Depth Distribution Of Hydrogen Research Articles

Weakening surface hydrogen to enhance permeation in hydrogen selective membranes

Hydrogen selective metallic membranes made of palladium and its alloys are superior to membranes made of other metallic materials due to their unique surface properties. However, the prohibitive cost of Pd has prevented their widespread application. Although the basic mechanisms are known, the link between hydrogen at the surface and that in the bulk has been missing to explain the prominent position of Pd. To provide the missing link between surface and bulk, we measured the hydrogen concentration and depth distribution on the downstream side of a Pd membrane at realistic permeation conditions (temperature and pressure) using a membrane electron spectroscopy setup. We find hydrogen in the vicinity of the surface with intermediate stability. In general, hydrogen on the surface is more stable and thus more concentrated than in the bulk. Subsurface hydrogen with intermediate stability mitigates the difference between surface and bulk concentration and thereby facilitates overall hydrogen permeation. The observations link the results of UHV-compatible hydrogen adsorption experiments with observations made on hydrogen permeation in membranes under technical conditions. This link enables the application of the wealth of surface science based knowledge to the optimization of hydrogen permeable membrane materials.

Active neutron interrogation experiments and simulation verification using the SIngle-scintillator Neutron and Gamma-Ray spectrometer (SINGR) for geosciences

We present a new SIngle-scintillator Neutron and Gamma-Ray spectrometer (SINGR) instrument for use with both passive and active measurement techniques. Here we discuss, the application of SINGR for planetary exploration missions; however, hydrology, nuclear non-proliferation, and resource prospecting are all potential areas where the instrument could be applied. SINGR uses an elpasolite scintillator, Cs2YLiCl6:Ce (CLYC), that has been shown to have high neutron efficiency even at small volumes, with a gamma-ray energy resolution of approximately 4% full-width-at-half-maximum at 662 keV. Active gamma-ray and neutron (GRNS) measurements were performed with SINGR at the NASA Goddard Space Flight Center (GSFC) Goddard Geophysical and Astronomical Observatory (GGAO) outdoor test site using a pulsed neutron generator (PNG) to interrogate geologically relevant materials (basalt and granite monuments). These experimental results, combined with simulations, demonstrate that SINGR is capable of generating neutron die-away curves that can be used to reconstruct the bulk hydrogen abundance and the depth distribution of hydrogen within the monuments. We compare our experimental results with Monte Carlo N-Particle (MCNP) 6.1 transport simulations to constrain the uncertainties in depth and hydrogen abundance from the neutron die-away data generated by SINGR. For future planetary exploration missions, SINGR provides a single detector system for interrogating the shallow subsurface to characterize the presence and abundance of hydrated phases and to provide bulk elemental analysis.

Blistering of potassium-tantalate single crystals induced by helium implantation

Potassium-tantalate crystals were implanted with helium ions at 190 keV and then thermally treated at different temperatures to study their blistering. The surface blistering, hydrogen depth distribution, and lattice damage induced by He+ implantation were characterized using secondary ion mass spectroscopy, optical and transmission electron microscopy, and Rutherford backscattering spectrometry. The blistering of potassium-tantalate crystals was achieved at certain ion fluences followed by thermal treatment.

Secondary-Ion Mass Spectroscopy for Analysis of the Implanted Hydrogen Profile in Silicon and Impurity Composition of Silicon-on-Insulator Structures

Theoretical and experimental data are reported for the distribution of hydrogen in silicon in SiO2–Si structures after the implantation of hydrogen. Hydrogen is implanted under conditions used in preparing silicon-on-insulator structures by the hydrogen transfer technology. A technique for quantitative estimation of implanted hydrogen high concentrations in silicon using secondary-ion mass spectrometry is suggested. It includes the quantitative calibration of the hydrogen atom concentration and normalization of the depth of analysis from sputtering time. Data for the implanted hydrogen depth distribution in silicon and in Si–SiO2 structures are presented. The lateral uniformity and temporal stability of implanted structures have been monitored.

Analysis of Active Neutron Measurements From the Mars Science Laboratory Dynamic Albedo of Neutrons Instrument: Intrinsic Variability, Outliers, and Implications for Future Investigations

