Hydrogen Incorporation Research Articles

Surface-plasmon-induced photoabsorption of Ag nanoparticle embedded a-Si solar cell

Effect of silver nanoparticles on the performance of the solar cell is presented. We fabricated an amorphous silicon solar cell with a high quality absorber layer, deposited by sputtering. We have investigated the quality variation in the absorber layer with three different power modes of sputtering. The effect of hydrogen incorporation on the bandgap, dark conductivity, photo conductivity and hence photo gain of absorber layer is studied for the three power modes of sputtering. Silver nanoparticles are embedded in the high quality absorber layer of the solar cell at a depth of 50 nm. We are able to visualize the effect of surface plasmon resonance in the vicinity of 625 nm. Along with the plasmon resonance we are able to visualize the scattering effects in the long wavelength regions. The effect of areal coverage of the silver nanoparticles inside the absorber layer on the transmittance, J-V characteristics and external quantum efficiency is reported. We are able to increase the light absorption in the weakly absorbing region of 600–675 nm by incorporating silver nanoparticles. The transmission is reduced to 46.6%, and in the vicinity of 625 nm we achieved 10.2% higher external quantum efficiency than the reference device.

Nanostructure evolution of magnetron sputtered hydrogenated silicon thin films

Hydrogenated silicon (Si:H) thin films have been prepared by radio frequency (RF) magnetron sputtering. The effect of hydrogen gas concentration during sputtering on the resultant film structural and optical properties has been investigated by real time spectroscopic ellipsometry (RTSE) and grazing incidence x-ray diffraction (GIXRD). The analysis of in-situ RTSE data collected during sputter deposition tracks the evolution of surface roughness and film bulk layer thickness with time. Growth evolution diagrams depicting amorphous, nanocrystalline, and mixed-phase regions for low and high deposition rate Si:H are constructed and the effects of process parameter (hydrogen gas concentration, total pressure, and RF power) variations on the deposition rate have been qualified. Virtual interface analysis of RTSE data provides nanocrystalline volume fraction depth profiles in the mixed-phase growth regime. GIXRD measurements show the presence of (111) and (220) oriented crystallites. Vibrational mode absorption features from Si-Hn bonding configurations at 590, 640, 2000, and 2090 cm−1 are obtained by ex-situ infrared spectroscopic ellipsometry. Hydrogen incorporation decreases as films transition from amorphous to nanocrystalline phases with increasing hydrogen gas concentration during sputtering.

The effect of titanium(Ti) doping on hydrogen incorporation in tungsten(W)：First-principles calculations

Using the first-principles methods, we investigated the structure, the mechanical properties, and solution and diffusion behavior of hydrogen impurity in the W-Ti lattice. The single H atom is energetically favorable sitting at the tetrahedral interstitial site nearest neighboring to the Ti atom in the W-Ti lattice. The minimum solution energy is about 0.498eV. By analyzing the energy barrier curves, it is shown that the effect of titanium-doped tungsten on hydrogen migration behavior is small in the W-Ti lattice. Base on the elastic constants analysis, titanium-doped tungsten can withstand the degradation of mechanical strength induced by hydrogen effect. On the other hand, it is found that the ductility of pure W metal and W-Ti alloys can be improved substantially by hydrogen effect from the B/G ratio and the Poisson's ratio ν. However, the effect of the improved ductility is more obvious in the bcc pure W metal than that in the W-Ti alloys.

Experimental and Computational Investigation of the Optical, Electronic, and Electrochemical Properties of Hydrogenated α-Fe2O3

With the combination of experimental and computational approaches, the impact of hydrogenation on the optical, electronic and electrochemical properties of Fe2O3 for water splitting have been studied. Under high pressure, hydrogen incorporation into the Fe2O3 lattice has been achieved, and hydrogen dopants can be released with heat treatment. With H-doping, magnetite Fe3O4 has been found to form at the edge of Fe2O3 nanoparticles. H-incorporation can narrow the band gap by ∼0.4 eV and slightly reduce the overpotential (by 140 mV) for oxygen evolution reaction, but due to the localization of hydrogen (bonded with oxygen), a slightly lower charge carrier density resulted. Computational studies reveal that all of the above changes are essentially related to the local states brought by H-dopants. This study provides an in-depth understanding of the optical, electronic, and catalytic properties of hydrogenated Fe2O3.

