Types Of Metal Oxides Research Articles

Eco‐Friendly Transition‐Metal‐Ion‐Doped rGO Nanocomposites with Enhanced Photocatalytic Activities

AbstractImproving the photocatalytic properties of various types of metal oxides is becoming increasingly important in terms of environmental factors. Carbon allotropes are eco‐friendly materials, and improving their photocatalytic properties via doping‐induced modifications is one of the most attractive research areas. In this context, various first‐row transition‐metal‐ion‐doped reduced graphene oxide samples are synthesized and characterized using high‐resolution transmission electron microscopy along with X‐ray absorption spectroscopy to investigate their morphological and electronic structures at the molecular level. Transition metal‐ion doping produces several defect structures at the oxygen functionalities of reduced graphene oxide nanocomposites (rGO). Such defect structures are well correlated with their photocatalytic activity; Cr@rGO and Fe@rGO exhibit decent activities among the four tested rGO samples in the photocatalytic degradation of organic pollutants and selective oxidation of 2,5‐hydroxymethylfurfural. To test the environmental factors, cytotoxicity tests are performed by incubating the modified rGO with human skin cells; Fe@rGO is found to be the least toxic. Therefore, Fe@rGO displayed both enhanced photocatalytic activity and environment‐friendly character as compared to the bare rGO, indicating that it is a plausible candidate for application in the petrochemical transformation of biomass without environmental concerns.

Room-Temperature Detection of Perfluoroisobutyronitrile with SnO2/Ti3C2Tx Gas Sensors.

Ti3C2Tx MXene is an emerging two-dimensional transition-metal carbide/nitride with excellent properties of large specific surface and high carrier mobility for room-temperature gas sensing. However, achieving high sensitivity and long-term stability of pristine Ti3C2Tx-based gas sensors remains challenging. SnO2 is a typical semiconductor metal oxide with high reaction activity and stable chemical properties ideal for a dopant that can comprehensively improve sensing performance. Ti3C2Tx and SnO2 are investigated for the first time in this study as functional materials for hybridization and room-temperature detection of the gas insulating medium fluorinated nitrile (C4F7N) with microtoxicity. A Ti3C2Tx-SnO2 nanocomposite sensor exhibits superior sensitivity, high selectivity, strong anti-interference ability, and excellent long-term stability. The enhanced sensing mechanism is ascribed to the synergistic effect between SnO2 and Ti3C2Tx and the strong adsorption ability of SnO2 to C4F7N similar to bait for fish. We also established an actual leakage scene and demonstrated the feasibility of the Ti3C2Tx-SnO2 sensor to provide distribution rules with high sensing efficiency for actual engineering applications. The results of this work can expand the gas sensing application of Ti3C2Tx MXene and provide a reference for maintaining C4F7N-based eco-friendly gas-insulated equipment.

Mode-locked Tm-doped fiber laser induced by ferroferric-oxide nanoparticles and a D-shaped fiber

• We demonstrate a passively mode-locked laser operating at 2 um region based on a saturable absorber (SA) of FONPs deposited on the D-shaped fiber (DF). This is the first use of FONPs to achieve mode-locking at 2um. • The mode-locking operates in 1931 nm, the 3 dB bandwidth is 5.9 nm, the repetition frequency is 24 MHz, and the pulse width is 1.29 ps. In addition, the signal-to-noise ratio is ∼67 dB, indicating the stability of the output spectrum. As a unique type of transition metal oxides, ferroferric-oxide nanoparticles (FONPs) have attracted much attention due to their outstanding physical and chemical properties. In this paper, we demonstrate a passively mode-locked laser operating at 2 um region based on a saturable absorber (SA) of FONPs deposited on the D-shaped fiber (DF). FONPs were deposited on DF to form FONP-DF SA devices. As inserted into the thulium-doped fiber laser (TDFL), a mode-locked pulse was realized at 1931 nm. For all we know, this is the first demonstration of FONP-DF SA in fiber lasers at 2 um region. This work fills the gap of FNOP in the realization of 2 um mode-locking and lays the foundation for us to use FNOP-DF for magnetic field sensing in the future.

