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1. High-current, high-voltage AlN Schottky barrier diodes

   https://doi.org/10.35848/1882-0786/ad81c9  

   Quiñones, C_E; Khachariya, D.; Reddy, P.; Mita, S.; Almeter, J.; Bagheri, P.; Rathkanthiwar, S.; Kirste, R.; Pavlidis, S.; Kohn, E.; et al (October 2024, Applied Physics Express)

   AlN Schottky barrier diodes with low ideality factor (<1.2), low differential ON-resistance (<0.6 mΩ cm²), high current density (>5 kA cm⁻²), and high breakdown voltage (680 V) are reported. The device structure consisted of a two-layer, quasi-vertical design with a lightly doped AlN drift layer and a highly doped Al_0.75Ga_0.25N ohmic contact layer grown on AlN substrates. A combination of simulation, current–voltage measurements, and impedance spectroscopy analysis revealed that the AlN/AlGaN interface introduces a parasitic electron barrier due to the conduction band offset between the two materials. This barrier was found to limit the forward current in fabricated diodes. Further, we show that introducing a compositionally-graded layer between the AlN and the AlGaN reduces the interfacial barrier and increases the forward current density of fabricated diodes by a factor of 10⁴. 

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2. Low Thermal Conductivity and Diffusivity at High Temperatures Using Stable High‐Entropy Spinel Oxide Nanoparticles

   https://doi.org/10.1002/adma.202406732  

   Chung, Ka_Man; Adapa, Sarath_R; Pei, Yu; Yeerella, Ram_Hemanth; Chen, Li; Shivakumar, Sashank; Huang, Wei; Liu, Zhaowei; Cai, Shengqiang; Luo, Jian; et al (December 2024, Advanced Materials)

   Abstract The realization of low thermal conductivity at high temperatures (0.11 W m⁻¹K⁻¹800 °C) in ambient air in a porous solid thermal insulation material, using stable packed nanoparticles of high‐entropy spinel oxide with 8 cations (HESO‐8 NPs) with a relatively high packing density of ≈50%, is reported. The high‐density HESO‐8 NP pellets possess around 1000‐fold lower thermal diffusivity than that of air, resulting in much slower heat propagation when subjected to a transient heat flux. The low thermal conductivity and diffusivity are realized by suppressing all three modes of heat transfer, namely solid conduction, gas conduction, and thermal radiation, via stable nanoconstriction and infrared‐absorbing nature of the HESO‐8 NPs, which are enabled by remarkable microstructural stability against coarsening at high temperatures due to the high entropy. This work can elucidate the design of the next‐generation high‐temperature thermal insulation materials using high‐entropy ceramic nanostructures. 

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3. High operating temperature plasmonic infrared detectors

   https://doi.org/10.1063/5.0077456  

   Nordin, L.; Muhowski, A. J.; Wasserman, D. (March 2022, Applied Physics Letters)

   III–V semiconductor type-II superlattices (T2SLs) are a promising material system with the potential to significantly reduce the dark current of, and thus realize high-performance in, infrared photodetectors at elevated temperatures. However, T2SLs have struggled to meet the performance metrics set by the long-standing infrared detector material of choice, HgCdTe. Recently, epitaxial plasmonic detector architectures have demonstrated T2SL detector performance comparable to HgCdTe in the 77–195 K temperature range. Here, we demonstrate a high operating temperature plasmonic T2SL detector architecture with high-performance operation at temperatures accessible with two-stage thermoelectric coolers. Specifically, we demonstrate long-wave infrared plasmonic detectors operating at temperatures as high as 230 K while maintaining dark currents below the “Rule 07” heuristic. At a detector operating temperature of 230 K, we realize 22.8% external quantum efficiency in a detector absorber only 372 nm thick ([Formula: see text]) with a peak specific detectivity of 2.29 × 10⁹cm Hz^1∕2W⁻¹at 9.6  μm, well above commercial detectors at the same operating temperature. 

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4. Novel Zwitterionic Polyurethane‐in‐Salt Electrolytes with High Ion Conductivity, Elasticity, and Adhesion for High‐Performance Solid‐State Lithium Metal Batteries

   https://doi.org/10.1002/aenm.202405676  

   Wang, Kun; Koverga, Volodymyr; Maslekar, Namrata; Wu, Fukang; Kuphl, Robert; Lyu, Xingyi; Deshpande, Piyush; Guo, Hanzeng; Seol, Hyang; Degraff, Wade; et al (May 2025, Advanced Energy Materials)

   Abstract This study presents a novel polymer‐in‐salt (PIS) zwitterionic polyurethane‐based solid polymer electrolyte (zPU‐SPE) that offers high ionic conductivity, strong interaction with electrodes, and excellent mechanical and electrochemical stabilities, making it promising for high‐performance all solid‐state lithium batteries (ASSLBs). The zPU‐SPE exhibits remarkable lithium‐ion (Li⁺) conductivity (3.7 × 10⁻⁴ S cm⁻¹at 25 °C), enabled by exceptionally high salt loading of up to 90 wt.% (12.6 molar ratio of Li salt to polymer unit) without phase separation. It addresses the limitations of conventional SPEs by combining high ionic conductivity with a Li⁺transference number of 0.44, achieved through the incorporation of zwitterionic groups that enhance ion dissociation and transport. The high surface energy (338.4 J m⁻²) and elasticity ensure excellent adhesion to Li anodes, reducing interfacial resistance and ensuring uniform Li⁺flux. When tested in Li||zPU||LiFePO₄ and Li||zPU||S/C cells, the zPU‐SPE demonstrated remarkable cycling stability, retaining 76% capacity after 2000 cycles with the LiFePO₄cathode, and achieving 84% capacity retention after 300 cycles with the S/C cathode. Molecular simulations and a range of experimental characterizations confirm the superior structural organization of the zPU matrix, contributing to its outstanding electrochemical performance. The findings strongly suggest that zPU‐SPE is a promising candidate for next‐generation ASSLBs. 

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5. A New Polystyrene–Poly(vinylpyridinium) Ionic Copolymer Dopant for n‐Type All‐Polymer Thermoelectrics with High and Stable Conductivity Relative to the Seebeck Coefficient giving High Power Factor

   https://doi.org/10.1002/adma.202201062  

   Han, Jinfeng; Tiernan, Emma; Lee, Taein; Chiu, Arlene; McGuiggan, Patty; Adams, Nicholas; Tomko, John_A; Hopkins, Patrick_E; Thon, Susanna_M; Tovar, John_D; et al (May 2022, Advanced Materials)

   Abstract A novel n‐type copolymer dopant polystyrene–poly(4‐vinyl‐N‐hexylpyridinium fluoride) (PSpF) with fluoride anions is designed and synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. This is thought to be the first polymeric fluoride dopant. Electrical conductivity of 4.2 S cm^–1and high power factor of 67 µW m^–1K^–2are achieved for PSpF‐doped polymer films, with a corresponding decrease in thermal conductivity as the PSpF concentration is increased, giving the highest ZT of 0.1. An especially high electrical conductivity of 58 S cm^–1at 88 °C and outstanding thermal stability are recorded. Further, organic transistors of PSpF‐doped thin films exhibit high electron mobility and Hall mobility of 0.86 and 1.70 cm²V^–1s^–1, respectively. The results suggest that polystyrene–poly(vinylpyridinium) salt copolymers with fluoride anions are promising for high‐performance n‐type all‐polymer thermoelectrics. This work provides a new way to realize organic thermoelectrics with high conductivity relative to the Seebeck coefficient, high power factor, thermal stability, and broad processing window. 

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