Glow Discharge Mass Spectrometry Research Articles

Radiopurity control in the NEXT-100 double beta decay experiment: procedures and initial measurements

The ``Neutrino Experiment with a Xenon Time-ProjectionChamber'' (NEXT) is intended to investigate the neutrinoless doublebeta decay of 136Xe, which requires a severe suppression ofpotential backgrounds. An extensive screening and material selectionprocess is underway for NEXT since the control of the radiopuritylevels of the materials to be used in the experimental set-up is amust for rare event searches. First measurements based on GlowDischarge Mass Spectrometry and gamma-ray spectroscopy usingultra-low background germanium detectors at the LaboratorioSubterr'aneo de Canfranc (Spain) are described here. Activity resultsfor natural radioactive chains and other common radionuclides aresummarized, being the values obtained for some materials like copperand stainless steel very competitive. The implications of theseresults for the NEXT experiment are also discussed.

Influence of Growth Conditions and Doping on Physical Properties of Gallium Antimonide Single Crystals

Gallium antimonide (GaSb) single crystals were grown by modi ed Czochralski method integrated with in situ synthesis in a owing atmosphere of pure hydrogen. The in uence of charge material purity as well as other technological parameters on GaSb crystals quality was investigated. High purity undoped GaSb single crystals were grown with residual acceptors concentration < 1.4 × 10 cm−3 and high mobility ≈ 690 cm/V s (at 300 K). P -type GaSb crystals were doped with silicon (carrier concentration up to 2 × 10 cm−3) and with zinc (up to 1× 10 cm−3). Tellurium doped n-type GaSb single crystals were obtained with concentration up to 2× 10 cm−3. Electrical parameters were investigated by the Hall measurements (300 K and 77 K). Temperature dependent Hall measurements (10 ÷ 300 K) were used to compare the quality of undoped GaSb (obtained from Sb of di erent purity). Dopant concentration was estimated by glow discharge mass spectroscopy analysis. Axial and radial distribution of carrier concentration were investigated especially for Te-doped crystals (low segregation coe cient of Te in GaSb). Great contribution of compensation and self-compensation mechanisms is shown especially for the beginning part of grown crystals and for low Te-doping level. Radial distribution of physical properties for crystals grown in ⟨100⟩ direction is not axisymmetrical especially for doped GaSb crystals.

Ion implanted inconel alloy – SIMS and GDMS depth profile analysis

Two analytical techniques – secondary ion mass spectrometry (SIMS) and glow discharge mass spectrometry (GDMS) – were applied for depth profile analysis of ion‐implanted nickel alloy inconel 600. Ion implantation with nitrogen, titanium, chromium and yttrium was performed in order to modify surface, mechanical and chemical properties. Implantation parameters were as follows: acceleration voltage 65 kV, ion fluence 1–2 mA/cm2. Series of ion implanted foils were then depth profiled using the two techniques applying ion sputtering. SIMS analysis was performed using 16 mm rods QMA‐410 Balzers quadrupole mass spectrometer and Physical Electronics ion gun (3 keV Ar+ ion beam directed at 45 deg to the surface). GDMS analysis was done with 6 mm rods SRS‐300 quadrupole spectrometer. Ion sputtering was performed due to glow discharge in ~0.1 Torr Ar with 1.5 kV DC voltage supplied to cathode (analysed sample). SIMS and GDMS data are quantified using internal standard method (main component elements) as well as ion implantation parameters. The two methods show similar distributions of ion‐implanted species: N, Ti and Y. Also the depletion‐enrichment of alloy components like Cr, Mn, Fe and Ni is observed in the 0–300 nm sputtering range using both methods. Nickel depletions, as well as chromium and manganese enrichments, are registered by both GDMS and SIMS. However, quantitation of these effects is difficult due to the strong mass interference of the polyatomic ions. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Influence of impurities on the fixed-point temperature of zinc: estimations by the SIE method and practical limitations

