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Abstract High‐entropy materials (HEMs) are extremely popular for electrochemical energy storage nowadays. However, the detailed effects of four core factors of high entropy on the electrochemical properties of HEMs are still unclear. Here, a high‐entropy La1/4Ce1/4Pr1/4Nd1/4Nb3O9 (HE‐LaNb3O9) oxide is prepared through multiple rare‐metal‐ion substitution in LaNb3O9, and uses HE‐LaNb3O9 as a model material to systematically study the effects of the four core factors of high entropy on electrochemical energy‐storage materials. The high‐entropy effect lowers the calcination temperature for obtaining pure HE‐LaNb3O9. The lattice distortion in HE‐LaNb3O9 leads to its decreased unit‐cell‐volume variations, which benefits its cyclability. Based on the restrained diffusion arising from the lattice distortion, the Li+ diffusivity of HE‐LaNb3O9 at room temperature (25 °C) is limited, which causes its lowered rate capability. However, the Li+ diffusivity of HE‐LaNb3O9 at high temperature (60 °C) becomes faster than that of LaNb3O9, which is attributed to the alleviated lattice distortion at the high‐temperature, resulting in higher rate capability. The cocktail effects in HE‐LaNb3O9 enable its larger electronic conductivity, better electrochemical activity, more intensive Nb5+ ↔ Nb3+ redox reaction, and larger reversible capacity. The insight gained here can provide a guide for the rational design of new HEMs with good energy‐storage properties.

In recent years, global warming has led to frequent high temperature weather, and occupational groups who have been exposed to high-temperature environment for a long time are vulnerable to heat casualties due to the combined impact from multiple meteorological factors (temperature, humidity, wind speed, and thermal radiation). In order to strengthen the health support for high-temperature workers, it is necessary to monitor the environment heat intensity of high-temperature environment in real time to guide relevant actions. Wet bulb globe temperature (WBGT) index takes into account multiple meteorological factors such as temperature, humidity, wind speed, and thermal radiation, and can more scientifically evaluate the environment heat intensity than individual thermal environment factors, thus guiding high-temperature operations for multiple working populations. This paper summarized the origin and development of WBGT index and its research and application status at home and abroad, and proposed possible development directions of the key technologies based on the WBGT index in China in the future.

The global climate change negatively affects the photovoltaic performance of traditional solar cell technologies. This article investigates the potential of organic photovoltaics (OPV) for high‐temperature environments, ranging from urban hot summers (30—40 °C) and desert regions (65 °C) up to (aero) space conditions (130 °C), the thermal window in which OPV can operate. The approach is based on a combination of experiments and simulations up to 180 °C, moving significantly beyond the conventional temperature ranges reported in the literature. New 2H‐benzo[d][1,2,3]triazole‐5,6‐dicarboxylic imide‐based copolymers with decomposition onset temperatures above 340 °C are used for this study, in combination with non‐fullerene acceptors. Contrary to their inorganic counterparts, OPV devices show a positive temperature coefficient up to ≈90 °C. At temperatures of 150 °C, they are still operational, retaining their room temperature efficiency. Complementary simulations are performed using an in‐house developed software package that numerically solves the drift‐diffusion equations to understand the general trends in the obtained current–voltage characteristics and the materials' intrinsic behavior as a function of temperature. The presented methodology of combined high‐temperature experiments and simulations can be further applied to investigate the thermal window of operation for other OPV material systems, opening novel high‐temperature application routes. [ABSTRACT FROM AUTHOR]

This study aimed to propose a silicon-on-insulator (SOI)-based charge-trapping synaptic transistor with engineered tunnel barriers using high-k dielectrics for artificial synapse electronics capable of operating at high temperatures. The transistor employed sequential electron trapping and de-trapping in the charge storage medium, facilitating gradual modulation of the silicon channel conductance. The engineered tunnel barrier structure (SiO2/Si3N4/SiO2), coupled with the high-k charge-trapping layer of HfO2 and high-k blocking layer of Al2O3, enabled reliable long-term potentiation/depression behaviors within a short gate stimulus time (100 μs), even under elevated temperatures (75 and 125 °C). Conductance variability was determined by the number of gate stimuli reflected in the maximum excitatory postsynaptic current (EPSC) and the residual EPSC ratio. Moreover, we analyzed the Arrhenius relationship between the EPSC as a function of the gate pulse number (N = 1–100) and the measured temperatures (25, 75, and 125 °C), allowing us to deduce the charge trap activation energy. A learning simulation was performed to assess the pattern recognition capabilities of the neuromorphic computing system using the modified National Institute of Standards and Technology datasheets. This study demonstrates high-reliability silicon channel conductance modulation and proposes in-memory computing capabilities for artificial neural networks using SOI-based charge-trapping synaptic transistors. [ABSTRACT FROM AUTHOR]

Capacity decay of an intercalating Li+‐storage material is mainly due to the its particle microcracks from stress‐causing volume change. To extend its cycle life, its unit‐cell‐volume change has to be minimized as much as possible. Here, based on a γ‐Li3VO4 model material, the authors explore selective doping as a general strategy to controllably tailor its maximum unit‐cell‐volume change, then clarify the relationship between its crystal‐structure openness and maximum unit‐cell‐volume change, and finally demonstrate the superiority of "zero‐strain" materials within 25–60 °C (especially at 60 °C). With increasing the large‐sized Ge4+ dopant, the unit‐cell volume of γ‐Li3+xGexV1−xO4 becomes larger and its crystal structure becomes looser, resulting in the decrease of its maximum unit‐cell‐volume change. In contrast, the doping with small‐sized Si4+ shows a reverse trend. The tailoring reveals that γ‐Li3.09Ge0.09V0.91O4 owns the smallest maximum unit‐cell‐volume change of 0.016% in the research field of intercalating Li+‐storage materials. Consequently, γ‐Li3.09Ge0.09V0.91O4 nanowires exhibit excellent cycling stability at 25/60 °C with 94.8%/111.5% capacity‐retention percentages after 1800/1500 cycles at 2 A g−1. This material further shows large reversible capacities, proper working potentials, and high rate capability at both temperatures, fully demonstrating its great application potential in long‐life lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