Transport of functional group modified polystyrene nanoplastics in binary metal oxide saturated porous media

Metal oxides exist in porous media in the form of composite metal oxides, which can significantly affect the transport and transformation of pollutants in the soil environment. In this study, binary metal oxide porous media were prepared to explore the effects of solution chemistry, and the presence of binary metal oxides on the transport of functional group modified polystyrene nanoplastics (PSNPs) in saturated porous media. The results show that the existence of binary metal oxides significantly affects the migration ability of PSNPs in saturated porous media. The increase of ionic strength and the presence of multivalent cations affect the transport capacity of PSNPs in porous media. The types of binary metal oxides affect the migration of PSNPs in saturated porous media. The surface roughness and electrostatic interaction are important factors affecting the retention of PSNPs on the surface of binary metal oxide saturated porous media. The surface morphology has a more far-reaching impact. In addition, DLVO theory cannot fully explain the interaction between PSNPs and saturated porous media in the presence of Al3+. This study's results help provide some theoretical support for the migration of microplastics in the soil environment.

High performance gas sensors based on layered cobaltite nanoflakes with moisture resistance

Metal oxide semiconductor have been widely used as sensing materials for detecting various gases with trace concentrations. However, the sensing properties of layered cobaltites with metallic conductivity have not been investigated to date. In this work, we developed a convenient preparation method of NaxCoO2 nanoflakes via aqueous ultrasonic exfoliation of NaxCoO2 single crystals. The sensor based on NaxCoO2 nanoflakes was fabricated, whose resistance is obviously smaller than that of the typical metal oxide based sensors. It shows less response to n-hexane, toluene, xylene, ammonia, methanol, ethanol and acetone. However, it exhibits excellent sensing performance to n-butanol and good moisture-resistance, and the sensitivity to 50 ppm n-butanol is up to 4.48 with the response time of 95 s and the recovery time of 154 s at the optimum working temperature of 200 °C. Owning to the high electric conductivity of NaxCoO2 layers, the sensor presents a very low noise and a high signal-to-noise ratio value with the detection limit at ppb level. The layered cobaltites exhibit the rich phase diagram and the nanoflakes are versatile surface functionalization. This work provides insight for layered cobaltites to be employed as highly sensitive sensors.

Effects and Mechanism of Two Nanoparticles (Titanium Dioxide and Silver) to Moina mongolica Daday (Crustacea, Cladocera)

The nearshore and estuary are the main gathering areas of nanoparticles (NPs), and salinity change is a crucial characteristic in these marine areas. Moina mongolica Daday is an important open-ended bait in the nearshore aquaculture environment. Investigating the toxicity mechanism of NPs to M. mongolica under different salinity conditions is crucial to exploring the biological impact of NPs in the nearshore environment. Two typical metal oxide and metal NPs of TiO2 and Ag were used in this study to test the acute, chronic, and reproductive toxicities of M. mongolica (Cladocera) in marine environments of different salinity gradients. The toxic effects and mechanisms of the two NPs on M. mongolica were discussed by ecotoxicology and transcriptional analysis, respectively. A total of 27,274 genes were assembled, and 11,056 genes were successfully compared. Results suggested that TiO2 and Ag NPs showed particle toxicity with oxidation generation and immune emergencies on M. mongolica. Compared with TiO2, Ag NPs showed strong toxicity with reproductive toxicity due to the release of Ag+, resulting in a reduction in reproduction, which is a decrease in the number of offspring and the rm. Critical DEGs involved in carapace showed carapace damage of M. mongolica, due to adhesion and accumulation (approximately 40%–60% of all accumulation) on carapace, which was one of the toxic mechanisms of the two NPs. The salinity factor caused the aggregation of both NPs, and Ag+ release of Ag NPs. The toxicity of TiO2 NPs to M. mongolica increases with salinity, but that of Ag NPs decreases.