Native point defects on hydrogen-passivated 4H-SiC (0001) surface and the effects on metal adsorptions.

With the continued expansion of silicon carbide's (SiC) applications, atomistic understanding on the native point defects of its surfaces, particularly on those of the hydrogen-passivated (HP) 4H-SiC (0001) surface, becomes imperative. Using first-principles calculations, the structures and formation energies of several typical native point defects (e.g., ISi, IC, VSi, VC, and SiC) on the (0001) HP-surface of 4H-SiC were systematically explored, including the effects of the unit cell size, environmental condition, charge state, and hydrogen incorporation. Furthermore, their adsorptions of Ag (Mo) atom on these defective sites were systematically investigated. The formation energies of these defects in the HP-surface, clean surface, and bulk SiC were concluded together with their thermodynamic concentrations in the HP-surface estimated. The influences of these defects to metal (Ag, Mo) adsorptions of HP-surfaces were concluded. Based on these conclusions, the wettability improvement between the metal liquid and ion (Ag or Mo) implanted SiC substrates in the previous studies can be well understood at the atomistic scale. This study provides a theoretical guideline to SiC surface modification for the production of metal-SiC composites, brazing of SiC with metals, fabrication of electronic devices, or the growth of two dimensional nanofilms.

The pyrite-type high-pressure form of FeOOH.

Water transported into Earth's interior by subduction strongly influences dynamics such as volcanism and plate tectonics. Several recent studies have reported hydrous minerals to be stable at pressure and temperature conditions representative of Earth's deep interior, implying that surface water may be transported as far as the core-mantle boundary. However, the hydrous mineral goethite, α-FeOOH, was recently reported to decompose under the conditions of the middle region of the lower mantle to form FeO2 and release H2, suggesting the upward migration of hydrogen and large fluctuations in the oxygen distribution within the Earth system. Here we report the stability of FeOOH phases at the pressure and temperature conditions of the deep lower mantle, based on first-principles calculations and in situ X-ray diffraction experiments. In contrast to previous work suggesting the dehydrogenation of FeOOH into FeO2 in the middle of the lower mantle, we report the formation of a new FeOOH phase with the pyrite-type framework of FeO6 octahedra, which is much denser than the surrounding mantle and is stable at the conditions of the base of the mantle. Pyrite-type FeOOH may stabilize as a solid solution with other hydrous minerals in deeply subducted slabs, and could form in subducted banded iron formations. Deep-seated pyrite-type FeOOH eventually dissociates into Fe2O3 and releases H2O when subducted slabs are heated at the base of the mantle. This process may cause the incorporation of hydrogen into the outer core by the formation of iron hydride, FeHx, in the reducing environment of the core-mantle boundary.

Evolution of Microstructure and Incorporation of Excess Hydrogen During the Growth of Hydrogenated Polymorphous Silicon at High Rate

Hydrogenated polymorphous silicon (pm-Si:H) is a material consisting of a small volume fraction of nanocrystals embedded in an amorphous matrix, and which can be grown at high deposition rates by increasing the radio-frequency power. When grown at high deposition rates, pm-Si:H films show a shift of their infrared (IR) absorption stretching band peak to higher wavenumbers and a sudden increase in their optical bandgap. The IR absorption spectrum was analyzed by deconvolution into three bands, including a medium stretching mode positioned at 2030 cm−1, which has been attributed to Si–H bonds at silicon nanocrystal surfaces. Secondary ion mass spectrometry measurements confirmed that an excess of hydrogen is incorporated in pm-Si:H grown at high deposition rate, leading to a sharp increase in the optical bandgap. We suggest that this sharp increase can be used as a simple tool to detect the deterioration of material quality when using high deposition rate processes.

