Jiuxiang Dai

A new design strategy that is structured around all-solid-state electrochromic device is developed to circumvent the critical problem in conventional all-solid-state electrochromic device, which offers personalized devices that exhibit vivid structural colors and dual anti-counterfeiting, accompanied by fast switching responses and excellent cycling performance.

Abstract

The fusion of electrochromic technology with optical resonant cavities presents an intriguing innovation in the electrochromic field. However, this fusion is mainly achieved in liquid electrolyte-based or sol–gel electrolyte-based electrochromic devices, but not in all-solid-state electrochromic devices, which have broader industrial applications. Here, a new all-solid-state electrochromic device is demonstrated with a metal–dielectric–metal (MDM) resonant cavity, which can achieve strong thin-film interference effects through resonance, enabling the device to achieve unique structural colors that have rarely appeared in reported all-solid-state electrochromic devices, such as yellow green, purple, and light red. The color gamut of the device can be further expanded due to the adjustable optical constants of the electrochromic layer. What is more, this device exhibits remarkable cycling stability (maintaining 84% modulation capability after 7200 cycles), rapid switching time (coloration in 2.6 s and bleaching in 2.8 s), and excellent optical memory effect (only increasing by 13.8% after almost 36 000 s). In addition, this exquisite structural design has dual-responsive anti-counterfeiting effects based on voltage and angle, further demonstrating the powerful color modulation capability of this device.

La₃MN₅ (M=Cr, Mn, and Mo) are the first examples of ternary antiperovskite (Cs₃CoCl₅-type) nitrides containing [MN₄]⁶⁻ anions for M=Cr and Mo, but for M=Mn off-stoichiometry modelled by excess-nitride clusters gives La₃MnN_5.30 with Mn oxidised almost to the +7 state. This is the first report of excess-anion incorporation into Cs₃CoCl₅-type materials, and this or other mechanisms may enable many other high oxidation state transition metal nitrides to be prepared.

Abstract

Three new nitrides La₃MN₅ (M=Cr, Mn, and Mo) have been synthesized using a high pressure azide route. These are the first examples of ternary Cs₃CoCl₅-type nitrides, and show that this (MN₄)NLa₃ antiperovskite structure type may be used to stabilise high oxidation-state transition metals in tetrahedral molecular [MN₄]ⁿ⁻ nitridometallate anions. Magnetic measurements confirm that Cr and Mo are in the M⁶⁺ state, but the M=Mn phase has an anomalously small paramagnetic moment and large cell volume. Neutron powder diffraction data are fitted using an anion-excess La₃MnN_5.30 model (space group I4/mcm, a=6.81587(9) Å and c=11.22664(18) Å at 200 K) in which Mn is close to the +7 state. Excess-anion incorporation into Cs₃CoCl₅-type materials has not been previously reported, and this or other substitution mechanisms may enable many other high oxidation state transition metal nitrides to be prepared.

The formation of supernarrow borophene nanoribbons has been experimentally realized. The ribbons have a uniform width of ∼10 Å and can be as long as 200 Å. They are embedded in the outermost layer of Au(111) and shielded on top by evacuated Au atoms. Distinct edge states are revealed from the ribbons, which are primarily attributed to the localized spin at their zigzag edges.

Abstract

Borophenes have sparked considerable interest owing to their fascinating physical characteristics and diverse polymorphism. However, borophene nanoribbons (BNRs) with widths less than 2 nm have not been achieved. Herein, we report the experimental realization of supernarrow BNRs. Combining scanning tunneling microscopy imaging with density functional theory modeling and ab initio molecular dynamics simulations, we demonstrate that, under the applied growth conditions, boron atoms can penetrate the outermost layer of Au(111) and form BNRs composed of a pair of zigzag (2,2) boron rows. The BNRs have a width self-contained to ∼1 nm and dipoles at the edges to keep them separated. They are embedded in the outermost Au layer and shielded on top by the evacuated Au atoms, free of the need for post-passivation. Scanning tunneling spectroscopy reveals distinct edge states, primarily attributed to the localized spin at the BNRs’ zigzag edges. This work adds a new member to the boron material family and introduces a new physical feature to borophenes.

A non-layered binary chalcogenide compound, Cr₂S₃, demonstrates inclined-standing growth of 2D nanosheets. Gate-controlled intercalation of Li⁺ ions into ordered vacancy channels induces a metal-insulator transition with a giant resistance change.

