Reduction Of Oxygen Vacancies Research Articles

Tuning oxygen vacancies in complex oxides using 2D layered materials

Abstract The hybrid interface between 2D materials and complex oxides offers a rich platform to explore fascinating physical phenomena like helical edge states, broken-symmetry phases, and giant magnetoresistance. While current research primarily focuses on the influence of complex oxides on layered 2D materials, the reverse - how layered 2D materials affect complex oxides - remains largely unexplored. Here, we examined the impact of graphene layers on the formation of oxygen vacancies in SrTiO3 (STO) during high-temperature annealing. Our findings, supported by Raman spectroscopy and X-ray photoelectron spectroscopy, indicate that increasing the number of graphene layers progressively leads to a reduced oxygen vacancy content in STO, demonstrating the efficacy of graphene in modulating oxygen vacancy formation in bulk STO. Additionally, using photoluminescence, we showed that graphene layers can tune the in-gap states induced by oxygen vacancies in STO. Our first principal calculations further revealed that graphene layers increase the energy barrier for the outward diffusion of oxygen atoms, thereby inhibiting the formation of oxygen vacancies in STO. These results highlight a new route for tailoring the physical properties of complex oxides by engineering the interface with layered 2D materials.

Revisiting Mo‐Doped SrFeO3‐δ Perovskite: The Origination of Cathodic Activity and Longevity for Intermediate‐Temperature Solid Oxide Fuel Cells

AbstractThe development of cathode materials for rapid and durable oxygen reduction reaction (ORR) is of great importance for intermediate‐temperature solid oxide fuel cells (IT‐SOFCs). Here, we reported a rationally designed minor acidic MoO3 incorporated SrFeO3‐δ‐based perovskite oxide, SrFe0.93Mo0.07O3‐δ instead of normally heavily doped one, with stable cubic phase, exceptional ORR activity, strong Sr segregation resistance and CO2 tolerance as a reliable cathode for IT‐SOFCs through a combined strategy of smith acidity and average metal‐oxygen bond energy regulations. Theoretical investigation on the origin of nonstoichiometric and associated electronic structure properties shows that significant hybridization of the Fe‐3d and O‐2p state, reduced oxygen vacancies formation energy and eased bulk oxide ion diffusivity through controllable amount of Mo‐doping contribute to remarkable ORR activity. The single cell with SrFe0.93Mo0.07O3‐δ cathode exhibits a peak power density of 0.24–1.12 W cm−2 at 600–800 °C, and excellent stability for 270 h at 700 °C. Furthermore, the single cell demonstrates excellent thermal cycling robustness and well‐integrated interfaces without any performance degradation after undergoing 20 rapid temperature fluctuations throughout 500 h. Therefore, this work embodies a combined strategy for designing active perovskite cathode and highlights the great potential for IT‐SOFCs as validated by multiple perspective considerations.

Superb thermal stability achieved in Na0.25K0.25Bi2.5Nb2O9-based piezoelectric ceramics via Bi deficiency

Na0.25K0.25Bi2.5Nb2O9-based ceramics woule become one of the excellent candidate materials suitable for high-temperature applications, given that their piezoelectric properties can be effectively improved. In this work, a strategy of reducing the Bi content was used to improve the piezoelectric properties and thermal stability of Na0.25K0.25Bi2.5Nb2O9-based ceramics by means of designing the compositions of the Na0.25K0.25Bi2.5+xNb2O9+3x/2 (−100xBi-NKBN, x = 0, −0.01, −0.03, −0.05, −0.07, −0.10). The effect of the Bi deficiency on the crystal structure, microscopic morphology, and electrical properties of NKBN-based ceramics was systematically investigated. By comparison, the Na0.25K0.25Bi2.45Nb2O8.925 ceramic obtains a large d33 of 20 pC/N, a high Tc of 651 ℃, and a high resistivity ρdc of 3.3 × 105 Ω cm at 600 ℃. The results demonstrate that the good d33 mainly stems from the increased lattice distortion and reduced oxygen vacancy concentration. More importantly, the d33 value can maintain 97 % of its initial value after it was annealed at 600 ℃, showing excellent thermal stability. This work provides a new idea for solving the problem of poor piezoelectricity of NKBN-based ceramics and lays the foundation for applying NKBN-based ceramics in the high-temperature field.

