H2 Plasma Research Articles

Sulfur vacancy-rich ZnIn2S4 nanosheet arrays for visible-light-driven water splitting

In this study, ZnIn2S4 nanosheet arrays (NSAs) were synthesized on transparent conductive F doped SnO2 (FTO) substrates via a facile hydrothermal method. S vacancies were introduced on the ZnIn2S4 surface by a H2–Ar plasma treatment. The sulfur vacancies were identified clearly by electron paramagnetic resonance (EPR). Under different plasma powers, the S vacancies concentration can be adjusted. With increasing the plasma power, both the photocurrent and H2 evolution rate of ZnIn2S4 were increased. Through a 60 W plasma treatment, ZnIn2S4 displayed a photocurrent density of 0.3 mAcm−2 at 0.3 VRHE, which was roughly 2 times higher than that of untreated ZnIn2S4. Correspondingly, the H2 evolution rate was 2.74 μmol cm−2 h−1 for ZnIn2S4 NSA, in contrast to that of 0.96 μmol cm−2 h−1 for pristine ZnIn2S4 NSA. The enhanced PEC performance was attributed to the enhancements of both the visible light absorption and carrier separation. Moreover, the S vacancies also acted as traps to retard the electron-hole recombination. This work provides a novel strategy for enhancing its PEC hydrogen evolution.

Oxygen incorporation in AlN films grown by plasma-enhanced atomic layer deposition

Oxygen is often detected as an impurity in III-nitride films deposited by atomic layer deposition (ALD). The presence of oxygen has deep and unfavorable influences on the structural and optical properties of AlN. We have studied the oxygen incorporation in AlN films prepared by hollow cathode plasma-assisted ALD by alternating H2 plasma. We report a decrease in the O concentration in the film upon the addition of H2 plasma flow. However, increasing the H2 plasma flow does not further decrease the O incorporation. Film composition became almost constant at the surface and beneath the surface of AlN films deposited using N2/H2 plasma. Only samples grown with N2/H2 plasma showed decreases in oxygen concentration from the surface to the bulk film. Oxygen produces important modifications in the structural, chemical, and electrical properties. The Al 2p, N 1s, and O 1s high-resolution x-ray photoelectron spectra represent that AlN films are composed of Al–N, Al–O, and N–Al–O bonds. X-ray photoelectron spectroscopy data suggest that the composition of the AlN film changes to AlON + AlN when N2 plasma is used. The valence band maximum position of the AlN film is found to be at ∼1.7 eV for oxygen atomic concentration ∼20 at. %. The TO and LO phonon modes are present in AlN films with oxygen contamination ∼20 at. % and disappear at high oxygen contamination (∼55 at. %).

Pulsed chemical vapor deposition of cobalt and cobalt carbide thin films

Cobalt and cobalt carbide films were successfully fabricated via a simple pulsed chemical vapor deposition (PCVD) technique. The PCVD process employs bis(1,4-di-tert-butyl-1,3-diazadienyl) cobalt as a cobalt precursor. The effect of the reducing agent, H2 gas or H2 plasma, on the chemical composition of the resulting films has been carefully investigated. In the presence of H2 gas, polycrystalline hexagonal close-packed Co was obtained through the thermal decomposition of the Co precursor. When H2 plasma was used as a coreactant, the cobalt carbide was successfully deposited instead. The crystal structure of the deposited film is orthorhombic Co2C. X-ray photoelectron spectroscopy and Raman spectroscopy results show that all the carbon contained in the films were in form of Co–C. The dependence of deposition temperature on cobalt and cobalt carbide characteristics has also been investigated.

