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We perform first-principles calculations to investigate the preferred positions of B and P dopants, both neutral and in their preferred charge state, in Si and Si/SiO2 core-shell nanowires (NWs). In order to understand the observed trends in the formation energy, we isolate the different effects that determine these formation energies. By making the distinction between the unrelaxed and the relaxed formation energy, we separate the impact of the relaxation from that of the chemical environment. The unrelaxed formation energies are determined by three effects: (i) the effect of strain caused by size mismatch between the dopant and the host atoms, (ii) the local position of the band edges, and (iii) a screening effect. In the case of the SiNW (Si/SiO2 NW), these effects result in an increase of the formation energy away from the center (interface). The effect of relaxation depends on the relative size mismatch between the dopant and host atoms. A large size mismatch causes substantial relaxation that reduces the formation energy considerably, with the relaxation being more pronounced towards the edge of the wires. These effects explain the surface segregation of the B dopants in a SiNW, since the atomic relaxation induces a continuous drop of the formation energy towards the edge. However, for the P dopants, the formation energy starts to rise when moving from the center but drops to a minimum just next to the surface, indicating a different type of behavior. It also explains that the preferential location for B dopants in Si/SiO2 core-shell NWs is inside the oxide shell just next to the interface, whereas the P dopants prefer the positions next to the interface inside the Si core, which is in agreement with recent experiments. These preferred locations have an important impact on the electronic properties of these core-shell NWs. Our simulations indicate the possibility of hole gas formation when B segregates into the oxide shell. [ABSTRACT FROM AUTHOR]

The conduction mechanism of the leakage current of a thermally grown oxide on 4H silicon carbide (4H-SiC) was investigated. The dominant carriers of the leakage current were found to be electrons by the carrier-separation current-voltage method. The current-voltage and capacitance-voltage characteristics, which were measured over a wide temperature range, revealed that the leakage current in SiO2/4H-SiC on the Si-face can be explained as the sum of the Fowler-Nordheim (FN) tunneling and Poole-Frenkel (PF) emission leakage currents. A rigorous FN analysis provided the true barrier height for the SiO2/4H-SiC interface. On the basis of Arrhenius plots of the PF current separated from the total leakage current, the existence of carbon-related defects and/or oxygen vacancy defects was suggested in thermally grown SiO2 films on the Si-face of 4H-SiC. [ABSTRACT FROM AUTHOR]

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Composition-dependent band alignment and dielectric constant for Hf1-xTixO2 thin films on Si (100) have been investigated. It was found with increasing Ti content, the band gap and band offsets (ΔEv and ΔEc) of Hf1-xTixO2 films against Si all decrease and the optimal Ti content in the films should be no higher than 21%, at which ΔEc is 1.06 eV. The dielectric constant of the films not only can increase up to 31.3, but show a linear increase with increasing TiO2 content. Compared with HfO2 thin film with similar equivalent oxide thickness, low leakage currents were obtained. [ABSTRACT FROM AUTHOR]

The study of structures based on nonstoichiometric SnO2-x compounds, besides experimentally observed, is a challenging task taking into account their instabilities. In this paper, we report on single crystal Sn3O4 nanobelts, which were successfully grown by a carbothermal evaporation process of SnO2 powder in association with the well known vapor-solid mechanism. By combining the structural data and transport properties, the samples were investigated. The results showed a triclinic semiconductor structure with a fundamental gap of 2.9 eV. The semiconductor behavior was confirmed by the electron transport data, which pointed to the variable range hopping process as the main conduction mechanism, thus giving consistent support to the mechanisms underlying the observed semiconducting character. [ABSTRACT FROM AUTHOR]

We study the hysteresis in threshold voltage shift during alternating gate bias ramps (drain current vs gate voltage (IdVg) sweeps) after negative bias temperature stress and compare the results with carefully recorded charge pumping measurements. This allows us to clearly identify three different types of defects. All defect types have in common that their charge state depends on the position of the Fermi level and that they introduce a broad density of states (DOS) in the vicinity or within of the silicon band gap. Defect I is fully recoverable, defect II is similar to defect I in terms of DOS but does not recover, while defect III can be attributed to the conventional interface states. With a precise microstructural model in mind, and by using specific test chips, which allow us to vary stress bias and temperature quasiarbitrarily, we come to the conclusion that the carrier trapping and detrapping characteristics of stress induced defects can be controlled by temperature and electric field in a similar way, but that irrevocable structural relaxation is mainly influenced by temperature. Based on these ideas, we present a measurement method which can be used to energetically profile the relaxation of stress induced oxide defects. [ABSTRACT FROM AUTHOR]