Solution-based surface modification method for high-performance ZnO transistors

A solution-based surface modification method is first proposed for improving electrical performance of the ZnO transistors. The ZnO transistors are infiltrated for treatment in the 0.01 mol/L NH4Cl solution, and the effects of treatment time on electrical properties are examined. We find that turn-on voltage (VON) positively correlates with the treatment time, consequently sub-threshold swing (SS) is optimized significantly. After treatment for 30 s, the device showed a shift of VON from −1.96 V to −1.24 V. Additionally, the SS decreased from 154.5 mV/dec to 104.4 mV/dec, and the μFE increased from 20.69 cm2/V·s to 25.55 cm2/V·s. The XPS results imply that the surface modification method effectively reduces oxygen vacancies of the ZnO active layer, which achieves the target of adjusting VON and SS. Besides, characterization results show that the surface is smoother and the wettability is enhanced after treatment. This solution-modified strategy is expected to be put into practical application due to the advantages of easy operation, low cost, low-temperature environmental protection, and capable of large-scale treatment.

Strain-Enhanced Low-Temperature High Ionic Conductivity in Perovskite Nanopillar-Array Films.

Solid oxide ionic conductors with high ionic conductivity are highly desired for oxide-based electrochemical and energy devices, such as solid oxide fuel cells. However, achieving high ionic conductivity at low temperatures, particularly for practical out-of-plane transport applications, remains a challenge. In this study, leveraging the emergent interphase strain methodology, we achieve an exceptional low-temperature out-of-plane ionic conductivity in Na0.5Bi0.5TiO3 (NBT)-MgO nanopillar-array films. This ionic conductivity (0.003 S cm-1 at 400 °C) is over one order of magnitude higher than that of the pure NBT films and surpasses all conventional intermediate-temperature ionic conductors. Combining atomic-scale electron microscopy studies and first-principles calculations, we attribute this enhanced conductivity to the well-defined periodic alignment of NBT and MgO nanopillars, where the interphase tensile strain reaches as large as +2%. This strain expands the c-lattice and weakens the oxygen bonding, reducing oxygen vacancy formation and migration energy. Moreover, the interphase strain greatly enhances the stability of NBT up to 600 °C, well above the bulk transition temperature of 320 °C. On this basis, we clarify the oxygen migration path and establish an unambiguous strain-structure-ionic conductivity relationship. Our results demonstrate new possibilities for designing applicable high-performance ionic conductors through strain engineering.

Nonlinear Bifunctional Memristor for Reprogrammable Programmable Read-Only Memory (PROM) Applications

