Rapid inactivation of human respiratory RNA viruses by deep ultraviolet irradiation from light-emitting diodes on a high-temperatureannealed AlN/Sapphire template

Efficient and eco-friendly disinfection of air-borne human respiratory RNA viruses is pursued in both public environment and portable usage.The AlGaN-based deep ultraviolet(DUV)light-emission diode(LED)has high practical potentials because of its advantages of variable wavelength,rapid sterilization,environmental protection,and miniaturization.Therefore,whether the emission wavelength has effects on the disinfection as well as whether the device is feasible to sterilize various respiratory RNA viruses under portable conditions is crucial.Here,we fabricate AlGaN-based DUV LEDs with different wavelength on high-temperature-annealed(HTA)AlN/Sapphire templates and investigate the inactivation effects for several respiratory RNA viruses.The AlN/AlGaN superlattices are employed between the template and upper n-AlGaN to release the strong compressive stress(SCS),improving the crystal quality and interface roughness.DUV LEDs with the wavelength of 256,265,and 278 nm,corresponding to the light output power of 6.8,9.6,and 12.5 mW,are realized,among which the 256 nm-LED shows the most potent inactivation effect in human respiratory RNA viruses,including SARS-CoV-2,influenza A virus(IAV),and human parainfluenza virus(HPIV),at a similar light power density(LPD)of~0.8 mW/cm2 for 10 s.These results will contribute to the advanced DUV LED application of disinfecting viruses with high potency and broad spectrum in a portable and eco-friendly use.

240 nm AlGaN-based deep ultraviolet micro-LEDs:size effect versus edge effect

240 nm AlGaN-based micro-LEDs with different sizes are designed and fabricated.Then,the external quantum efficiency(EQE)and light extraction efficiency(LEE)are systematically investigated by comparing size and edge effects.Here,it is revealed that the peak optical output power increases by 81.83%with the size shrinking from 50.0 to 25.0μm.Thereinto,the LEE increases by 26.21%and the LEE enhancement mainly comes from the sidewall light extraction.Most notably,transversemagnetic(TM)mode light intensifies faster as the size shrinks due to the tilted mesa side-wall and Al reflector design.However,when it turns to 12.5μm sized micro-LEDs,the output power is lower than 25.0μm sized ones.The underlying mechanism is that even though protected by SiO2 passivation,the edge effect which leads to current leakage and Shockley-Read-Hall(SRH)recombination deteriorates rapidly with the size further shrinking.Moreover,the ratio of the p-contact area to mesa area is much lower,which deteriorates the p-type current spreading at the mesa edge.These findings show a role of thumb for the design of high efficiency micro-LEDs with wavelength below 250 nm,which will pave the way for wide applications of deep ultraviolet(DUV)micro-LEDs.

Boosting the kinetics of PF_(6)^(-) into graphitic layers for the optimal cathode of dual-ion batteries:The rehearsal of pre-intercalating Li^(+)

Large anions exhibit slow diffusion kinetics in graphite cathode of dual-ion batteries(DIBs);particularly at high current density,it suffers severely from the largely-reduced interlayer utilization of graphite cathode,which as a bottleneck limits the fast charge application of DIBs.To maximize interlayer utilization and achieve faster anion diffusion kinetics,a fast and uncrowded anion transport channel must be established.Herein,Li^(+)was pre-intercalated into the graphite paper(GP)cathode to increase the interlayer spacing,and then hosted for the PF_(6)^(-)anion storage.Combined with theoretical calculation,it shows that the local interlayer spacing enlargement and the residual Li^(+)reduce the anion intercalation energy and diffusion barrier,leading to better rate stability.The obtained GP with Li^(+)pre-intercalation(GP-Li)electrode exhibits a discharge capacity of 23.1 m Ah g^(-1) at a high current of 1300 m A g^(-1).This work provides a facile method to efficiently improve the interlayer utilization of graphite cathode at large currents.

Preface to the Special Topic on Deep Ultraviolet Light-Emitting Materials and Devices

In recent years,materials and devices operating in the ultraviolet(UV)regime have attracted significant attention and therefore experienced rapid development.On the one hand,following the thriving advancement of GaN-based blue and white LEDs,which have brought a revolution in lighting sources,various groups are expanding their research work in Al(Ga)N materials and Al(Ga)N-based UV devices with the aim to explore more potential applications in shorter wavelength regime of group III-nitrides.While on the other hand,some binary alloys such as SiC,Ga2O3,BN,etc,whose bandgaps lie in the UV region,have been accomplished for a variety of applications.The development of UV materials laid the foundation for UV devices.Nevertheless,each material has its own benefits and constraints.More efforts should be devoted to overcoming the obstacles and challenges,in order to improve the material quality and devices performance.