Measurements of atoms and metastable species in N2 and H2–N2 nanosecond pulse plasmas

Time-resolved, absolute number densities of metastable N2(A3Σ u +, v = 0, 1) molecules, ground state N2 and H atoms, and rotational–translational temperature have been measured by tunable diode laser absorption spectroscopy and two-photon absorption laser-induced fluorescence in diffuse N2 and N2–H2 plasmas during and after a nanosecond pulse discharge burst. Comparison of the measurement results with the kinetic modeling predictions, specifically the significant reduction of the N2(A3Σ u +) populations and the rate of N atom generation during the burst, suggests that these two trends are related. The slow N atom decay in the afterglow, on a time scale longer than the discharge burst, demonstrates that the latter trend is not affected by N atom recombination, diffusion to the walls, or convection with the flow. This leads to the conclusion that the energy pooling in collisions of N2(A3Σ u +) molecules is a major channel of N2 dissociation in electric discharges where a significant fraction of the input energy goes to electronic excitation of N2. Additional measurements in a 1% H2–N2 mixture demonstrate a further significant reduction of N2(A3Σ u +, v = 0, 1) populations, due to the rapid quenching by H atoms accumulating in the plasma. Comparison with the modeling predictions suggests that the N2(A3Σ u +) molecules may be initially formed in the highly vibrationally excited states. The reduction of the N2(A3Σ u +) number density also diminishes the contribution of the energy pooling process into N2 dissociation, thus reducing the N atom number density. The rate of N atom generation during the burst also decreases, due to its strong coupling to N2(A3Σ u +, v) populations. On the other hand, the rate of H atom generation, produced predominantly by the dissociative quenching of the excited electronic states of N2 by H2, remains about the same during the burst, resulting in a nearly linear rise in the H atom number density. Comparison of the kinetic model predictions with the experimental results suggests that the yield of H atoms during the quenching of the excited electronic state of N2 by molecular H2 is significantly less than 100%. The present results quantify the yield of N and H atoms in high-pressure H2–N2 plasmas, which have significant potential for ammonia generation using plasma-assisted catalysis.

Controlling the carrier density of surface conductive diamond

By placing a diamond in a H2 plasma and exposing it to air or overcoating it with Al2O3/SiO2, evaporated WO3, or other transition metal oxides a 2 dimensional, 2D, conductive hole gas forms on the diamond surface. Field effect transistors, FETs, made using this 2 D hole gas have the potential of replacing GaN FETs for use in high-power switching and high-frequency power applications. To achieve this goal, it is necessary to control the hole carrier density. When the carrier density is too high the device cannot be turned off and will have a low operational drain voltage due to electric-field break-down of diamond. On the other hand, too low a carrier density results in limited drain current, reduced power handling capability, and high on resistance. For diamond surface FETs using Al2O3/SiO2 as a gate oxide a carrier density between 1 × 1013 to 6 × 1013 cm−2 is the most desirable, depending on the intended operating voltage and the drain current density.This article discusses H-terminated procedure to controllably vary the carrier density from 1 × 1013 to 6 × 1013 cm−2. This is accomplished by varying the H-termination parameters; temperature, termination time, H2 pressure, and the microwave plasma power. During termination the diamond surface is etched and the density and type of crystal sets that form on the diamond surface is determined by these parameters. A model is presented of how the crystal step density and their character, single and double steps, can affect the carrier density.

Effect of substrate temperature on plasma-enhanced self-assembling formation of high-density FePt nanodots

We formed FePt magnetic nanodots (NDs) by exposing an ultrathin bilayer metal stack on ∼3.0 nm SiO2/Si(100) substrates to a remote H2 plasma (H2-RP) and studied the effect of external heating during the exposure to H2-RP on the formation and magnetic properties of NDs. The ultrathin bilayer with a uniform surface coverage drastically changed to NDs with an areal density as high as ∼3.5 × 1011 cm−2 by exposing to H2-RP with external heating. We also found that NDs formed by the exposure to H2-RP at 400 °C exhibited a perpendicular anisotropy with a perpendicular coercivity of ∼1.5 kOe, reflecting the magneto-crystalline anisotropy of (001)-oriented L10 phase FePt.