Optical Properties of Chemical Vapour Etching Based Porous Silicon for Multicrystalline Solar Cells

In this paper, we report a study on the possibility of fabricating porous silicon by exposing a multicrystalline silicon surface to gaseous etchants. The structural and optical properties of porous silicon (PS) layers prepared by vapour –etching (VE) are investigated. FTIR analysis confirms the existence of hydrogen incorporation bonding to the silicon atoms. Photoluminescence measurements reveal an efficient emission around 640 nm. The optical behaviour in the 350-1000 nm wavelength range was determined before and after PS formation, resulting in a notable reduction of reflectance and an enlargement of low reflectance region into short wavelengths and near IR region after PS formation. A significant increase of the quantum efficiency particularly in the short wavelength region is observed. The results make the use of such thin film very promising for multicrystalline silicon solar cell application.

Theoretical Raman spectrum and anharmonicity of tetrahedral OH defects in hydrous forsterite

Substitutional mechanisms involving hydrogen incorporation at vacant tetrahedral sites play a major role in water incorporation in olivine. Infrared (IR) absorption spectra of hydrous forsterite samples usually display a cluster of narrow and weakly anharmonic OH stretching bands at wavenumbers above 3500 cm −1 . A broader absorption band displaying pronounced temperature-dependent shift and broadening is commonly superimposed to this diagnostic spectrum and was tentatively assigned to interstitial OH groups. A less frequently observed band with similar temperature-dependent characteristics is related to a coupled incorporation of hydrogen and boron at the tetrahedral site. Here, we re-examine these interpretations by computing the theoretical Raman spectrum and investigating the local vibrational properties of OH groups at the tetrahedral site of forsterite. The present results show that the two anharmonic bands are both to be ascribed to the protonated O2 site in the clumped ( B , H ) Si x and the ( 4 H ) Si x defects. The peculiar orientation of the corresponding OH groups does not allow H-bond sharing and leads to efficient vibrational phase relaxation of the stretching mode through a hindered rotational mode coupled to the vibrational density of states of the host. The occurrence of interstitial OH groups previously proposed to interpret specific anharmonic bands of the forsterite IR spectrum is highly challenged by this new explanation. These results confirm that, at high pressure and high temperature, hydrogen incorporation in forsterite is essentially dominated by ( 4 H ) Si x defects.

(Invited) Mesoscale Modeling Approaches for Hydrogen Generation and Storage

Many of the biggest challenges in the hydrogen energy research are associated with the fact that the operating mechanisms often involve the complicated coupling of chemical/physical processes over vast ranges of multiple length and time scales. These kinetic phenomena tend to occur at or near several types of solid/solid, solid/liquid, and solid/gas interfaces, which in turn play key roles in determining the overall performance of hydrogen generation and storage processes. Examples include surface reactions with hydrogen gas or water; surface, bulk, and interface mass transport processes; structural modifications occurring under operation; and intermediate phase nucleation-and-growth processes associated with hydrogen incorporation or corrosion. Essentially, these are collective dynamic processes of atomic/molecular species that determine the thermodynamics and kinetics of nano- or micro-level characteristics. However, the lack of clear understanding of associated mechanisms and their impacts on hydrogen generation and solid-state storage reactions has hampered the acceleration of materials discovery and development. Therefore, it is obvious that several modeling approaches that cover different length and time scales ought to be properly integrated in order to comprehensively explore the underlying mesoscale science during the co-evolution of relevant processes. Mesoscale continuum modeling frameworks can provide a unified platform for integrating the necessary atomistic approaches, which typically provide higher accuracy for nanoscale chemical processes, and continuum approaches, which offer far greater flexibility and scalability and can describe materials at the microstructural level. In this talk, we present our integrated effort as part of the new DOE Advanced Water Splitting Materials consortium (HydroGEN) and Hydrogen Storage Materials—Advanced Research Consortium (HyMARC) under the Energy Materials Network (EMN) towards the multiscale modeling of solid-state hydrogen storage and hydrogen production via water splitting. In particular, we will discuss our recent efforts on the development of an integrated mesoscale modeling framework that can directly incorporate parameters derived from predictive atomistic modeling approaches such as ab initio calculations and molecular dynamics simulations. Several case studies will be presented, such as modeling phase transformations of complex metal hydrides during the (re/de)hydrogenation and modeling physical/chemical processes during the water splitting and corrosion. *This work of was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