Analysis of radiation effects of semiconductor devices based on numerical simulation Fermi–Dirac

Abstract To study the radiation effect of Fermi–Dirac (F–D) semiconductor devices based on numerical simulation, two methods are used. One is based on the combination of F–D statistical method and computer simulation. The method discusses the influence of temperature and light energy on the carrier number by starting from an intrinsic silicon semiconductor and carries out computer simulation on the carrier number in intrinsic silicon semiconductor. TID Sim, a three-dimensional parallel solver for ionizing radiation effects of semiconductor devices, is developed. The ionization radiation damage of typical metal oxide semiconductor (MOS) FET NMOS and bipolar transistor GLPNP is simulated. It was proved that the variation trend was close to a straight line in the temperature range (278–358 K) studied in this article. The results are consistent with those of the statistical distribution of semiconductor carriers. This method is suitable for calculating the number of semiconductor carriers, and it is an effective method to study the problems related to carrier distribution.

Lightest Metal Leads to Big Change: Lithium‐Mediated Metal Oxides for Oxygen Evolution Reaction

AbstractAs the lightest metal, the reversible insertion/extraction properties of lithium have been key findings in lithium metal oxide chemistry. Lithium has been widely used in the oxygen evolution reaction (OER), and the reaction mechanism of lithium‐mediated metal oxides has both similarities and uniqueness compared to typical dual metal oxides. Notably, the insertion/extraction of lithium during the OER is also crucial for the construction of novel surface reconstruction models. This review aims to provide the concepts of general OER pathways and key features of dual metal oxides for the OER. As a comparison then the development of lithium metal oxides for the OER is introduced and the chemistry underlying lithium metal oxide catalysts is unveiled. This review also examines the challenges remaining for the relevant catalysts, with prospects for further improving their OER activities.

Relationship between Hg0 capture performance and physicochemical properties of CeO2-CrOx mixed oxides

To effectively reduce the emission of Hg0, developing an adsorbent with a superior Hg0 removal performance constituted an important step. As a typical rare earth metal oxide, CeO2 was always used for Hg0 capture because of its tunable physicochemical properties. However, the weak acidity and the intermediate oxidative ability restrained its effective removal of Hg0, especially from the flue gas with a high Hg0 content. Thanks to the superior acidity and oxidability, CrOx addition could ensure the sufficient physisorption of Hg0 and accelerate its oxidation to HgO. Thus in this study, a serial CeO2-CrOx mixed oxides were prepared. The sample with Ce/Cr molar ratio of 3/1 exhibited the best performance; ca. 90 % Hg0 removal efficiency could be reached at 150 °C. Compared with virgin CeO2 and CrOx, the combination of these two metal oxides brought out a larger specific surface area, which would provide an increased number of active sites for Hg0 removal. Meanwhile, the presence of plentiful acid sites and reactive oxygen species favored the physisorption and oxidation of Hg0, hence contributing to a relatively high Hg0 removal efficiency of CeO2-CrOx mixed oxides. During the Hg0 adsorption cycles, Mars-Maessen route dominated; Cr6+ played the role of an active site to oxidize Hg0, while Ce4+ acted as a promoter-like site to boost the regeneration of Cr6+. Finally, CeO2-CrOx mixed oxide exhibited a satisfactory recyclability and a relatively weak gas component adaptability, suggesting that further modification should be conducted to improve the practicality of CeO2-CrOx mixed oxide.