Switching Optimally Balanced Fe-N Interaction Enables Extremely Stable Energy Storage

The interaction between electrode materials and charge carriers is one of the central issues dominating underlying energy storage mechanisms.To address the notoriously significant volume changes accompanying intercalation or formation of alloy/compounds,we aim to introduce and utilize a weak,reversible Fe-N interaction during the(de)intercalation of ammonium ions(NH_(4)^(+))within iron(Ⅲ)hexacyanoferrate(FeHCF),inspired by manipulating the electrostatic adsorption between N and Fe in the early stages of ammonia synthesis(Bosch-Harber Process,Chemical Engineering)and steel nitriding processes(Metal Industry).Such strategy of switching well-balanced Fe-N interaction is confirmed in between the nitrogen of ammonium ions and highspin Fe in FeHCF,as observed by using X-ray absorption spectroscopy.The resulting material provided an extremely stable energy storage(58 mAh g^(-1) after 10000 cycles at current density of 1 A g^(-1))as well as high-rate performance(23.6 mAh g^(-1) at current density of 10 A g^(-1)).

Structure designing,interface engineering,and application prospects for sodium-ion inorganic solid electrolytes

All-solid Na-ion batteries(ASNIBs)present significant potential for integration into large-scale energy storage systems,capitalizing on their abundant raw materials,exemplary safety,and high energy density.Among the pivotal components propelling the advancement of ASNIBs,inorganic solid electrolytes(ISEs)have garnered substantial attention in recent years due to their high ionic conductivity(σ),wide electrochemical stability window(ESW),and high shear modulus.Herein,this review systematically encapsulates the latest strides in Na-ion ISEs,furnishing a comprehensive panorama of various ISE systems along with their interface engineering strategies against the electrodes.The prime focus resides in accentuating key strategies for refining ion conduction properties and interfacial compatibility of ISEs through structure design and interface modification.Furthermore,the review explores the foremost challenges and prospects inherent to sodium-ion ISEs,striving to deepen our understanding of how to engineer more robust and efficient ISEs and interface stability,poised for the forthcoming era of advanced ASNIBs.

Efficient ORR catalysts for zinc-air battery: Biomass-derived ultra-stable Co nanoparticles wrapped with graphitic layers via optimizing electron transfer

The poor stability of non-noble metal catalysts in oxygen reduction reaction(ORR) is a main bottleneck that limits their big-scale application in metal-air batteries. Herein, we construct a chainmail catalyst(Co-NC-AD) with outstanding stability, via the competitive complexation and post absorption strategy,consisting of highly graphitic layers wrapped uniform-size Co nanoparticles(Co-NPs). Experiments combined with density functional theory(DFT) calculations jointly confirmed that the electron transfer occurred from the inner Co-NPs to the external graphitic layers. It facilitated the adsorption process of oxygen molecules and the hybridization of the O-2 p and C-1 p orbitals, which accelerated the ORR reaction kinetics. Consequently, our prepared Co-NC-AD shows excellent ORR activity, offered with a more positive initial potential(E_(onset)= 0.95 V) and half-wave potential(E_(1/2)= 0.86 V). The remarkable stability and resistance of methanol poisoning are merited from the protection effect of stable graphitic layers. In addition, the high electrochemical performance of Co-NC-AD-based zinc-air battery demonstrates their potential for practical applications. Therefore, our work provides new ideas for the design of nanoconfined catalysts with high stability and activity.

Performance of High Indium Content InGaAs p-i-n Detector: A Simulation Study

In this work, we investigate the performance of InGaAs p-i-n photodetectors with cut-off wavelengths near 2.6 μm. The influences of different substrate materials on the optoelectronic properties of InGaAs detector are also compared and discussed. GaAs-based device shows a significant enhancement in detector with a better performance for a InGaAs photodetector compared to InP- based device. In addition, our results show that the device performance is influenced by the conduction band offset. This work proves that InAlAs/InGaAs/GaAs structure is a promising candidate for high performance detector with optimally tuned band gap.