Capacity decay of an intercalating Li+‐storage material is mainly due to the its particle microcracks from stress‐causing volume change. To extend its cycle life, its unit‐cell‐volume change has to be minimized as much as possible. Here, based on a γ‐Li3VO4 model material, the authors explore selective doping as a general strategy to controllably tailor its maximum unit‐cell‐volume change, then clarify the relationship between its crystal‐structure openness and maximum unit‐cell‐volume change, and finally demonstrate the superiority of "zero‐strain" materials within 25–60 °C (especially at 60 °C). With increasing the large‐sized Ge4+ dopant, the unit‐cell volume of γ‐Li3+xGexV1−xO4 becomes larger and its crystal structure becomes looser, resulting in the decrease of its maximum unit‐cell‐volume change. In contrast, the doping with small‐sized Si4+ shows a reverse trend. The tailoring reveals that γ‐Li3.09Ge0.09V0.91O4 owns the smallest maximum unit‐cell‐volume change of 0.016% in the research field of intercalating Li+‐storage materials. Consequently, γ‐Li3.09Ge0.09V0.91O4 nanowires exhibit excellent cycling stability at 25/60 °C with 94.8%/111.5% capacity‐retention percentages after 1800/1500 cycles at 2 A g−1. This material further shows large reversible capacities, proper working potentials, and high rate capability at both temperatures, fully demonstrating its great application potential in long‐life lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

Li4Ti5O12 (LTO) is the most famous Li+‐storage anode material with fast‐ and stable‐charging capability, but suffers from several disadvantages, such as poor electron conduction, low energy density, and disappointing high‐temperature performance. Here, LaCeNb6O18 (LCNO) micrometer‐sized particles are explored as a fast‐ and stable‐charging anode material superior to LTO sub‐micrometer‐sized particles in terms of the working potential, rate capability, and high‐temperature performance. The conductive Ce3+ and Nb5+↔Nb3+ reactions in LCNO, respectively, enable its significantly larger electronic conductivity and lower working potential than those of LTO. LCNO owns a very open A‐site‐cation‐deficient perovskite structure, in which (vacancy/La/Ce)O12 layers with electrochemical inactivity and superior volume‐buffering capability locate between active NbO6 layers, leading to not only fast Li+ diffusivity but also low‐ and negative‐strain behavior at different temperatures. At 25 °C, LCNO exhibits higher rate capability (50 vs 0.1 C capacity ratio of 67.9%) than that of LTO, and excellent cyclability. At 60 °C, LCNO maintains excellent cyclability, and achieves larger reversible capacity and even higher rate capability, whereas the high temperature lowers all the electrochemical properties of LTO. Therefore, LCNO holds great promise for fast‐ and stable‐charging applications in a wide temperature range, even when its particle sizes are on the order of micrometers. [ABSTRACT FROM AUTHOR]

The bonding between copper and epoxy resin is investigated using a CHSi thin film to achieve highly adhesive and reliable bonding between the resin mold and the copper substrate in power modules. In this study, high-temperature (473 K) testing is performed to improve the reliability of this junction after high-temperature operation. The bond strength decreases and delamination occurs at the filmcopper interface after high-temperature testing. The decrease in bond strength may be due to the decrease in the filmcopper interfacial strength because of the decrease in the binding force between copper and oxygen upon heating. When Fe and Cr, which have high oxygen bond disassociation energies, are intercalated at the filmcopper interface, the bond strength improves after high-temperature testing and a bond strength above 30MPa was retained after 1000 h. This study is a novel method of dissimilar bonding based on chemical and physical effects of CHSi film existing between copper and resin. Further, it is an effective method of bonding to achieve high-temperature operation of a resin-molded power module, which can contribute to future advancements in power electronics products. [ABSTRACT FROM AUTHOR]

Abstract Phase-change memory (PCM) has considerable promise for new applications based on von Neumann and emerging neuromorphic computing systems. However, a key challenge in harnessing the advantages of PCM devices is achieving high-speed operation of these devices at elevated temperatures, which is critical for the efficient processing and reliable storage of data at full capacity. Herein, we report a novel PCM device based on Ta-doped antimony telluride (Sb2Te), which exhibits both high-speed characteristics and excellent high-temperature characteristics, with an operation speed of 2 ns, endurance of > 106 cycles, and reversible switching at 140 °C. The high coordination number of Ta and the strong bonds between Ta and Sb/Te atoms contribute to the robustness of the amorphous structure, which improves the thermal stability. Furthermore, the small grains in the three-dimensional limit lead to an increased energy efficiency and a reduced risk of layer segregation, reducing the power consumption and improving the long-term endurance. Our findings for this new Ta–Sb2Te material system can facilitate the development of PCMs with improved performance and novel applications.

Herein, high‐temperature (over 200 °C) perovskite solar cells (PSCs) are fabricated and studied for the first time. Inorganic CsPbI2Br perovskite is used as absorber and carbon nanotubes (CNTs) are directly used as the hole extraction electrode. Such device retains over 80% of its initial power conversion efficiency (PCE) after heating at 200 °C for 45 h, enabling its operation at high temperatures. By recording reverse and forward J–V curves at different temperatures (25–220 °C), temperature coefficients of photovoltaic parameters are obtained. Compared with conventional high‐temperature solar cells (Si, CuInGaSe, and GaAs), CsPbI2Br devices show superior VOC and FF temperature coefficients but inferior JSC temperature coefficients. As a result, PCE temperature coefficients of CsPbI2Br devices are superior over Si and CuInGaSe solar cells, and are comparable with those of GaAs solar cells. Meanwhile, the mitigation of charge accumulation at elevated temperatures results in a gradual decrease in J–V hysteresis. Therefore, this study may expand the application of PSCs into high‐temperature fields, such as space exploration. [ABSTRACT FROM AUTHOR]

