Reduction Of Oxygen Vacancies Research Articles

Boosting cation desorption, anion adsorption and surface redox reaction kinetics of Co3O4 by oxygen vacancy

Although defect engineering is widely reported in catalysis, the influence of defects on electrochemical performance is less reported and the defect-related electrochemical mechanism is not fully understood. In this work, the oxygen vacancy concentration is controlled simply by calcining different precursors. The Co3O4 samples by prepared cobalt-thiourea coordination and cobalt nitrate precursors are named as S1 and S2, respectively. It is found that cobalt-thiourea coordination compound can provide an oxygen-rich skeleton, thus reducing oxygen vacancy; the specific capacitance of S1 (79.5 F/g) is 12.5 times higher than that of S2 (5.9 F/g) at 0.2 A/g. The remarkably improved capacitance is mainly attributed to the appropriate amount of oxygen vacancy for S1. Theory calculations confirm that an appropriate concentration of oxygen vacancy favors the desorption of K+ and the adsorption of OH–, and the kinetics of surface redox reaction; while excessive oxygen vacancies are disadvantageous to the electrochemical process. Additionally, the S1-based asymmetric supercapacitor (ASC) displays a high energy density of 176 μWh/cm3, a high power density of 218 mW/cm3, and a long cycling life (72.6% capacitance retention after 2500 charge/discharge cycles). The ASC is so flexible that it can be easily assembled in series to drive a light-emitting diode to work. This work provides a simple, low-cost method for producing high-quality electrode materials on a large scale.

Surface plasma treatment reduces oxygen vacancies defects states to control photogenerated carriers transportation for enhanced self-powered deep UV photoelectric characteristics

Ga2O3 is an ideal wide bandgap semiconductor for deep ultraviolet photodetectors due to the suitable band gap and excellent material stability, but the inevitable escape of oxygen ions from the lattices always leaves oxygen vacancies and leads to the persistent photoconductivity effect. Plasma treatment technology can use highly chemically active plasma to modify materials' surfaces at room temperature, which is environment-friendly and low carbon. In this work, we have prepared β-Ga2O3 films by plasma-enhanced chemical vapor deposition (PECVD) and used plasma treatment to reduce the oxygen vacancies in-situ. Whereafter, we constructed a Schottky-type photodetector to explore the effect of plasma treatment on the photoelectronic properties of β-Ga2O3 thin film. After plasma treatment, the oxygen vacancy reduces from 44.5 % to 27.3 %, and the photocurrent of β-Ga2O3 photodetector increases from 11 nA to 67 nA at 0 V. Furthermore, the decrease of oxygen vacancy also improves the photoresponse speed (<0.2 s) of the photodetector. The present study provides an efficient treatment method of oxygen vacancies by plasma technology to obtain high-performance self-powered deep-ultraviolet photodetectors.

Oxygen annealing induced enhancement in output characteristics of ZnO based flexible piezoelectric nanogenerators

