Hydrogen Getter Research Articles

Pebble divertor concept for high power density fusion reactors

The pebble divertor is a new concept applicable to the strike zone with very high heat (>20 MW/m 2) and particle load (>10 24 atoms/m 2s). In this concept, a large number of small pebbles made from refractory materials with multifunctions are used as a moving surface. A marked feature of our pebble divertor concept is the use of multi-layer pebbles. The multi-layer pebble consists of a kernel, a plasma facing layer (PFL) and an intermediate tritium permeation barrier. In the case of the pebble with a diameter of 1–2 mm, it is found that the pebble can resist high heat loads of about 30 MW/m 2. When the PFL of the pebble is made from carbon material, pebbles also perform fuel gas pumping due to the hydrogen gettering characteristic of carbon. From the estimation of the energy conversion in the pebble divertor system, the maximum operation temperature should be larger than about 800 K to obtain a energy gain, which is the ratio of recovery energy in Calnot cycle to the additional heat energy, larger than one in the divertor system.

Influence of high-power plasma streams irradiation on surface erosion behavior of reversible hydrogen getters

The paper presents results of investigations of the shielding effect observed at the interaction of pulsed plasma streams with metal-hydrides on the base of Zr 55V 40Fe 5 alloys. A reversible hydrogen getter tablet was initially saturated with pure hydrogen and then irradiated with pulsed plasma beams. The total content of accumulated hydrogen was 2 dm 3 (under normal conditions). The plasma irradiation induced desorption of accumulated hydrogen, due to the high-speed heating and the formation of gas shield layer in front of the tablet surface. That layer decreased considerably the value of an energy density, which was delivered to the sample surface. The energy densities delivered to the sample and mass losses of material have been determined as a function of a number of pulses. It was found that hydrogen buildup promotes an increase of the shielding effect.

The low-temperature reduction of Pd-doped transition metal oxide surfaces with hydrogen

The reaction of hydrogen with a series of polyvalent metal oxides (Fe 2O 3, WO 3, MoO 3, V 2O 5, Sb 2O 3, PbO 2, Cr 2O 3, NiO, CuO, Co 3O 4, MnO 2, PdO, Ag 2O) was investigated at low temperatures (77–320 K) and pressures (0.001–0.7 kPa). Pd-doped (0.1–0.5 wt.%) transition metal oxides can be reduced by hydrogen at 77–320 K whereas the onset of the reduction of the pure oxides occurs at temperatures higher than 500–700 K. It is shown that oxides, possessing a low stability of the metal–oxygen bond, a significant oxygen-diffusion coefficient from the oxide volume, and a large specific surface area are promising low-temperature vacuum hydrogen getters. Two temperature regions with different kinetics have been found for the most active oxides (Co 3O 4, CuO, MnO 2): 77–210 and 220–320 K. At 77–180 K, the chemical interaction between hydrogen and the Pd-doped oxides proceeds with an apparent zero activation energy according to the equation P= ln τ . At 195–320 K, a first-order reaction is found. XPS studies of the low-temperature reduction catalysts show Pd on oxides. A possible reaction mechanism is discussed. It is supposed that proton spillover into the lattice is critical for the low-temperature oxide reduction. A electron tunnel mechanism is probable too.

Effect of PECVD of SiO 2 passivation layers on GaN and InGaP

Thin (200 Å) layers of SiO 2 were deposited by plasma enhanced chemical vapor deposition onto GaN and InGaP patterned with transmission line measurement contact pads. The sheet resistance of n-GaN and n- and p-InGaP was measured as a function of N 2O/SiH 4 ratio, rf chuck power, pressure and substrate temperature during the SiO 2 deposition. The sheet resistance ratio before and after the deposition varied from 0.7 to 1.2, reflecting a competition between mechanisms that decrease doping (hydrogen passivation, ion-induced deep traps) and those that increase it (creation of shallow donor states in n-type material through preferential ion of the group V elements, gettering of hydrogen in p-type material). Under most conditions, SiO 2 deposition creates minimal changes to the electrical properties of GaN and InGaP.