Plasma-assisted ammonia synthesis in a packed-bed dielectric barrier discharge reactor: effect of argon addition

The effect of argon (Ar) addition on plasma-assisted ammonia (NH3) synthesis in a packed-bed dielectric barrier discharge (DBD) reactor is investigated in this work. Both higher normalized NH3 concentration and N2 conversion are achieved by adding Ar to N2–H2 plasma. The 18.6% increment of normalized NH3 concentration and 15% increment of N2 conversion are realized with 30 vol.% Ar addition compared with the case of N2–H2 plasma only, indicating that Ar addition would contribute to NH3 formation. The mechanisms of NH3 synthesis with Ar addition are proposed based on electrical characteristics and electron energy distribution function of the N2–H2–Ar plasma. The intensity of microdischarges, mean electron energy and quantity of energetic electrons increase upon Ar addition. Hence, the electron-impact reactions would be enhanced upon Ar addition. Meanwhile, the effective capacitance of the plasma reactor is improved, which suggests Ar addition contributes to achieve fully-bridged plasma discharge and transfer energy into chemical process in plasma. Moreover, the presence of Ar introduces Penning excitation and ionization reactions in N2-H2 plasma, which would benefit N2 conversion and then accelerate NH3 formation as well.

Plasma-Tuned nitrogen vacancy graphitic carbon nitride sphere for efficient photocatalytic H2O2 production

Graphitic carbon nitride (CN) is a promising photocatalyst for sustainable energy conversion. Meanwhile, N vacancies are useful for H2O2 generation; however, they are hard to control. In this study, the N vacancy CN sphere (NVCNS) is synthesized by H2 plasma treatment to tune the NV. The as-synthesized NVCNS exhibits an efficient and stable photocatalytic H2O2 yield of 4413.1 μmol gcat−1h−1, which is 2.5 and 4.6 times higher than that of CNS (1766.4 μmol gcat−1h−1) and bulk CN (956.6 μmol gcat−1h−1), respectively, using a Xe lamp with an intensity of 100 mWcm−2. In particular, the charges recombination rate is remarkably reduced by introducing N defect state, promoting electron accumulation and O2 adsorption, through theoretical calculation and experiments. Furthermore, the NV creates abundant unsaturated sites and induces strong interlayer interactions, leading to effective electronic excitation and the promotion of charge transport.

Preparation of tungsten-based thin films using a F-free W precursor and tert-butyl hydrazine via 2- and 3-step atomic layer deposition process

This article reports the preparation of tungsten metal (W) and other tungsten-based thin films using a F-free W metalorganic precursor tris(3-hexyne) mono-carbonyl tungsten [W(EtCCEt)3(CO)] (Et = C2H5), THMCT], tert-butyl hydrazine (TBH), and H2 plasma via 2- and 3-step atomic layer deposition (ALD) process. Density functional theory (DFT) calculations were performed to simulate the possible mechanisms of W4(EtCCEt)4(CO)4, as the model of chemisorbed THMCT on the growing surface, with TBH. The experimental findings agree well with the DFT results that the thermal ALD of THMCT and TBH could not deposit the pure W metal films. Instead, THMCT and TBH led to form an amorphous, tungsten oxycarbide, WOxCy (with a minor nitrogen content and a negligible amount of W metal phase), resulting in a very high resistivity of ∼80,000 μΩ-cm (at 300 °C). Nevertheless, the typical characteristics of ALD, such as the self-limiting growth, and a linear dependency of the film thickness with cycle variation, were obtained with a growth-per-cycle (GPC) of ∼0.4 Å. Post-annealing of the films in the H2 atmosphere resulted in a slight increase in the metallic phase formation with a significant drop in resistivity to ∼3500 μΩ-cm. However, the annealing also facilitated the formation of the tungsten oxide phase owing to the oxygen incorporated in the as-deposited films. Introducing an additional H2 plasma pulse step at the end of each ALD cycle (3-step ALD process) significantly altered the film composition and helped reduce the as-deposited film's resistivity drastically to ∼650 μΩ-cm. Also, the process results in the formation of tungsten carbide (WCx) as the predominant phase. Finally, the additional high-temperature-post-annealing of these 3-step ALD grown films resulted in extremely low resistivity of ∼200 μΩ-cm owing to the formation of body-centered-cubic (BCC) α-W. Thus, the envisaged path in this study to achieve W thin films also provides rooms to grow oxide or carbide dominant phase of W as studied in detail with the help of X-ray photoelectron spectroscopy