In current von Neumann computing systems, tremendously separate processing and memory units are involved. However, data movement is costly in terms of time and energy, and this problem is aggravated by the recent explosive growth in highly data-centric applications related to artificial intelligence (AI) on the hardware, especially performance and reliability [1-3]. Sneak path current (SPC) is an inevitable problem in large memory array, deteriorating the read/write margin of crossbar configuration, where the leakage current from neighboring cells results in operation errors. The 1T-1R or 1S-1R configuration with good SPC suppressing ability is proposed for most emerging memory technologies, while with significant cost and fabrication complexity (Fig. 1). To reduce the SPC with cost efficiency, nonlinear self-rectified memory with thin film stacking fabrication is presented as the highly scalable non-volatile memory for storage and computing configurations (Fig. 1). Meanwhile, the one-time fusing state is implemented with hybrid function in nonlinear memristor, as “reprogrammable programmable-read-only memory (PROM)” for future security applications.On the pristine state of devices, electroforming processes were conducted as followed with the first RESET process. The self-selectivity (i.e. nonlinearity) of three various structures was stabilized after 30-cycle seasoning. Nonlinearity (NL) is defined as ratio of the LRS current at Vread divided by the LRS current at 1/3Vread. The greater SPC immunity of 1R-only self-rectified memory is demonstrated with the higher the NL. The NL modulated with the SET compliance current limit (CCL) is shown in Fig. 2 (a), where the NL of HfOx/SiOx stacked devices (i.e. H4S9, H11S2) is optimized with CCL of 1 mA and 2 mA, respectively. That is, the H4S9 shows improved energy efficiency as compared to H11S2 devices. The I-V characteristics of H11S2 under three various ambient conditions (i.e. nitrogen, vacuum, and RT) depicts the memory window (MW) shrinks under the nitrogen and vacuum (Fig. 2 (b)), which is suggested as resulting from the reduction of oxygen vacancies. Noted the NL reduces with the ambient changes in both reading polarities (Fig. 2 (c)), where the switching voltages reduces under the vacuum (~10-3 torr). Unlike the single layer SiOx which should be operated under vacuum/nitrogen condition, bilayer self-rectified memory performed well under the RT ambient [4]. Figure 3 shows the transfer curves for a single layer of SiOx, single layer of HfOx, and bilayer device. With the high dielectric layer insertion (i.e. HfOx), the current under voltage larger than -1 V has ~0.5 order of magnitude higher than single layer low dielectric layer. This is thought to be suggested that the high-k layer provides higher current distribution under higher voltage, and remains the same with bilayer when voltage is less than 1 V [4-5]. With the high-k/low-k configurations for selectorless memristor devices, the graphite and graphite oxide are also studied as stacked with HfOx (6 nm). Noted the HfOx/RuOx stacked devices are fabricated as the reference for investigating the reprogrammable PROM memory (Fig. 4 a-b). The dielectric fusing occurs in the graphite-based nonlinear memristor with the functional write-erase cycles before finalized the fuse state (I <10-9 A) under the voltage around -2.4 ~-2.8 V (Fig 4 c-d). The fusing voltage is independent of the high-k/low-k stacking, but only correlated to the thickness of effective dielectrics. This could be beneficial for realizing the hybrid functional memristor in OTP applications, according to the margin to modulate the stack configuration whereas fixed the fusing voltage.In this work, the bilayer self-rectified memristors have been realized in the bilayer stacked structures for suppressing the sneak path current without an additional switch device integration. The ambient response and switching gap determination, and defect distribution has been investigated. Nonlinear bifunctional memristor with low voltage dielectric fusing operation is presented for reprogrammable PROM Applications as the future features for security applications.

Exploring the Stability of Azto Tfts: The Critical Role of Oxygen Partial Pressure in Performance Optimization

Amorphous oxide semiconductors, such as indium-gallium-zinc oxide (IGZO), have attracted significant attention due to their high electron mobility and low processing temperatures compared to amorphous silicon (a-Si). These characteristics make IGZO suitable for large-area applications, and its transparency holds promise for next-generation electronic devices. However, the commercialization and large-scale production of IGZO are limited by the toxicity of indium and the high cost of gallium. In this context, AZTO can emerges as a cost-effective and less toxic alternative. This study explores the fabrication and characterization of bottom-gate thin-film transistors (TFTs) using aluminum-zinc-tin oxide (AZTO) as an alternative channel material. AZTO films were deposited at room temperature via radio frequency (RF) magnetron sputtering with varying ratios of oxygen and argon. Comprehensive measurements, including temperature stress (TS), negative bias temperature stress (NBTS), activation energy, and density of states (DOS), were conducted to evaluate the electrical properties and stability of the TFTs. The results indicate that increasing the oxygen partial pressure during deposition reduces oxygen vacancies, significantly enhancing the stability of the devices. These findings highlight AZTO as a cost-effective and less toxic alternative to IGZO, particularly in display applications. Additionally, the study provides insights into the fundamental mechanisms governing the electrical behavior of AZTO-based TFTs, further confirming their suitability for advanced display technologies.