Blistering on Silicon Surface Caused by Gettering of Hydrogen on Post-Implantation Defects

ABSTRACTA well-known process for thinning of silicon by slicing submicron-thick crystalline films from substrates uses direct implantation of protons. In this paper we describe a different way of delivering hydrogen to a cleavage plane. In our process a defect-rich buried layer is first formed with ion implantation. Defects in the as-implanted silicon work as traps for hydrogen. Next monatomic hydrogen is delivered to the trap layer by electrolytic charging. To check sliceability, the samples were annealed and blistering was observed. Evidence of blistering is a sign of potential cleavage. The electrolytic charging was performed using a simple two-electrode cell. The front side of the as-implanted silicon wafer was exposed to an electrolyte. The backside of the wafer was contacted with an aluminum layer and connected to a current source. The acidic electrolyte was buffered with ethylene glycol. Buffering was used to suppress bubbling on the wafer surface and to improve the uniformity of charging. To increase charging current the wafer was illuminated with visible light. A graphite rod was used as the positive electrode in the cell. A few Coulombs per square centimeter of the wafer were passed through the cell during the hydrogenation process. The depth of blisters is about 1/2 of projection range of the implanted ions. It means that the hydrogen platelets are formed in the region of maximum of vacancy- enriched post-implantation defects. This process of electrolytic hydrogen charging may be used in future to manufacture silicon-on-insulator wafers with very thin top silicon layer. Thin SOI offers important advantages in the production of substrates for mainstream CMOS integrated circuit manufacturing.

Hydrogen uptake mechanism of a silicone-rubber DEB getter mixture

The kinetics of the hydrogen getter 1,4-bis(phenylethynyl)benzene (DEB) blended with carbon-supported Pd (DEB-Pd/C) dispersed uniformly in silicone [DEB-Pd/C-poly(dimethyl siloxane)] were studied with a thermogravimetric method as a function of the hydrogen pressure and temperature. A diffusion-controlled reaction model was developed to explain the experimental results. The diffusion coefficient, solubility coefficient, and permeability of hydrogen through silicone rubber were determined. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 425–431, 2001

The hydrogen gettering at post-implantation hydrogen plasma treatments of helium- and hydrogen implanted Czochralski silicon

The effect of the gettering of hydrogen at buried defect layers at post-implantation hydrogen plasma treatments and the loss of hydrogen at these layers at high-temperature annealing of helium-implanted (at 300 keV, 1×10 16 cm −2; at 1 MeV, 1×10 15, 1×10 16 and 1×10 17 cm −2) and, for comparison, of hydrogen-implanted (at 70 keV, 1×10 15, 1×10 16 and 3×10 16 cm −2) Czochralski silicon was studied. The samples were annealed at 450 and 1000°C in flowing nitrogen or hydrogen ambient. As-implanted and annealed samples were treated by a d.c. hydrogen plasma at 150°C. Secondary ion mass spectroscopy (SIMS) was applied to measure the hydrogen concentration profiles of the samples. The buried defect layers, which were created by hydrogen or helium implantation, act as good getter centers for hydrogen at appropriate hydrogen plasma or heat treatments. It is shown that the loss of hydrogen from the buried layers depends on the temperature, the time of annealing and the annealing ambient. The loss of hydrogen at 450°C and the decrease of the hydrogen SIMS signal do not only result from a formation of H 2 molecules captured by cavities and platelets, but also from the penetration of atomic hydrogen into the wafer bulk. This penetration leads to a thermal donor formation, as can be proved by spreading resistance probe analysis.

Problems of determining true equilibrium pressures of hydrogen getters over a wide range of getter temperature and hydrogen sorption

We have assessed a conventionally configured apparatus to measure hydrogen equilibrium pressures of getter alloys over the temperature range of 25 to 400 °C and hydrogen concentration range of 0.02 to 1 H/A. An in situ approach has been proposed to correlate the measurements of different gauges using one of the precisely calibrated gauges as a standard reference. The pressure range of interest was 10−7–105 Pa and was covered using a Bayart–Alpert gauge, a spinning rotor gauge, and different capacitance gauges. The approach involves measuring the characteristic response of these instruments prior to determining hydrogen equilibrium pressures over the relevant range of wall and getter bed temperature. To evaluate the accuracy of the measurements, we performed an error propagation analysis. The use of a porous filter to avoid fines contamination and the adsorption/desorption kinetics of the walls of the system were both addressed.

Influence of Retarding Hydrogen Diffusion in Boron Phosphosilicate Glass on Annealing Damage of Metal‐Oxide Semiconductor Transistors

This paper reports results on an investigation of the influence of titanium film in interconnects on incomplete transistor annealing. Annealing damage may be impeded when titanium directly overlays transistors. This may be due to not only gettering of hydrogen by titanium films but also to retarding hydrogen diffusion of the interlayer between the gate electrode of transistors and the titanium‐containing interconnects in boron phosphosilicate glass. The hydrogen diffusion coefficient in the boron phosphosilicate glass film was approximately at 400°C, which is three orders of magnitude smaller than that in the thermal oxide. © 1999 The Electrochemical Society. All rights reserved.