The crystal field splittings and Jahn–Teller (J-T) distortions in Hf-based high-κ dielectric oxides on n-type Ge (100) substrates were investigated through the examination of O K1 edge spectra, obtained via x-ray absorption spectroscopy. Second derivative analysis of these O K1 edge spectra provided unambiguous evidence of J-T d-state degeneracy removal, resulting from the symmetry of the local atomic bonding environment. Additionally, two distinct defect states were found below the conduction band edge. The conduction band’s molecular orbital energy structure, including defect states, was determined based on the results of these investigations. Moreover, the thermal evolution of the defect states was found to be dependent on both postdeposition annealing temperature and Hf-based high-κ dielectric oxides. These subband-edge defect states were determined to be electrically active, and their density and the local atomic bonding symmetry were found to be correlated with the effective electron charge trapping measured in related device structures. [ABSTRACT FROM AUTHOR]

The thermal and chemical stability of potential dielectrics for GaN-based devices in a GaN metal organic chemical vapor deposition (MOCVD) environment is investigated, and their suitability for use as a gate dielectric and as a regrowth mask for the selective area growth of GaN is discussed. Thin films of MgO, Sc2O3, and Sc2O3/MgO were grown by molecular beam epitaxy on GaN/sapphire substrates and then annealed in a MOCVD reactor under GaN growth conditions except for the lack of trimethylgallium. All films were processed into metal-oxide-semiconductor diodes and were characterized before and after being annealed using atomic force microscopy, x-ray reflectivity, x-ray photoelectron spectroscopy, current-voltage (I-V), and capacitance-voltage (C-V) measurements. The Gibbs free energy of all possible reactions was calculated, and their probability and possible influence on the characterization results is examined. After being annealed, the atomic force microscopy of the oxide films showed some degree of roughening for all of them. Despite the surface roughening, all the oxide films examined showed potential for use as a regrowth mask. The MOCVD anneal caused the electrical properties of the MgO film to degrade considerably, and the Sc2O3 films were unable to be electrically characterized after annealing due to shorting, which is believed to be caused by the formation of a ScN layer on the surface. The effect of the thickness of the Sc2O3 cap for MgO films was investigated. The characterization results indicate that the Sc2O3 film dissolved into MgO during annealing and that a ScN film did not form on the surface. Of all the oxide films examined in this study, the Sc2O3/MgO stack with the thinner Sc2O3 cap exhibited the greatest stability with respect to its electrical properties. [ABSTRACT FROM AUTHOR]

The structure and magnetic properties of Cr2O3 and Cr nanoparticles have been investigated. The as-prepared Cr nanoparticles show a core/shell structure, consisting of a Cr core and a thin Cr oxide shell with a thickness of 1.5–2.5 nm. Annealing the Cr nanoparticles in air leads to the formation of Cr2O3 nanoparticles with spherical morphology. The temperature dependence of the magnetization indicates that these Cr2O3 nanocrystals are antiferromagnetic below their Néel temperature of 320 K and undergo an antiferromagnetic to weak-ferromagnetic transition below about 140 K due to spin canting at disordered surfaces. Below 100 K, a spin-flop transition is induced by an external field with a critical field lower than about 7 T. [ABSTRACT FROM AUTHOR]

In this work, we study two distinct electrical behaviors, which are often observed in Si nanocrystal memory gate stacks: the transient peak of the current-voltage characteristics and the frequency dependence of the admittance characteristics at strong accumulation. These effects are manifestations of a high electrical transparency tunnel oxide in conjunction with a good quality control oxide. The high electrical transparency tunnel oxide results from hydrogen-related defects that are formed within it during the high temperature processing steps and promotes the electrical communication between the silicon substrate and the silicon nanocrystal layer at low electric fields, while no significant charge transfer is observed at low voltages between the silicon nanocrystals and the gate electrode. These conditions favor the electrical charging/discharging of the silicon nanocrystal layer via the trap-assisted tunneling mechanism and to the appearance of electrostatic screening effects. These dynamic phenomena appear either as a displacement current peak at the onset of accumulation or as frequency dependent admittance characteristics at strong accumulation. [ABSTRACT FROM AUTHOR]

In this work, we study two distinct electrical behaviors, which are often observed in Si nanocrystal memory gate stacks: the transient peak of the current-voltage characteristics and the frequency dependence of the admittance characteristics at strong accumulation. These effects are manifestations of a high electrical transparency tunnel oxide in conjunction with a good quality control oxide. The high electrical transparency tunnel oxide results from hydrogen-related defects that are formed within it during the high temperature processing steps and promotes the electrical communication between the silicon substrate and the silicon nanocrystal layer at low electric fields, while no significant charge transfer is observed at low voltages between the silicon nanocrystals and the gate electrode. These conditions favor the electrical charging/discharging of the silicon nanocrystal layer via the trap-assisted tunneling mechanism and to the appearance of electrostatic screening effects. These dynamic phenomena appear either as a displacement current peak at the onset of accumulation or as frequency dependent admittance characteristics at strong accumulation. [ABSTRACT FROM AUTHOR]