Greater than 190 °C continuous wave (CW) lasing is achieved from 905 nm high-efficiency vertical cavity surface-emitting lasers (VCSELs). The maximum power conversion efficiency (PCE) of 46.3% for 4 μm VCSELs was demonstrated under the ambient temperature of 30 °C. The maximum PCE decreases only 10% of its value from 30 °C to 90 °C, showing stable high-temperature characteristics. The thermal resistances and active region temperatures of the device versus ambient temperature are determined experimentally. Besides, size-dependent thermal characteristics are also analyzed by characterizing the spectral and spatial properties of devices with various apertures. It is found that the higher the ambient temperature is, the less the number of high-order modes is, and single fundamental mode operation can be realized in 4 μm VCSELs even at a relatively high temperature of 190 °C. The design and characterization of these high-temperature VCSEL devices might present the basis for future laser radar application. [ABSTRACT FROM AUTHOR]

Highlights: Phase-change memory based on Ta-doped antimony telluride (Sb2Te) exhibits both high-speed characteristics and excellent high-temperature characteristics, allowing improved performance and new applications. The high coordination number of Ta and the strong bonds between Ta and Sb/Te atoms enhance the robustness of the amorphous structure, ensuring good thermal stability. Through the three-dimensional limit, the formation of small grains reduces the power consumption and improves the long-term endurance.Phase-change memory (PCM) has considerable promise for new applications based on von Neumann and emerging neuromorphic computing systems. However, a key challenge in harnessing the advantages of PCM devices is achieving high-speed operation of these devices at elevated temperatures, which is critical for the efficient processing and reliable storage of data at full capacity. Herein, we report a novel PCM device based on Ta-doped antimony telluride (Sb2Te), which exhibits both high-speed characteristics and excellent high-temperature characteristics, with an operation speed of 2 ns, endurance of > 106 cycles, and reversible switching at 140 °C. The high coordination number of Ta and the strong bonds between Ta and Sb/Te atoms contribute to the robustness of the amorphous structure, which improves the thermal stability. Furthermore, the small grains in the three-dimensional limit lead to an increased energy efficiency and a reduced risk of layer segregation, reducing the power consumption and improving the long-term endurance. Our findings for this new Ta–Sb2Te material system can facilitate the development of PCMs with improved performance and novel applications. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the effects of the separator thickness on not only the heat and mass transfer characteristics, but also the power generation characteristics of a polymer electrolyte membrane fuel cell (PEMFC) with a thin polymer electrolyte membrane (PEM) and thin gas diffusion layer (GDL) operated at higher temperatures of 363 and 373 K. The in-plane temperature distributions on the back of the separator at the anode and cathode, which are the opposite sides to the GDL, are measured using a thermograph at various initial cell temperatures (Tinit), relative humidity (RH) levels, and supply gas flow rates. The total voltage corresponding to the load current is measured in order to evaluate the performance of the PEMFC. As a result, it is revealed that the effect of the RH on the power generation characteristics is more significant when the separator thickness decreases. It is revealed that the power generation performance obtained at high current densities decreases with the increase in Tinit with thinner separator thicknesses. According to the investigation of the in-plane temperature distribution, it is clarified that the temperature decreases at corner positions in the separator with the separator thickness of 2.0 mm, while the temperature gradually increases along with the gas flow with separator thicknesses of 1.5 mm and 1.0 mm.

There is a strong interest in the development of high-temperature electrical machines, both from academic research and industrial consumers. Conventional electrical machines cannot operate much beyond 250°C, and this limits their application in certain sectors such as oil, gas, and aerospace. The key technology for high-temperature operation is high-temperature wire insulation systems for the motor windings. This study presents an experimental study on the temperature dependence of the wire insulation resistance of a standard Class H (180°C) enamel wire, a high-temperature MAGNETEMP CA-200 wire, a photonis glass-coated wire, a mica-taped VonRoll SK650 wire, a ceramic-based CERAFIL500 wire, and a newly developed S-2 glass-fibre insulated wire. The results show that motor operation above ∼300°C for any length of time using conventional polymer-based wire is difficult. It is possible, however, to operate motors up to 600°C using inorganic insulation coatings. The new wire using the S-2 glass-fibre insulation performed very well showing good insulation resistance up to 600°C: excellent flexibility and robustness, capable of very small bend diameters, and with packing factors almost identical to the conventional copper wire.

There is a strong interest in the development of high-temperature electrical machines, both from academic research and industrial consumers. Conventional electrical machines cannot operate much beyond 250°C, and this limits their application in certain sectors such as oil, gas, and aerospace. The key technology for high-temperature operation is high-temperature wire insulation systems for the motor windings. This study presents an experimental study on the temperature dependence of the wire insulation resistance of a standard Class H (180°C) enamel wire, a high-temperature MAGNETEMP CA-200 wire, a photonis glass-coated wire, a mica-taped VonRoll SK650 wire, a ceramic-based CERAFIL500 wire, and a newly developed S-2 glass-fibre insulated wire. The results show that motor operation above ∼300°C for any length of time using conventional polymer-based wire is difficult. It is possible, however, to operate motors up to 600°C using inorganic insulation coatings. The new wire using the S-2 glass-fibre insulation performed very well showing good insulation resistance up to 600°C: excellent flexibility and robustness, capable of very small bend diameters, and with packing factors almost identical to the conventional copper wire. [ABSTRACT FROM AUTHOR]

This paper presents a Time‐to‐Digital Converter (TDC)‐based all‐digital temperature sensor with small inaccuracy even at wide temperature range. The proposed sensor utilized CMOS inverters show different temperature characteristics to embed an oscillator that previous sensors have used as external component. Moreover, the temperature characteristic of a diode is used to improve the temperature inaccuracy. The sensor in 180‐nm CMOS process tested from −40°C to 200°C shows −2.56°C to +2.84°C inaccuracy. [ABSTRACT FROM AUTHOR]