Solution for pressure measurement problems in finding PCT equilibrium characteristics of hydrogen getters

The extent of problems and limitations prevailing in the determination of pressure–concentration–temperature (PCT) equilibrium characteristics of metallic hydrogen getters are brought out in this work. This work also presents an approach to determine the equilibrium pressures at various wall and getter temperatures precisely. Results of an experimental study using a thermally stabilized Baratron gauge in combination with Spinning Rotor and Shultz–Phelps gauges in a thermostatically controlled ultra-low-leak vacuum system loaded with a zirconium alloy getter are reported. The work is relevant to the application of metallic getters for hydrogen isotope control and recovery in fusion research.

Thermochemical properties of the hydrogen getter DEB

Vapor pressures of the hydrogen getter 1,4 bis(phenylethynyl)benzene (DEB), together with two of its derivatives namely DEB mixed with carbon-supported Pd (DEB–Pd/C) and hydrogenated DEB–Pd/C, are measured from room temperature to the melting temperature (179°C). The corresponding thermodynamic information, such as the enthalpy of vaporization, boiling point, and the deviation from ideal solution behavior of DEB–Pd/C, has been derived from the vapor pressure–temperature relationships. In addition, the hydrogenation kinetics of DEB–Pd/C (powder form and rod-like) has also been investigated at a fixed pressure of 13.3 Pa (0.1 Torr) and at four temperatures, 21°C, 35°C, 45°C and 55°C.

Hydrogen redistribution and enhanced thermal donor formation at post implantation annealing of p-type hydrogen implanted Czochralski silicon

The hydrogen redistribution and the enhanced conversion of the region near the surface of hydrogen implanted p-type Czochralski (Cz) silicon wafers into n-type by thermal donor (TD) formation at low-temperature (450°C) post-implantation annealing have been investigated. For comparison low-temperature (260°C) RF hydrogen plasma treated Cz Si with subsequent annealing at 450°C was studied, too. Spreading resistance probe (SRP) analysis and secondary ion mass spectrometry (SIMS) were used for the samples characterization. It is shown that the hydrogen redistribution and hydrogen enhanced thermal donor formation in hydrogen implanted or hydrogen plasma treated p-type Cz Si leads to the formation of deep p–n junctions after 450°C annealing. The buried defect layer in hydrogen implanted Cz Si samples acts as an effective getter for hydrogen and therefore a delay in the formation of deep p–n junctions was observed as compared to hydrogen plasma treated samples with subsequent annealing at 450°C.

Comparison of Oxygen and Hydrogen Gettering at High-Temperature Post-Implantation Annealing of Hydrogen and Helium Implanted Czochralski Silicon

AbstractP-type Czochralski (Cz) Si was implanted with H (180 keV, 2.7.1016 cm−2) or He (300 keV, 1.1016 cm−2) ions. The gettering of O and H atoms by the buried implantation damage layers during annealing up to 4 hours (1000°C in H2 or N2 ambient) was studied by secondary ion mass spectroscopy (SIMS) and spreading resistance probe (SRP) measurements. Buried defect layers act as good getter centers for O and H atoms at appropriate heat treatments. The enhanced gettering of O atoms in H implanted Cz Si (as compared to the gettering of O in He implanted samples) as well as the enhanced gettering of O during annealing in H2 flow (as compared to N2 ambient) can be explained by a hydrogen enhanced O diffusion towards the defect layers. According to a strong accumulation of O at the buried damage layers and near the surface some anomalies of the SRP profiles can be observed after post-implantation annealing.

5625742 Thermally insulating jacket under reversible vacuum utilizing hydrogen getter in combination with non-evaporable promoter getter : Boffito Claudi; Conte Andrea; Ferrario Bruno; della Porta Paolo Milan, Italy assigned to Saes Getters S p A

5625742 Thermally insulating jacket under reversible vacuum utilizing hydrogen getter in combination with non-evaporable promoter getter : Boffito Claudi; Conte Andrea; Ferrario Bruno; della Porta Paolo Milan, Italy assigned to Saes Getters S p A

Gettering of hydrogen in titanium caused by nitrogen implantation

Hydrogen is gettered into the near-surface region of titanium during nitrogen implantation. The hydrogen absorption depends on the nitrogen fluence during the implantation. This effect was investigated in the range of fluences from 2.6 × 10 16 to 4.5 × 10 17 at/cm 2 with ion energies from 100 to 460 keV. Hydrogen depth profiles were obtained by using the first resonance at 6.396 MeV of the nuclear reaction 15N 1H,αγ) 12C. The hydrogen gettering effect can have important consequences, because excessive hydrogen absorption generally leads to precipitating hydrides in the matrix lattice and metals undergo degradation of their mechanical properties.