(Invited) Advancement in Neuromorphic Devices for Detection of Complex Stimuli with Low Power Consumption Utilizing Cross-Linked Electrolyte

In the quest to create computing systems that mimic the brain’s remarkable ability to process data efficiently and in parallel, researchers have recognized the need for in-memory computing devices that can overcome the limitations of the traditional von Neumann architecture. Recently, neuromorphic devices like memristors and synaptic transistors have been developed to emulate the process of neurons. However, memristors face challenges in simultaneously handling signal transmission and learning tasks. As an alternative, synaptic transistors have gained attention owing to their adjustable weight and improved non-volatile synaptic functionality. Notably, synaptic transistors with electrolyte insulating layers can form electric double layers (EDLs) with high capacitance per unit area, because of mobile ions and dipoles. This enables efficient gate-controlled synaptic behavior. Additionally, amorphous oxynitride semiconductors, used as n-type channels, exhibit superior mobility compared to other materials like 2D transition metals, perovskites, organic materials, and oxides. In our investigation, therefore, we employed a cross-linked poly-4-vinyl phenol (PVP) gate insulator to enhance the synaptic properties of oxynitride thin film transistors.In our study, we employed zinc oxynitride (ZnON) as the channel material. ZnON offers greater stability compared to oxide materials due to its reduced oxygen vacancy concentration. We precisely controlled the solution composition and the curing process during the deposition of the electrolyte insulating layer. To optimize the formation of electric double layers (EDLs), we varied the weight ratio of poly(melamine-co-formaldehyde) methylated (PMF) and poly-4-vinyl phenol (PVP). Our investigation focused on synaptic properties, including excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF), long-term memory, and high-band filtering. All samples exhibited a counter-clockwise hysteresis curve and a memory window exceeding 2 V at 1 V of drain voltage (Vd), except for the PVP:PMF 2:1 sample. Notably, the device with a 10:1 weight ratio demonstrated the most effective EPSC response, showing a gradual increase in EPSC with repeated gate voltage (Vg) pulses. Additionally, we analyzed the EPSC characteristics under various Vg pulse conditions (width, frequency, period). To understand the behavior of internal ions and dipoles in the cross-linked PVP insulating layer, we measured the frequency-dependent capacitance. Interestingly, the capacitance decreased as the frequency increased, suggesting that internal ions could be easily influenced by electrical bias in the cross-linked PVP electrolyte, forming an EDL layer. These findings suggest that the cross-linked PVP/ZnON-based transistor could potentially serve as a significant synaptic transistor component in artificial intelligence technology.

Improving the Nonvolatile Memory Characteristics of Sol-Gel-Processed Y2O3 RRAM Devices Using Mono-Ethanolamine Additives.

In this study, Y2O3-based resistive random-access memory (RRAM) devices with a mono-ethanolamine (MEA) stabilizer fabricated using the sol-gel process on indium tin oxide/glass substrates were investigated. The effects of MEA content on the structural, optical, chemical, and electrical characteristics were determined. As the MEA content increased, film thickness and crystallite size decreased. In particular, the increase in MEA content slightly decreased the oxygen vacancy concentration. The decreased film thickness decreased the physical distance for conductive filament formation, generating a strong electric field. However, owing to the lowest oxygen vacancy concentration, a large electrical field is required. To ensure data reliability, the endurance cycles across several devices were measured and presented statistically. Additionally, endurance performance improved with the increase in MEA content. Reduced oxygen vacancy concentration can successfully suppress the excess formation of the Ag conductive filament. This simplifies the transition from the high- to the low-resistance state and vice versa, thereby improving the endurance cycles of the RRAM devices.