Nonvolatile and reconfigurable two-terminal electro-optic duplex memristor based on Ⅲ-nitride semiconductors

With the fast development of artificial intelligence(AI),Internet of things(IOT),etc,there is an urgent need for the technology that can efficiently recognize,store and process a staggering amount of information.The AlScN material has unique advantages including immense remnant polarization,superior temperature stability and good latticematch to other III-nitrides,making it easy to integrate with the existing advanced III-nitrides material and device technologies.However,due to the large band-gap,strong coercive field,and low photo-generated carrier generation and separation efficiency,it is difficult for AlScN itself to accumulate enough photo-generated carriers at the surface/interface to induce polarization inversion,limiting its application in in-memory sensing and computing.In this work,an electro-optic duplex memristor on a GaN/AlScN hetero-structure based Schottky diode has been realized.This twoterminal memristor shows good electrical and opto-electrical nonvolatility and reconfigurability.For both electrical and opto-electrical modes,the current on/off ratio can reach the magnitude of 104,and the resistance states can be effectively reset,written and long-termly stored.Based on this device,the“IMP”truth table and the logic“False”can be successfully reproduced,indicating the huge potential of the device in the field of in-memory sensing and computing.

Quantum engineering of non-equilibrium efficient p-doping in ultra-wide band-gap nitrides

Ultra-wide band-gap nitrides have huge potential in micro-and optoelectronics due to their tunable wide band-gap,high breakdown field and energy density,excellent chemical and thermal stability.However,their application has been severely hindered by the low p-doping efficiency,which is ascribed to the ultrahigh acceptor activation energy originated from the low valance band maximum.Here,a valance band modulation mode is proposed and a quantum engineering doping method is conducted to achieve high-efficient p-type ultra-wide band-gap nitrides,in which GaN quantum-dots are buried in nitride matrix to produce a new band edge and thus to tune the dopant activation energy.By non-equilibrium doping techniques,quantum engineering doped AIGaN:Mg with Al content of 60%is successfully fabricated.The Mg activation energy has been reduced to about 21 meV,and the hole concentration reaches higher than 10^(18)cm^(-3)at room temperature.Also,similar activation energies are obtained in AIGaN with other Al contents such as 50%and 70%;indicating the universality of the quantum engineering doping method.Moreover,deep-ultraviolet light-emission diodes are fabricated and the improved performance further demonstrates the validity and merit of the method.With the quantum material growth techniques developing,this method would be prevalently available and tremendously stimulate the promotion of ultra-wide band-gap semiconductor-based devices.

Polarization-enhanced AlGaN solar-blind ultraviolet detectors

AlGaN solar-blind ultraviolet detectors have great potential in many fields,although their performance has not fully meet the requirements until now.Here,we proposed an approach to utilize the inherent polarization effect of AlGaN to improve the detector performance.AlGaN heterostructures were designed to enhance the polarization field in the absorption layer,and a high built-in field and a high electron mobility conduction channel were formed.As a result,a high-performance solar-blind ultraviolet detector with a peak responsivity of 1.42 A/W at 10 V was achieved,being 50 times higher than that of the nonpolarization-enhanced one.Moreover,an electron reservoir structure was proposed to further improve the performance.A higher peak responsivity of 3.1 A/W at30 V was achieved because the electron reservoir structure could modulate the electron concentration in the conduction channel.The investigation presented here provided feasible approaches to improve the performance of the AlGaN detector by taking advantage of its inherent property.

Full-duplex light communication with a monolithic multicomponent system

A monolithic multicomponent system is proposed and implemented on a III-nitride-on-silicon platform,whereby two multiple-quantum-well diodes(MQW-diodes)are interconnected by a suspended waveguide.Both MQW-diodes have an identical low-In-content InGaN/Al0.10Ga0.90N MQW structure and are produced by the same fabrication process flow.When appropriately biased,both MQW-diodes operate under a simultaneous emission-detection mode and function as a transmitter and a receiver at the same time,forming an in-plane full-duplex light communication system.Real-time full-duplex audio communication is experimentally demonstrated using the monolithic multicomponent system in combination with an external circuit.

Review on the Progress of AlGaN-based Ultraviolet Light-Emitting Diodes

AlGaN-based materials have exhibited considerable potential for fabricating ultraviolet(UV)light-emitting diodes(LEDs)owing to their direct,wide,and adjustable energy bandgap.AlGaN-based devices have extensive appli-cability owing to their stable physico-chemical properties.With decades of research effort,significant progress has been achieved in enhancing the working efficiency of AlGaN-based LEDs by optimizing the crystalline qual-ity,doping efficiency,and device design.In this review,methods to obtain high-quality AlGaN-based materials,achieve high doping efficiency,and design UV-LED structures are summarized and discussed.Finally,the issues that need to be addressed in AlGaN-based UV-LED devices are highlighted.