Compositional variations of spinel oxides to a reference composition Mn1.68-XCu0.6+X+Y+ZCo0.24-YNi0.48-ZO4 (x and z=0.2, 0.4 and y=+/-0.1) are made. Thermopower and electrical conductivity of these materials are measured in thin film forms obtained through metal organic decomposition. This low-temperature fabrication technique allows the concentration of metastable Mn4+ and Cu1+ ions, which are essential to charge transport in the oxide spinel, to be controlled. All compositions have n-type behavior, and the conduction occurs via polaron hopping between neighboring Mn3+oct and Mn4+oct sites. Compositional variations alter the Mn and Cu oxidation state concentrations, and modify the conductivity and thermopower. Charge balance models are used in some cases to interpret the influences that doping and fluctuating oxygen content have on the variable valence Mn and Cu. After accounting for changes in oxygen concentration, we found that replacing portions of Co with Cu raise both the conductivity and thermopower magnitude, and substituting small amounts of Cu for Ni reduces these thermoelectric factors. Surprisingly, the effects of doping show parallel rises or declines in conductivity and thermopower magnitude. This implies that conductivity is more strongly impacted by the activated carrier mobility than by the number of charge carriers in these oxides. [ABSTRACT FROM AUTHOR]

The experimental research shows that ceramic top coat (TC) exhibits obvious strength difference (SD) in tension and compression, called SD property. This property significantly affect stress evolution, however, there are few attentions to it. In this paper, the stress evolution in TC layer is investigated by considering SD property. To reflect its property, a return mapping algorithm model for unified strength theory (UST), proposed by us, is applied. The results reveal that SD property leads to the movement of maximum tensile stress from interface to the position above it. It suggests that the crack might not be directly initiated at interface but above it, which has been reported in experimental studies too. The results also reveal that the possibility of above-interface cracking could be increased by varying the material properties, such as elevating compressive-tensile strength ratio and reducing yield strength of TC, and by changing the coating geometries, such as thickening thermally grown oxide (TGO) layer and increasing TC interfacial amplitude-wavelength ratio. [ABSTRACT FROM AUTHOR]

Due to its highest conductivity of any oxide material, the delta phase of Bi 2 O 3 (δ-Bi 2 O 3 ) is recognized as one of the most technologically important materials for various applications, including photocatalysis. Nevertheless, the δ-Bi 2 O 3 phase is not stable at room temperature. Herein, we demonstrate that δ-Bi 2 O 3 can be synthesized at low temperature through a facile sol-gel route in the presence of metavanadate oxyanion (VO 3 − ). The chemical state and local structure of V are investigated by synchrotron-based techniques, such as X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). Our findings demonstrate the critical role of VO 3 − in stabilizing the δ-Bi 2 O 3 phase. The crystallinity of δ-Bi 2 O 3 is dramatically increased by the addition of VO 3 − . In the absence of VO 3 − , amorphous product is obtained. The as-synthesized δ-Bi 2 O 3 possesses 3D hierarchical nanostructures constructed by ultrathin nanosheets with a few nanometers thick (~ 5 nm). The nanosheets are composed of ultrasmall nanoparticles in the range of 1–2 nm in size. Such a unique hierarchitecture of δ-Bi 2 O 3 allows efficient light utilization due to multiple reflections and scattering, indicated by its excellent photocatalytic activity for the degradation and mineralization of atrazine in aqueous solution. [ABSTRACT FROM AUTHOR]

This study aims to provide an insight into the effect of CaO-MgO-Al 2 O 3 -SiO 2 (CMAS) on the thermal cycling performance of plasma sprayed yttria partially stabilized zirconia (YSZ) coatings. The microstructural evolution and thermal cycling lives of YSZ coatings with and without CMAS corrosion were comparatively studied by a burner rig corrosion test. The experimental and simulation results showed that the molten CMAS that penetrated into the coatings reduced the porosity and increased the in-plane modulus and stiffness of coatings. During cooling, the large in-plane stress in the CMAS penetrated layer promoted the formation of through-thickness cracks, which significantly accelerated the oxidation of bond coat. Compared to the non-corroded coatings, the large out-of-plane stress that was normal to the YSZ/bond coat in the CMAS corroded coatings promoted the diffusion of Cr, Co and Ni ions, which significantly improved the growth of mixed oxides (such as Cr 2 O 3 , NiO and spinels) and thickened the TGO layer which eventually resulted in the spallation of TBCs. [ABSTRACT FROM AUTHOR]

Four novel Deep Eutectic Solvents (DESs) were prepared by mixing phenylacetic acid (which is a natural molecule present in honey) with amine N -oxides, which are molecules easily biodegradable in nature. Three of these N -oxides are amphiphilic. The novel DESs have very low freezing points (from − 34 °C to 20 °C) and they have very low viscosity, much lower than the most common and used DES in literature so far (choline chloride/urea mixture). The conductivity values resulted low and the ionicity analysis showed these DESs to be “super ionic”. Their polarity resulted high enough and it can be compared with other commonly used solvents or ionic liquids. [ABSTRACT FROM AUTHOR]