Abstract

Gate-controlled ionic intercalation in the van der Waals gap of 2D layered materials can induce novel phases and unlock new properties. However, this strategy is often unsuitable for densely packed 2D non-layered materials. The non-layered rhombohedral Cr₂S₃ is an intrinsic heterodimensional superlattice with alternating layers of 2D CrS₂ and 0D Cr_1/3. Here an innovative chemical vapor deposition method is reported, utilizing strategically modified metal precursors to initiate entirely new seed layers, yields ultrathin inclined-standing grown 2D Cr₂S₃ nanosheets with edge instead of face contact with substrate surfaces, enabling rapid all-dry transfer to other substrates while ensuring high crystal quality. The unconventional ordered vacancy channels within the 0D Cr_1/3 layers, as revealed by cross-sectional scanning transmission electron microscope, permitting the insertion of Li⁺ ions. An unprecedented metal-insulator transition, with a resistance modulation of up to six orders of magnitude at 300 K, is observed in Cr₂S₃-based ionic field-effect transistors. Theoretical calculations corroborate the metallization induced by Li-ion intercalation. This work sheds light on the understanding of growth mechanism, structure-property correlation and highlights the diverse potential applications of 2D non-layered Cr₂S₃ superlattice.

In this study, nitrogen is doped into VO₂ thin films through mist chemical vapor deposition, and the effect of the doping on metal–insulator transition (MIT) temperatures is investigated. The sample grown at 425 °C exhibits a considerable change in resistance because of MIT at approximately 29.5 °C. These results prove the potential for smart window applications to address future energy problems.

Abstract

In this study, nitrogen (N) is doped into VO₂ thin films through mist chemical vapor deposition (CVD), and the effect of the doping on metal–insulator transition (MIT) temperatures is investigated. The N-doped VO₂ thin films are grown on an SnO₂ buffer layer. The N-doped VO₂ lattice spacing tends to expand as the growth temperature decreased, which indicates that the incorporation of N into the lattice is derived from the Ethylenediamine. Secondary ion mass spectrometry (SIMS) is conducted to investigate the relationship between the decrease in the transition temperature and N concentration. The results reveal that the sample grown at 425 °C contains approximately 2 × 10²⁰ cm⁻³ of N. Thus, efficient nitrogen doping can be achieved through mist CVD. The temperature-resistance characteristics of VO₂ thin films are measured to investigate their electrical properties and MIT temperatures. The results reveal that for undoped samples, the transition temperature slightly decreases with the decrease in the growth temperature. Furthermore, the sample grown at 425 °C exhibits a considerable change in resistance because of MIT at approximately 29.5 °C. These results prove the potential of using mist CVD N-doped thin films for smart window applications to address future energy problems.

Herein, the structure of the integrated M3D inverters where a CVD-synthesized monolayer WSe₂ p-type nanosheet FET is vertically integrated on top of CVD synthesized monolayer MoS2 n-type film FET arrays is realized. The integrated M3D inverters show an average voltage gain of approximately 9 at V_DD = 2 V with an ultra-low power consumption of 0.112 nW at a V_DD of 1 V.

Abstract

Herein, the structure of integrated M3D inverters are successfully demonstrated where a chemical vapor deposition (CVD) synthesized monolayer WSe₂ p-type nanosheet FET is vertically integrated on top of CVD synthesized monolayer MoS₂ n-type film FET arrays (2.5 × 2.5 cm) by semiconductor industry techniques, such as transfer, e-beam evaporation (EBV), and plasma etching processes. A low temperature (below 250 °C) is employed to protect the WSe₂ and MoS₂ channel materials from thermal decomposition during the whole fabrication process. The MoS₂ NMOS and WSe₂ PMOS device fabricated show an on/off current ratio exceeding 10⁶ and the integrated M3D inverters indicate an average voltage gain of ≈9 at V_DD = 2 V. In addition, the integrated M3D inverter demonstrates an ultra-low power consumption of 0.112 nW at a V_DD of 1 V. Statistical analysis of the fabricated inverters devices shows their high reliability, rendering them suitable for large-area applications. The successful demonstration of M3D inverters based on large-scale 2D monolayer TMDs indicate their high potential for advancing the application of 2D TMDs in future integrated circuits.