Highly selective hydrogenation of 5-hydroxymethylfurfural to 2,5-bis(hydroxymethyl)furan over metal-oxide supported Pt catalysts: The role of basic sites

Catalytic hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-bis(hydroxymethyl)furan (BHMF) is an important reaction for biomass valorization. We report that metal oxides (including MgO, ZnO, SiO2 and TiO2) supported Pt catalysts show vastly different BHMF selectivity towards the hydrogenation of HMF. The basic metal oxide MgO supported Pt catalyst affords 99 % selectivity of BHMF, while the typical acidic metal oxide TiO2 supported Pt catalyst displays only 28 % selectivity of BHMF. HMF chemisorption on these catalysts show that the basic sites of metal oxide bonding to the CO group of HMF promote the BHMF selectivity, while the acidic sites of metal oxide favor the adsorption of CC group of HMF, which decreases the BHMF selectivity. It is proposed that the cooperation between basic sites and Pt atoms (activating H2) boosted the BHMF selectivity. Comprehensive studies including reactivity, recyclability, stability, solvent effect on the Pt/MgO catalyst were also carried out.

Studies on nanomaterial-based p-type semiconductor gas sensors.

The development of various metal oxide semiconductor materials has resulted in better performance of the gas sensors in terms of selectivity, sensitivity, and response time. Different types of nanostructured materials, i.e., 2D materials, carbon nanotubes, and metal oxides, are used in the gas sensing applications. Generally, the metal oxide-based gas sensor operates at higher temperature to activate the adsorption process between the material surface and the target gas. The higher operating temperature of the gas sensor leads to more power consumption and produces defects in the grain boundary of metal oxide. To improve the selectivity and minimize the power consumption, nanoparticle-based p-type semiconductor materials are being developed. P-type metal oxide-based semiconductor materials have the ability to produce a hole accumulation layer which can chemisorb the oxygen molecules of higher concentration and these materials are not affected by humidity. The structure of p-type nanomaterial-based gas sensor depends upon the fabrication techniques which can affect the sensing properties of semiconductor materials. The hole accumulation layer is also known as conduction layer which is developed in the outer shell of p-type semiconductor material and the sensing mechanism is controlled by grain boundaries which is different from the n-type semiconductor material. This paper reviews the preparation methods, morphological analysis, and sensing mechanisms of nanomaterial-based p-type metal oxide-based gas sensors.

Revealing M (M = Cu, Co and Zr) oxides doping effects on anti-PbCl2 poisoning over Mn-Ce/AC catalysts in low-temperature NH3-SCR reaction

Lead salts poisoning was a great challenge for the catalysts application in selective catalytic reduction (SCR) reaction of NOx with NH3 in stationary sources. Herein, several typical transition metal (Cu, Co and Zr) oxides modified Mn-Ce/AC catalysts were prepared by impregnation method, and the effects of Cu, Co and Zr doping on resistance PbCl2 poisoning for the catalyst were investigated. The addition of three transition metal oxides improved the PbCl2 resistance of Mn-Ce/AC catalyst and maintained excellent low-temperature denitrification activity of the catalyst. The lead resistance performance of the three metal oxides followed: Cu > Co > Zr oxides. The NO conversion of Cu-doping catalyst after PbCl2 poisoning was only ca. 10% lower than that of fresh Mn-Ce/AC catalyst at 225 °C. Cu, Co and Zr doping could decrease the loss of specific surface area caused by poisoning, while Cu-doped catalyst showed lowest crystallinity of active components. Meanwhile, the contents of Mn4+ and chemisorbed oxygen in Cu-doped catalyst were higher than those in Co- or Zr-doped catalysts. Cu, Co and Zr doping improved the surface acidity and redox performance of the poisoned catalysts, with Cu-doped poisoned catalyst exhibiting nearly the same surface acidity and redox performance as the fresh Mn-Ce/AC catalyst. Furthermore, Cu doping could also improve NO adsorption and was in favor to the SCR process. Besides, in situ DRIFTS results showed that the catalytic reaction pathways of all the poisoned or modified catalysts were in accordance with both Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms. Finally, a possible anti-PbCl2 poisoning mechanistic model of (Cu, Co and Zr) oxides modified on Mn-Ce/AC catalyst was proposed.