Research activities on Na-ion battery materials have gained importance in recent years as Na-ion batteries are considered as an economical substitute for the Li-ion batteries in some future applications. In the present work, P2-type Na0.67Mn0.65Fe0.20Ni0.15O2 was synthesized in microspherical morphology and characterized. Microspheres of FeCO3 were first prepared and used to synthesize Mn0.65Fe0.20Ni0.15CO3, followed by its thermal decomposition to the corresponding oxide and finally the thermal fusion of the oxide with Na2CO3 to produce P2-type Na0.67Mn0.65Fe0.20Ni0.15O2. The sodiated mixedmetal oxide formed inmicrospherical morphology is in a pure crystalline phase with a mesoporous structure of average pore size 29 nm. Cyclic voltammograms of electrodes are characterized by well-defined two pairs of peaks corresponding to the oxidation and reduction processes in two different stages. The sodiated oxide provides an initial discharge capacity of about 216 mAh g-1 with an excellent cycling stability upon cycling at C/15 rate. The rate of decay in discharge capacity is about 0.3% per cycle at C/15 rate, but it increases to 0.9% per cycle over 100 continuous charge-discharge cycles at higher rates. The rate capability is also high and the discharge capacity is about 100 mAh g-1 at 2C rate. The high discharge capacity and high rate capability are attributed to the porous microspherical morphology. [ABSTRACT FROM AUTHOR]

In the present study two types of oxide ceramic particles In2O3 (2.0 g/L) and WO3 (4.0 g/L) were reinforced into the Ni-Fe alloy matrix by electro-codeposition for the first time. Despite lower concentration in the bath solution, incorporation of In2O3 particles was higher (up to 5.5 wt%) as compared to the WO3 particles (up to ~3.0 wt%). Coatings obtained under optimum condition show permalloy composition (80 wt% Ni-20 wt% Fe) between the range of current density 3.0-5.0 A dm-2. The coatings were characterized by XRD, FESEM, EDAX, TEM and AFM. The effect of incorporation of these oxide particles and current density on the structure and properties of the nanocomposite coatings was investigated. XRD and TEM studies showed fcc lattice of the matrix with preferred orientation along (111) plane but the relative texture coefficient along (111) plane decreases with increasing current density. Dominance of In2O3 particles on the surface morphology of the coatings was also observed. However, results showed that electrical resistivity, corrosion resistance and microhardness (up to 1025 Hv) of the Ni-Fe/In2O3-WO3 nanocomposite were found between those for the Ni-Fe/In2O3 and Ni-Fe/WO3 nanocomposite coatings. Magnetic studies revealed the soft magnetic nature of the nanocomposite coatings. [ABSTRACT FROM AUTHOR]

Defects, particularly porosity and oxides, in high-pressure die casting can seriously compromise the in-service behavior and durability of products subjected to static or cyclic loadings. In this study, the influence of dimension, orientation, and position of casting defects on the mechanical properties of an AlSi12(b) (EN-AC 44100) aluminum alloy commercial component has been studied. A finite element model has been carried out in order to calculate the stress distribution induced by service loads and identify the crack initiation zones. Castings were qualitatively classified on the basis of porosities distribution detected by X-ray technique and oxides observed on fracture surfaces of specimens coming from fatigue and tensile tests. A damage criterion has been formulated which considers the influence of defects position and orientation on the mechanical strength of the components. Using the proposed damage criterion, it was possible to describe the mechanical behavior of the castings with good accuracy. [ABSTRACT FROM AUTHOR]

The mechanism of current conduction through thin tunnel oxide during erase operation of flash electrically erasable programmable read-only memory devices has been studied both theoretically and experimentally. The floating gate (FG) leakage current measured between 25 and 300 °C and at oxide fields ranging from 6 to 10 MV/cm is primarily attributed to Poole-Frenkel (PF) emission of trapped electrons from the electron traps located at about 1.0 eV below the silicon dioxide conduction band in addition to Fowler-Nordheim (FN) tunneling of electrons from the degenerately doped n-type polycrystalline silicon (n+-polySi) FG. It is observed that PF emission current IPF dominates FN electron tunneling current IFN at oxide electric fields Eox between 6 and 10 MV/cm and throughout the temperature range studied here. The observed thickness dependence of FG leakage current at a given applied oxide field arises due to different electron trap concentrations in the oxide. A physics based new temperature dependent analytical formula has also been developed for FN tunneling of electrons from the accumulation layer of semiconductors. In addition, the authors present theoretical results showing the effect of the FG doping concentration on the leakage current. [ABSTRACT FROM AUTHOR]