Er3+:Y3Al5O12/Pt/ZnO material for photocatalytic hydrogen production under UV–Vis light

Hydrogen is a promising energy source, requiring increasingly efficient photocatalysts for production under UV–Vis light. For the first time, this study evaluated the photocatalytic generation of H2 using the Er3+:Y3Al5O12/Pt/ZnO material. The effect of the Er3+:Y3Al5O12 garnet on the photocatalytic activity of Pt/ZnO under UV–Vis light was evaluated. Firstly, both the ZnO and the Er3+:Y3Al5O12 garnet were synthesized by a sol-gel method, and the Pt-coating of the ZnO was performed using a sonochemical method. The samples were characterized through XRD, SEM-EDX, Raman, UV–Vis-DRS, N2 adsorption-desorption, XPS, and fluorescence spectroscopy. The H2 production under UV–Vis light was measured using mass spectrometry, and the effect of methanol as a sacrificial agent was evaluated. The synthesis method allowed obtaining ZnO with a defined spherical morphology and high crystallinity, with the H2 generation of 676 μmolh−1g−1. In the meantime, the Pt-coating reduced oxygen vacancies and the recombination rate of e−/h+ pairs, and the garnet addition in a mass ratio of Pt/ZnO:garnet at 1.0:0.3 led to the highest H2 production (1304 μmolh−1g−1), with only a 20 % decrease after 5 production cycles. Finally, adding 10 % v/v methanol significantly enhanced the H2 generation (3026 μmolh−1g−1). Altogether, the Er3+:Y3Al5O12/Pt/ZnO material with the sacrificial agent (10 % v/v methanol) improved H2 production from ZnO by a factor of 4.5. Thus, this study demonstrates that the Er3+:Y3Al5O12 garnet is an efficient alternative for significantly increasing H2 production from Pt/ZnO.

High-temperature operation of Al2O3/Ga2O3 bi-layer gate stack GaN MOS-HEMT up to 450 °C with suppressed gate leakage

Abstract In this work, we report the reduced gate leakage current by using aluminum oxide (Al2O3) and gallium oxide (Ga2O3) as a bi-layer gate stack for GaN MOS-HEMT on a silicon substrate up to 450 °C. The bi-layer gate stack MOS-HEMTs suppressed the gate leakage by more than four orders of magnitude compared to only Al2O3-based GaN MOS-HEMT at 450 °C. The low gate leakage current is attributed to the reduced oxygen vacancies present in the Ga2O3 layer, which effectively impede the conduction path of the Poole-Frenkel emission at high temperatures, thereby enhancing the overall performance of GaN HEMTs.

Synergistic removal of nitrogen oxides and toluene and their interaction mechanism on Cu-MnO2 catalyst

Volatile organic compounds (VOCs) and nitrogen oxides (NOx) contribute significantly to the formation of haze and photochemical smog, posing substantial threats to both the environment and human health. Toluene, a typical VOCs, often coexists with NOx in various mobile or stationary flue gases. However, the current understanding of the mutual influence of their synergistic removal remains limited. In this work, the Cu-MnO2 catalyst was prepared using the precipitation method, which demonstrated synergistic removal activity for both NOx and toluene, as well as selectivity towards N2 and CO2. The interaction mechanism was investigated, particularly focusing on the effect of NOx on the adsorption and oxidation performance of toluene. The degree to which NOx inhibits toluene increases with NOx concentration. Furthermore, multiple inhibition ways of NOx on toluene oxidation were discovered, including competitive adsorption of NOx and toluene on the catalyst surface, as evidenced by the breakthrough experiments. TPD and XPS characterization indicated that the addition of NOx reduces oxygen vacancies, thereby weakening toluene oxidation performance. In addition, in-situ DRIFT characterization was conducted, and it was found that the addition of NOx affected the oxidation process of toluene. Apart from benzyl alcohol, benzaldehyde, and benzoic acid, intermediate nitrite species also appeared, and their deposition was also the reason for the decrease in toluene oxidation ability. This work provides new insights into the interaction mechanisms between various components in the collaborative removal of NOx and VOCs.