Piezoelectric nanogenerators (PENG), which convert random mechanical energy into electrical energy, have attracted considerable attention due to their application potential in self-powered micro and nano electronics devices, wearable electronics, sensors etc. PENGs based on ZnO nanostructures are particularly important due to their low cost, flexibility and bio-compatibility. Flexible PENGs based on ZnO nanostructures dispersed in Polydimethylsiloxane (PDMS) in ITO/ZnO:PDMS/ITO device configuration were fabricated and characterized for vibration energy harvesting applications. Surfactant free ZnO nanostructures were grown using co-precipitation route and ZnO:PDMS nano-composite films with ZnO content varying in the range of 1.5–7.5 wt% were deposited on ITO/PET substrates for PENG fabrication. The maximum open circuit voltage and short circuit current of ~ 2.5 V and ~ 4 µA respectively were obtained in PENG fabricated with 6 wt% ZnO. The output characteristics were further enhanced to 5 V and 6 µA with flowing oxygen ambient annealing of ZnO nanostructures generating an instantaneous power density of ~9.55 µWcm −2 . X-ray photoelectron spectroscopy studies confirmed reduction in oxygen vacancy and enhancement in oxygen interstitial concentrations on oxygen annealing which leads to the suppression of free carrier induced internal screening in ZnO nanostructures. This suppression of internal screening effect is the possible reason for the enhancement in output characteristics of ZnO:PDMS PENG fabricated with oxygen annealed ZnO nanostructures. The electrical energy generated by the ZnO:PDMS PENG was rectified and effectively stored in capacitors and used to power LEDs and LCD display. • ZnO nanostructures were grown by co-precipitation method with air and oxygen annealing. • ZnO:PDMS PENG with variable wt% of ZnO in PDMS were fabricated in ITO/ZnO:PDMS/ITO configuration. • The output performance of ZnO:PDMS PENG is improved significantly by annealing ZnO nanostructures in flowing oxygen ambient. • XPS established a correlation between the oxygen related point defects in ZnO and output characteristics of ZnO based PENG. • The output energy from ZnO:PDMS PENG was rectified and effectively stored in capacitor to flash LEDs and LCD display.

Polycrystalline InGaO Thin-Film Transistors with Coplanar Structure Exhibiting Average Mobility of ≈78 cm2 V-1 s-1 and Excellent Stability for Replacing Current Poly-Si Thin-Film Transistors for Organic Light-Emitting Diode Displays.

Highly ordered polycrystalline indium gallium oxide (PC-IGO) film is obtained by the crystallization of room temperature sputtered amorphous IGO on a hot plate at 350°C for 1 h and then annealed for 1 h in an N2 O environment. A high-density PC-IGO of ≈7.15g cm-3 with reduced oxygen vacancy (≈14.83%) and hydroxyl (OH) related defects (≈10.96%) has been obtained by N2 O annealing. Self-aligned coplanar thin-film transistor (TFT) with the PC-IGO exhibits the average saturation mobility of 78.73 cm2 V-1 s-1 , threshold voltage of -1.07V, subthreshold swing of 0.147V dec-1 , and the on/off current ratio of over 108 . The TFTs show excellent stability under bias-temperature stress with a negligible threshold voltage shift (ΔVTH ) of + 0.1 and -0.1V for the positive and negative bias stresses, respectively. The TFTs exhibit very stable environmental stability when the TFTs are stored under high humidity (85%) and a high temperature (85°C) for 2 days. The ring oscillator and the gate driver mode of the PC-IGO TFTs exhibit the propagation delay of 7.44ns/stage with rising/falling times of less than 0.7 μs, respectively. Therefore, the PC-IGO TFTs are suitable for large area, high-resolution active-matrix organic, and inorganic light-emitting diodes displays.

Sintering parameters influence on dielectric properties of modified nano-BaTiO3 ceramics

BaTiO3 (BTO) is considered the most commonly used ceramic material in multilayer ceramic capacitors due to its desirable dielectric properties. Considering that the miniaturization of electronic devices represents an expanding field of research, modification of BTO has been performed to increase dielectric constant and DC bias characteristic/sensitivity. This research presents the effect of N2 and air atmospheres on morphological and dielectric properties of BTO nanoparticles modified with organometallic salt at sintering temperatures of [Formula: see text]C, [Formula: see text]C, [Formula: see text]C, and [Formula: see text]C. Measured dielectric constants were up to 35,000, with achieved very high values in both atmospheres. Field emission scanning electron microscopy (FESEM) was used for morphological characterization, revealing a porous structure in all the samples. The software image analysis of FESEM images showed a connection between particle and pore size distribution, as well as porosity. Based on the data from the image analysis, the prediction of dielectric properties in relation to morphology indicated that yttrium-based organometallic salt reduced oxygen vacancy generation in N2 atmosphere. DC bias sensitivity measurements showed that samples with higher dielectric constant had more pronounced sensitivity to voltage change, but most of the samples were stable up to 100 V, making our modified BTO a promising candidate for capacitors.