This publication deals with the practical challenge of describing the impurity influence on the fixed-point temperature of zinc. For this, the sum of individual estimate (SIE) approach is applied to miniaturized fixed-point cells (MFPC) filled with high-purity zinc that can be used in industrial applications. This includes comparative analyses by glow discharge mass spectroscopy as well as mass spectroscopy with inductive coupled plasma to quantify the impurity concentrations in zinc. Furthermore, the element-specific and concentration-dependent temperature deviations are presented for the fixed-point material zinc. For this, binary phase diagrams as well as thermal calculations and experimental data were analysed to extract the relevant sensitivity coefficients. Besides, results from SIE analyses of MFPCs are presented and their uncertainties are compared. On this basis, practical limits of the SIE method are identified and discussed.

Temperature‐dependent Hall‐effect measurements of p‐type multicrystalline compensated solar grade silicon

ABSTRACTIn this study, we have investigated the Hall majority carrier mobility of p‐type, compensated multicrystalline solar grade silicon (SoG‐Si) wafers for solar cells in the temperature range 70–373 K. At low temperature (~70 K) the difference in the mobilities measured for the compensated and the uncompensated reference samples is the highest, and the measured mobility shows dependence on the compensation ratio. Mobilities decrease with increasing temperature, and towards room temperature, the mobilities of the different samples are in the same range. The measurements show that, for these samples, the contribution from lattice scattering is dominating over ionized impurity scattering at room temperature. In the range of interest for silicon solar cells (above room temperature), the trend in carrier mobility is similar for all the samples, and the measured value for the sample with low compensation ratio and low doping density is comparable to the uncompensated references. A comparison of resistivity and majority carrier density measured by the Hall setup at room temperature and by four‐point probe and glow discharge mass spectroscopy, respectively, is reported as well. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Na-doped optical Germanium bulk crystals

In an effort to develop a material for infrared (IR) optics with improved parameters, bulk crystals of optical germanium doped with Na have been first grown and studied. Single-crystalline and coarse-crystalline Ge:Na boules of different shapes and dimensions, up to 10 kg by weight, have been grown. Sodium was incorporated into the Ge crystal during the crystal growing from the melt. Despite the fact that Na contamination in the source material was not strictly controlled, the density of Na in the grown crystals determined by the neutron activation analysis as well as by the glow discharge mass spectrometry did not exceed 1015 cm−3. Just this value may be supposed to be close to the solubility limit of Na incorporated in Ge in the course of bulk crystal growth. A first demonstration of donor behavior of Na in bulk Ge crystals is made by means of a thermoelectric type of testing. An interstitial location of Na impurity has been verified by experiments on donor drift in the dc electric field. The crystals are grown with free electron density in the range from 5⋅1013 to 4⋅1014 cm−3 which is optimal for using Ge crystals as an optical material for fabricating passive elements of the IR technique. A comparison between the properties of Ge:Na crystals and Ge crystals doped with Sb, a conventional impurity in optical germanium, grown under the same technological conditions and from the same intrinsic Ge as a source material, revealed a number of advantages of Ge:Na crystals; among them, the higher transparency in the IR region, smaller radiation scattering and higher regular optical transmission, lower dislocation density, more uniform distribution of electrical and optical characteristics over the crystal volume, the identity of optical parameters in the single-crystalline, and coarse-crystalline boules. No degradation of optical elements fabricated from Ge:Na crystals was detected in the course of their commercial application, starting from 1998.

Effect of Si-induced defects on 1 µm absorption losses in laser-grade YAG ceramics

High sensitivity optical absorption at 1 µm was measured in 40 undoped and Nd-doped Y3Al5O12 (YAG) transparent ceramics and single crystals using photothermal common-path interferometry. Concurrently, chemical trace analysis was performed on those samples by glow discharge mass-spectroscopy. Silicon and calcium were found to be the major impurities with concentrations up to 250 wt. ppm. A univocal linear correlation between the Si content and the absorption loss at 1 µm is revealed and a possible mechanism for the formation of Si-induced color centers based on a bound polaron model is discussed. Solutions to reduce this optical absorption in ceramics are also proposed.