Anatase to rutile transition in TiO2 thin films: Role of tantalum and oxygen

The present study discusses the optimal solubility limit of tantalum in anatase TiO2 thin films (dopant solubility limit) and its effect on crystal structure transformation to the rutile phase. The study also focuses on the role of lattice oxygen in this structural phase transition. The detailed chemical composition, constitution, and phase of these sputter-deposited thin films are correlated with their electrical and optical properties to understand the disparity between total impurity concentration in these films and actual impurity substitution into the host lattice sites (dopant content). Reduced oxygen vacancies from the oxygen lattice sites and/or Ta substitution in Ti lattice sites are found to hinder the anatase to rutile phase transformation in TiO2 thin films. Our experimental data indicates the solubility limit of Ta being < 5 at% in TiO2. Similar behavior is seen when Ta is replaced with Nb in TiO2 thin films. Moreover, an increased oxygen and/or impurity concentration is found to lead to impurity-rich-oxides in these films, degrading the electrical conductivity.

Promoting metal oxides–zeolite electron interaction on MnCeOx/HY catalyst for boosting nitrogen oxides reduction

The MnOx-CeO2 metal oxides are considered as promising alternative catalysts for selective catalytic reduction with NH3 (NH3-SCR) to remove NOx due to its excellent low temperature performance. However, their strong oxidative ability can lead to NH3 over-oxidation, narrowing the active temperature range and reducing N2 selectivity. Moreover, their weak surface acidity hampers medium to high-temperature activity and alkali metal resistance. Hence, in this study, MnCeOx metal oxides were coupled with HY zeolite to create MnCeOx/HY, demonstrating excellent NH3-SCR performance. The high dispersion of metal oxides on the zeolite surface and their close integration promoted strong electron interaction, effectively reducing oxygen vacancies and surface adsorbed oxygen concentrations. Consequently, the oxidative ability of active metal oxides was appropriately weakened, suppressing undesirable side reactions. MnCeOx/HY also notably suppressed NO adsorption and nitrate formation, promoting the catalytic reaction solely through the E-R mechanism and enhancing N2 selectivity. The abundant strong acid sites on the zeolite surface facilitates NH3 adsorption at moderate to high temperatures, notably expanding the active temperature window. Furthermore, the acid sites of HY zeolite serve as sacrificial sites, preferentially reacting with alkali metals, thus exhibiting excellent resistance to alkali metal poisoning on MnCeOx/HY. Combining with the DFT results, the structure-activity relationships in this study also reveal the importance of the effective synergy between acid sites and redox sites for optimal catalytic performance, offering valuable insights into the development of highly active and alkali-resistant denitrification catalysts.

Enhanced Photocatalytic Performance under Ultraviolet and Visible Light Illumination of ZnO Thin Films Prepared by Modified Sol-Gel Method.

Semiconductor oxides are frequently used as active photocatalysts for the degradation of organic agents in water polluted by domestic industry. In this study, sol-gel ZnO thin films with a grain size in the range of 7.5-15.7 nm were prepared by applying a novel two-step drying procedure involving hot air treatment at 90-95 °C followed by conventional furnace drying at 140 °C. For comparison, layers were made by standard furnace drying. The effect of hot air treatment on the film surface morphology, transparency, and photocatalytic behavior during the degradation of Malachite Green azo dye in water under ultraviolet or visible light illumination is explored. The films treated with hot air demonstrate significantly better photocatalytic activity under ultraviolet irradiation than the furnace-dried films, which is comparable with the activity of unmodified ZnO nanocrystal powders. The achieved percentage of degradation is 78-82% under ultraviolet illumination and 85-90% under visible light illumination. Multiple usages of the hot air-treated films (up to six photocatalytic cycles) are demonstrated, indicating improved photo-corrosion resistance. The observed high photocatalytic activity and good photo-corrosion stability are related to the hot air treatment, which causes a reduction of oxygen vacancies and other defects and the formation of interstitial oxygen and/or zinc vacancies in the films.