Detailed knowledge of the structure and degree of oxidation of platinum surfaces under operando conditions is essential for understanding catalytic performance. However, experimental investigations of platinum surface oxides have been hampered by technical limitations, preventing in situ investigations at relevant pressures. As a result, the time-dependent evolution of oxide formation has only received superficial treatment. In addition, the amorphous structures of many surface oxides have hindered realistic theoretical studies. Using near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) we show that a time scale of hours ( t≥4 h) is required for the formation of platinum surface oxides. These experimental observations are consistent with ReaxFF grand canonical Monte Carlo (ReaxFF-GCMC) calculations, predicting the structures and coverages of stable, amorphous surface oxides at temperatures between 430-680 K and an O2 partial pressure of 1 mbar. [ABSTRACT FROM AUTHOR]

The reactions have been accompanied ultraviolet (UV) radiation and electron impact with discharge plasmas in water–gas mixture, which can generate oxides, such as ozone (O3), hydrogen peroxide (H2O2), and nitrogen oxides (NOx). In this paper, two nonthermal plasma processing systems were established by means of a dielectric barrier discharge (DBD) arrays in water mist spray and an atmospheric pressure plasma jet (APPJ) immersed water. The yield characteristics of oxides (O3, NOx, and H2O2) in treated water were compared between the APPJ and DBD system under different applied voltages and energy densities. The results show that the relative intensity of UV from both the APPJ and DBD in water–gas mixture are stronger than the ones in air. The concentrations of O3 and NOx in treated water increased with increasing treatment time by using of both the APPJ and the DBD. Meanwhile, the APPJ-treated water is more acid than the DBD-treated one. However, it does not exist H2O2 in APPJ-treated water, rather it is enhanced in DBD-treated water with increasing discharge time. Moreover, the yields of produced oxides in water with discharge in water–gas mixture increased with increasing energy density, and decreased with decreasing applied voltage. This paper clearly demonstrates the close coupling of the yields of oxides and applied voltage, and thus is helpful in the study of the mechanism and application of discharge in water–gas mixture. [ABSTRACT FROM PUBLISHER]

Data on the study of thermally stable manganese oxide catalysts for deep oxidation of lean CH and propane-butane mixtures in air into CO are presented in the paper. New approaches to the synthesis of polyoxide catalysts based on Mn, modified with rare earth elements (La, Ce) and alkaline earth elements (Ba, Sr) when its supporting from nitrate solutions onto the alumina granules stabilized with 2 % Ce were used in the preparation of catalysts. Polyoxide thermally stable (up to 1473 K) high-performance Mn-containing catalyst for deep oxidation of CH and propane-butane in gas-air mixture was developed. Prototype of the catalytic heat generator for environmentally friendly burning of methane and propane-butane mixture was created. Experienced tests of the catalytic heat generator for heating of greenhouses were performed and carbon dioxide fertilizing of plants by combustion products of propane-butane mixture was carried out. [ABSTRACT FROM AUTHOR]

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We have theoretically investigated the product of elastic modulus and linear coefficient of thermal expansion for 20 thermoelectrics. The product is inversely proportional to equilibrium volume, which is consistent with the Debye-Grüneisen model. Oxides exhibit larger products, while the products of Te-containing thermoelectrics are considerably smaller. This is likely due to strong bonding in these oxides, which makes them prone to thermal stress, thermal shock, and thermal fatigue. As this product is rarely available in literature and the equilibrium volume is easily measurable, this work provides a quick estimation for the thermomechanical response of thermoelectric phases. [ABSTRACT FROM AUTHOR]

In this paper, CoNiCrAlY alloy coatings were deposited by high-efficiency supersonic atmospheric plasma spraying (SAPS) and high-velocity oxygen fuel (HVOF) spraying. The microstructural evolution of coatings during thermal cycling test was investigated. The results suggested that the as-sprayed SAPS coating consisted of lamellar structures and unmelted particles. However, the as-sprayed HVOF coating primarily consisted of the unmelted particles. The β-NiAl phase mainly existed in the unmelted particles, and its content increased with the increase of unmelted particles. The thermal cycling life of SAPS coating was 258 cycles, about 117 % higher than that of HVOF coating. During thermal cycling, significant internal oxidation and large cracks formed in the HVOF coating, which was one of the reasons that led to the spallation of HVOF coating. [ABSTRACT FROM AUTHOR]

The integral emissivity of oxide materials at high temperatures are evaluated by means of the band model; its behavior is explained. A simplified model of the band structure at high temperatures is proposed, and the expression for the calculation of the relative population of the states under thermodynamic equilibrium is obtained. The urgency of the measurements of absorption and emission of oxide materials for the determination of the density-of-states distribution and the band structure of substances at high temperatures and melting is demonstrated. [ABSTRACT FROM AUTHOR]