전자빔용해법(溶解法)에 의한 탄탈럼 스크랩의 재활용(再活用) 및 정련(精鍊)

The refining effect of tantalum by electron beam melting(EBM) process for recycling tantalum scraps was investigated in the study. The purity of the tantalum metals refined by EBM was evaluated using glow discharge mass spectrometry (GDMS). From the result of GDMS, most impurities in the tantalum metals were removed by EBM down to a few mass ppm levels. The purity of the refined tantalum scraps was improved up to 5N (99.9991%) from 4 N (99.996%) of the initial tantalum scraps. The amount of metallic impurities in the tantalum was decreased from 30 ppm to 8 ppm. In addition, the gaseous impurities in the tantalum were decreased from 470 ppm to 50 ppm. Therefore a possibility of refining method for recycling tantalum scraps by EBM process was confirmed in this study.

Analytical glow discharge mass spectrometry

Various types of glow discharge mass spectrometric systems as well as their applications are considered. Special attention is paid to radiofrequency and pulsed glow discharges combined with time-of-flight mass spectrometers. Along with typical application fields of glow discharge mass spectrometry, analysis of semiconductors, polymers, and dielectrics, as well as isotope analysis and depth profiling are also reviewed. Some methods of standard-free mass spectrometric analysis of solids are considered. Prospects for combining glow discharge mass spectrometry with preliminary chromatographic separation are discussed.

Purification of cadmium by selective volatilization in vacuum in presence of oxide phase on its melt

Purification of cadmium in the presence of a thin (~0·001 mm) oxide layer on the surface of the molten metal was carried out using a simple system designed and fabricated locally. The analytical results revealed that the distillation through oxide layer gave better separation for Co, Ni, Cu, Zn, Ag, Sn, Hg and Tl, when compared to the distillation without oxide layer. This was attributed due to the impurity metal oxide phases formation on the surface of the molten metal. The influence of oxygen flow time on the distillation rate of cadmium was established. There was no excess oxygen (O) retained in the distillate after two consecutive vacuum distillations through oxide route. The experiments were conducted at the level of nearly 1·5 kg a batch to study the impurities behaviour due to upscaling. The detailed chemical analysis of 58 impurity elements in Cd in presence and absence of oxide layer was carried out by glow discharge mass spectrometry (GDMS).

Low-Temperature Purification of Silicon by Dissolution and Solution Growth in Sodium Solvent

Efficient low-cost processes for solar-grade Si production are needed to overcome the deficiency in the supply of Si. We have demonstrated a new method for the purification of Si crystal. Low-purity Si powder was dissolved in a Na melt (solvent), and Si grains were crystallized by Na evaporation from the Na-Si solution at 1173 K. Glow discharge mass spectrometry analysis revealed that the concentrations of impurity elements, except Na and B, were decreased in the crystallized Si grain. In particular, the concentration of Fe which was mainly included in the Si powder decreased from 3200 ppm by mass to 1.5 ppm by mass in a refined Si grain. Iron disilicide was crystallized from the solution before the crystallization of Si. It was suggested that impurities were reduced not only by crystallization from the Na-Si melt but also by the dissolution of Si into the melt. Na contaminating the refined Si grain was eliminated down to 0.055 mass ppm by heating at 1723 K under vacuum.