The nucleation and growth of graphene under a controlled atmosphere during radio frequency-plasma-enhanced chemical vapor deposition

Plasma-enhanced chemical vapor deposition (PECVD) has emerged as a potential method for the industrial synthesis of graphene due to its low growth temperature, energy savings and in situ graphene growth. Unlike traditional thermal chemical vapor deposition (TCVD), PECVD usually leads to rapid nucleation and growth of graphene from the promoting effect of plasma on the dissociation of the hydrocarbon precursor, resulting in a significantly higher nucleation density of graphene and small grain size, which reduces its electrical performance. Understanding and controlling graphene nucleation and growth during PECVD are of great significance for the synthesis of high-quality graphene. In this study, we noted that the nucleation density and grain size of graphene were significantly affected by various atmospheric conditions, including the Ar flow, H2/CH4 ratio and pressure. In particular, a higher H2/CH4 ratio notably decreased the nucleation density and enlarged the grain size from the effect of the H2 plasma. Furthermore, we studied the energies of the nucleation density, grain size and growth rate of graphene under various pressures by measuring the activation energy and demonstrated that low pressure and high growth temperature enabled to the growth of graphene with low nucleation and large grain size.

Plasma Driven Exsolution for Nanoscale Functionalization of Perovskite Oxides.

Perovskite oxides with dispersed nanoparticles on their surface are considered instrumental in energy conversion and catalytic processes. Redox exsolution is an alternative method to the conventional deposition techniques for directly growing well-dispersed and anchored nanoarchitectures from the oxide support through thermochemical or electrochemical reduction. Herein, a new method for such nanoparticle nucleation through the exposure of the host perovskite to plasma is shown. The applicability of this new method is demonstrated by performing catalytic tests for CO2 hydrogenation over Ni exsolved nanoparticles prepared by either plasma or conventional H2 reduction. Compared to the conventional thermochemical H2 reduction, there are plasma conditions that lead to the exsolution of a more than ten times higher Ni amount from a lanthanum titanate perovskite, which is similar to the reported values of the electrochemical method. Unlike the electrochemical method, however, plasma does not require the integration of the material in an electrochemical cell, and is thus applicable to a wide range of microstructures and physical forms. Additionally, when N2 plasma is employed, the nitrogen species are stripping out oxygen from the perovskite lattice, generating a key chemical intermediate, such as NO, rendering this technology even more appealing.

Reaction Mechanism and Selectivity Control of Si Compound ALE Based on Plasma Modification and F-Radical Exposure.

In this work, atomic layer etching (ALE) of Si compounds using H2 or N2 plasma modification followed by fluorine radical exposure is discussed. It is shown that the H2 plasma modification process promotes the selective etching of SiN, SiC, and SiCO versus SiO2. The N2 plasma modification, on the other hand, enables the selective etching of SiC and SiCO versus SiN and SiO2. The origin of the etching selectivity between different Si compounds is investigated using a combination of in situ SE and FTIR supported by several ex situ analysis techniques. It is shown that the formation of a hydrogen-rich layer after plasma modification is essential to enable the ALE process. The hydrogen-rich layer can be formed due to ion and radicals of the modification plasma (H2 plasma modification) or be a result of the reconfiguration of hydrogen that is already present in the film (N2 plasma modification). The obtained insights are expected to further enhance the etching selectivity of Si compound ALE processes. Furthermore, it is anticipated that the process can be extended to many other compound materials such as Ti and Hf, as well as enable selective etching between their oxides, carbides, and nitrides.