Out of many applications of hydrogen plasma, reduction of metal oxides is an important one. The reduction can be carried out using carbon or hydrogen. While carrying out the reduction of hematite (FeO) in hydrogen plasma, an attempt was made to characterize the hydrogen plasma by optical emission spectroscopy. The spectroscopic results provide some new and useful information. In addition to the hydrogen emission lines, two prominent lines at 589 and 589.6 nm were observed. These two lines are confirmed to be sodium D1 and D2 (Na D lines) by comparing with a low pressure sodium vapour lamp (LPSVL). The source of the trace amount of sodium is also confirmed to be from the metal oxide sample as an impurity. These lines are found to be very sensitive to various process parameters such as gas flow rate, microwave power, and reduction chamber pressure. The temporal variation of these two Na D lines also shows a characteristic trend during metal oxide reduction in hydrogen plasma. The weight loss and the X-ray diffraction analyses of reduced FeO sample for different time duration provides the evidence of correlation with Na D lines' intensity trend. This trend can be used to monitor the state and completion of hydrogen plasma based reduction reaction. In processes where Na is not associated with metal oxide, trace amount of Na in its molecular form such as NaOH can be introduced for monitoring the plasma process parameters as well as the plasma based reduction process. [ABSTRACT FROM AUTHOR]

The impact of postdeposition annealing (PDA) ambient on electrical properties of thin equivalent oxide thickness (EOT) Al2O3/GeOx/Ge gate-stacks is investigated. It is found that the surface states inside the conduction band of Ge are significantly suppressed by 40% through PDA with atomic deuterium ambient. As a result, enhancement of the effective mobility in the Ge nMOSFETs is realized in high normal field region. The electron mobility of 396 cm2/Vs is achieved at Ns of 10^13 cm ^-2 with small EOT of $\sim 1$ nm, which is similar to the highest mobility reported so far at such small EOT range. [ABSTRACT FROM AUTHOR]

The quasi-harmonic approximation (QHA) model is often used nowadays for prediction of the thermodynamic properties of materials subjected to high pressures and temperatures. However, QHA is not accurate enough in many cases and, as shown in this work, it is not thermodynamically consistent because it leads to violations of the Maxwell relations. The aim of this work is to propose a new thermodynamically self-consistent (TSC) method based on Density Functional Theory (DFT). The proposed method requires minimum information from DFT and no sophisticated equation of state is needed. The TSC method is applied to predicting the thermophysical properties of B1 CaO and K 2 O up to 2000 K and 100 GPa. It is shown that the TSC method is consistent with Maxwell relations and is more accurate than the QHA. [ABSTRACT FROM AUTHOR]

High-temperature oxide melt solution calorimetry using 3Na 2 O·MoO 3 at 802 °C was performed for interlanthanide perovskites La Ln ׳O 3 ( Ln ׳=Ho, Er, Tm and Yb) and lanthanide oxides (La 2 O 3 , Ho 2 O 3 , Er 2 O 3 , Tm 2 O 3 and Yb 2 O 3 ). The enthalpies of formation of these interlanthanide perovskites from binary lanthanide oxides at room temperature (25 °C) were determined to be −8.3±3.4 kJ/mol for LaHoO 3 , −9.9±3.0 kJ/mol for LaErO 3 , −10.8±2.7 kJ/mol for LaTmO 3 and −12.3±2.9 kJ/mol for LaYbO 3 . There is a roughly linear relationships between these enthalpy values and the tolerance factor for these and for other La M 3+ O 3 ( M =In, Sc, Ga, Al, Fe and Cr) perovskites, confirming that the distortion of the perovskites as results from ionic radius difference of A -site and B -site cations, is the main factor determining the stability of these compounds. [ABSTRACT FROM AUTHOR]

The release of nitrogen oxides (NO, NO, NO) accompanying the dissolution of UN in HNO with concentration 3-16 mol/liter and the ratio S:L = 1:7.5 and in 7.2 mol/liter HNO with S:L varying from 3 to 30 in atmospheric air or argon is studied. In the indicated HNO concentration range NO is formed mainly as a result of the oxidation of UN and secondarily as a result of the reduction of HNO. The presence or absence of oxygen in the atmosphere has no effect on the amount of NO formed. The formation of NO is due to the reduction of HNO. The presence of oxygen increases the amount of NO formed as a result of the oxidation of NO. The amount of nitrogen monoxide NO released into atmospheric air is higher than the amount released into an argon atmosphere. The amount of NO formed increases with increasing nitric acid concentration. The release of nitrogen oxides from UN as well as from nitric acid results in considerable dilution of nitride nitrogen, which casts doubt on the possibility of recycling N in the case where UN is used as fuel. [ABSTRACT FROM AUTHOR]