Oxygen-, Boron- and Nitrogen-Containing Zirconium-Vanadium Alloys as Hydrogen Getters with Enhanced Properties*

Oxygen-, Boron- and Nitrogen-Containing Zirconium-Vanadium Alloys as Hydrogen Getters with Enhanced Properties*

Effect of ion beam modification on hydrogen absorption by metals

Excessive hydrogen absorption by metals, generally causing precipitation of hydrides, leads to degradation of the mechanical properties. Recently, some studies have successfully demonstrated that ion implantation is effective in suppressing hydrogen absorption by the metals. In the present paper, we have reviewed the published studies concerned with modifying the interactions between metals and hydrogen. The results of these studies have provided different ways in preventing the hydrogen penetration into the bulk. These are based on either modifying the hydrogen evolution reaction or retarding the hydrogen diffusion into the bulk. Noble metals such as platinum and palladium are catalytically active, and ion implantation with such ions can prevent the hydrogen absorption through stimulating the recombination and desorption reactions of hydrogen in its evolution reaction. The implanted foreign elements such as titanium, which has a strong affinity for hydrogen, are responsible for hydrogen gettering. Although the gettering enhances hydrogenation in the implanted region, the distribution of hydrogen over the bulk can be inhibited. This results in suppressing the hydrogen embrittlement of the metals. Trapping behaviors are also observed in titanium implanted with nitrogen ions at relatively low fluences. However, nitrogen implantation at higher fluences causes the formation of titanium nitride in the implanted layer, which acts as a barrier to inward migration of hydrogen. As a consequence, a barrier layer such as titanium nitride can completely inhibit hydrogen absorption. These results have demonstrated that ion implantation offers an effective way to prevent hydrogen embrittlement.

On Hydrogen Transport and Edge Plasma Modeling of Liquid-Metal Divertors

The steady-state operational conditions for large tokamaks impose high performance requirements that cast suspicion on the employment of conventional solid surface divertors. Flowing liquid-metal divertors are thus being considered as an alternative. A preliminary evaluation is made of some aspects of this concept. To understand the hydrogen (i.e., deuterons and tritons) recycling behavior in liquid metals, the transport and chemistry aspects of the hydrogen/liquid-metal interaction are investigated, including hydrogen gettering, tritium inventory, and blistering caused by hydrogen bubble eruptions. It is shown that when operating in the high-recycling model (i.e., as the liquid metal is filled with deuterons and tritons, one implanting ion will immediately cause the emission of one neutral particle), lithium would have a large tritium inventory. Gallium, on the other hand, does not have the same problem because of its negligible hydrogen solubility and the decomposition of its hydrides in the temperature range of interest. However, to avoid blistering, the flow speed of a gallium neutralizer has to be high. An edge plasma simulation model is briefly introduced, and its outcome for the high-recycling liquid-metal (lithium and gallium) divertors is presented. This model gives more realistic predictions of plasma temperature than some of the existing simulation models.more » Results of this model show that denser and cooler edge plasmas can be achieved by liquid-metal divertors than by conventional stationary surface divertors. Evaporation and sputtering of liquid-metal divertors are shown not to be as serious a problem as might be suspected at first glance. 22 refs., 2 figs., 1 tab.« less

Gettering of hydrogen and oxygen by alkali-metal graphite intercalation compounds

Gettering of hydrogen and oxygen by alkali-metal graphite intercalation compounds, MC8 (M=K, Rb, and Cs), was investigated by the constant-volume closed method. The rate constants for hydrogen gettering kH are found to be in the order of RbC8 (∼10−3 s−1)≳KC8 (∼10−4 s−1)≫CsC8 (<10−6 s−1), while the rate constants for oxygen gettering kO are all within the range 0.2×10−1–1×10−1 s−1 for MC8 studied. The ratio kO/kH is found to be 34, 69, and more than 5.2×104 for KC8, RbC8, and CsC8, respectively, which indicates that CsC8 has a large pumping selectivity for oxygen in a hydrogen-rich atmosphere.

Alloying Effects on Hydrogen Gettering Properties for Zr-Al System

This paper discusses alloying effects on absorption and desorption kinetics of deuterium for Zr-Al alloys, studied with mass analyzed thermal desorption spectroscopy using a conventional high vacuum system. It is found that the absorption rate of deuterium was proportional to the 1/2 power of deuterium gas pressure. On the other hand, the desorption process obeyed the second order kinetics with respect to the amount of absorbed deuterium. The temperature dependence of the rate constants revealed that the activation energies for both the absorption and desorption processes were lowered by the increase in the Al content in the alloys. Through potential diagrams for the absorption and desorption of deuterium, it was also found that the heat of deuterium (hydrogen) solution decreased with increasing Al composition. In addition, the x-ray diffraction spectroscopy showed the formation of a Zr{sub 4}Al{sub 3} phase in the Zr{sub 3}Al{sub 2} sample owing to repeated absorption and desorption cycles. The results suggest that the electronic factors, for example, work function, electron density, d-band character and so on, play an important role for the alloying effects rather than crystallographic structures.