Monolithic integration of MoS2-based visible detectors and GaN-based UV detectors

With the increasing demand for high integration and multi-color photodetection for both military and civilian applications, the research of multi-wavelength detectors has become a new research hotspot. However, current research has been mainly in visible dual-or multi-wavelength detectors, while integration of both visible light and ultraviolet(UV) dual-wavelength detectors has rarely been studied. In this work, large-scale and high-quality monolayer MoS2 was grown by the chemical vapor deposition method on transparent free-standing GaN substrate. Monolithic integration of MoS2-based visible detectors and GaN-based UV detectors was demonstrated using common semiconductor fabrication technologies such as photolithography, argon plasma etching, and metal deposition. High performance of a 280 nm and 405 nm dual-wavelength photodetector was realized.The responsivity of the UV detector reached 172.12 A/W, while that of the visible detector reached 17.5 A/W.Meanwhile, both photodetectors achieved high photocurrent gain, high external quantum efficiency, high normalized detection rate, and low noise equivalent power. Our study extends the future application of dual-wavelength detectors for image sensing and optical communication.

Scalable,thin asymmetric composite solid electrolyte for high-performance all-solid-state lithium metal batteries

All-solid-state Li metal batteries(ASSLMBs)have been considered the most promising candidates for next-generation energy storage devices owing to their high-energy density and safety.However,some obstacles such as thick solid electrolyte(SSEs)and unstable interface between the solid-state electrolytes(SSEs)and the electrodes have restricted the practical application of ASSLBs.Here,the scalable polyimide(PI)film reinforced asymmetric ultrathin(~20μm)composite solid electrolyte(AU-CSE)with a ceramic-rich layer and polymer-rich layer is fabricated by a both-side casting method and rolling process.The ceramic-rich layer not only acts as a“securer”to inhibit the lithium dendrite growth but also redistributes Li-ions uniform deposition,while the polymer-rich layer improves the compatibility with cathode materials.As a result,the obtained AU-CSE demonstrates an ionic conductivity of 1.44×10^(−4)S cm^(−1)at 35°C.The PI-reinforced AU-CSE enables Li/Li symmetric cell stable cycling over 1200 h at_(0.2)mA cm^(−2)and_(0.2)mAh cm^(−2).Li/LiNi_(0.6)Co_(0.2)Mn_(0.2)O2 and Li/LiFePO4 ASSLMBs achieve superior performances at 35°C.This study provides a new way of solving the interface problems between SSEs and electrodes and developing high-energy-density ASSLMBs for practical applications.

Multiple-quantum-well-induced unipolar carrier transport multiplication in AlGaN solar-blind ultraviolet photodiode

AlGaN solar-blind ultraviolet(SBUV)detectors have potential application in fire monitoring,corona discharge monitoring,or biological imaging.With the promotion of application requirements,there is an urgent demand for developing a high-performance vertical detector that can work at low bias or even zero bias.In this work,we have introduced a photoconductive gain mechanism into a vertical AlGaN SBUV detector and successfully realized it in a p-i-n photodiode via inserting a multiple-quantum-well(MQW)into the depletion region.The MQW plays the role of trapping holes and increasing carrier lifetime due to its strong hole confinement effect and quantum confinement Stark effect.Hence,the electrons can go through the detector multiple times,inducing unipolar carrier transport multiplication.Experimentally,an AlGaN SBUV detector with a zero-bias peak responsivity of about 0.425 A/W at 233 nm is achieved,corresponding to an external quantum efficiency of 226%,indicating the existence of internal current gain.When compared with the device without MQW structure,the gain is estimated to be about 103 in magnitude.The investigation provides an alternative and effective approach to obtain high current gain in vertical AlGaN SBUV detectors at zero bias.