Self‐Assembly Metal Chelate as Ultraviolet Filterable Interface Layer for Efficient Organic Solar Cells

AbstractInterface engineering plays a vital role in the further improvement of efficiency and stability for organic solar cells (OSCs). Herein, a self‐assembly metal chelate based on hafnium and a designed ligand, N‐(4‐(3‐oxobutanoyl)phenyl)acetamide (ACBN) is applied as both interfacial modification layer and UV‐light filter in OSCs. The strong hydrogen‐bond induced intermolecular interaction enables Hf(ACBN)4 with the prerequisite of adequate solvent resistance to work as an electron transport layer (ETL) in the inverted OSCs. The self‐assembly behavior of Hf(ACBN)4 on the SnO2 film surface via constructing compact coordination structure has been verified via systematic theory calculations. In addition to optimizing the energy level alignment, the Hf(ACBN)4 modification effectively passivates the surface defect of SnO2 films for less surface charge recombination and a more efficient charge collection process. Thus, the OSCs with Hf(ACBN)4 layer yield a maximum PCE of 18.1%, better than that based on the bare SnO2 layer. Moreover, beneficial from the reduced oxygen vacancies via coordination effect and the UV‐light filter function of Hf(ACBN)4, the OSCs based on SnO2/ Hf(ACBN)4 composite ETL exhibit preferable stabilities under UV‐light irradiation or continuous operational conditions.

Kinetic Origin of Planar Gliding in Single-Crystalline Ni-Rich Cathodes.

Single-crystalline Ni-rich cathodes with high capacity have drawn much attention for mitigating cycling and safety crisis of their polycrystalline analogues. However, planar gliding and intragranular cracking tend to occur in single crystals with cycling, which undermine cathode integrity and therefore cause capacity degradation. Herein, we intensively investigate the origin and evolution of the gliding phenomenon in single-crystalline Ni-rich cathodes. Discrete or continuous gliding forms are revealed with new surface exposure including the gliding plane (003) and reconstructed (-108) under surface energy drive. It is also demonstrated that the gliding process is the in-plane migration of transition metal ions, and reducing oxygen vacancies will increase the migration energy barrier by which gliding and microcracking can be restrained. The designed cathode with less oxygen deficiency exhibits outstanding cycling performance with an 80.8% capacity retention after 1000 cycles in pouch cells. Our findings provide an insight into the relationship between defect control and chemomechanical properties of single-crystalline Ni-rich cathodes.

A Dual‐Ligand Strategy to Regulate the Nucleation and Growth of Lead Chromate Photoanodes for Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting for renewable hydrogen production has been regarded as a promising solution to utilize solar energy. However, most photoelectrodes still suffer from poor film quality and poor charge separation properties, mainly owing to the possible formation of detrimental defects including microcracks and grain boundaries. Herein, a molecular coordination engineering strategy is developed by employing acetylacetone (Acac) and poly(ethylene glycol) (PEG) dual ligands to regulate the nucleation and crystal growth of the lead chromate (PbCrO4 ) photoanode, resulting in the formation of a high-quality film with large grain size, well-stitched grain boundaries, and reduced oxygen vacancies defects. With these efforts, the nonradiative charge recombination is efficiently suppressed, leading to the enhancement of its charge separation efficiency from 47% to 90%. After decorating with Co-Pi cocatalyst, the PbCrO4 photoanode achieves a photocurrent density of 3.15mA cm-2 at 1.23V (vs RHE under simulated AM1.5G) and an applied bias photon-to-current efficiency (ABPE) of 0.82%. This work provides a new strategy to modulate the nucleation and growth of high-quality photoelectrodes for efficient PEC water splitting.