Numerical Analysis of the Interactions between Plasma Jet and Powder Particles in PS-PVD Conditions

Plasma spray-physical vapor deposition (PS-PVD) refers to a very low-pressure (~100 Pa) deposition process in which a powder is injected in a high-enthalpy plasma jet, and mostly vaporized and recondensed onto a substrate to form a coating with a specific microstructure (e.g., columnar). A key issue is the selection of the powder particle size that could be evaporated under specific spray conditions. Powder evaporation takes place, first, in the plasma torch between the injection location and nozzle exit and, then, in the deposition chamber from the nozzle exit to the substrate location. This work aims to calculate the size of the particles that can be evaporated in both stages of the process. It deals with an yttria-stabilized zirconia powder and two commercial plasma torches operated at different arc powers with gas mixtures of argon and helium or argon and hydrogen. First, it used computational fluid dynamics simulations to calculate the velocity and temperature fields of the plasma jets under very low-pressure plasma conditions. Then, it estimated the evaporation of the particles injected in both plasma jets assuming an isothermal evaporation process coupled with momentum and heat transfer plasma-particle models in a rarefied plasma. The calculations showed that, for different powers of the Ar–H2 and the Ar–He operating conditions of this study, the heat flux from the plasma jet to particles inside the torch is much higher than that transferred in the deposition chamber while the specific enthalpy transferred to particles is comparable. The argon-helium mixture is more efficient than the argon-hydrogen mixture to evaporate the particles. Particles less than 2 μm in diameter could be fully evaporated in the Ar–He plasma jet while they should be less than 1 µm in diameter in the Ar–H2 plasma jet.

Formation of inverse cones in crystalline silicon by selective etching of amorphous regions resulting from epitaxial breakdown

We report on a process to form micron-scale inverse cones in crystalline silicon without any masking steps using a selective, low temperature (<175 °C) plasma process. The selectivity of the process originates from the use of a H2 plasma that preferentially etches away amorphous cones, formed as a result of epitaxial breakdown, leaving the surrounding crystalline material behind. Efficient etching is realized by pre-coating the reactor walls with hydrogenated amorphous silicon oxide (a-SiO x :H) to prevent any chemical transport of silicon towards the substrate. The etch depth of the amorphous cones is linked directly to the time of exposure to plasma. When densely packed, such structures exhibit useful optical properties, such as specular reflectance as low as 2% (with the sample appearing visibly black in the high density and fully etched regions) and iridescence (in regions of partial etching).

Tunning the defects in lignin-derived-carbon and trimetallic layered double hydroxides composites (LDH@LDC) for efficient removal of U(VI) and Cr(VI) in aquatic environment

Utilizing different absorbents to remove heavy metals from aquatic environment has been extensively investigated because of its simple operation, good reusability, and low cost. The removal efficiency of these adsorbents, nevertheless, need to be further enhanced to meet the practical requirement. In this study, we demonstrate defect engineering as an effective approach to enhance the performance of biochar-based composites for U(VI) and Cr(VI) removal. Lignin derived carbon and Ca/Fe/Al-trimetallic layered double hydroxide composites (LDH@LDC) is prepared by hydrothermal method. Defects are introduced into the LDH layer by H2 plasma treatment. The obtained defective LDH@LDC exhibits outstanding removal efficiency for U(VI) (267.65 mg/g at pH = 5.0, T = 308.15 K, CInitial = 30 mg/L), which is much higher than LDH@LDC as-prep (190.47 mg/g at pH = 5.0, T = 308.15 K, CInitial = 30 mg/L). Similar defect-induced enhancement is observed for the removal of Cr(VI). The thermodynamic and kinetic studies of the removal process, as well as the surface analyze suggest that the removal mechanism of U(VI) and Cr(VI) by the as-prepared and plasma-treated LDH@LDC were both dominated by ion exchange. The plasma treatment introduces defects into the LDH layer, which effectively promote the ion exchange between the LDH layer and the heavy metal in the aquatic environment, leading to strongly enhanced removal performance. This study clarifies the critical role of defects in heavy metal removal process and provides a new pathway of designing high performance absorbents for water remediation.