High-energy ball milling viz. mechanochemical process is being utilized to mechanically activate ceramic powders for low temperature solid state reactions. The process can help to select low-cost commercially available oxides and can produce powders with nanometer size granules. On the other hand, high alumina cement provides high service temperature when used as refractory castable. Therefore, the effects of high-energy ball milling and subsequent calcinations on the formation of high alumina cementing phases using mixtures of Al2O3 and CaCO3 were investigated. Nano-meter sized high alumina cement (HAC) powders were synthesized by mechanochemical treatment of Al2O3 and CaCO3 in weight ratios 7:3 and 8:2. This paper compares the calcined high alumina cement obtained by mechanically activated precursor mix for 1, 2 and 3 h. Low cement castables were prepared from calcined Chinese bauxite as aggregate matrix, prepared HAC acting as hydraulic binder and micro-fine additives as pore filling agents. The bonding of high alumina cement as well as sinterability in these castable was studied with ZrO2, α-Al2O3 and SiC as micro-fine additives. Castables formulated by prepared high alumina cement demonstrate remarkably improved bulk density and apparent porosity as when compared with those prepared by commercially available cement. Casting water demand was also reduced, as a result quick setting behavior was observed. The addition of mechanochemically processed cements in refractory castables improved the thermo-mechanical properties to a significant extent. [ABSTRACT FROM AUTHOR]

Volatile threshold switching (TS) and non-volatile memory switching (MS) are two typical resistive switching (RS) phenomena in oxides, which could form the basis for memory, analog circuits, and neuromorphic applications. Interestingly, TS and MS can be coexistent and converted in a single device under the suitable external excitation. However, the origin of the transition from TS to MS is still unclear due to the lack of direct experimental evidence. Here, conversion between TS and MS induced by conductive filament (CF) morphology in Ag/SiO2/Pt device is directly observed using scanning electron microscopy and high-resolution transmission electron microscopy. The MS mechanism is related to the formation and dissolution of CF consisting of continuous Ag nanocrystals. The TS originates from discontinuous CF with isolated Ag nanocrystals. The results of current-voltage fitting and Kelvin probe force microscopy further indicate that the TS mechanism is related to the modulation of the tunneling barrier between Ag nanocrystals in CF. This work provides clearly experimental evidence to deepen understanding of the mechanism for RS in oxide-electrolyte-based resistive switching memory, contributing to better control of the two RS behaviors to establish high-performance emerging devices. [ABSTRACT FROM AUTHOR]

Highlights: [•] A152/low alloy steel dissimilar metal weld (DMW) was used for oxide characterization. [•] As-welded and thermally aged DMWs were exposed to a simulated PWR primary condition. [•] Changes of oxide chemistry in DMWs were analyzed by in-situ Raman spectroscopy. [•] The alloy constituents in interface of DMW were changed by thermal aging. [•] This elemental change mainly causes the oxide change in the interface region of DMW. [ABSTRACT FROM AUTHOR]

Thermoelectric properties of complex oxide mixtures have been studied to achieve high figure-of-merit. It is shown that for mixtures of oxide having highly anisotropic thermopower, near the percolation thresholds, Seebeck coefficient can be larger than the highest one of the components. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings (TBCs) of Sr(Y0·05Yb0·05Zr0·9)O2·95 (SYYZ) and Sr(Y0·05Gd0·05Zr0·9)O2·95 (SYGZ) were prepared by air plasma spraying. The present study investigated the hot corrosion performance of the SYYZ and SYGZ coatings in the presence of molten Na2SO4+V2O5 salts at 900°C for 10 h. Changes in the coatings were studied using a scanning electron microscope (SEM) to observe the microstructure and X-ray diffraction (XRD) technique to analyse the phase composition. XRD results together with SEM observations indicated that, both the SYYZ and SYGZ coatings reacted with the molten Na2SO4+V2O5 salts at 900°C to form SrSO4, Sr3V2O8, YbVO4 and SrSO4, Sr3V2O8, GdVO4 respectively. The m-ZrO2 was also developed due to the decomposition of both the SYYZ and SYGZ coatings during the corrosion process. The excess Yb2O3 and Gd2O3 in the as sprayed SYYZ and SYGZ coatings respectively, can aggravate the degradation of both the SYYZ and SYGZ coatings by molten Na2SO4+V2O5 salts. The phase transformation and chemical interaction are the main corrosion mechanisms for deterioration of the SYYZ and SYGZ coatings. The YSZ coating was also investigated under the same corrosion condition for comparison. [ABSTRACT FROM AUTHOR]

A comprehensive review of the thermodynamic properties of the oxide compounds of the lanthanide and actinide elements is presented. The available literature data for the solid, liquid, and gaseous state have been analysed and recommended values are presented. In case experimental data are missing, estimates have been made based on the trends in the two series, which are extensively discussed. [ABSTRACT FROM AUTHOR]

Whereas the atomic structure of surface of crystals is known to be distinct from that of bulk, experimental evidence for thickness-induced structural transitions in amorphous oxides is lacking. We report the NMR result for amorphous alumina with varying thickness from bulk up to 5 nm, revealing the nature of structural transitions near amorphous oxide surfaces/interfaces. The coordination environments in the confined amorphous alumina thin film are distinct from those of bulk, highlighted by a decrease in the fractions of high-energy clusters (and thus the degree of disorder) with thickness. The result implies that a wide range of variations in amorphous structures may be identified by controlling its dimensionality. [ABSTRACT FROM AUTHOR]