AbstractThe Dynamic Albedo of Neutrons (DAN) instrument onboard Mars Science Laboratory uses neutron die‐away, an active nuclear spectroscopy technique, to measure the abundance and depth distribution of hydrogen and neutron‐absorbing elements (e.g., Fe and Cl) in the top ∼0.5 m of the Mars subsurface. We examined the intrinsic variability in neutron die‐away data using simulated DAN measurements with a range of compositions relevant to equatorial and high‐latitude environments on Mars. Our analysis shows that the total neutron counts and timing of neutron arrival explain most variability in thermal neutron die‐away curves for a DAN‐like instrument configuration over homogeneous subsurfaces. We analyzed the variability in thermal neutron die‐away across a variety of elemental compositions that might be observed by DAN or future instruments. We found that when H concentration is low (e.g., in equatorial regions including Gale crater), neutron die‐away is most sensitive to variations in H. Conversely, when H concentration is high (e.g., in poleward regions of Mars or icy bodies), neutron die‐away is most sensitive to variations in neutron absorbers. We estimated that the H and neutron absorber concentrations in DAN measurements acquired Sols 1–2080 in Gale crater and found that most measurements had low H and moderate absorber content. We presented an outlier analysis of these measurements to identify targets with high potential scientific impact and found that most outliers along the traverse corresponded with abnormally low or high neutron absorber content measurements, some of which may be associated with high‐silica fracture‐associated halos and felsic igneous material.

Diffusion and reaction kinetics governing surface blistering in radio frequency sputtered hydrogenated a-SixGe1-x (0 ≤ x ≤ 1) thin films

The preparation of blister free layers of hydrogenated a-SixGe1-x (0 ≤ x ≤ 1) is a primary requisite for their technological applications. In RF (Radio Frequency) sputtered layers the formation of blisters is temperature dependent, as also shown here. This dependence is used to propose a theoretical model aimed at a better understanding of the mechanisms determining the blistering. Beside the reaction kinetics responsible for the release of H atoms from SiH and/or GeH complexes the model takes into particular account the contribution of the diffusion of H. The activation energy for blistering also enters in the model. The validation of the theoretical frame of the model is confirmed by the fact that it predicts a blistering threshold temperature in reasonable agreement with the experiment. The amorphous hydrogenated thin layers were deposited on polished silicon by RF co-sputtering. They were annealed between 150 and 350 °C. The structural changes of the surface of the SiGe films have been explored systematically by light beam reflection, scanning electron microscopy while the depth distribution of hydrogen was measured by secondary neutral mass spectrometry.

Hydrogen-Accelerated Phase Transition and Diffusion in TiO2 Thin Films

TiO2 thin films have received attention as intermetallic diffusion barriers in hydrogen-permeable membranes used for the extraction of purified H2 from chemical reactors. We report the fabrication of thin (∼100 nm) TiO2 films on Si(111) substrates by pulsed laser deposition. Anatase and rutile phases are found to coexist in the as-deposited TiO2 films by X-ray diffraction. Upon H2 annealing at 773–973 K, the phase transformation from anatase to rutile occurs and completes at a strongly (100–380 K) reduced temperature as compared to bulk TiO2. Atomic force microscopy shows that the surface roughness of the thin films increases only slightly (from 3 to 6 nm) in this H-accelerated phase transition. The hydrogen depth distributions in the TiO2 thin films are revealed with resonant 1H(15N,αγ)12C nuclear reaction analysis and evaluated in terms of a one-dimensional diffusion model, which allows the determination of the temperature-dependent diffusion coefficient of hydrogen as D(T) = (5.27 ± 0.89) × 10–8 exp(−0...

Water vapor interaction with borosilicate glass

Hydration of borosilicate glass (Corning Pyrex glass) in isotopic water H218O vapor was performed at different temperatures. The depth distributions of 1H and 18O in the borosilicate glass measured by the Time-of-Flight Secondary Ion Mass-Spectrometry (TOF-SIMS) were found to be drastically different. The activation energies for the 18O diffusion and for the glass hydrogenation were measured experimentally. The depth distribution of the 18O isotope was described well by the complementary error function, whereas the depth distribution of hydrogen represented the so-called “S-curve”. A similar hydrogen distribution was observed earlier in hydrated natural aluminosilicate glasses (obsidians). This led us to the conclusion that the hydrogenated layer was formed due to a solid state chemical reaction between protons and the glass network. The protons were the result of another solid state chemical reaction between the absorbed water molecules and glass network occurring in a top surface layer (<30 nm).

Hydrogenation of Zr-2.5Nb alloy after plasma-immersion titanium implantation

The study results of the influence of plasma-immersion ion implantation of titanium in Zr-2.5Nb on hydrogenation are presented. The titanium implantation was carried out in two modes: with active plasma filtering (APF) and passive plasma filtering (PPF). The results of total hydrogen concentration, absorption rate, XRD analyses and depth distribution of elements revealed that modified surface layer after titanium ion implantation is formed hydrogen diffusion barrier reduces hydrogen absorption by Zr-2.5Nb.