A two-step, plasma-driven method for synthesizing Janus 2D SnSSe, featuring selective atomic stripping and selenization. It demonstrates reduced work function and enhanced carrier mobility. These findings are crucial for advancing high-performance 2D electronic and optoelectronic devices.

Abstract

The recent emergence of Janus 2D materials like SnSSe, derived from SnS₂, reveals unique electrical and optical features, such as asymmetrical electronic structure, enhanced carrier mobility, and tunable bandgap. Previous theoretical studies have discuss the electronic properties of Janus SnSSe, but experimental evidence is limited. This study presents a two-step method for synthesizing Janus SnSSe, involving hydrogen plasma treatment and in situ selenization. Optimized conditions (38 W, 1.5 min, 250 °C) are determined using Raman spectroscopy and AFM analysis. XPS confirmed SnSSe's elemental composition, while KPFM reveals a significant reduction in the work function (from 5.26 down to 5.14 eV) for the first time, indicating asymmetrically induced n-type doping. Finally, field-effect transistors (FETs) derived from SnSSe exhibited significantly enhanced mobility and on-current, as well as n-type doping, compared to SnS₂-based FETs. These findings lay a crucial foundation for developing high-performance 2D electronic and optoelectronic devices.

A confinement-structured Fe₂Mo₃O₈@C@MoS₂ with local-expanded interlayer spacing is designed, which achieves a high reversible specific capacity, excellent rate capability, and ultralong cycling stability. The sodium storage mechanism and detailed structural evolution of Fe₂Mo₃O₈ are established for the first time by in situ X-ray diffraction. Density functional theory calculations further indicate the merits of the unique structure.

Abstract

Developing multicomponent composite materials with delicate morphology and tailored structure is of vital importance for designing advanced sodium-ion batteries (SIBs). Herein, a confinement-structured Fe₂Mo₃O₈@C@MoS₂ with local-expanded interlayer spacing is designed via high-temperature phase transition from FeMoO₄ to Fe₂Mo₃O₈ and the tactically introducing dopamine molecules into the interlayer of MoS₂ nanosheets. By analysis of the in situ generated solid electrolyte interphase film in different electrolytes, the favorable compatibility of Fe₂Mo₃O₈@C@MoS₂ in ether-based electrolytes is well illustrated. Importantly, the sodium storage mechanism and detailed structural evolution of Fe₂Mo₃O₈ are established for the first time by in situ X-ray diffraction. Furthermore, theoretical calculations indicate the unique structure facilitates internal charge transfer and enhances Na⁺ adsorption ability. Thanks to the unique confinement structure, local-expanded interlayers and robust framework, the Fe₂Mo₃O₈@C@MoS₂ composite achieves a high reversible specific capacity of 636 mAh g^‒1 at 0.1 A g^‒1, excellent rate capability (301 mAh g^‒1 at 5.0 A g^‒1) and ultralong cycling stability (365 mAh g^–1 after 6000 cycles at 2.0 A g^–1). The study provides an essential understanding of the Na storage mechanism of Fe₂Mo₃O₈ and a promising strategy for constructing high-performance anodes for SIBs.

A four-terminal van der Waals junction field effect transistor fabricated by thinned Te with high materials quality and electrical performance and n-type ReS₂ flakes demonstrates an excellent multifunctional integration of a rectifying diode, p- and n-channel transistor in one single device. The novel architecture's high mobility and ideal slope show a promise to high performance and low-power transistor applications.

Abstract

Two-dimensional non-layered tellurene (Te) can serve as a promising candidate in transistor applications because of its high carrier mobility and air stability. However, it is still quite challenging in aspect of ultra-thin channel and gate-control ability in conventional metal-oxide-semiconductor field-effect transistor architecture. This work proposes a facile thinning strategy for solution-proceed Te flakes and fabricates a junction field-effect transistor (JFET) architecture, that has well addressed the above-mentioned two issues. Through a mild oxidative thinning process, the post-growth Te flakes are thinned from bulk to few-layer, guaranteeing the highly efficient electrostatic doping as a transistor channel. Then, a four-terminal JFET-based on p-Te and n-ReS₂ is designed, achieving a multifunctional integration of rectification diode, p- and n-channel transistor in one single device. By accessing different contact scheme, the ReS₂/Te p-n diode is explored with a rectification ratio of 10³, the p-channel JFET exhibits a high hole mobility of 317.6 cm²V⁻¹s⁻¹, ideal low subthreshold swing of 84 mV dec⁻¹. While the n-channel JFET is obtained with electron mobility of 67.6 cm² V⁻¹s⁻¹ and SS of 229 mV dec⁻¹. Both p- and n-channel devices showcase clear saturation characteristic with ultra-small pinch-off voltage (≈0.4 V), which is crucial for low-power logical and integrated circuit applications.