The device characteristics of semiconductor lasers have been improved with progress in active layer structures. Carrier confinement dimension plays an important role especially in temperature sensitivity as well as slope efficiency. Three-dimensional carrier confinement to nano-scale semiconductor crystal, known as “quantum dots (QDs)” had been predicted to show ultimately superior device performances. Self-assembly formed InAs QDs grown on GaAs had been intensively promoted in order to achieve QD lasers with superior device performances. Now high-density, high-optical quality QDs have been realized through improved molecular beam epitaxy growths and QD lasers with better temperature characteristics are in the stage of mass-production for a data-com market. Fabry–Perot type, as well as distributed feedback type QD lasers show quite improved laser characteristics. Also, the unique device characteristics of QD lasers opened new application fields such as the use for resource searching by utilizing high-temperature operation such as lasing at higher than 200 °C. For silicon-photonics, QD lasers are used as an optical source for athermal operation. In this paper, the evolution of QDs, as well as improved device performances for novel application fields are discussed. [ABSTRACT FROM PUBLISHER]

Conversion electron Mössbauer spectroscopy (CEMS) is a surface-sensitive technique because of the shallowness of the escape depth of conversion electrons. The proportional counter with the sample built-in is usually used for CEMS with a flow of He mixed with a quenching gas. This flow-type proportional counter with a mixed gas, however, is not suited to high-temperature measurements. For high-temperature operation, we fabricated a sealed-off proportional counter operated above 850 K for CEMS, which is filled with pure He at a pressure of 1-8 × 10 Pa. The distribution of the output pulse voltage revealed an inflection point suggesting that two multiplication mechanisms are operative. The multiplication factor of the proportional counter was estimated to be about 10-10. By means of the fabricated proportional counter, we investigated the magnetic phase transition of FeO, whose Curie temperature is 858 K. We successfully observed the ferromagnetic-paramagnetic phase transition without the reduction of the sample. [ABSTRACT FROM AUTHOR]

Novel 3-kV 4H-SiC reverse blocking (RB) metal–oxide–semiconductor field-effect transistors (MOSFETs) have been demonstrated for high-voltage bidirectional switching applications. To achieve RB capability, a series Schottky barrier diode structure was introduced onto the backside of the 4H-SiC MOSFET. The developed SiC RB MOSFET exhibits bidirectional blocking voltage over 3 kV and a differential specific on-resistance of 20 \textm\Omega ~\cdot cm2 at room temperature. In an inductive-load switching measurement, the RB MOSFET showed good turn-ON/-OFF characteristics at 1 kV. The bidirectional switch configured by the developed RB MOSFETs exhibited lower ON-state power loss than the series connection of the standard SiC MOSFETs at wide range of temperature and operation current, demonstrating the advantage of the SiC RB MOSFET as a high-performance bidirectional switch. [ABSTRACT FROM PUBLISHER]

This paper analyses the effect of employing an Si on semi-insulating SiC (Si/SiC) device architecture for the implementation of 600-V LDMOSFETs using junction isolation and dielectric isolation reduced surface electric field technologies for high-temperature operations up to 300 °C. Simulations are carried out for two Si/SiC transistors designed with either PN or silicon-on-insulator (SOI) and their equivalent structures employing bulk-Si or SOI substrates. Through comparisons, it is shown that the Si/SiC devices have the potential to operate with an off-state leakage current as low as the SOI device. However, the low-side resistance of the SOI LDMOSFET is smaller in value and less sensitive to temperature, outperforming both Si/SiC devices. Conversely, under high-side configurations, the Si/SiC transistors have resistances lower than that of the SOI at high substrate bias, and invariablewith substrate potential up to −200 V, which behaves similar to the bulk-Si LDMOS at 300 K. Furthermore, the thermal advantage of the Si/SiC over other structures is demonstrated by using a rectanglepower pulse setup in TechnologyComputer-Aided Design simulations. [ABSTRACT FROM PUBLISHER]

AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs) have become a promising candidate for use in efficient power conversion applications. In order to realize converter circuit control function and overcurrent protection of device itself, we have designed, fabricated, and experimentallymeasured the Au-free AlGaN/GaN MIS-HEMTs with embedded current sensing structure. A floating ohmic current sensing electrode is inserted between source and gate electrode of which the sensing voltage signal can represent the drain current. We have achieved stable current sensing ratios at various operating conditions including quasi-static, transient state, and under high temperature. The proposed structure is highly useful in monolithic power integrated circuit on CMOS-compatible AlGaN/GaN technologies. [ABSTRACT FROM PUBLISHER]

The application of current polymer lithium-ion batteries is still challenged with the limited electrochemical performance and thermal stability of polymeric electrolyte membranes as battery separators. In this report, an efficient route to polymeric polyvinylidene fluoride-hexafluoropropylene electrolyte membranes with interparticle chain microstructure is presented. The structure is capable of hosting sufficient electrolyte for efficient migration of electrolyte salts. The electrolyte uptake ratio is up to 188.4% and the highest ionic conductivity reaches 1.08 mS cm−1 at room temperature. In particular, the membrane exhibits higher thermal resistance compared with traditional separators, only giving rise to a subtle shrinkage at 175 °C and allows for efficient battery operation for a record number of charge/discharge cycles at 110 °C. The electrolyte membrane through such a single-step method shows promising application potentials in electric vehicles and wearable electronics, especially in extreme operation conditions. [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration membranes have been prepared from poly(ether-ether-ketone) (PEEK) by phase inversion. Remarkably, these membranes undergo negligible ageing, even under extreme conditions of high temperature air annealing, and high temperature solute filtration with aggressive solvents. This negligible ageing of PEEK membranes is contrasted with substantial ageing of crosslinked polybenzimidazole (PBI) and polyimide (PI) membranes. After air annealing at 120 °C, PBI and PI membranes become brittle and lose all permeance, whereas PEEK membranes remain flexible and retain a constant permeance of ~0.2 L h −1 m −2 bar −1 for tetrahydrofuran (THF). The structural change in PBI and PI membranes is attributed to polymer transition from a non-equilibrium glassy state towards an equilibrium state at which chain packing precludes permeation of solvent. High temperature filtrations in DMF up to 140 °C for the three polymeric membranes showed PEEK performance to be stable and consistent with negligible ageing, whereas PBI and PI rapidly loose stability. [ABSTRACT FROM AUTHOR]

Temperature-dependent threshold voltage (Vth) stability is a significant issue in the practical application of semi-conductor power devices, especially when they are undergoing a repeated high-temperature operation condition. The Vth analytical model and its stability are dependent on high-temperature operations in wide-bandgap gallium nitride (GaN)-based high electron mobility transistor (HEMT) devices that were investigated in this work. The temperature effects on the physical parameters—such as barrier height, conduction band, and polarization charge—were analysed to understand the mechanism of Vth stability. The Vth analytical model under high-temperature operation was then proposed and developed to study the measurement temperatures and repeated rounds dependent on Vth stability. The validity of the model was verified by comparing the theoretical calculation data with the experimental measurement and technology computer-aided design (TCAD) simulation results. This work provides an effective theoretical reference on the Vth stability of power devices in practical, high-temperature applications.