Temperature dependence of hydrogen depth distribution in the near-surface region of stainless steel

The depth profile of hydrogen at a type 304 stainless steel surface was investigated with 1H(15N, αγ)12C nuclear reaction analysis at various temperatures. Hydrogen was predominantly distributed in the region shallower than 10 nm (surface hydrogen) with an area density of ∼1 × 1016 cm−2. Hydrogen was found to also exist in a deeper region (>30 nm) with a constant volume density of ∼4 × 1020 cm−3 (bulk hydrogen). While both bulk and surface components gradually decreased as the temperature rose, part of the intensities remained even at 975 K. From the temperature dependence of the amount of the surface hydrogen, the distribution of the activation energy for desorption is discussed.

Study of depth profile of hydrogen in hydrogenated diamond like carbon thin film using ion beam analysis techniques

The Hydrogenated Diamond Like Carbon (HDLC) thin films are deposited on Silicon substrate at room temperature using asymmetric capacitively coupled RF plasma with varying flow rates of methane. These films are undergone annealing at high vacuum (∼10−7torr) and high temperature (750 and 1050°C) furnace. The as-prepared and annealed HDLC films have been depth profiled for hydrogen using the resonance at 6.44MeV in 1H(19F,αγ)16O nuclear reaction. The as prepared films exhibit non-uniform depth distribution of hydrogen: it decreases with depth. Annealing in vacuum brings about is a significant desorption of hydrogen from the films. Loss of hydrogen, albeit in much lower proportions, is also induced by the bombarding beam. The films also experience a mild loss of carbon, as shown by proton backscattering spectrometry, during high vacuum annealing. The depth profiles of hydrogen in the annealed films are indicative of the prevalence of graphitic carbon near film–substrate interface.

Hydrogen Redistribution and Performance Improvement of Silicon Avalanche Photodiode by Low-Temperature Annealing

We report the performance improvement of the silicon avalanche photodiode (APD) for electron detection by annealing. It was found that the dark current is reduced and that the gain and energy resolution are improved by annealing at 500 K for 10 h. By means of the nuclear reaction analysis, the depth distribution of hydrogen in APD was measured before and after annealing. The hydrogen concentration in the near-surface region was significantly increased by annealing. We discuss that passivation of the impurity and/or defect levels by hydrogen atoms is a possible reason for the performance improvement of the photodiode.

Dynamic Albedo of Neutrons (DAN) Experiment Onboard NASA’s Mars Science Laboratory

The description of Dynamic Albedo of Neutrons (DAN) experiment is presented, as a part of the NASA’s Mars Science Laboratory mission onboard the mars rover Curiosity. The instrument DAN includes Pulsing Neutron Generator (PNG) producing pulses of 14.1 MeV neutrons for irradiation of subsurface material below the rover, and Detectors and Electronics (DE) unit, which operates the instrument itself and measures the die-away time profiles of epithermal and thermal neutrons following each neutron pulse. It is shown that the DAN investigation will measure a content of hydrogen along the path of the MSL rover, and it will also provide information about a depth distribution of hydrogen at 10–20 regions selected for the detailed studies and sampling analysis.

An investigation of hydrogen depth profiling using ToF‐SIMS

Hydrogen depth distributions in silicon, zinc oxide, and glass are of great interest in material research and industry. Time‐of‐flight SIMS has been used for hydrogen depth profiling for many years. However, some critical information, such as optimal instrumental settings and detection limits, is not easily available from previous publications. In this work, optimal instrumental settings and detection limits of hydrogen in silicon, zinc oxide, and common glass were investigated. The recommended experimental settings for hydrogen depth profiling using time‐of‐flight SIMS are: (i) keeping pressure in the analysis chamber as low as possible, (ii) using a cesium beam for sputtering and monitoring the H– signal, (iii) employing monatomic ion analysis beams with the highest currents, and (iv) using interlace mode. In addition, monatomic secondary ions from a matrix are recommended as references to normalize the H– signal. Detection limits of hydrogen are limited by the pressure of residual gases in the analysis chamber. The base pressure of the analysis chamber (with samples) is about 7 × 10−10 mbar in this study, and the corresponding detection limits of hydrogen in silicon, zinc oxide, and common glass are 1.3 × 1018 atoms/cm3, 1.8 × 1018 atoms/cm3, and 5.6 × 1018 atoms/cm3, respectively. Copyright © 2011 John Wiley &amp; Sons, Ltd.

H Quantification and Profiling in SiO[sub 2]/SiC Submitted to Annealing in Water Vapor

The incorporation and depth distribution of hydrogen, after annealings in low pressure water vapor of Si0 2 films thermally grown in O 2 on SiC and on Si, are determined using nuclear reaction analyses. Water isotopically enriched simultaneously in deuterium ( 2 H or D) and in 18 O was used. While in Si0 2 /SiC, the amount of incorporated hydrogen increases continuously with temperature and with initial oxide thickness; in SiO 2 /Si, there is no such dependence. In SiO 2 /SiC, hydrogen profiling reveals its presence in the surface, bulk, and interface regions, whereas in SiO 2 /Si, hydrogen is observed only in near-surface regions of the oxide film.