High-Rate Etching of Copper By High-Pressure Hydrogen-Based Plasma

The copper wiring technique is a vital manufacturing technology for the current ultra-large-scale integrated (ULSI) circuits. In general, these Cu wiring are fabricated by the dual damascene process. The damascene process is mainly composed of chemical mechanical polishing (CMP) and electrical Cu plating techniques. Although these processes are well-established, these processes are fundamentally demonstrated in a wet environment and require expensive consumables and toxic chemicals. Furthermore, since CMP requires the adequate processing load for the efficient machining, the usage of a low-k material as an interlayer insulator, which has low mechanical strength, requires a prolonged processing time. From above background, it is longed-for that the dry etching process for Cu can replace the conventional wet machining process. In the previous study on the conventional dry etching for Cu, chlorine is often used as the typical etchant gas. The chlorine gas is harmful for humans and aggressive toward many of the metals constructing the etching apparatus. Furthermore, because the chlorinated Cu products exhibit a low vapor pressure around room temperature, substrate heating is generally required. On the other hand, it has been revealed that a hydrogen-based plasma can be applied for Cu dry etching at low temperature. This hydrogen dry etching seems attractive in terms of preserving the environment and suppressing the use of toxic chemicals. If a higher etching rate greater than 100 nm/min can be obtained by pure hydrogen plasma etching, it is expected that a hydrogen dry etching method with no toxic chemicals could be substituted for the CMP process. In this study, therefore, we applied the high-pressure hydrogen glow plasma (>100 Torr) to Cu etching in an attempt to achieve a higher Cu etching rate. In the experiment, a localized hydrogen-based plasma is generated at 100 Torr around the tip of a syringe needle electrode (outer diameter of 1mm). The very-high-frequency (VHF; 150 MHz) power source was used for the plasma generation. The samples used in this study were a 1 mm-thick Cu plate for investigating the Cu etching property, a 0.7 mm-thick Si(001) wafer and 0.7 mm-thick SiO2 glass to compare the etching behavior of Cu with other ULSI construction materials. The sample stage temperature was controlled from −20 to 330°C. The H2 gas was supplied to the plasma directly from the needle bore via a mass flow controller during the etching. In this study, to confirm the role of hydrogen in Cu etching, He, Ar and N2 gases were used as the process gas instead of H2. As a result, the Cu etching occurs only when the process atmosphere contains H2 gas, and the etching rates decrease with diluting the hydrogen concentration by He gas. The impact of plasma heating on the Cu etching is negligible, so the etching mechanism of the high pressure H2 plasma differs from that of the electrospark machining. When the sample stage temperature is varied from −20 to 330°C, the Cu etching rate has no obvious dependence on the stage temperature. On the other hand, the Cu etching rate increases linearly with increasing the input power from 30 W to 100 W. The emission intensity of Balmer α line of H atom observed in optical emission spectrum of the plasma also increases linearly with the input power. The Cu etching rate of 500 nm/min can be achieved around the stage temperature of 0°C. Meanwhile, the etching rates for Si and SiO2 around the stage temperature of 0°C are 100 μm/min and 50 nm/min, respectively. The selectivity of the etching rates for Cu and SiO2 suggests that this etching technique could be applied to Cu wiring on a trenched SiO2 layer. The etched Cu surface morphology is rough and exhibits many round pits and bumps. This surface roughening might be due to excessive hydrogen incorporation in the Cu bulk.

Multi-sample loading technique for comparative physical property measurements in the diamond-anvil cell

ABSTRACT We present a method to perform improved measurements of the effects of chemical variability on physical properties of single-crystal samples in the diamond-anvil cell by employing a multi-sample approach. By customizing the sizes and shapes of the samples using a focused ion beam machine the simultaneous loading of relatively large crystals into a single sample chamber becomes feasible. To illustrate the potential of this approach, elastic properties of four single crystals of ringwoodite with different chemical compositions have been measured at high pressure. Our results suggest that the multi-sample approach allows for the quantification of small effects of chemical variations, such as iron and hydrogen incorporation, on physical properties. Furthermore, we discuss the possibility of using the multi-sample approach to load several crystals with different crystallographic orientations of the same material into one sample chamber in order to map out the direction dependence of anisotropic physical properties.