In vacuo XPS investigation of surface engineering for lithium metal anodes with plasma treatment

Lithium (Li) metal is an attractive anode material with high capacity (3860 mAh g−1) and low potential (−3.04 V vs. standard hydrogen electrode) that shows highly promising for applications requiring high energy density. However, the low electrochemical potential of Li metal makes it extremely reactive and inevitably forming a native oxidized layer in the ambient environment and repeatedly being consumed when exposed to liquid electrolytes. It is therefore beneficial to replace the poorly controlled native passivation layer with a tailored artificial SEI to improve interface management between Li and electrolyte and enhance the stability of Li metal battery. Here, we use an integrated glovebox-atomic layer deposition (ALD)- X-ray photoelectron spectroscopy (XPS) setup to in-situ investigating the pristine Li surface and the surface composition after Ar, H2, O2, N2 and NH3 plasma treatment processes. We find that the pristine Li foil is naturally being covered with a native oxidized layer, which is mainly composed of LiOH, Li2O and Li2CO3. These investigated plasmas can efficiently remove the oxidized layer from the Li metal surface, in which metallic Li surface is obtained after Ar or H2 plasma treatments, where Ar plasma is more efficient. While O2 plasma treatment produces a Li2O layer, and N2 or NH3 plasma treatment leads to a Li3N (including a certain amount of LiON) layer on the Li surface. When employing the representative metallic Li (by Ar plasma treatment), Li2O layer coated Li (by O2 plasma treatment) and Li3N layer coated Li (by N2 plasma treatment) foils as electrodes in symmetric Li metal batteries, the Li3N coated Li electrode exhibits much higher stability than that of metallic and Li2O layer coated Li foils. Improved electrochemical performance has also been achieved in LiMn2O4 (LMO)||Li full cells using Li anode with Li3N protective coating layer. Our work reveals the detailed process of surface engineering of Li metal anodes with plasma treatments by in vacuo XPS, which may also be extended to other gas-treatment or plasma-treatment for stabilization of high energy density Li metal anodes and other metal-based anodes.

EUV-induced hydrogen plasma: pulsed mode operation and confinement in scanner

In recent years, EUV lithography scanner systems have entered high-volume manufacturing for state-of-the-art integrated circuits, with critical dimensions down to 10 nm. This technology uses 13.5-nm EUV radiation, which is shaped and transmitted through a near-vacuum H2 background gas. This gas is excited into a low-density H2 plasma by the EUV radiation, as generated in pulsed mode operation by the laser-produced plasma in the EUV source. Thus, in the confinement created by the walls and mirrors within the scanner system, a reductive plasma environment is created that must be understood in detail to maximize mirror transmission over the lifetime and to minimize molecular and particle contamination in the scanner. In addition to the irradiated mirrors, reticle, and wafer, the plasma and radical load to the surrounding construction materials also must be considered. We provide an overview of the EUV-induced plasma in the scanner context. Special attention is given to the plasma parameters in a confined geometry, such as that found in the scanner area near the reticle. It is shown that plasma confinement and resulting contributions from secondary electron emission delay the formation of the plasma sheath and thereby reduce the peak ion energies to below the sputtering threshold for mirrors and construction materials. Furthermore, for a confined pulsed plasma with a pulse period shorter than the decay time of the plasma, the plasma consists of a quasi-steady-state cold background plasma and periodic transient peaks in ion energy and ion flux. In terms of modeling, this means that no assumptions can be made on the electron distribution functions and a (Monte-Carlo) particle-in-cell (PIC) model is needed. We present an extension of the PIC model approach to complex three-dimensional geometries and to multiple pulses using a hybrid PIC-diffusion approach. Also, the translation of these specific plasma parameters to off-line setups and the aspects that must be included to make a meaningful translation from off-line laboratory EUV setups to the scanner plasma are discussed.