Synthesis of high purity, stoichiometric controlled, TeO2 powders

The growth of high quality TeO2 single crystals for acousto-optic devices usually requires a starting powder of relatively high purity (99.995% or better). In addition to foreign metallic impurities, even minute amounts of excess Te precipitating in TeO2 can play a role in the crystal growth behavior and in the resulting properties of the crystal. In this paper, two different approaches for the synthesis of high quality TeO2 starting material have been tested, both using 99.9995% Te as precursor. In the first case, basically a high temperature oxidation process, fine Te powder was subjected to a multi-stage oxidizing process occurring either in vapor or solid phase. In the second case, a hydro-metallurgical method, Te powder was dissolved in nitric acid and then precipitated in form of TeO2. The purity was measured by glow discharge mass spectroscopy and the tellurium fraction in TeO2 was determined by measuring the absorption at 442nm of the gas phase in equilibrium with a solid sample. This technique, used for the first time to measure free Te in TeO2, has proven to apply to this system, leading to good sensitivity and good repeatability. While high temperature oxidation (vapor phase oxidation or solid state diffusion) of 99.9995% Te powder allowed for preserving the purity of the material, the incorporation of impurities was observed when the TeO2 was synthesized through a wet chemical process, leading to a 99.999% purity. This last technique, however, offered the lowest deviation from stoichiometry.

An Intercomparison Study of Analytical Methods for the Determination of Magnesium in Low Alloy Steel

AbstractIn an intercomparison study three low alloy steel materials were analyzed on their content of the trace element Mg, and five different analytical techniques were used, namely spark‐OES, inductively coupled plasma optical emission spectrometry (ICP‐OES), inductively coupled plasma time of flight mass spectrometry (ICP‐TOFMS), inductively coupled plasma quadrupole mass spectrometry (ICP‐QMS), and glow discharge mass spectrometry (GD‐MS). Solid steel discs were used for analysis with spark‐OES and GD‐MS. For the analyses with ICP‐OES, ICP‐TOFMS, and ICP‐QMS steel chips were wet‐digested in aqua regia, and the wet‐digestion was performed either in polypropylene tubes placed in a heating block or in Teflon pressure vessels using a microwave assisted system. The Mg concentrations obtained for the three steel materials were: 2.0, 2.8, and 10.3 µg g−1, respectively, and the spread in results was acceptable, giving RSD values in the range of 20–30%.

Purification of 6N Aluminum by Ultrahigh-Vacuum Melting

To improve the purity of 6N-grade aluminum, it was melted in a vacuum of 3­6 © 10 ¹6 Pa for 30min and solidified gradually. The melted samples were cut into several pieces and the residual impurities of each portion were analyzed by glow discharge mass spectrometry (GDMS). The residual resistivity ratio (RRR) of each portion was also measured and the relationship between RRR and residual impurities was investigated. The purity of the melted sample was improved in comparison with that of the raw material, and the measured RRR was almost doubled to 40000. GDMS analysis revealed that the concentration of the elements with partition coefficient k 1 was not reduced. While each impurity concentration ratio in this study is about one-tenth of that in our previous report, the purification efficiency of each element in this study and that in the previous report were in good agreement. Although the values of RRR estimated from composition analysis were larger than the measured RRR values, both exhibited similar tendencies with regard to the specimen position and also corresponded well with impurity distribution. [doi:10.2320/matertrans.M2012041]

Determination of Relative Sensitivity Factors ofImpurities in Poly-Silicon by Derect Current Glow Discharge Mass Spectrometry

Determination of Relative Sensitivity Factors ofImpurities in Poly-Silicon by Derect Current Glow Discharge Mass Spectrometry

Determination of Relative Sensitivity Factors ofImpurities in Poly-Silicon by Derect Current Glow Discharge Mass Spectrometry

Determination of Relative Sensitivity Factors ofImpurities in Poly-Silicon by Derect Current Glow Discharge Mass Spectrometry

Asymmetric charge transfer involving the ions of added gases (oxygen or hydrogen) in Grimm-type glow discharges in argon or neon