Modification Strategies of Ni-Based Catalysts with Metal Oxides for Dry Reforming of Methane

Syngas generated from the catalytic dry reforming of methane (DRM) enables the downstream production of H2 fuel and value-added chemicals. Ni-based catalysts with metal oxides, as both supports and promoters, are widely applied in the DRM reaction. In this review, four types of metal oxides with support confinement effect, metal-support interaction, oxygen defects, and surface acidity/basicity are introduced based on their impacts on the activity, selectivity, and stability of the Ni-based catalyst. Moreover, the structure–performance relationships are discussed in-depth. Finally, conclusive remarks and prospects are proposed.

Research Progress on Humidity-Sensing Properties of Cu-Based Humidity Sensors: A Review

Novel humidity sensors based on semiconducting metal oxides with good humidity-sensing properties have attracted extensive attention, which due to their high sensitivity at room temperature, high safety, low hysteresis, and long-term stability. As a typical p-type semiconductor metal oxide, CuO is considered to be a high-performance moisture-sensitive material; however, with the development of production, the complex working environment has put forward higher requirements for its humidity sensitivity, especially sensitivity and stability. In this regard, workers around the world are working to improve the moisture-sensing properties of sensing elements. In this review, the humidity-sensing properties of CuO-based moisture-sensitive materials are comprehensively summarized, focusing on effective measures to improve the moisture-sensing properties of CuO-based moisture-sensitive materials, including surface modification and nanocomposites. The future research of semiconducting metal oxide humidity-sensitive materials is also prospected.

RGO/ReO3 nano composite modified electrode for the ultra-sensitive determination of dopamine and uric acid

Development of suitable modified electrode in generating the electrochemical signals from dopamine (DA), uric acid (UA) and ascorbic acid (AA) has remained challenging issue even after decades of research in the related field. Under the present investigation the perovskite type metal oxide nano particle has been used in the form of composite with the reduced graphene oxide (rGO) as the active material for sensing. The superior electrical conductivity of Rhenium oxide (ReO3) combined with the adsorptive and conducting nature of rGO has been utilised in enhancing the electrochemical responses form the molecules. Thin films of Nafion was used over the rGO/ReO3 composite materials for stabilization of the modification. The electron transfer property of the molecules has been evaluated from the cyclic voltammetry and electrochemical impedance measurements. The standard electron transfer rate constants have been obtained from the Laviron formulations of the cyclic voltammetry measurements. Simultaneous electrochemical response has been obtained from the three molecules over the rGO/ReO3 nano composite modified electrode, the analytical method has been developed with the detection limit (S/N = 3) of 0.08 nM, 0.06 μM and 0.89 μM for DA, UA and AA respectively. For simultaneous determination however, the determination of DA and UA has been proposed and the interference test was carried out through simultaneous detection of the signals of the molecules. The analytical method has been applied for the detection of analytical signals of DA and UA in synthetic serum samples through spiked recovery test.