Solution-based coating and printing of polycrystalline Ge films using GeO2 solution by moderate-pressure hydrogen plasma reduction

A printable-formation method for Ge films using a GeO2 solution was developed in this study. The GeO2 film was prepared by applying GeO2 ink on a glass substrate and reducing it using high-pressure H2-based plasma. The crystallinity, electrical conductivity, and photosensitivity of the films were examined before and after the plasma treatment. The film transformed from amorphous GeO2 to crystalline Ge after treatment with the H2-based plasma. The Ge film obtained after H2 plasma reduction exhibited an electrical resistivity of 4000 Ω cm and a photosensitivity of 1.9 under AM 1.5G illumination of 100 mW cm−2. In addition, the dependence of the reduction behavior of the GeO2 film on the process parameters, such as the input power, substrate temperature, treatment time, and hydrogen concentration, were investigated systematically. The reduction of GeO2 by H2 plasma proceeded with an increase in the input power. The thickness of the reduced Ge film depended strongly on the substrate temperature, and the plasma reduction process required a low reduction temperature and short reaction time as compared to those of the thermal reduction process. The presence of only 4% H2 gas in the process atmosphere played an important role in the reduction and crystallization of the Ge film, although pure He plasma could also reduce the GeO2 film. Thus, we demonstrated the position-controlled preparation of Ge films using a commercial inkjet printer loaded with a GeO2 ink solution.

Role of in-situ hydrogen plasma treatment on gate bias stability and performance of a-IGZO thin-film transistors

This work investigates the effect of an in situ hydrogen plasma treatment on gate bias stability and performance of amorphous InGaZnO thin-film transistors (TFTs) deposited by using atmospheric-pressure PECVD. The H2 plasma-treated a-IGZO channel has shown significant improvement in bias stress induced instability with a minuscule threshold voltage shift (ΔV th) of 0.31 and −0.17 V under positive gate bias stress (PBS) and negative gate bias stress (NBS), respectively. With the aid of the energy band diagram, the proposed work demonstrates the formation of negative species O2 − and positive species H2O+ in the backchannel under PBS and NBS in addition to ionized oxygen vacancy (Vo) defects at a-IGZO/ZrO2 interfaces are the reason for gate bias instability which could be effectively suppressed with in situ H2 plasma treatment. From the experimental result, it is observed that the electrical performance such as field-effect mobility (μ FE), on-off current ratio (I on/I off), and subthreshold swing improved significantly by in situ H2 plasma treatment with passivation of interface trap density and bulk trap defects.

Circulating levels of hydrogen sulphide negatively correlate to nitrite levels in gestational hypertensive and preeclamptic pregnant women.

Endothelial dysfunction is a hallmark of preeclampsia and the role of nitric oxide (NO) has been extensively studied in this pregnancy complication. In recent years, hydrogen sulphide (H2 S) has arisen as a new gasotransmitter with an impact on endothelial function. However, the involvement of H2 S in the pathophysiology of preeclampsia is not fully understood, and only a few studies with limited sample size have investigated circulating levels of H2 S in preeclamptic patients. Moreover, H2 S levels have not been previously evaluated in gestational hypertension. Furthermore, the relationship between H2 S and NO in these hypertensive disorders of pregnancy has yet to be determined. We measured H2 S levels in plasma of 120healthy pregnant women, 88gestational hypertensive and 62 preeclamptic women. We also measured plasma nitrite in a subset of patients and carried out correlation analysis between plasma H2 S and nitrite in these three groups. We found that plasma H2 S was elevated in preeclampsia and further increased in gestational hypertension compared to healthy pregnancy. Plasma nitrite was reduced in gestational hypertension and preeclampsia, and these levels were negatively correlated with H2 S in both gestational hypertension and preeclampsia, but not in healthy pregnancy. Our results indicate that increases in H2 S may represent a mechanism triggered as an attempt to compensate reduced NO in gestational hypertension and preeclampsia. Future studies are warranted to investigate the mechanisms underlying H2 S/NO interaction on mediating endothelial dysfunction in these hypertensive disorders of pregnancy.