These days, the demand on electronic systems operating at high temperature is increasing owing to bursting interest in applications adaptable to harsh environments on earth, as well as in the unpaved spaces in the universe. However, research on memory technologies suitable to high-temperature conditions have been seldom reported yet. In this work, a novel one-transistor dynamic random-access memory (1T DRAM) featuring the device channel with partially inserted wide-bandgap semiconductor material toward the high-temperature application is proposed and designed, and its device performances are investigated with an emphasis at 500 K. The possibilities of the program operation by impact ionization and the erase operation via drift conduction by a properly high drain voltage have been verified through a series of technology computer-aided design (TCAD) device simulations at 500 K. Analyses of the energy-band structures in the hold state reveals that the electrons stored in the channel can be effectively confined and retained by the surrounding thin wide-bandgap semiconductor barriers. Additionally, for more realistic and practical claims, transient characteristics of the proposed volatile memory device have been closely investigated quantifying the programming window and retention time. Although there is an inevitable degradation in state-1/state-0 current ratio compared with the case of room-temperature operation, the high-temperature operation capabilities of the proposed memory device at 500 K have been confirmed to fall into the regime permissible for practical use.

This work reports on the modification of electrical properties of amorphous vanadium oxide (a-VO x) thin film thermistor by growth temperature and its effects on the performances of a cooler-free microbolometer. The a-VO x thin films have been deposited by pulsed DC sputtering processes under various growth temperatures from 160 to 230 ℃. The sheet resistance of the samples at room temperature decreases from 330 to 70 kΩ/▢ with increasing growth temperature. This is due to the increase of oxygen vacancies at higher growth temperature, which have been confirmed by XPS analysis. Temperature dependence of resistance of a-VO x films shows non-hysteresis behaviors up to 120 ℃, which in turn shows clear activation energies. The activation energy of a-VO x films also decreases from 0.190 to 0.145 eV with increasing growth temperature, which confirms the decrease of temperature coefficient of resistance (TCR) from 2.80 to 2.44 (-%/K) at 25 ℃ and from 1.48 to 1.14 (-%/K) even at 120 ℃. The responsivities of fabricated microbolometers based on the a-VO x thin film thermistors have been measured from 3.04 × 103 to 1.14 × 103 V/W at room temperature and from 9.54 × 102 to 3.02 × 102 V/W even at 120 ℃ with increasing growth temperature. • Amorphous VO x thin film thermistors are deposited with pulsed DC sputtering at varying T gr from 160 to 230 °C. • R sh of a-VO x decreases from 330 to 70 kΩ/□ with increasing T gr due to the increase of oxygen vacancies. • The thermistors show non-hysteresis transitions with a higher than -1 %/K of TCR at high ambient temperatures of 120 °C. • Microbolometers based on a-VO x show Rv of 3.04 × 103 V/W and τ of 1.03 ms at RT, and 9.54 × 102 V/W and 1.31 ms at 120 °C. [ABSTRACT FROM AUTHOR]

This letter demonstrates quasi- and fully vertical GaN-on-Si pn diodes with record performance. The optimized device structure employs a highly conductive ( \textN\mathrm { {D}}> 10^{\mathrm { {20}}} cm ^\mathrm -3 ) current collecting layer and a lightly carbon-doped drift layer. With this optimization, a differential specific on -resistance ( {R} _{ {\mathrm{ ON}}} ) of 0.8–1 \text{m}\Omega \cdot cm ^\mathrm 2 , a breakdown voltage (BV) over 500 V, and a high forward current (~kA/cm ^\mathrm 2 ) were demonstrated. Excellent R \mathrm{ ON} and BV performance up to 300 °C were also obtained. A small reverse recovery time of 50 ns was demonstrated under switching conditions. With Baliga’s figure of merit over 0.32 GW/cm ^\mathrm 2 , these devices show the great potential of low-cost GaN-on-Si vertical devices for future power applications. [ABSTRACT FROM PUBLISHER]

This article reports on flexible hard Al-Si-N films prepared by reactive magnetron sputtering. The structure and mechanical properties of Al-Si-N films were controlled by the content of Si in the film, partial pressure of nitrogen p N2 used in sputtering and the power delivered to the magnetron. The Al-Si-N films with a low (≤ 10 at.%) Si content and with a high (≥ 20 at.%) Si content were prepared. Correlations between the structure, microstructure, mechanical properties and their thermal stability of the Al-Si-N films are analyzed in detail. Thermal stability of Al-Si-N films was assessed by thermal annealing in air and water vapor up to annealing temperature T a = 1200 °C. It is shown that (1) the increase of Si content in the Al-Si-N film leads to the change of its crystalline structure from polycrystalline to X-ray amorphous and (2) the flexible hard Al-Si-N films with high (i) hardness H ≈ 20 GPa, (ii) ratio H/E ⁎ ≥ 0.1, and (iii) elastic recovery W e ≥ 60% exhibit enhanced resistance to cracking and (3) the thermal stability of Al-Si-N films with a high (≥ 20 at.%) Si content achieves up to T a ≈ 1200 °C in air and up to T a ≈ 800 °C in water vapor; here the effective Young's modulus E ⁎ = E / (1 − ν 2 ), E is the Young's modulus and ν is the Poisson's ratio. Conditions under which the flexible hard Al-Si-N films with enhanced resistance to cracking and high thermal stability can be prepared are described in detail. [ABSTRACT FROM AUTHOR]