(Invited) Modification of Dielectric Properties of Film Dielectric Materials by Solid Solution System

Compound semiconductor based power devices such as SiC and GaN require high temperature operating passive devices such as a capacitor. SiC-based active devices can operate above 250 °C. The development of high-temperature operational passives is urgently needed to advance to the module and system level. In the case of capacitors, currently available capacitors can only operate efficiently up to 175 °C. Therefore, a thin film capacitor that can operate at high temperatures and be monolithically integrated near the active device should be developed. In this talk, I will present our achievements in the development of high-temperature operating dielectric film materials using the solid solution system. One topic is A2B2O7 pyrochlore ferroelectrics. The ferroelectric materials with the pyrochlore structure such as Sr2Nb2O7 exhibited the high dielectric constant above 100 at high and low temperature ranges. However, due to the crystallographic direction dependence of the Curie-Weiss temperature, the temperature stability of the dielectric constant from room temperature to 300 °C was not available. In order to obtain the high temperature stability of dielectric constant from room temperature to 300 °C with high dielectric constant over 100, the pyrochlore ferroelectric solid solution thin films were investigated by employing the combinatorial synthesis. Composition spread thin films of solid solution of two or three kinds of materials were deposited on substrates by physical vapor deposition technique, which provided the systematic physical properties. High-throughput combinatorial synthesis method is effective in the rapid optimization of the correlation between the crystallization and the dielectric property change behavior. For the composition spread solid solution film, the Sr- or La-containing A2B2O7 pyrochlore ferroelectrics were selected from the viewpoints of ion radios and crystallographic direction dependence of the Curie-Weiss temperature. The composition spread films were formed on a Pt/Ti/SiO2/Si substrate by combinatorial RF sputtering with stoichiometric composition targets. The X-ray fluorescence spectrum of the composition-spread film showed a linear variation of the metal composition. After deposition, the samples were annealed at different temperatures under oxygen atmosphere to reduce oxygen vacancies and improve crystallinity. The crystallization of the composition-spread solid solution thin film was confirmed by X-ray diffraction patterns, indicating the composition dependence of the crystallographic orientation. Some compositions showed high dielectric constant over 100 and high temperature stability from room temperature to 300 °C. In the presentation, the correlation between film composition, orientation and dielectric constant will be discussed in detail. In the presentation, we also introduce our achievement of the BaTiO3 based relaxor ferroelectrics and other dielectric materials development using the solid solution system. For the relaxor ferroelectrics, among the BaTiO3 based relaxor ferroelectrics, we have selected x[BaTiO3]-(1-x)[Bi(Mg2/3Nb1/3)O3] . The permittivity of 400 and the stability <8% from room temperature to 400 °C were obtained, which are promising as high-temperature dielectric medium.

Large-Area Perovskite Solar Module Produced by Introducing Self-Assembled L-Histidine Monolayer at TiO2 and Perovskite Interface.

Perovskite solar cells have been proven to enhance cell characteristics by introducing passivation materials that suppress defect formation. Defect states between the electron transport layer and the absorption layer reduce electron extraction and carrier transport capabilities, leading to a significant decline in device performance and stability, as well as an increased probability of non-radiative recombination. This study proposes the use of an amino acid (L-Histidine) self-assembled monolayer material between the transport layer and the perovskite absorption layer. Surface analysis revealed that the introduction of L-Histidine improved both the uniformity and roughness of the perovskite film surface. X-ray photoelectron spectroscopic analysis showed a reduction in oxygen vacancies in the lattice and an increase in Ti4+, indicating that L-Histidine successfully passivated trap states at the perovskite and TiO2 electron transport layer interface. In terms of device performance, the introduction of L-Histidine significantly improved the fill factor (FF) because the reduction in interface defects could suppress charge accumulation and reduce device hysteresis. The FF of large-area solar modules (25 cm2) with L-Histidine increased from 55% to 73%, and the power conversion efficiency (PCE) reached 16.5%. After 500 h of aging tests, the PCE still maintained 91% of its original efficiency. This study demonstrates the significant impact of L-Histidine on transport properties and showcases its potential for application in the development of large-area perovskite module processes.