Highlights: [•] The TGO growth rate and Al depletion with heat-resisting iron substrate is faster. [•] Cr3+ and Al3+ ions may influence the mechanisms of phase transformation in TGO. [•] The TGO with heat-resisting iron substrate have a shorter stage of θ-Al2O3 →α-Al2O3. [•] The area of spinel oxide formed relies on the value of b/a geometric parameter. [•] Slow θ→α-Al2O3 stage retards to form spinel around the convex of undulated TGO. [ABSTRACT FROM AUTHOR]

Thermal oxidation (TO) and abrasive polishing were combined for atomic-scale planarization of 4H-SiC. It was found that the oxide/SiC interface was atomically flat regardless of the thickness of the oxide. The specimen prepared by TO was dipped in HF solution to remove the oxide. However, owing to the residual silicon oxycarbide (Si-C-O), the step/terrace structure of 4H-SiC could not be observed. Nanoindentation tests revealed that the hardness of Si-C-O was much lower than that of SiC. A thermally oxidized SiC surface was polished using CeO2 abrasives, which resulted in an atomically flat surface with a well-ordered two-bilayer step/terrace structure. [ABSTRACT FROM AUTHOR]

Abstract: The thermal conductivities of UO2+ x , (U0.8,Pu0.2)O2− x and UO2 (induced Schottky defects) have been investigated by non-equilibrium molecular dynamics (NEMD) simulation from the viewpoints of the oxygen-to-metal ratio (O/M ratio), temperature, and point defect concentration. In the NEMD simulation, the thermal conductivity was determined by the temperature gradient and heat flux using Fourier’s law. The calculated thermal conductivity decreased with increasing temperature and defect concentration i.e. excess oxygen and oxygen vacancy concentrations. The calculated thermal conductivity decreased with increase of the deviation x from stoichiometry and number of defects. By comparing the hyperstoichiometric and hypostoichiometric oxides, it was found that the effect of Pu3+ and oxygen vacancy on the thermal conductivity was larger than that of U5+ and excess oxygen. Further, the cuboctahedral defect clusters were observed in the hyperstoichiometric UO2+ x supercell. [Copyright &y& Elsevier]

A tunable metamaterial is proposed by combining a thermochromic oxide with a fishnet structure. The reflection and transmission coefficients are calculated by finite-difference time-domain (FDTD) method. The effective electromagnetic parameters of the metamaterial are retrieved on the basis of these data. The results reveal that an effective negative refractive index is obtained by this proposed structure and the wavelength region with negative refractive index can be self-regulated by simply tuning the temperature, which is of importance to extend the applications of negative refractive index materials. The effects of structural sizes on the negative refractive index are discussed. The size-dependence indicates that the wavelength range in which the apparent refractive index is negative can be tuned to be located at the desired position by dexterously tailoring the structural parameters. [ABSTRACT FROM AUTHOR]

Radiation effects in thick isolation oxides of modern CMOS technologies are investigated using dedicated test structures designed using two commercial foundries. Shallow Trench Isolation and Pre-Metal Dielectric are studied using electrical measurements performed after X-ray irradiations and isochronal annealing cycles. This paper shows that trapping properties of such isolation oxides can strongly differ from those of traditional thermal oxides usually used to process the gate oxide of Metal Oxide Semiconductor Field Effect Transistors. Buildup and annealing of both radiation-induced oxide-trap charge and radiation-induced interface traps are discussed as a function of the oxide type, foundry and bias condition during irradiation. Radiation-induced interface traps in such isolation oxides are shown to anneal below 100^\circC contrary to what is usually observed in thermal oxides. Implications for design hardening and radiation tests of CMOS Integrated Circuits are discussed. [ABSTRACT FROM PUBLISHER]

Although successful examples of thermoelectric materials with the 'rattler-in-a-cage' structure include filled skutterudites and clathrate compounds, there has been no report on 'rattling' oxides. Here we report the thermal properties of defect pyrochlore ( β-pyrochlore) oxides with smaller cations in an oversized cage-like crystal structure. It is clearly shown that the thermal diffusivity, α, and the thermal conductivity, κ, are lower for the oxides containing lighter A-site cations, contradicting the conventional prediction of the phonon thermal conductivity, in which lighter comprising atoms must give higher α and hence κ. These results strongly suggest that the smaller A-site cations with larger size mismatch to the surrounding cage structure enhance the phonon scattering and thereby reduce α and κ. These findings directly evidence the 'rattling' effect of the loosely bound cations on the thermal transport properties of oxide materials. [ABSTRACT FROM AUTHOR]

Thermal behavior of the mixed oxides LaSrCoO (0.1 < x < 1.5) in the temperature range 1200-1700 K was studied. The use of the ceramic synthesis method makes it possible to obtain homogeneous samples at the calcination temperature of 1673 K. It was found by the high-temperature mass-spectrometry method that a charge can be depleted of cobalt oxide during the high-temperature synthesis. [ABSTRACT FROM AUTHOR]