neutron flux in stabilities and assymetries, flux monitoring was done with aluminum foils on either side of the samples for N analysis, and which were counted for²⁴Na. Two samples of foodstuff were analyzed correction for C and O interference, agreed with conventional analysis within ±10%.     

The determination of trace oxygen in lead by helium-3 and helium-4 activation analysis

The determination of oxygen in lead by³He and⁴He activation analysis was studied. Both methods were applied to the same material containing 0.9 μg·g^?1 of oxygen. The¹⁸F formed from oxygen was separated from matrix activities by extraction of Po with N-benzoyl-N-fenylhydroxylamine, followed by distillation of fluorosilicic acid and precipitation of lead fluorochloride (⁴He activation) or by distillation followed by precipitation (³He activation). The yield of the separation, which amounted on the average to 68%, was determined via the¹⁹F(n,⁴He)¹⁶N reaction. The coefficients of variation were 21 and 45% for⁴He and³He activation analysis, respectively, thus indicating a less homogeneous distribution of the oxygen. Nuclear interferences of sodium and fluorine were shown to be negligible.     

Stable carbon and oxygen isotopic analysis of carbon monoxide in natural waters

Techniques have been developed to allow on-line simultaneous analysis of concentration and stable isotopic compositions ((13)C and (18)O) of dissolved carbon monoxide (CO) in natural water, using continuous-flow isotope ratio mass spectrometry (CF-IRMS). The analytical system consisted sequentially of a He-sparging bottle of water, a gas dryer, CO(2)-trapping stage using both Ascarite trap and silica-gel packed gas chromatography (GC), on-line oxidation to CO(2) using the Schütze reagent, cryofocusing, GC purification using a capillary column and measurement by CF-IRMS. Each sample analysis takes about 40 minutes. The detection limit with delta(13)C standard deviation of 0.5 per thousand is 300 pmol and that with delta(18)O deviation of 1.0 per thousand is 750 pmol. Analytical blanks associated with these methods are 21+/-9 pmol. The procedures are evaluated through analyses of temporally varying concentration and isotopic compositions of CO in an artificial lake on the university campus. The delta(13)C and delta(18)O values of CO showed wide variation in accordance with diurnal variation of CO concentration, probably due to significant isotopic effects during photochemical production and microbial oxidation of CO in the aquatic environment. The delta(13)C and delta(18)O values of CO should be a useful tool in studies of the mechanism and pathways of CO production and consumption in natural waters.     

Charged particle activation analysis for surface oxygen under various ambient pressures

Charged particle activation analysis has proved to be useful for the determination of surface oxygen under any atmospheric conditions. The¹⁶O(³He, p)¹⁸F reaction was used for activation. The sample in a form of two plates was contacted intimately with each other and bombarded with³He particles of such an energy as to give the maximum cross section at the inside surfaces of the plates. The¹⁸F thus formed in the forward plate was then measured. Oxygen in the gap between the two plates can be shown to cause no noticeable interference. This method was applied to silicon, aluminium and lead in four different ambient pressures.     

Thermodynamic interaction functions for 4He and 3He quantum liquids

The method of interaction functions is applied to quantum liquids. The interaction energies at 0 K are found as 14.3 cal/mole for ⁴He and 11.0 cal/mole for ³He. The interaction energy as a function of volume for all temperatures along the saturation line is deduced as an expression common to the two isotopes. The two isotopes have a region of anomaly in the interaction entropy, where the liquid appears less ordered than an ideal gas. These anomalies can be eliminated for ³He by allowance for the spin entropy and for ⁴He via the difference between the concentrations of the component with zero entropy in the liquid and Bose gas.