With an increased demand for high-power and hightemperature electronics, Ag sintering paste has been considered a promising Pb-free die-attach material candidate for these applications. Extensive research has been carried out investigating pressure and pressureless Ag sintering for die attach. In this work, passive component (chip resistor) attachment with Ag sintering was explored. Due to termination geometry differences between resistors and dies, different processing procedures and parameters were developed. For PtAu terminated resistors, the mean shear force of as-built samples on thick-film Ag metallized substrates was 90 N, but dropped to 18.6 N after 1,500 h at 300°C. Formation of a dense Ag layer near the PtAu resistor termination and a void region near the thick-film metallization was observed in cross sections after 1,000 h at 300°C. For PdAg terminated resistors with a plated Ni/Au finish, the initial shear force results were low due to Ag diffusion along Au metallization surface. For PdAg terminated resistors with Ag thick-film substrates, the initial shear force was ~60 N and remained in the range of 50-70 N during aging at 300°C for 1,500 h. A new thick-film metallization (Au + Ag) was developed to enable the use of thick-film Au interconnect metallization. [ABSTRACT FROM AUTHOR]

This paper presents the design and optimization of a 600 V silicon-on-silicon carbide (Si/SiC) laterally diffused MOSFET with linear doping profile in the drift region for high-temperature applications. The proposed structure has an embedded silicon-on-insulator (SOI) layout through which the traditional graded doping theory for SOI can be applied in the Si/SiC architecture. An SOI counterpart is introduced as a benchmark and modeled alongside the proposed structure. Comparisons between them show that they have the near-identical OFF-state and breakdown characteristics, with a significant tunneling leakage component emerging above 450 V. In the ON state, the Si/SiC device has higher electrical resistance but much lower thermal resistance, leading to less self-heating and higher reliability. [ABSTRACT FROM AUTHOR]

Quantum dot infrared photodetectors (QDIPs) are receiving attention as next generation infrared photodetectors that offer high‐sensitivity and high‐temperature operation. The realisation of QDIPs on silicon (Si) substrates offer further great advantages in terms of cost reduction and higher‐resolution focal plane arrays. Indium arsenide/gallium arsenide QDIPs grown directly on on‐axis Si (100) substrates are demonstrated. These are expected to further reduce fabrication costs by utilising both the monolithic integration of QDIPs with Si readout integrated circuits and also the bare substrate cost (compared with offcut Si substrates). In the device, the peak detectivity at a temperature of 32 K is measured to be 5.8 × 107 cm Hz1/2/W of 6.2 μm at a bias 0.6 V, with a corresponding responsivity of 27 mA/W. This result indicates that QD structures directly grown on on‐axis Si substrates are very promising for the realisation of high‐performance QDIPs with low fabrication cost. [ABSTRACT FROM AUTHOR]

Data centers have attracted increasing attention worldwide over the last decades due to their high energy consumption. Cooling accounts for about 30–40% of the total energy consumption of data centers. High-temperature data centers could save large amounts of cooling energy by changing their cooling mechanism. More effective use of "free cooling" is the basic and effective means for high-temperature data centers to reduce cooling energy consumption. It is possible to build chiller-less or even chiller-free data centers. They require less capital investment for cooling and allow more hours of "free cooling". However, a few essential concerns need to be addressed before the wide application of high-temperature data centers, particularly the technical bottlenecks and the reliability and performance of servers and IT equipment. Though many reviews on data centers exist in the existing research, a systematic review of high-temperature data centers, particularly on the above essential concerns, is still unavailable. This paper is intended to fill in these gaps and provide a comprehensive review of these critical aspects. The main benefits and the major bottlenecks for implementing high-temperature data centers as well as the existing efforts and latest technologies to tackle the bottlenecks are categorized and analyzed systematically. In addition, a through review of the main temperature-sensitive IT components (e.g., hard disk drives and CPU) is done, and their current states and potential solutions are analyzed. Finally, the paper elaborates on future perspectives for the development and applications of the high-temperature data center. [Display omitted] • A comprehensive review of high-temperature data center development is done. • Bottlenecks and benefits for implementing high-temperature data centers are analyzed. • Existing efforts and latest technologies to tackle the bottlenecks are analyzed. • A review of temperature-sensitive IT components & technology development is given. • Future perspectives for high-temperature data center development are elaborated. [ABSTRACT FROM AUTHOR]

First-ever 28 nm embedded split-gate MONOS (SG-MONOS) flash macros have been developed to increase memory capacity embedded in micro controller units and to improve performance over wide junction temperature range from -40^\circ\ C to 170^\circ\ C as demanded strongly in automotive uses. Much attention has been paid to the degradation of the reliability characteristics along with the process shrinkage. Temperature-adjusted word-line overdrive scheme improves random read access frequency by 15% and realizes both of 6.4 GB/s read throughput by 200 MHz no-wait random access of code flash macros and more than ten times longer TDDB lifetime of WL drivers. Temperature-adaptive step pulse erase control (TASPEC) improves the TDDB lifetime of dielectric films between metal interconnect layers by three times. TASPEC is particularly useful for a data flash macro with one million rewrite cycles. Source-side injection (SSI) program with negative back-bias voltage achieves 63% reduction of program pulse time and, consequently, realizes 2.0 MB/s write throughput of code flash macros. A spread spectrum clock generation and a clock phase shift technique are introduced for charge pump clock generation in order to suppress EMI noise due to high write throughput of code flash macros, and peak power of EMI noise is reduced by 19 dB. [ABSTRACT FROM PUBLISHER]

