Search

Lanthanum oxide (La2O3) is the most competitive alternative to gate dielectric HfO2 with its outstanding performance, such as high dielectric constant, suitable band gap and excellent stability on Si substrate. In this work, a series of Fe-doped La2O3 (LFO) films were prepared by reactive co-sputtering. The effects of Fe impurity on La2O3 as a gate dielectric were systematically investigated by surface roughness, band gap and dielectric electrical properties. Our results show that with the Fe contents increasing from 0 to 12.29%, the surface roughness of LFO films increases from 0.166 to 1.094 nm. In addition, the corresponding band gaps of LFO films decrease from 5.64 to 4.67 eV. When it comes to electrical properties, the presence of metallic Fe also destroys dielectric performance of La2O3, such as decreasing dielectric constant and increasing leakage current density. Hence, there is no doubt that metal Fe is an extremely harmful impurity for La2O3 as a gate dielectric, even if it is present in a trace amount (∼0.94%). Therefore, the content of Fe impurity in La or La2O3 should be reduced as low as possible for integrated circuits using. Finally, some methods for removing Fe impurity in La are given, which are useful for reference.

Lanthanum fluoride (LaF3) thin films were deposited on the Ge substrate using the molybdenum boat evaporation method. The effect of films’ oxygen impurity on the infrared optical properties has been investigated for the first time in this report. With the increase in oxygen content in the films, the F content decreases, and the O/F ratio decreases from 0.160 to 0.055. XRD patterns reveal that the presence of O impurity destroys the crystal structure integrity of the LaF3 films and leads to the intensification of infrared absorption. The average transmittance decreases from 58.1% to 52.2%, and the peak transmittance decreases from 59.9% to 54.5%. Additionally, the refractive index and extinction coefficient of LaF3 films with different oxygen content are obtained by fitting the transmittance test data. The results show that the refractive index and extinction coefficient of the films in 8–12 μm increase with the increase in oxygen content, the average refractive index increases from 1.339 to 1.478, and the extinction coefficient increases from 0.001 to 0.030. In this paper, the influence of oxygen impurity in the LaF3 film on its infrared optical properties is revealed, which lays a theoretical foundation for the development of high-performance LaF3 infrared antireflective film.

Zinc (Zn), an essential micronutrient, is absorbed by plant roots and redistributed to leaves. This process must be finely regulated in order to avoid toxic Zn2+ overaccumulation, which can arise due to Zn2+ oversupply or Zn2+ hyperaccumulation induced by Fe2+ deficiency. Although several proteins in Arabidopsis thaliana are essential for retaining Zn in the root and partitioning it from roots to leaves, how Zn2+ homeostasis in leaves is maintained is largely unknown. In this study, we identified a novel Golgi-localized protein named ZINC NUTRIENT ESSENTIAL1 (AtZNE1,At3g08650) in Arabidopsis. AtZNE1 contains 14 putative transmembrane domains. AtZNE1 promoter has strong activity in the root and leaf. Its expression complemented the increased sensitivity of a yeast mutant to excess Zn2+. The disruption of AtZNE1 in the T-DNA insertion mutant atzne1 caused growth defect under excess-Zn or Fe deficit conditions, but had no effects on the total Zn and Fe contents. We propose that AtZNE1 plays a vital role in plant adaptation to excess Zn or Fe deficiency.

Ca2+ is absorbed by roots and transported upward through the xylem to the apoplastic space of the leaf, after which it is deposited into the leaf cell. In Arabidopsis (Arabidopsis thaliana), the tonoplast-localized Ca2+/H+ transporters CATION EXCHANGER1 (CAX1) and CAX3 sequester Ca2+ from the cytosol into the vacuole, but it is not known what transporter mediates the initial Ca2+ influx from the apoplast to the cytosol. Here, we report that Arabidopsis CYCLIC NUCLEOTIDE-GATED CHANNEL2 (CNGC2) encodes a protein with Ca2+ influx channel activity and is expressed in the leaf areas surrounding the free endings of minor veins, which is the primary site for Ca2+ unloading from the vasculature and influx into leaf cells. Under hydroponic growth conditions, with 0.1 mm Ca2+, both Arabidopsis cngc2 and cax1cax3 loss-of-function mutants grew normally. Increasing the Ca2+ concentration to 10 mm induced H2O2 accumulation, cell death, and leaf senescence and partially suppressed the hypersensitive response to avirulent pathogens in the mutants but not in the wild type. In vivo apoplastic Ca2+ overaccumulation was found in the leaves of cngc2 and cax1cax3 but not the wild type under the 10 mm Ca2+ condition, as monitored by Oregon Green BAPTA 488 5N, a low-affinity and membrane-impermeable Ca2+ probe. Our results indicate that CNGC2 likely has no direct roles in leaf development or the hypersensitive response but, instead, that CNGC2 could mediate Ca2+ influx into leaf cells. Finally, the in vivo extracellular Ca2+ imaging method developed in this study provides a new tool for investigating Ca2+ dynamics in plant cells.