Study in the effect of annealing on hydrogen retention properties of C‐90%SiC films

AbstractCarbon‐rich silicon carbide (C‐90%SiC) films as hydrogen barriers were deposited on the surface of stainless steel substrates with magnetron sputtering, and then bombarded by argon ion beam. In order to remove the argon atoms reserved during films preparation, some samples with the prepared C‐90%SiC films were thermally annealed for 30 min at 473, 673 and 873 K in vacuum, respectively. These samples together with the un‐annealed ones were then irradiated by a 5 keV hydrogen ion beam. SEM was used to investigate the surface micrograph of those films and SIMS was used to measure the mass spectra of positive species and the depth distribution of argon and hydrogen in the samples. A remarkable decrease in hydrogen intensity in the substrates with annealing indicates that annealing for removing argon can effectively improve hydrogen retention properties of the C‐90%SiC films. Copyright © 2008 John Wiley &amp; Sons, Ltd.

X-ray reflectivity study of hydrogen implanted silicon

The X-ray reflectivity (XRR) technique was used to study monocrystalline silicon samples implanted with H 2 ions at an energy of 31 keV and to the dose of 2 × 10 16 hydrogen atoms/cm 2. All samples were subsequently isochronally annealed in vacuum at different temperatures in the range from 100 to 900 °C. Although the hydrogen depth distribution was expected to be smooth initially, fringes in the XRR spectra were observed already in the implanted but not annealed sample, revealing the presence of a well-defined film-like structure. Annealing enhances the film top to bottom interface correlation due to structural relaxation, resulting in the appearance of fringes in the larger angular range, already at low annealing temperatures. The thickness of the film decreases slowly up to 350 °C where substantial changes in the roughness are observed, probably due to the onset of larger clusters formation. Further annealing at higher temperatures restores the high correlation of the film interfaces, while the thickness decreases with the temperature more rapidly.

Ion beam analysis of hydrogen retained in carbon nanotubes and carbon films

Carbon nanotubes (CNTs) are studied as a possible hydrogen storage medium for future energy needs. Typically, hydrogen is stored in the CNTs by exposure of the material to a high-pressure H2 atmosphere at different temperatures. The maximum hydrogen concentrations stored following this method and measured using ion beam analysis do not exceed 1wt.%. Introduction of defects by ion irradiation (i.e. implantation) prior to high-pressure H2 treatment, offers an alternative method to activate H adsorption and enhance the chemisorption of hydrogen. This is a preliminary work where hydrogen was introduced into single-wall nanotubes and carbon films by low-energy (13.6keV) hydrogen ion implantation. Elastic recoil detection was used to measure the quantity and depth distribution of hydrogen retained in the carbonaceous materials. Results show that there are substantial differences in the measured profiles between the CNT samples and the vitreous carbon. On another hand, only ∼43% of the implanted hydrogen in the CNTs is retained in the region where it should be located according to the SRIM simulations for a solid carbon sample.

Characterization of hydrogen contained in passivated poly‐Si and microcrystalline‐Si by ERDA technique

AbstractPolycrystalline Si (poly‐Si) thin films produced by atmospheric pressure chemical vapour deposition (APCVD) were treated by hydrogen passivation in the remote plasma system. Such materials could be potentially used for photovoltaics applications. The purpose of the present study was to investigate the effects of hydrogen passivation on poly‐Si thin film properties, such as hall mobility and photoluminescence. Elastic recoil detection analysis (ERDA) was used to determine the depth distribution and concentration of hydrogen. ERDA was also applied to determine the hydrogen content of amorphous/microcrystalline silicon produced by plasma enhanced chemical vapour deposition (PECVD) with various dilution ratios of the working gases (H2 and SiH4). A dependence of the hydrogen content on the crystallinity was observed. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Miss MaRPel – a 3 MV pelletron accelerator for hydrogen depth profiling

The 3 MV Pelletron tandem accelerator MaRPel (Material Research Pelletron) of the II. Physikalisches Institut in Göttingen is equipped with a low-level target station for applying the Resonant Nuclear Reaction Analysis technique. This combination allows high-resolution hydrogen depth distribution profiling using a 15N beam with an energy higher than 6.385 MeV, which is the resonance energy of the 1H(15N, α γ)12 C nuclear reaction. The installed AMSEL-steerers are used for an easy variation of the beam energy and a computer-controlled automated measurement of depth profiles. Here, the experimental set-up is described and the strategy of the energy calibration of MaRPel and the AMSEL-steerers is explained. The resolution and sensitivity of hydrogen depth profiling are presented together with some measured profiles as examples for possible applications of this analytic tool.