To achieve high-temperature operation of all-solid lithium batteries (ASLBs), LATP (Li 1.3 Al 0.3 Ti 1.7 (PO 3) 4) was coated on the surface of a high-nickel cathode material, NCM-811 powder (LiNi 0.8 Co 0.1 Mn 0.1 O 2), by evaporation-induced self-assembly (EISA). Using EISA, the fine LATP precursor in ethanol was deposited on NCM-811 powder at loadings of 0.1–3 wt%, after which the precursor was dried and calcined at 750 °C. Although the X-ray diffraction (XRD) patterns of the coated samples were not significantly changed, the main peaks of NCM-811 were slightly shifted to lower angle by increasing LATP amount on NCM-811. Therefore, due to cation mixing in LATP-coated NCM-811, the lattice constant increased slightly, accompanied by a decrease in the factor c/3a. Transmission electron microscopy (TEM) showed that the thickness of the coating was 2, 5, and 8 nm for 0.5 wt%-, 1 wt%-, and 3 wt%-LATP-coated NCM-811, respectively. The LATP-coated NCM-811 samples were utilized as the active material in the composite cathode for ASLBs. The electrochemical behavior of single cells (LATP-coated NCM//composite solid electrolyte sheets//lithium metal) was evaluated at 70 °C. The cycle capacity retention was higher for the cell employing the cathode with 0.5 wt%-LATP-coated NCM-811 than for the other cells, with an initial discharge capacity of 138 mAh g−1 in the range of 3.0–4.1 V and capacity retention of 85% over 45 cycles. Moreover, the cycle retention of the cell was significantly improved compared with the electrochemical behavior of the existing ASLBs in which the cathode is prepared by simply mixing LATP powder with polyethylene oxide/salt and NCM-811 powder. • LATP was coated on the surface of NCM-811 powder by evaporation-induced self-assembly. • Effect of LATP content (0.1–3 wt%) on NCM-811 was investigated for ASLBs. • 0.5 wt% LATP coated NCM-811 enhanced cycle characteristics under high-temperature operation at 70 °C. [ABSTRACT FROM AUTHOR]

The fabrication and performance of a sintered Peltier cooler (SPC) based on bismuth telluride with sintered silver interconnects are described. Miniature SPC modules with a footprint of 20 mm were assembled using pick-and-place pressure-assisted silver sintering at low pressure (5.5 N/mm) and moderate temperature (250°C to 270°C). A modified flip-chip bonder combined with screen/stencil printing for paste transfer was used for the pick-and-place process, enabling high positioning accuracy, easy handling of the tiny bismuth telluride pellets, and immediate visual process control. A specific contact resistance of (1.4 ± 0.1) × 10 Ω cm was found, which is in the range of values reported for high-temperature solder interconnects of bismuth telluride pellets. The realized SPCs were evaluated from room temperature to 300°C, considerably outperforming the operating temperature range of standard commercial Peltier coolers. Temperature cycling capability was investigated from 100°C to 235°C over more than 200 h, i.e., 850 cycles, during which no degradation of module resistance or cooling performance occurred. [ABSTRACT FROM AUTHOR]

First-ever 40-nm embedded split-gate MONOS (SG-MONOS) flash macros for automotive micro-controller unit (MCU) have been successfully developed. A SG-MONOS cell realizes high performance with low power consumption and intrinsically high data reliability thanks to the combination of split-gate and charge-trapping structure. In addition, newly developed circuit techniques greatly enhance the advantages of SG-MONOS cells and enable fast and reliable operations even at the junction temperature (Tj) of 170 ^\circC with small peripheral circuit area; 1) a sense amplifier with digital offset cancellation (SA-DOC) provides fast read operation over 160 MHz; 2) adaptable program current control scheme (APCCS) and intelligent erase scheme (IES) significantly decrease the program and erase time, which also results in improving the memory cells' reliability; and, 3) 3-D stacked unit capacitors achieve area-efficient charge pump. Two types of embedded flash (eFlash) macros with these technologies, code macro of 2 MB and data macro of 64 KB, were fabricated in a 40-nm eFlash process. The code macro demonstrates the capability of 160-MHz random read operation at Tj=\ 170 ^\circC, reaching 5.1 GB/s read throughput by simultaneous 256 bits read-out from two code macros. The data macro achieves the program/erase endurance over 10 million cycles at Tj=\ 170 ^\circC without any software-assisted techniques. [ABSTRACT FROM PUBLISHER]

A hermetic multichip power package for silicon carbide devices that will operate at 200^\circC ambient and switch 50–100 A has been developed. The Al2O3/MoCu structure, in which the SiC junction field-effect transistors and diodes are attached, was designed to hermetically seal the device areas. Details of the materials and processes used to fabricate the package are discussed. Die attach, ribbon bonding, and lid attach, as well as thermal modeling, electrical testing, and thermal cycling results are also described. [ABSTRACT FROM PUBLISHER]

We report on the first demonstration of long-pulse (milliseconds) operation of aluminum-free active-region 8xx-nm diode laser bar at heat-sink temperature of 180 °C. This is, to the best of our knowledge, the highest published operating temperature for a long-pulse 8xx-nm laser bar with Al-free active region. The laser bars have very robust performance at 130 °C without any active cooling. At this high temperature, the laser bars provide both high peak power (60 W at 100 A) and good pulse shape for tens of milliseconds pulse width, maintaining high energy per pulse. The dependence of laser output pulse shape on the pulse width and pump current is experimentally investigated at 130 °C. We find that the transient output power of the laser bar follows P(t) = A exp(−t /t_0) + Bt + C, where A, B, C, and t _0 are fitting parameters that are pulse width and current dependent. We have also investigated the transient thermal behavior of the laser bar at high temperature and high pump current. [ABSTRACT FROM PUBLISHER]

Abstract: New Pt/C cathodes with many reaction sites for the oxygen reduction reaction as well as high tolerance to Pt corrosion have been designed for high-temperature proton exchange membrane fuel cells (PEMFCs), wherein a composite mixture of Sn0.9In0.1P2O7 (SIPO) and sulfonated polystyrene-b-poly(ethylene/butylene)-b-polystyrene (sSEBS) functioned as an ionomer. The microstructure of the Pt-SIPO-sSEBS/C cathode was characterized by homogeneous distribution of the ionomer over the catalyst layer and close contact between the ionomer and the Pt/C powder. As a result, the activation and concentration overpotentials of the Pt-SIPO-sSEBS/C cathode between 100 and 200°C were lower than those of an H3PO4-impregnated Pt/C cathode, which suggests that the present ionomer can avoid poisoning of Pt by phosphate anions and the limitation of gas diffusion through the catalyst layer. Moreover, agglomeration of Pt in the Pt-SIPO-sSEBS/C cathode was not observed during a durability test at 150°C for 6 days, although it was significant in the Pt-H3PO4/C cathode. Therefore, it is concluded that the Pt-SIPO-sSEBS/C electrode is a very promising cathode candidate for high-temperature PEMFCs. [Copyright &y& Elsevier]