Carrier behavior in the vicinity of pit defects in GaN characterized by ultraviolet light-assisted Kelvin probe force microscopy

Surface potentials in the vicinity of V-pits(cone bottom) and U-pits(blunt bottom) on epitaxial GaN surface have been systematically studied using ultraviolet(UV) light-assisted Kelvin probe force microscopy(KPFM). The band structure models are established to understand variation of the surface potentials at the pits and planar surface with and without UV light. The photo-generated carrier behavior at the pit defects is studied. According to the surface potential results, it can be deduced that the carrier distributions around the V-and U-pits are uneven. In dark, the electron concentration at the bottom of V-pit(30 n_0) and Upit(15 n_0) are higher than that at planar surface(n_0). Under UV light, for V-pit, the electron concentration at the cone bottom(4.93×10^(11) n_0) is lower than that at the surrounding planar surface(5.68×10^(13) n_0). For U-pit, the electron concentration at the blunt bottom is 1.35×10^(12) n_0, which is lower than that at the surrounding planar surface(6.13×10^(13) n_0). The non-equilibrium electron concentrations at different locations are calculated. Based on the non-equilibrium electron concentration, it can be concluded that the carrier recombination rate at pit defects is higher than that at planar surface.

N‑doped carbon anchored CoS_(2)/MoS_(2) nanosheets as efficient electrocatalysts for overall water splitting

The oriented two-dimensional porous nitrogen-doped carbon embedded with CoS_(2) and MoS2 nanosheets is a highly efcient bifunctional electrocatalyst.The hierarchical structure ensures fast mass transfer capacity in improving the electrocatalytic activity.And the greatly increased specifc surface area is benefcial to expose more electrocatalytically active atoms.For oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)tests in 1 mol/L KOH solution,only 194 and 140 mV overpotential are required to achieve a current density of 10 mA/cm^(2),respectively.Our research provides an efective strategy for synergizing the individual components in nanostructures for a wide range of electrocatalytic reactions.

Tunable piezoelectric and ferroelectric responses of Al1-xScxN:The role of atomic arrangement

In this study,we present first-principles investigations of the atomic structure of Al_(1-x)Sc_(x)N and its influence on its piezoelectric and ferroelectric properties.The unbiased structure searching revealed that Al_(1-x)Sc_(x)N with phase separation feature,where Al N and Sc N form a layered structure with different symmetries,is more stable than the corresponding wurtzite structure.The piezoelectric response of Al_(1-x)Sc_(x)N is strongly dependent on the atomic arrangements;in particular,Al_(0.5)Sc_(0.5)N with a wurtzite structure exhibits a large positive e33of 4.79 C/m^(2),whereas Al_(0.5)Sc_(0.5)N with a phase separation structure exhibits a negative e33of-0.67 C/m^(2).Moreover,the ferroelectric switching of Al_(1-x)Sc_(x)N demonstrated two distinct pathways for the wurtzite and phase separation structures,and the spontaneous polarization thus calculated exhibits entirely different values.Accordingly,we demonstrated that Al_(1-x)Sc_(x)N with a phase separation structure exhibits a low polarization switching barrier of 0.15 e V/f.u.and a large spontaneous polarization of-0.77 C/m^(2);thus,it can serve as a novel Al_(1-x)Sc_(x)N-based ferroelectric material.As the dipoles in Al_(1-x)Sc_(x)N with a phase separation structure are localized in the AlN region,they are individually switchable at no domain wall energy cost and are stable against extrinsic effects.

Configuration design of a 2D graphene/3D AlGaN van der Waals junction for high-sensitivity and self-powered ultraviolet detection and imaging

Two-dimensional(2D)graphene has emerged as an excellent partner for solving the scarcity of ultraviolet photodetectors based on three-dimensional(3D)AlGaN,in which the design of a 2D graphene/3D AlGaN junction becomes crucial.This study investigates the response mechanisms of two distinct graphene/AlGaN(Gr-AlGaN)photodetectors in the lateral and vertical configurations.For the lateral Gr-AlGaN photodetector,photogenerated electrons drifting into p-type graphene channel induce negative photoconductivity and a persistent photoconductive effect,resulting in a high responsivity of 1.27×10^(4) A∕W and detectivity of 3.88×10^(12) Jones.Although the response capability of a vertical Gr-AlGaN device is inferior to the lateral one,it shows significantly reduced dark current and self-powered detection.The photogenerated electron-hole pair can be spontaneously separated by the junction electric field and generate a photocurrent at zero bias.Hence,the vertical Gr-AlGaN photodetector array is satisfied for passive driving imaging like deep space detection.Conversely,the exceptional response of the lateral Gr-AlGaN device emphasizes its prospects for steady object recognition with low-light emission.Moreover,the improved imaging sharpness with light illumination duration makes it suitable for biomimetic visual learning,which follows a recognition to memory process.This study elucidates an efficient approach for diverse photodetection applications through the configuration design of Gr-AlGaN junctions.