Sol-gel Derived (Pb0.65Sr0.35)(Zr0.5, Ti0.5)O3 Ferroelectric Thin Films: Structural and Electrical Properties

The Pb(Zr0.5, Ti0.5)O3 (PZT) is one of the ferroelectric materials used in the non-volatile memories. However, PZT usually suffers from fatigue that degrades the polarization with metallic electrodes. The high stability associated with Sr-O bonding reduces oxygen vacancies which in turn lessens fatigue and hence Sr in introduced at Pb site. In the present study (Pb0.65Sr0.35)(Zr0.5, Ti0.5)O3 (PSZT) ferroelectric thin films were successfully prepared by sol-gel method. The structural and morphological properties of the thin film were studied by x-ray diffraction and atomic force microscopy, respectively. The crystallization of the film was completed at 600°C of annealing and the root mean square roughness of the 300 nm film was around 4.5 nm. When Pb in Pb(Zr0.5, Ti0.5)O3 was substituted with 35% Sr, the coercive field increased and the remnant polarization reduced as compared to pure PZT. The films were ferroelectric at room temperature with the phase transition temperature at ~375°K. The dielectric constant and the loss tangent at room temperature were 257 and 0.023, respectively at 100 kHz.

A Simple Strategy to Realize Super Stable Ferroelectric Capacitor via Interface Engineering

AbstractFluorite‐structure ferroelectric thin films have been extensively studied as promising candidates for next‐generation non‐volatile memory. However, these ferroelectric thin films have fatal issues such as the irregular formation of the ferroelectric phase, low cycling endurance, and wake‐up and fatigue during endurance cycling tests. These problems are reportedly caused by oxygen vacancies, which form due to the interface reaction between the thin films and bottom electrodes during deposition and the post‐annealing process. Therefore, in this work, the enhanced ferroelectric characteristics of Hf1‐xZrxO2 thin films that control the oxygen vacancies in thin films through interfacial pretreatment are investigated. Interfacial treatment using an oxygen source can reduce oxygen vacancies and improve crystallinity through intentional oxidation of the bottom electrode. As a result, the remanent polarization value is increased by ≈1.6 times by applying the optimized pretreatment condition, and the measured 2Pr is a very high value of 73 µC cm−2. Furthermore, it exhibits very stable ferroelectric properties without a wake‐up effect or significant fatigue, up to 108 cycles even under a severe electric field of 3.5 MV cm−1. This simple strategy provides a new avenue to effectively improve the performance and cycling endurance of devices with ferroelectric thin films.

Solution-processed Y-doped SnSrO3 electron transport layer for Ga2O3 based heterojunction solar-blind photodetector with high sensitivity

Since the transport behavior of carriers is crucial to the photodetection process, selecting a suitable electron transport layer (ETL) is an effective strategy for preparing high-performance photodetectors. However, developing high-efficiency and comprehensive bandgap ETL materials for deep UV photodetectors remains challenging. In this work, we used wide-bandgap SrSnO3 nanoparticles to construct heterojunction solar-blind photodetectors with Ga2O3 by a simple solution-processing method. To improve carrier transportation efficiency, the SrSnO3 was annealed in an oxygen atmosphere and doped with Y elements to reduce oxygen vacancies and increase conductivity. Compared to the untreated SrSnO3, the oxygen vacancy of SrSnO3 annealed under oxygen (O2–SrSnO3) decreased from 54.2% to 22.8%, while the conductivity of the Y doped SrSnO3 (Y–O2–SrSnO3) increased about one order of magnitude. Thanks to this ETL engineering, the Y–O2–SrSnO3 exhibits the best carrier transportation efficiency, and the photodetector based on β-Ga2O3/Y–O2–SrSnO3 shows excellent photoelectrical performances with an Ion/Ioff ratio of 4.3 × 106, a detectivity of 1.3 × 1013 Jones, and a solar-blind/visible (R238 nm/R400 nm) rejection ratio of 4.1 × 103. Our work provides a general strategy for building construct highly sensitive photodetectors, thus may push forward their applications.