The demand for flexible and high-performance devices is increasing with the development of flexible electronics. This study proposes a novel CVD-processable polymer dielectric, Parylene-OH, as a crucial alternative to brittle inorganic dielectrics. Parylene-OH offers a high-quality smooth film with high dielectric constant and photopatternability, positioning it as a promising choice for future flexible devices.

Abstract

The development of flexible and stretchable devices is crucial for realizing future electronics. In particular, for dielectric layer, conventional inorganic materials are limited by their brittle nature, while organic materials suffer from a low dielectric constant. Here, a novel intrinsically photopatternable high-k Parylene-based thin film (Parylene-OH) is fabricated via a chemical vapor deposition process based on the Gorham method, which provides pin-hole free, conformal polymeric film on any type of surface. Parylene-OH can be photo-patterned by UV crosslinking without further lithography processes and dielectric constant of Parylene-OH increases from 6.05 to 7.53 after crosslinking, without degrading other parameters, making it comparable to conventional high-k dielectric, Al₂O₃. Flexible In─Ga─Zn─O (IGZO) thin-film transistors (TFTs) with patterned dielectric layers can withstand higher strain owing to the localized pattern of each unit. A CMOS inverter integrated with n-type IGZO and p-type Te TFTs is successfully fabricated. Parylene-OH can be used in the future of state-of-the-art flexible electronic devices.

Low growth rates in AlScN/GaN heterostructures grown by metal-organic chemical vapor cause the formation of linearly graded interlayers and degradation of the electrical characteristics. Growth rates are enhanced with novel Sc precursors, and high interface abruptness and homogeneous layers are achieved. Structural quality strongly affects the performance of the 2D electron gas, which is the core of high-electron-mobility transistors.

Abstract

Aluminum scandium nitride barrier layers increase the available sheet charge carrier density in gallium nitride-based high-electron-mobility transistors and boost the output power of high-frequency amplifiers and high voltage switches. Growth of AlScN by metal-organic chemical vapor deposition is challenging due to the low vapor pressure of the conventional Sc precursor Cp₃Sc, which induces low growth rates of AlScN and leads to thermally-induced AlScN/GaN-interface degradation. In this work, novel Sc precursors are employed to reduce the thermal budget by increasing the growth rate of the AlScN layer. The AlScN/GaN interfaces are investigated by high-resolution X-ray diffraction, high-resolution transmission electron microscopy, time-of-flight secondary ion mass spectrometry, capacitance–voltage, current–voltage and temperature-dependent Hall measurements. Linearly graded interlayers with strain-induced stacking faults, edge, and screw dislocations form at the AlScN/GaN interface at growth rates of 0.015 nms⁻¹. Growth rates of 0.034 nms⁻¹ and higher allow for abrupt interfaces, but a compositional grading in the barrier remains. Homogeneous barrier layers can be achieved at growth rates of 0.067 nms⁻¹ or by growing an AlN interlayer. The electrical properties of the heterostructures are sensitive to Sc accumulations at the cap/barrier interface, residual impurities from precursor synthesis, and surface roughness. This study paves the way for high-performing devices.

The dual-functionality of molybdenum hexafluoride (MoF₆) is utilized for dual-material area-selective deposition (ASD). Mo atomic layer deposition (ALD) using MoF₆ and 1 wt% silane creates Mo ASD on hydrogen-terminated Si versus hydroxylated SiO₂ (SiO₂‒OH), while SiO₂‒OH is simultaneously fluorinated by MoF₆. Subsequent ZnO and TiO₂ ALD are inhibited on the fluorine-passivated SiO₂, resulting in self-aligned Mo/metal oxide nanoribbons.