Reducing oxygen vacancies of MoO3 by polyaniline functionalization for stable and efficient inorganic tri-brominated perovskite solar cells

The photovoltaic performance of perovskite solar cells (PSCs) is closely dependent on the efficient carrier extraction and transport at the interface. Here, a polyaniline (PANI) functionalized MoO3 (PANI/MoO3) hole transport material (HTM) is exploited to perfect the interface between the perovskite layer and carbon electrode in all-inorganic CsPbBr3 PSCs. After functionalization with PANI, the p-type behavior and the hole mobility and conductivity of MoO3 are improved by reducing the oxygen vacancies, which boosts the hole extraction and transport, energy level arrangement at the interface of CsPbBr3 perovskite/(PANI/MoO3) HTM. Meanwhile, the PANI/MoO3 with rich C–N and N–H groups introduced by PANI passivates the ions trap states of perovskite films by the C–N⋯Pb2+ (Cs+) Lewis acid-base coordination and the N–H⋯Br− hydrogen bonding, leading to an effective suppression of non-radiative recombination for improved carrier extraction. As a result, the PANI/MoO3 HTMs-based CsPbBr3 PSCs obtain a remarkably increased power conversion efficiency of 10.41 %, in comparison with the efficiency of the original device (6.55 %). In addition, the unencapsulated device with PANI/MoO3 HTMs shows excellent long-term stability with 93.9 % maintenance of the initial efficiency after storing in air with 85 % relative humidity and at 85 °C for 30 days.

Junctionless Structure Indium-Tin Oxide Thin-Film Transistors Enabling Enhanced Mechanical and Contact Stability.

In recent years, considerable attention has focused on high-performance and flexible crystalline metal oxide thin-film transistors (TFTs). However, achieving both high performance and flexibility in semiconductor devices is challenging due to the inherently conductive and brittle nature of crystalline metal oxide. In this study, we propose a facile way to overcome this limitation by employing a junctionless (JL) TFT structure via oxygen plasma treatment of the crystalline indium-tin oxide (ITO) films. The oxygen plasma treatment significantly reduced oxygen vacancies in the ITO films, contributing to the significant reduction in the carrier concentration from 4.67 × 1020 to 1.39 × 1016. Importantly, this reduction was achieved without inducing any noticeable structural changes in the ITO, enabling the successful realization of ITO JL TFTs with an adjustable threshold voltage. Furthermore, the ITO JL TFTs demonstrate good stability and reliability under various bias stress conditions, aging in the air atmosphere, and high-temperature processes. In addition, the ITO JL TFTs exhibit low light sensitivity due to the wide bandgap of ITO and further suppression of Vo defects, making them suitable for applications requiring stable performance under light exposure. To compare and analyze the flexibility of the JL structure and conventional structure with additional source/drain (S/D) junction in ITO TFTs with nonencapsulation, we utilized mechanical simulations and transmission line method (TLM). By employing the JL structure in ITO TFT through carefully optimized oxygen plasma treatment, we successfully mitigated stress concentration at the S/D-channel interface. This resulted in a JL ITO TFT that exhibited a change in contact resistance of less than 20% even after 20,000 bending cycles. Consequently, a stable and flexible ITO TFT with field-effect mobility (μFE) of 12.74 cm2/(V s) was realized, outperforming conventionally structured ITO TFTs with additional S/D junction, where the contact resistance nearly tripled.

Mn doping as a simple strategy for improving energy storage in BaBi4Ti4O15 thin films

To obtain high energy storage density in ferroelectric films, polarization and breakdown field Eb are two crucial factors. The inversely coupled relationship between polarization and Eb is commonly observed and it remains a challenge to realize high Eb without deteriorating polarization. Selecting a suitable element doping should largely enhance the Eb since of the optimization of microstructures as well as the decrease in defects, meanwhile the doping should induce extra polarization contribution from lattice distortion. In this work, we reported that Eb can be largely enhanced via Mn doping in BaBi4Ti4O15 thin films due to grain refining, densification, and oxygen vacancy reduction. Interestingly, the polarization is not deteriorated since of the Mn doping effect induced extra polarization from the lattice distortion. Consequently, an ultrahigh energy storage density of 96 J/cm3 with a high efficiency of 76.6% was achieved in BaBi4Ti3.95Mn0.05O15 thin films with excellent stability and reliability. This work will provide a simple and effective route to improve the energy storage in dielectric capacitors.