Optical and magnetic properties of fluoride-doped CeO2 obtained by an oxidative insertion method

• CeO 2 : F sample is synthesized using molten flux promoted oxidative insertion method. • PXRD and Raman spectral measurements confirmed the fluorite structure of CeO 2 :F. • Besides Ce and O, EDX analysis also revealed the presence of 18 at. % of fluoride. • PL and magnetic studies revealed a lower concentration of O vacancies in CeO 2 :F. • The F-doped sample had a higher concentration of Ce 3+ in CeO 2 :F. In the present study, we generated a fluoride-doped CeO 2 sample through the molten hydroxide flux promoted oxidative insertion approach using CeF 3 as the precursor. We analyzed the results and compared them with pure CeO 2 prepared by the same approach starting from Ce(NO 3 ) 3 . High-resolution powder X-ray diffraction, FTIR, and Raman spectral measurements confirmed both samples’ fluorite structure. The CeO 2 resulted from the oxidative flux treatment of CeF 3 had 18 at.% of fluoride ion-doped in it. The optical band gap narrowed marginally from 2.98 to 2.88 eV upon fluoride doping in CeO 2 . The blue emission intensity decreased with fluoride doping, indicating a reduction in oxygen vacancies compared to undoped CeO 2 . F-doped CeO 2 showed ferromagnetic behavior with magnetization, H c, and M r values higher than the undoped sample. A higher concentration of Ce 3+ and a lower concentration of oxygen vacancies were the consequences of fluoride doping in CeO 2 by this synthetic method.

Enhanced ferroelectric polarization with less wake-up effect and improved endurance of Hf0.5Zr0.5O2 thin films by implementing W electrode

1. Ferroelectric polarization value and o-/t- mixed phase fraction of HZO thin films can be largely enhanced by implementing W capping electrode. 2. Less wake-up effect (10.1%) and superior fatigue properties up to 1.5 × 10 10 cycles were obtained for W/HZO/W capacitor. 3. The influence of the top electrode on the ferroelectricity of metal/HZO/metal capacitor is more important than that of the bottom electrode. This paper reports the improvement of electrical, ferroelectric and endurance of Hf 0.5 Zr 0.5 O 2 (HZO) thin-film capacitors by implementing W electrode. The W/HZO/W capacitor shows excellent pristine 2 P r values of 45.1 μC/cm 2 at ±6 V, which are much higher than those of TiN/HZO/W (34.4 μC/cm 2 ) and W/HZO/TiN (26.9 μC/cm 2 ) capacitors. Notably, the maximum initial 2 P r value of W/HZO/W capacitor can reach as high as 57.9 μC/cm 2 at ±7.5 V. These strong ferroelectric polarization effects are ascribed to the W electrode with a fairly low thermal expansion coefficient which provides a larger in-plane tensile strain compared with TiN electrode, allowing for enhancement of o-phase formation. Moreover, the W/HZO/W capacitor also exhibits higher endurance, smaller wake-up effect (10.1%) and superior fatigue properties up to 1.5 × 10 10 cycles compared to the TiN/HZO/W and W/HZO/TiN capacitors. Such improvements of W/HZO/W capacitor are mainly due to the decreased leakage current by more than an order of magnitude compared to the W/HZO/TiN capacitor. These results demonstrate that capping electrode material plays an important role in the enhancement of o-phase formation, reduces oxygen vacancies, mitigates wake-up effect and improves reliability.

The influence of in situ ozone on structure and transport properties for perovskite stannate La-doped BaSnO3 epitaxial films

Here we investigate the influence of in situ ozone treatment on structure and carrier transport in La-doped BaSnO3 BLSO) films. It is found that introducing ozone during the film growth significantly inhibits the formation of oxygen vacancies and the occurrence of Sn2+ ions. The amount of oxygen vacancies decreases consistently with the increase of the ozone content, which further increases the in-plane lattice constant along with the relief of the in-plane compressive strain. More importantly, the reduction of oxygen vacancies gives rise to the augment of the threading dislocation density in the BLSO films, leading to the deterioration of carrier mobility. These findings demonstrate that the existence of Sn2+ ions does not apparently suppress the electron mobility in BLSO films, and the presence of oxygen vacancies is beneficial for reducing the density of threading dislocations, facilitating the mobility enhancement. All these findings would be beneficial for understanding the role of oxygen vacancy in carrier transport properties and for further optimizing the mobility of BLSO films.