Abstract: An anhydrous proton conductor, Sn0.95Al0.05P2O7 (SAPO), composed of polystyrene-b-poly(ethylene/propylene)-b-polystyrene (SEPS), was developed and characterized using morphological, structural, and electrochemical analyses. In the composite membrane with 20wt% SEPS, a homogeneous distribution of SAPO particles in the matrix was obtained in the thickness range of 65–90μm, yielding a proton conductivity of 3.4×10−3 Scm−1 at 200°C, tensile strength of 4.6MPa and an elongation at break of 711.0% at room temperature. Fuel cell tests verified that the open-circuit voltage was maintained at a constant value of approximately 1V between 100 and 250°C. The peak power densities achieved with unhumidified H2 and air were 77.0mWcm−2 at 100°C, 121.0mWcm−2 at 150°C, and 163.1mWcm−2 at 225°C. [Copyright &y& Elsevier]

Abstract: The thermal design of weatherproof power supply system has been evaluated by experiments and simulation. Nickel-metal hydride batteries developed for stationary use were employed in the system due to their high charge/discharge performance in high-temperature environments. As the weatherproof power supply system has a sealed cabinet, we evaluated the temperature characteristics of the battery in a 40°C environment. In order to predict the temperature of the power system, it was necessary to obtain the rate of heat generation from the battery. For this purpose, we developed an estimation method in which the measured temperature of the battery is approximated as a function of cubic spline interpolation. The temperatures of critical items mounted in the system were calculated on the basis of the experimental results. This paper describes the procedure for estimating the heat generation rate of the battery and the temperature of the system. Our results show that the weatherproof power system is useful for operation in high-temperature environments. [Copyright &y& Elsevier]

A comprehensive physical model for the analysis, characterization, and design of 4H-silicon carbide (SiC) MOSFETs has been developed. The model has been verified for an extensive range of bias conditions and temperatures. It incorporates details of interface trap densities, Coulombic interface trap scattering, surface roughness scattering, phonon scattering, velocity saturation, and their dependences on bias and temperature. The physics-based models were implemented into our device simulator that is tailored for 4H-SiC MOSFET analysis. By using a methodology of numerical modeling, simulation, and close correlation with experimental data, values for various physical parameters governing the operation of 4H-SiC MOSFETs, including the temperature-dependent interface trap density of states, the root-mean-square height and correlation length of the surface roughness, and the electron saturation velocity in the channel and its dependence on temperature, have been extracted. Coulomb scattering and surface roughness scattering limit surface mobility for a wide range of temperatures in the subthreshold and linear regions of device operation, whereas the saturation velocity and the high-field mobility limit current in the saturation region. [ABSTRACT FROM AUTHOR]

Abstract: The high-temperature operation of a GaN MOSFET is reported. The MOSFETs were operated up to 250°C, best reported to date. The MOSFETs showed good dc characteristics with field-effect mobilities of 138cm2/Vs and 133cm2/Vs at room temperature and 250°C, respectively. The field-effect mobility, threshold voltage, and sub-threshold slope did not changed significantly up to 250°C. Also, we compared the activation annealing condition for n+ layer fabrication. A high-temperature annealing condition of 1300°C led to a low contact resistance, but caused slight degradation of the field-effect mobility compared with the 1100°C annealing condition. [Copyright &y& Elsevier]

Abstract: A double gate normally-off silicon carbide (SiC) trench junction field effect transistors (JFET) design is considered. Innovative migration enhanced embedded epitaxial (ME3) growth process was developed to replace the implantation process and realize high device performance. Strong anisotropic behavior in electrical characteristics of the pn junction fabricated on (11−20) and (1−100) trench a-planes was observed, although quality of the pn diodes was found to be independent of trench plane orientations. Fabricated normally-off trench 4H-SiC JFET demonstrates the potential for lower specific on-resistance (R onS) in the range of 5–10mΩcm2 (1200V class). A relative high T −2.6 dependence of R onS is observed. A breakdown voltage of 400V in the avalanche mode was confirmed at zero gate bias conditions for cell design without edge termination. It was demonstrated that the normally-off JFETs are suitable for high temperature applications. Average temperature coefficient of threshold voltage (V th) was calculated as −1.8mV/°C, which is close to the MOS based Si power devices. [Copyright &y& Elsevier]

Abstract: Steady-state and transient characteristics of packaged 6-kV 4H-SiC junction diodes have been investigated in the temperature range T =300–773K. Analysis of the forward current–voltage characteristics and reverse current recovery waveforms shows that the lifetime τ of non-equilibrium carriers steadily increases with temperature across the entire temperature interval. The rise in τ and decrease in carrier mobilities and diffusion coefficients with increasing temperature nearly compensate each other as regards their effect on the differential resistance of the diode, R d. As a result, R d is virtually temperature independent. The bulk reverse current is governed by carrier generation in the space-charge region via a trap with activation energy of 1.62eV. The surface leakage current of packaged structures does not exceed 2×10−6 A at T =773K and a reverse bias of 300V. [Copyright &y& Elsevier]

Chemical-looping combustion is the indirect combustion by use of solid medium. This combustion with circulation of solid particles was investigated experimentally. There were two reactors: a reduction column and an oxidation column. The slurry of solid powder of NiO mixed with Al2O3 prepared by a dissolution method was fed into a spray dryer, and a spherical particle of diameter about 97 μm was obtained. The rates of both reduction and oxidation for the produced fine particles were measured in advance by a thermogravimetric analyzer.Then reactions with circulation of reacting solid particles were performed at elevated temperatures. In this paper, the results at 1200 °C by use of hydrogen as fuel are presented. The features of the reactions are discussed based on the analyses of the composition of the exhaust gas. Examination of the surface of the solid particles by a scanning microscope revealed that the condition of the solid particle in both reduction and oxidation columns was much milder than that in the TGA experiment, and significant change of the particle was not observed. [Copyright &y& Elsevier]