Prediction and molecular mechanism of phosphate adsorption by metal oxides

<p indent="0mm">Metal oxide adsorbents have emerged as promising phosphate removal materials due to their excellent adsorption performance, low price, and stability. However, the relationship between the structure of metal oxides and the performance of phosphate adsorption is still unclear, and the molecular mechanism of phosphate adsorption by metal oxides remains to be elucidated. Understanding the major influencing factors and mechanisms of phosphate adsorption by metal oxides is critical for the design of metal-based materials for phosphate adsorption. In this study, the kinetics and thermodynamics of phosphate adsorption by Gd₂O₃ and CeO₂ were analyzed, and the phosphate adsorption capacity of 32 metal oxides was determined. ReliefF algorithm was used to identify the key descriptors of metal oxides affecting phosphate adsorption. Based on the descriptors, prediction models for phosphate adsorption were developed based on six machine learning algorithms, and the applicability domain of the models was characterized. Phosphate adsorption on the surface of six typical metal oxides was investigated by using molecular simulations based on density functional theory (DFT). The results demonstrated that the maximum adsorption capacity of Gd₂O₃ for phosphate was 4.14 times higher than that of CeO₂. The crystal structure of Gd₂O₃ was changed after adsorbing phosphate and resulted in Gd₂O₃ transformation into urchin shaped structures, but the crystal structure of CeO₂ remained basically unchanged before and after adsorption. The results of phosphate adsorption of 32 metal oxides showed that rare earth metal oxides (except CeO₂) and ZnO had higher adsorption capacity than other metal oxides. The electronegativity and cationic charge of metal oxides were identified as two important factors for phosphate adsorption using ReliefF algorithm. Six machine learning algorithms were utilized to build the prediction models for screening metal oxides with high adsorption capacity, and the predictive accuracy of the decision tree model exceeded 90% for both training and test sets. Classification rules of the decision tree model indicated that metal oxides with electronegativity ≤ 1.23 had high adsorption potential for phosphate. Characterization of the model’s applicability domain showed that all metal oxides were within the applicability domain. DFT analysis showed that adsorption energies of Gd₂O₃ and Y₂O₃ for phosphate were −3.97 and <sc>−4.56 eV,</sc> which were higher than those of CeO₂, NiO, ZnO and Cr₂O₃<sc>(–1.61− –0.26 eV).</sc> The adsorption configuration of Gd₂O₃ and Y₂O₃ with higher adsorption energy for phosphate was bidentate binuclear, while that of CeO₂, NiO, ZnO and Cr₂O₃ with lower adsorption energy was monodentate mononuclear. Combined with molecular orbital theory and density of states analysis, it was found that the d orbitals from Gd and Y atoms higher than the Fermi level interact with the p orbitals of the oxygen atom from the phosphate, splitting into antibonding orbitals higher than the Fermi level. Theoretical calculations revealed a new mechanism that the d orbitals energy level of metal atoms determines the phosphate adsorption energy. The prediction model established in this study can provide a basis for screening metal-based materials that can effectively adsorb phosphate, and the molecular mechanism deciphered by DFT calculations can provide a theoretical basis for the design of adsorbents.

Stability, aggregation, and sedimentation behaviors of typical nano metal oxide particles in aqueous environment

The wide use of nano metal oxide particles (NMOPs) brings about their inevitable release into the water environment, affecting the environment and human health. Therefore, the stability, aggregation, and sedimentation process of four typical NMOPs (ZnO NPs, CeO2 NPs, TiO2 NPs, and CuO NPs) were investigated in artificial water and real municipal sewage to reveal their complicated behavior. Results showed that NMOPs aggregated at the pH of zero-charge point, and their hydrodynamic diameters and aggregation rates could reach the maximum values. The hydrodynamic diameters and aggregation rates of ZnO NPs, CeO2 NPs, TiO2 NPs, and CuO NPs at the zero-charge point were 617, 1760, 870, 1502 nm, and 31.7, 1158.1, 48.3, 115.7 nm/min, respectively. In addition, the dissolution of NMOPs led to the sedimentation rates under acidic conditions being much lower than those under neutral and alkaline conditions. The aggregation and sedimentation performance of NMOPs were affected by not only pH but also ionic strength (IS) and species. The aggregation rates of NMOPs increased with the increase of IS (0–10 mM), and the maximum aggregation rate of CeO2 NPs was 470.1 nm/min (pH = 7 and CaCl2 = 10 mM). According to Coulomb's law, divalent cations (Mg2+, Ca2+) were more competitively adsorbed on the surface of NMOPs than monovalent cations (K+, Na+), which increased the zeta potential and aggregation rate of NMOPs. Furthermore, the NMOPs were easier to aggregate in municipal sewage because of the homogeneous aggregation between nanoparticles and heterogeneous aggregation with natural colloids. The total interaction energy between NMOPs was calculated by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theoretical formula, which was consistent with the experimental results.