Abstract

Area-selective deposition (ASD) is a forefront nanopatterning technique gaining substantial attention in the semiconductor industry. While current research primarily addresses single-material ASD, exploring multi-material ASD is essential for mitigating complexity in advanced nanopatterning. This study describes molybdenum hexafluoride (MoF₆)-mediated fluorination/passivation of the hydroxylated SiO₂ (SiO₂‒OH) at 250 °C as a new method to pacify nucleation during subsequent ZnO and TiO₂ atomic layer deposition (ALD). In contrast, Al₂O₃ ALD is not passivated on the fluorinated SiO₂ (SiO₂‒F). The study further shows that Mo ALD using MoF₆ and silane (1 wt% SiH₄ in Ar) selectively proceeds on hydrogen-terminated Si (Si‒H), whereas SiO₂‒OH becomes fluorine-passivated without observable Mo deposition. This enables subsequent ZnO and TiO₂ ASD on Mo versus SiO₂‒F, as confirmed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM). Proposed growth and inhibition mechanisms highlight the importance of the metal oxide precursor in achieving selectivity. Taken together, self-aligned Mo/ZnO and Mo/TiO₂ nanoribbons are demonstrated on coplanar nanoscale Si‒H/SiO₂‒OH patterns by sequentially integrating two individual ASD processes: 1) Mo ASD on Si‒H versus SiO₂‒OH; and 2) ZnO or TiO₂ ASD on Mo versus SiO₂‒F. This work highlights the potential for this approach in new ASD systems.

Oxyselenide Bi₂O₂Se has emerged as a new type of layered quasi-2D materials, drawing considerable attention recently due to its excellent physicochemical properties. This review focused on the recent progress related to Bi₂O₂Se, encompassing structural characteristics, fundamental properties, preparation techniques, and potential applications in devices, which show its great potential for future-generation electronics and optical technology.

Abstract

Layered two-dimensional (2D) materials have garnered marvelous attention in diverse fields, including sensors, capacitors, nanocomposites and transistors, owing to their distinctive structural morphologies and superior physicochemical properties. Recently, layered quasi-2D materials, especially layered bismuth oxyselenide (Bi₂O₂Se), are of particular interest, because of their different interlayer interactions from other layered 2D materials. On this basis, this material offers richer and more intriguing physics, including high electron mobility, sizeable bandgap, and remarkable thermal and chemical durability, rendering it an utterly prospective contender for use in advanced electronic and optoelectronic applications. Herein, this article reviews the recent advances related with Bi₂O₂Se. Initially, its structural characterization, band structure, and basic properties are briefly introduced. Further, the synthetic strategies for the preparation of Bi₂O₂Se are presented. Furthermore, the diverse applications of Bi₂O₂Se in the field of electronics and optoelectronics, photocatalytic, solar cells and sensing were summarized in detail. Ultimately, the challenges and future perspectives of Bi₂O₂Se are included.

Nanoflakes of inorganic molecular crystals (Sb₂O₃) show polarization-sensitive waveguiding property based on total internal reflection and large polarization mode dispersion, which can be combined with plasmonic waveguide to form hybrid beam splitters and routers with relative low loss.

Abstract

Photonic and plasmonic hybrid nanostructures are the key solution for integrated nanophotonic circuits with ultracompact size but relative low loss. However, the poor tunability and modulability of conventional waveguides makes them cumbersome for optical multiplexing. Here we make use of two-dimensional molecular crystal, α-Sb₂O₃ as a dielectric waveguide via total internal reflection, which shows polarization-sensitive modulation of the propagating beams due to its large polarization mode dispersion. Both experiments and simulations are performed to verify such concept. These Sb₂O₃ nanoflakes can be coupled with plasmonic nanowires to form nanophotonic beam splitters and routers which can be easily modulated by changing the polarization of the incidence. It thus provides a robust, exploitable and tunable platform for on-chip nanophotonics.

Herein, van der Waals Schottky-gated MoS₂ metal–semiconductor field-effect transistors are developed, mitigating two primary sources of Fermi-level pinning—metal-induced gap states and disorder-induced gap states. Consequently, the devices exhibit ideal hysteresis-free transistor characteristics with a subthreshold swing of 60 mV dec⁻¹ at 300 K, approaching to the fundamental Boltzmann switching limit.