Enhanced Sodium-Ion Mobility and Electronic Transport of Hydrogen-Incorporated V2O5 Electrode Materials

Although α-V2O5 as an attractive electrode material for electrochemical energy storage devices exhibits a high theoretical capacity, its atomic structure with the confined size of channels for Na-ion transport and low electronic conductivity lead to the poor rate performance. Here we demonstrate that hydrogen incorporation in α-V2O5 is an effective way to improve the kinetics of ionic and electronic transports by using the density functional theory. Among various structures of hydrogen-incorporated α-V2O5, H2V2O5 presents enlarged diffusion channels along the [010] and [001] directions where the diffusion energy barriers decrease to 0.844 eV (−34.93%) and 1.737 eV (−41.81%), respectively. Improved electronic conductivity is also achieved for H2V2O5 due to the insulator–metal transition attributed by the high concentration of hydrogen atoms. As H2V2O5 has smaller volume expansion occurring during the Na-intercalation process, H2V2O5 at the comparable specific capacity exhibits higher rate capability and cyclability than α-V2O5.

Influence of deposition rate on the structural properties of plasma-enhanced CVD epitaxial silicon

Solar cells based on epitaxial silicon layers as the absorber attract increasing attention because of the potential cost reduction. In this work, we studied the influence of the deposition rate on the structural properties of epitaxial silicon layers produced by plasma-enhanced chemical vapor deposition (epi-PECVD) using silane as a precursor and hydrogen as a carrier gas. We found that the crystalline quality of epi-PECVD layers depends on their thickness and deposition rate. Moreover, increasing the deposition rate may lead to epitaxy breakdown. In that case, we observe the formation of embedded amorphous silicon cones in the epi-PECVD layer. To explain this phenomenon, we develop a model based on the coupling of hydrogen and built-in strain. By optimizing the deposition conditions to avoid epitaxy breakdown, including substrate temperatures and plasma potential, we have been able to synthesize epi-PECVD layers up to a deposition rate of 8.3 Å/s. In such case, we found that the incorporation of hydrogen in the hydrogenated crystalline silicon can reach 4 at. % at a substrate temperature of 350 °C.

Hydrogen incorporation mechanisms in forsterite: New insights from1H and29Si NMR spectroscopy and first-principles calculation

The presence of water (hydrogen) in nominally anhydrous mantle minerals may have profound effects on their physical properties (e.g., electrical conductivity, diffusivity, rheology), and these effects are expected to depend on how water is incorporated in the crystal structure. For olivine, the most abundant upper mantle mineral, despite extensive studies, mostly using vibrational spectroscopy, the interpretations are still not well constrained. To provide better understanding on this issue, we carried out a comprehensive 1 H and 29 Si NMR study on an Mg 2 SiO 4 forsterite sample containing about 0.5 wt% H 2 O synthesized at 12 GPa and 1200 °C, complemented by Raman measurement and first-principles calculation of the geometry, stability, and NMR parameters of model structures. The Raman spectra contain relatively sharp O-H stretching bands near 3612, 3579, and 3567 cm −1 and a broader band near 3547 cm −1 , similar to previous reports. The 1 H static and MAS NMR data revealed that there are two main populations of protons in the hydrous forsterite structure, one experiencing strong 1 H- 1 H homonuclear dipolar couplings and contributing to a broad peak near 2.4 ppm, and another with weaker dipolar couplings and contributing to a narrower peak near 1.2 ppm in the MAS NMR spectrum at 30 kHz. Two-dimensional 1 H CRAMPS-MAS NMR measurements confirmed that the two proton components belong to the same phase and the contrast in MAS NMR peak width is largely due to difference in the strength of 1 H- 1 H homonuclear dipolar couplings. In addition, there is also a very weak, narrow 1 H MAS NMR peak near 7.3 ppm (contributing to Si ] in a tetrahedral site of olivine, but unlike hydrogarnet with one of the protons pointing away from the tetrahedral center and located in an adjacent interstitial site, thus experiencing weaker dipolar couplings than those in the vicinity of the vacant tetrahedron; the very weak narrow peak near 7.3 ppm can be attributed to the substitution mechanism of two H ions for one Mg in an M1 site [(2H) M1 ] of forsterite. The 1 H- 29 Si CP-MAS NMR spectra revealed both a broad peak encompassing the position for OH defect-free forsterite (−61.7 ppm) and a narrower peak at higher frequency (−60.9 ppm). First-principles calculation indicates that these peaks are accountable by the same models as for the 1 H NMR data. Thus, this study has provided unambiguous evidence supporting that hydrogen is incorporated in forsterite at relatively high-pressure dominantly as (4H) Si defects, with (2H) M1 defects playing only a very minor role. The much larger 1 H chemical shift for protons associated with the latter (than the former) is correlated with stronger hydrogen bonding for the latter, which in turn reflects difference in bonding environments of the OH groups (with the latter bonded to a Si, and the former only bonded to Mg). Similar correlation applies to the O-H stretching frequency. The (4H) Si defects are responsible for the observed high-frequency O-H stretching bands (>3450 cm −1 ), and the (2H) M1 defects give lower frequencies (undetected here due to low abundance, but most likely near 3160–3220 cm −1 as previously reported) in vibrational spectra. These results can serve as a guide for (re-)interpretation of infrared and Raman spectroscopic data on hydrous olivine produced under different pressure and silica activity conditions, and require reconsideration of any models for the effects of water on physical properties of olivine based on different interpretations of such data. This study also demonstrated the usefulness of the combined solid-state NMR and first-principles calculation approach in unraveling the hydrogen incorporation mechanisms in nominally anhydrous minerals.