Microstructure and atmospheric oxidation behavior of CrCuFeMnNiCox high‐entropy alloys fabricated by vacuum hot‐press sintering

AbstractThe CrCuFeMnNiCox high‐entropy alloys (HEAs) were prepared by vacuum hot‐press sintering. The microstructure and atmospheric oxidation behavior at 800°C were studied. The phase structure of the Co0 alloy comprised the Cr‐rich FCC1 major phase, Cu‐rich FCC2 secondary phase, and a small amount of intermetallic compound ρ phase when x = 0. The bulk alloys comprised FCC2 major and FCC1 secondary phases when x ≥ 0.5. The oxidation kinetics curves approximately followed the parabolic law. A high Co content leads to a large oxidation weight gain of the alloys. The oxidation weight gain of the Co0 alloy was the smallest at approximately 4.46 mg cm−2 after atmospheric oxidation for 50 h, while the oxidation weight gain of the Co2.0 alloy was the largest at approximately 5.94 mg cm−2. The Co0 alloys exhibited the best oxidation resistance. Therefore, Co is not beneficial to the improvement of the oxidation properties of the CrCuFeMnNiCox HEAs. The main oxidation products of the HEAs mainly comprised MO, M2O3, M3O4, and (M,Cr)3O4 type metal oxides. The main oxidation mechanism was selective oxidation.

Enhancement of the electrochemical performance in MgO stabilized ZrO2 oxygen sensors by co-doping trivalent metal oxides

The present work looked at the co-doping effect of the typical trivalent metal oxides on the electrochemical performance of 8 mol% of MgO stabilized ZrO2 (Mg-PSZ) electrolyte ceramics used for oxygen sensors. An appreciable increase in the ionic conductivity occurred on substituting MgO with trivalent metal oxides except La2O3 in the Mg-PSZ electrolyte ceramics across the measured temperature range. The conductivity was related to the co-dopant ionic radius and the ionic conductivity increased with the co-dopant ionic radius of the trivalent metal oxides, reached a maximum at about 1.02 Å, and thereafter decreased. Through comparison and analysis, the Y2O3 exhibited excellent superiority than other trivalent metal oxides and the oxygen sensor assembled by 1Y7Mg-PSZ electrolyte possessed more excellent response speed and stability.

Effect of high-radiation-dose-induced structural modifications of HfSiO4/n-Si on electrical characteristics

High-k/n-Si structures were formed with HfSiO4 films annealed at the temperature range of RT (room temperature)-900 °C and radiation-induced structural modifications were determined by XRD (X-ray diffraction) and XPS (X-ray photoelectron spectroscopy) techniques in the study. The effect of oxygen-deficient bond contents on the electrical characteristics of HfSiO4 pMOS (n type Metal Oxide Semiconductor) capacitors whose radiation response was investigated in the 0–50 kGy dose range was investigated. While no XRD peak was observed before and after irradiation at RT and 500 °C-HfSiO4/n-Si, crystallization started with irradiation at 900 °C. The dielectric constant of the film was found in the range of 16–23. It was determined that Hf–Hf oxygen-deficient bonds act as negative charge trapping centers, while Hf–Si and Si–Si oxygen-defective bonds act as positive charge trapping centers. The direction of the C–V (Capacitance-Voltage) curve changed continuously with increasing radiation dose. The change in the interface trap charge density was found to be higher than the change in the oxide trap charge density for all doses in RT-HfSiO4 pMOS capacitor and for 1 kGy at 500 °C-HfSiO4 pMOS capacitor. Oxygen defective bond content and Hf-O-Si/Si–O–Si ratios were sufficient to establish a link between structural analyses and electrical characteristics at some doses. In some cases, the frequency-dependent charges had a more dominant effect on the radiation response of the device compared to the oxide trap charges.