Emission Spectroscopy Investigation of the Enhancement of Carrier Collection Efficiency in AgBiS2-Nanocrystal/ZnO-Nanowire Heterojunction Solar Cells.

Eco-friendly solar cells were fabricated using interdigitated layers comprising ZnO nanowires (NWs) and infrared absorbing AgBiS2 nanocrystals (ITO/ZnO NWs/AgBiS2/P3HT/Au). The quality of ZnO NWs was studied using photoluminescence and Raman spectroscopy to identify the defects in ZnO NWs influencing solar cell performance. Oxygen vacancies and Zn interstitial sites, among various recombination sites, were observed to be the main sites for carrier recombination, which hinders the carrier collection in the solar cells. Accordingly, the power conversion efficiency of AgBiS2 solar cells exhibited a good correlation with the number of oxygen vacancies. The structural order and electron-phonon interaction in ZnO NWs were also investigated via Raman scattering spectroscopy. A lower concentration of oxygen vacancies and zinc interstitials (Zni) resulted in a higher structural order as well as a weaker electron-phonon interaction in ZnO NWs. When ZnO NWs were treated at 500 °C in oxygen with the lowest oxygen vacancy concentration, the solar cells (500-O2 solar cell (SC)) demonstrated an external quantum efficiency of approximately 70% in the visible region and a corresponding internal quantum efficiency of more than 80%. The 500-O2 SC exhibited a power conversion efficiency of 5.41% (JSC = 22.21 mA/cm2, VOC = 0.41 V, and FF = 60%) under quasi one-sun illumination. New methods that can efficiently reduce oxygen vacancies and Zni without affecting the structural order of ZnO NWs would further enhance the carrier collection efficiency. Moreover, since ZnO is a key electron transport material for constructing not only colloidal quantum dot solar cells but also other emerging solar cells, such as organic thin-film solar cells, the present findings provide significant information for improving their performance.

Effect of annealing on the structural, optical and electrical properties of (F, Zn) double doped SnO2 nanoparticles obtained by the laser pyrolysis method

SnO2 nanoparticles have a great potential in photocatalytic and optoelectronic applications by extending their absorbtion and emission from UV to the visible domain. The effect of annealing at 750 °C and 1000 °C for 3 h in ambient conditions on structural, optical and electrical properties of F&Zn double doped SnO2 nanoparticles synthesized by continuous wave CO2 laser pyrolysis method were investigated for the first time. X-Ray diffraction studies confirmed the expected crystallite size increasing and also the vanishing of divalent tin phases (SnF2, SnO) upon air annealing. Detailed X ray photoelectron spectroscopy (XPS) analysis confirmed that fluorine disappears completely from SnO2 structure at 1000 °C. The annealing also induced a reduction in oxygen vacancies as confirmed by Raman spectroscopy and XPS. Transmission FTIR spectroscopy was used for revealing the existence of Sn–O, O–Sn–O, O–H and H–O–H vibrational modes. The optical band gap energies of all annealed samples are in the visible region, decreasing for those that were initially doped with F, and increasing for the only Zn doped sample. Photoluminescence (PL) measurements showed a broad dominant peak in green visible region, around 530 nm. For the sample with the highest content of Zn, PL spectrum shifted to higher wavelengths, respectively to the orange and red regions. The oxygen vacancies concentrations after annealing are correlated with the electrical conductivity of F, F&Zn, and Zn doped SnO2 samples.