In low pressure glow discharges such as the Grimm-type source, the relative intensities of lines in the analyte spectrum depend primarily on the plasma gas. The probability of selective excitation of certain analyte spectral lines by asymmetric charge transfer (ACT) involving carrier gas ions is increased if excited levels are close to resonance. Traces of light gaseous elements, present either as constituents in the sample such as oxide, hydrides, nitrides or occluded within the sample, can be involved in selective excitation or affect selective excitation by the plasma gas. Asymmetric charge transfer involving oxygen ions (O-ACT) has been observed in spectra recorded with the Imperial College high resolution vacuum UV Fourier transform spectrometer (FTS). In addition, analyte lines excited by asymmetric charge transfer with argon ions (Ar-ACT) are relatively weaker, probably due to quenching of argon ions and corresponding reduction of Ar-ACT. Recent glow discharge mass spectrometry results have shown that significant quenching of the argon ion population occurs with the progressive addition of oxygen to glow discharges. ACT by oxygen ionic metastable states is reported and discussed.

Structural characterization of synthetic polymers using thermal-assisted atmospheric pressure glow discharge mass spectrometry

With the development of material science and the practical needs of the polymer industry, rapid characterization of synthetic polymers using mass spectrometry is of sustainable interest. Herein a new method for characterizing synthetic polymers using thermal-assisted atmospheric pressure glow discharge mass spectrometry (TA-APGD-MS) is established. After illustration of the mechanism of ion formation, typical polymer samples such as polystyrene (PS), polyoxymethylene (POM) and poly (butanediol succinate) (PBS) were directly characterized at the molecular level using TA-APGD-MS. The thermal degradation products of synthetic polymers including monomer units and/or other fragments were rapidly detected by tandem mass spectrometry, providing rich information about the chemical composition for the structural characterization of homo- and co-polymers. The result suggests that TA-APGD-MS allows direct and rapid analysis of both synthetic homo-polymers and co-polymers under ambient conditions without any sample pretreatment. This method features high throughput, high sensitivity and rich information, showing promising applications in polymer science.

Enhancements in specimen preparation of Cu(In,Ga)(S,Se) 2 thin films

When producing slices from Cu(In,Ga)(S,Se) 2 thin films for solar cells by use of a focused ion beam (FIB), agglomerates form on the Cu(In,Ga)(S,Se) 2 surfaces, which deteriorate substantially the imaging and analysis in scanning electron microscopy. Similar problems are also experienced when depth-profiling Cu(In,Ga)(S,Se) 2 thin films by means of glow-discharge or secondary ion mass spectrometry. The present work shows that the agglomerates are composed of (mainly) Cu, and that their formation may be impeded considerably by either cooling of the sample or by use of reactive gases during the ion-beam sputtering. The introduction of XeF 2 during FIB slicing resulted in excellent images, in which the microstructures of most layers in the Cu(In,Ga)(S,Se) 2 thin film stack are visible, including the microstructure of the 20 nm thin MoSe 2 layer. Acquisition of high-quality two-dimensional and also three-dimensional electron backscatter diffraction data was possible. The present work gives a basis for enhanced SEM imaging and analysis not only in the case of Cu(In,Ga)(S,Se) 2 thin films but also when dealing with further material systems exhibiting similar formations of agglomerates.

Strong visible and near infrared luminescence in undoped YAG single crystals

Strong luminescence peaks were observed at 700 and 800 nm in undoped yttrium aluminum garnet (YAG) single crystals. They were attributed to low level of iron impurities as confirmed by Glow Discharge Mass Spectrometry analysis. The 800 nm was only excited by high energy band at 270 nm; the reason behind that was discussed. Photoluminescence measurements revealed a large number of luminescence peaks in all YAG crystals regardless of the growth conditions due to native defects and low-level impurities. These luminescence centers have significant effects on the optical properties of rare-earth doped YAG crystals and their performance in laser and scintillation applications. Excitons released in the lattice may be easily captured by iron ions instead of Ce3+ ions and the scintillation output is substantially decreased. Nevertheless, Undoped YAG crystals may have the potential to be developed into efficient scintillators.