Diazonium-based ion-imprinted polymer/clay nanocomposite for the selective extraction of lead (II) ions in aqueous media

Ion imprinted polymer/montmorillonite clay nanocomposite (MMT/IIP) was prepared by the combination of diazonium salt chemistry and photopolymerization process, and used for the selective removal of Pb(II). Toward this end, clay was ion exchanged with dimethylaminobenzenediazonium (DMA) to facilitate incorporation of hydrogen donating sites to the aluminosilicate layers. Upon irradiation of the mixture of the intercalated clay, acrylamide, bisacrylamide and Pb(II)–dithizone complex in the presence of benzophenone in DMSO, the copolymerization initiated by the free radicals formed by the hydrogen abstraction of photoexcited benzophenone from the dimethylamino groups of the intercalated clay. The resulting ion imprinted network nanocomposite and the precursors pristine and diazonium cation intercalated clays were thoroughly characterized by detailed FT-IR, XPS, XRD and SEM. Particularly, XRD analysis brought strong supporting evidence for high exfoliation of the clay upon photopolymerization, whereas XPS permitted to demonstrate that the final nanocomposite has polyacrylamide-rich surface. The adsorption and recognition properties of MMT/IIP for Pb(II) were evaluated using atomic absorption technique. The adsorption capacity was found to be as high as 301mg/g after about 30min contact time, and the relative selectivity coefficients to Zn2+ and Fe3+ were 9.2 and 93, respectively. Compared with non-imprinted clay/polymer nanocomposites, the MMT/IIP exhibited much higher affinity for Pb(II) therefore stressing the importance of the artificial receptor sites within the nanocomposite. Altogether, the results are consistent with an MMT/IIP nanocomposite that is specific to lead II. This work demonstrates for the first time the potential of aryldiazonium chemistry combined with photopolymerization for the fabrication of high performance clay/ion imprinted nanocomposites for the removal of toxic heavy metals.