Defect dipole induced improved electrocaloric effect in modified NBT-6BT lead-free ceramics

The Rietveld refinement of the polycrystalline powders of 1% Fe and Mn-doped (Na0.5Bi0.5)0.94Ba0.06Ti0.98V0.02O3 at the Ti-site confirmed a single rhombohedral (R3c) phase. The bandgap, (Eg) was affected by the anti-phase octahedral tilt angle and the spin-orbit splitting energy of Ti4+2p3/2 and Ti4+2p1/2 states. The decrease in Bi loss and increase in the binding energy of Ba due to Fe/Mn doping has been correlated to the strengthening of Bi-O and Ba-O bonds which was revealed from the XPS studies thereby further related to the average A-O bond length from structural studies. Hence, a reduction of oxygen vacancy (VO) for the doped samples has been justified. A significant improvement of the dielectric constant, relaxation time (τ0), and the decrease in conductivity due to doping was revealed from the frequency-dependent (10 Hz-1 MHz) dielectric measurement study. The conduction and relaxation process are dominated by the short-range movement of defects. The activation energy (Ea~1 eV) revealed that there is a presence of double-ionized VOs. The ECE study showed a significant enhancement of the changes in entropy, ΔS, and the adiabatic temperature difference, ΔT, due to doping, with ΔT being highest in the Fe-doped sample. Such improvement of dielectric and ECE properties was confirmed due to the reduction of the mobility of oxygen vacancy because of the formation(MnTi′′−Vo••)/(MnTi′−Vo••)• and FeTi′′−Vo••/(FeTi′−Vo••)• defect dipoles.

High energy storage performance in tungsten bronze-based relaxor ceramic via doping with CuO

Developing high-performance lead-free ceramics for capacitive applications has become more and more critical owing to the increasing concern about environmental protection and electronics industry. Here, a dual defect manipulation strategy was proposed to boost energy storage performance in CuO-modifided Sr2NaNb5O15-based lead-free tungsten bronze relaxor ceramic. Induced defect dipoles and reduced oxygen vacancy concentration generate a pinched polarization hysteresis loop and high breakdown strength, thus giving rise to a high recoverable energy density of 4.17 J/cm3 and efficiency of 89.5% at 350 kV/cm, together with an ultrafast discharge speed of 55 ns and a high power density of 118.4 MW/cm3. This proposed strategy is generalizable for realizing high capacitive performance in tungsten bronze-based dielectrics and other lead-free ceramics that benefit from dual defect manipulation.

Defect Passivation and Carrier Reduction Mechanisms in Hydrogen-Doped In-Ga-Zn-O (IGZO:H) Films upon Low-Temperature Annealing for Flexible Device Applications.

Low-temperature activation of oxide semiconductor materials such as In-Ga-Zn-O (IGZO) is a key approach for their utilization in flexible devices. We previously reported that the activation temperature can be reduced to 150 °C by hydrogen-doped IGZO (IGZO:H), demonstrating a strong potential of this approach. In this paper, we investigated the mechanism for reducing the activation temperature of the IGZO:H films. In situ Hall measurements revealed that oxygen diffusion from annealing ambient into the conventional Ar/O2-sputtered IGZO film was observed at >240 °C. Moreover, the temperature at which the oxygen diffusion starts into the film significantly decreased to 100 °C for the IGZO:H film deposited at hydrogen gas flow ratio (R[H2]) of 8%. Hard X-ray photoelectron spectroscopy indicated that the near Fermi level (EF) defects in the IGZO:H film after the 150 °C annealing decreased in comparison to that in the conventional IGZO film after 300 °C annealing. The oxygen diffusion into the film during annealing plays an important role for reducing oxygen vacancies and subgap states especially for near EF. X-ray reflectometry analysis revealed that the film density of the IGZO:H decreased with an increase in R[H2] which would be the possible cause for facilitating the O diffusion at low temperature.

Hidden piezoelectric performances of BiFeO3-based textured ceramics

A 33% enhancement of the d33 value was obtained in the quenched sample, which was ascribed to the distorted structure and reduced oxygen vacancies.