Ultra-high purification of terbium (Tb) by vacuum distillation and external getter was investigated. More than 20 kinds of impurity elements were analyzed by glow discharge mass spectrometry (GDMS) and inert gas analysis (IGA). The analysis results show that total impurities decrease from 1114 ppm to 63 ppm. High volatile metallic impurities such as Mg, Ca, Mn, Zn, and Tm can be reduced effectively after distillation. The oxygen (O) concentration can be decreased to 1.8 ppm after deoxidation process, which currently is one of the best results in the contemporary studies. The chemical driving force for deoxidation has been calculated in this paper. The different deoxidation results of Tb metal with various purity have been discussed in detail using the secondary ion mass spectroscopy (SIMS). Finally, a ultra-high purity Tb with low concentration of O can be obtained through vacuum distillation and external getter method.

The application of terbium involved in giant magnetostrictive materials, phosphors, magneto-optical storage materials, magneto-optical glass, and so on. The requirement of content of nickel is stringent for most of the materials. The distributions of nickel in terbium by Laser induced breakdown spectroscopy-original position statistic distribution analysis (LIBS-OPA) and the reason of difficult removal of nickel by vacuum distillation but easy removal by SSE had been mainly discussed in this paper. Terbium ingot prepared by electron-beam smelting after vacuum distillation was processed into rod of 0.76 cm in diameter and 15 cm in length. The solid state electrotransport (SSE) experiment was done to the rod at 1100°C and 450 A cm-2 for 100 h under UHV (10-7 Pa) conditions. LIBS-OPA was used to acquire the local distribution of nickel in terbium after SSE purification in this study. The result of this study showed that nickel particles transported by the passing current from anode to cathode. This result was consistent with the result of glow discharge mass spectrometry (GDMS) analysis to the whole rod. LIBS-OPA is a promising approach which could be used to analyze the distributions of micro and trace impurities in other metals and alloys. Highlights: Distribution of Ni in terbium after SSE had been obviously observed by LIBS-OPA. Nickel in Terbium is difficult to be removed by vacuum distillation, but after Solid State Electrotransport (SSE) for relative long time, content of Nickel can be greatly reduced. The main reason of the difficult removal of nickel by vacuum distillation and easy removal by SSE had been discussed in detail in this study.

Purification of yttrium by vacuum distillation was carried out and the purification process of yttrium was studied. More than 60 metallic impurity elements of input as well as purified Y were analysed using glow discharge mass spectrometry (GDMS) and C, N, O, and S were analysed by interstitial gas analysis (IGA). The analysis confirmed the reduction of total impurity content from −4 Pa; meanwhile, C, N, O, and S were decreased to low content, in which O was 75 ppmw. The evaporation rate and mean free path were calculated under the experimental conditions in this paper.

Composite membranes for direct methanol fuel cells (DMFCs) were prepared by using Nafion115 membrane modification with polyvinyl alcohol (PVA), polyimide (PI) and 8-trimethoxysilylpropyl glycerin ether-1,3,6-pyrenetrisulfonic acid (TSPS). The performance of the composite membranes was evaluated in terms of water sorption, dimensional stability, thermal stability, proton conductivity, methanol permeability and cell performance. The proton conductivity was slightly decreased by 1–3% compared with Nafion115, which still kept the high proton conduction of Nafion115. The methanol permeability of Nafion/PI–PVA–TSPS composite membranes was remarkably reduced by 35–55% compared with Nafion115. The power density of DMFCs with Nafion/PI–PVA–TSPS composite membranes reached to 100 mW/cm 2 , exceeding that with Nafion115 (68m W/cm 2 ).

A series of novel composite membranes was prepared by using poly(vinyl alcohol) (PVA) with polyimide (PI) as base material and 8-trimethoxysilylpropyl glycerine ether-1,3,6-pyrenetrisulfonic acid (TSGEPS) as proton conductor for direct methanol fuel cells (DMFCs). The parameters of membranes, including water sorption, hydrolysis stability, dimensional stability, proton conductivity, and methanol permeability were studied. The proton conductivity of the membranes is in the order of 10–2 S/cm, and the membranes show better resistance to methanol permeability (1.51 × 10–7 cm2 s–1) and better selectivity (20.6 × 104 S cm–3 s) than those of Nafion115 under the same measurement conditions.

The effect of carbon type, carbon loading and microporous layer structure in the microporous layer on the performance of a direct methanol fuel cell (DMFC) at low temperature was investigated using electrochemical polarization techniques, electrochemical impedance spectroscopy, scanning electron microscope and other methods. Vulcan XC-72 carbon was found to be most suitable as a microporous layer for low temperature DMFC. Maximum fuel cell performance was obtained utilizing a microporous layer with carbon loading of 1.0 mg cm −2 when air was used as an oxidant. A membrane electrode assembly with 1.0 mg cm −2 Vulcan XC-72 carbon with 20 wt.% Teflon in the cathode and no microporous layer in the anode showed a maximum power density of 36.7 mW cm −2 at 35 °C under atmospheric pressure. The AC impedance study proved that a cell with a dissymmetrical microporous layer structure had lower internal resistance and mass transfer resistance, thus obtaining better performance.