Tunable Doping in Hydrogenated Single Layered Molybdenum Disulfide

Structural defects in the molybdenum disulfide (MoS2) monolayer are widely known for strongly altering its properties. Therefore, a deep understanding of these structural defects and how they affect MoS2 electronic properties is of fundamental importance. Here, we report on the incorporation of atomic hydrogen in monolayered MoS2 to tune its structural defects. We demonstrate that the electronic properties of single layer MoS2 can be tuned from the intrinsic electron (n) to hole (p) doping via controlled exposure to atomic hydrogen at room temperature. Moreover, this hydrogenation process represents a viable technique to completely saturate the sulfur vacancies present in the MoS2 flakes. The successful incorporation of hydrogen in MoS2 leads to the modification of the electronic properties as evidenced by high resolution X-ray photoemission spectroscopy and density functional theory calculations. Micro-Raman spectroscopy and angle resolved photoemission spectroscopy measurements show the high quality of the hydrogenated MoS2 confirming the efficiency of our hydrogenation process. These results demonstrate that the MoS2 hydrogenation could be a significant and efficient way to achieve tunable doping of transition metal dichalcogenides (TMD) materials with non-TMD elements.

Structure and properties of hydrogen-intercalated YBa2Cu3O y

The effect of hydrogenation at 150 and 200°С on the structure and magnetic susceptibility of YBa2Cu3Oy (123) with different hydrogen contents has been studied. Upon the incorporation of hydrogen, the phase transition of the 123 phase into a defect tetragonal 124 phase occurs. In contrast to the transition upon hydration, the phase transition upon hydrogenation takes place only for compounds characterized by high oxygen contents (y > 6.5). Depending on the compound structure and oxygen content, hydrogen atoms can both occupy interstitials in Cu–O planes to form HYBa2Cu3O6 and join with oxygen to form an oxide–hydroxide. In contrast to hydration, upon hydrogenation of YBa2Cu3Oy, the substitution of europium for yttrium and alloying with cerium and zirconium oxides do not block the intercalation of hydrogen into the structure of the 123 compound.

High mobility hydrogenated zinc oxide thin films

In this work we present a comprehensive study of the role of hydrogen in the structure, morphology, composition and electro-optical properties of zinc oxide thin films deposited by rf reactive magnetron sputtering at room temperature.The transparency and conductivity of the in situ hydrogenated zinc oxide films (ZnO:H) are improved with the addition of H2 to the sputtering atmosphere, where the resistivity dropped one order of magnitude (from 3×10−2 to 2.8×10−3Ωcm) for an optimal dilution of 1.5% in argon. The effect of hydrogen in the conductivity of undoped ZnO thin films has been attributed to the shallow donor behaviour. However, we observed that the increase in the conductivity came essentially from the improvement of the mobility that reached 47.1cm2/Vs for a carrier concentration of 4.4×1019cm−3. This improvement in the mobility happens with an effective hydrogen incorporation into the bulk of the sputtered ZnO:H films, being attributed to the passivation of grain boundaries trap states while carrier concentration is dominated by the formation of Zn interstitials.

Effect of iron and trivalent cations on OH defects in olivine

Hydrogen incorporation in olivine involves many OH defects, which will control the hydrogen solubility at mantle conditions. Several of these OH defects are identified from the investigation of forsterite (the olivine Mg end-member). We study here the effect of Fe 2+ , Fe 3+ , Al 3+ , and Cr 3+ on OH defects to improve our understanding of the hydrogen speciation in natural olivine. Low-temperature infrared spectra (−194 °C) are collected on synthetic and natural olivines. These spectra are then interpreted in the light of the theoretical determination of the structural, vibrational, and infrared spectroscopic properties of Fe-related OH defects, using first-principles calculations based on density functional theory. The presence of Fe 2+ changes the cationic environment around the fully protonated vacancies in forsterite, leading to a slight modification of their infrared signatures. In particular, the presence of Fe 2+ in an octahedral site adjacent to a hydrogarnet-type defect is likely responsible for the additional bands observed at 3599 cm −1 and around 3520–3550 cm −1 in Fe-doped olivines. Results show that the OH bands between 3310 and 3380 cm −1 are associated with the presence of trivalent cations. Specifically, two bands at 3323 and 3358 cm −1 , commonly observed in natural olivine, are associated with the substitution of Mg 2+ by Cr 3+ while two similar bands at 3328 and 3353 cm −1 are associated with the substitution of Mg 2+ by Fe 3+ . The presence of these defects and the “titanoclinohumite” defect in natural olivine clearly underlines the prominent role of trace elements on the hydrogen incorporation in lithospheric olivine.