Abstract

A gate stack that facilitates a high-quality interface and tight electrostatic control is crucial for realizing high-performance and low-power field-effect transistors (FETs). However, when constructing conventional metal-oxide-semiconductor structures with two-dimensional (2D) transition metal dichalcogenide channels, achieving these requirements becomes challenging due to inherent difficulties in obtaining high-quality gate dielectrics through native oxidation or film deposition. Here, a gate-dielectric-less device architecture of van der Waals Schottky gated metal–semiconductor FETs (vdW-SG MESFETs) using a molybdenum disulfide (MoS₂) channel and surface-oxidized metal gates such as nickel and copper is reported. Benefiting from the strong SG coupling, these MESFETs operate at remarkably low gate voltages, <0.5 V. Notably, they also exhibit Boltzmann-limited switching behavior featured by a subthreshold swing of ≈60 mV dec⁻¹ and negligible hysteresis. These ideal FET characteristics are attributed to the formation of a Fermi-level (E _F) pinning-free gate stack at the Schottky–Mott limit. Furthermore, authors experimentally and theoretically confirm that E _F depinning can be achieved by suppressing both metal-induced and disorder-induced gap states at the interface between the monolithic-oxide-gapped metal gate and the MoS₂ channel. This work paves a new route for designing high-performance and energy-efficient 2D electronics.

This study demonstrates that rhombohedral layers of binary compounds exhibit polarization saturation beyond a critical stack thickness. The underlying saturation mechanism points to a purely electronic redistribution involving bandgap closure that allows for cross-stack charge transfer and the emergence of free surface charge. The findings, which are of general nature, should be accounted for when designing switching and/or conductive devices based on ferroelectric layered materials.

Abstract

Van der Waals polytypes of broken inversion and mirror symmetries  have been recently shown to exhibit switchable electric polarization even at the ultimate two-layer thin limit. Their out-of-plane polarization has been found to accumulate in a ladder-like fashion with each successive layer, offering 2D building blocks for the bottom-up construction of 3D ferroelectrics. Here, it is demonstrated experimentally that beyond a critical stack thickness, the accumulated polarization in rhombohedral polytypes of molybdenum disulfide saturates. The underlying saturation mechanism, deciphered via density functional theory and self-consistent Poisson–Schrödinger calculations, point to a purely electronic redistribution involving: 1. Polarization-induced bandgap closure that allows for cross-stack charge transfer and the emergence of free surface charge; 2. Reduction of the polarization saturation value, as well as the critical thickness at which it is obtained, by the presence of free carriers. The resilience of polar layered structures to atomic surface reconstruction, which is essentially unavoidable in polar 3D crystals, potentially allows for the design of new devices with mobile surface charges. The findings, which are of general nature, should be accounted for when designing switching and/or conductive devices based on ferroelectric layered materials.

Nature Electronics, Published online: 24 April 2024; doi:10.1038/s41928-024-01158-4

A method for integrating polycrystalline molybdenum disulfide using processes in a 200 mm fab facility can create transistors with high robustness and performance comparable with single-crystalline devices.

Nature, Published online: 24 April 2024; doi:10.1038/s41586-024-07339-7

Diamond crystals and polycrystalline diamond films can be grown using liquid metal at standard pressure and high temperature instead of conventional high pressure and high temperature.

Nature Materials, Published online: 24 April 2024; doi:10.1038/s41563-024-01858-4

By combining nano-spot angle-resolved photoemission spectroscopy and atomic force microscopy, the authors resolve the fine electronic structure of the flat band and remote bands of twisted bilayer graphene as the twist angle varies, revealing a spectral weight transfer between remote bands that is attributed to lattice relaxations.

Nature Materials, Published online: 25 April 2024; doi:10.1038/s41563-024-01888-y

A strategy of on-device phase engineering of two-dimensional materials is proposed, allowing the in situ realization of various lattice phases with distinct stoichiometries and versatile functions.

Nature Communications, Published online: 23 April 2024; doi:10.1038/s41467-024-47688-5

The authors characterize the phonon modes at the FeSe/SrTiO3 interface with atomically resolved electron energy loss spectroscopy and correlate them with accurate atomic structure in an electron microscope. They find several phonon modes highly localized at the interface, one of which engages in strong interactions with the electrons in FeSe.

The N-type GaN nanochannel with a GaON layer on a centimeter scale is designed as an integrated electrode and assembled GaN-based SCs. The device displays excellent performance at 140 °C and behaves with great prospects as power electronic accessories compatible with GaN-based platform.

Abstract

Gallium Nitride (GaN), as the representative of wide bandgap semiconductors, has great prospects in accomplishing rapid charge delivery under high-temperature environments thanks to excellent structural stability and electron mobility. However, there is still a gap in wafer-scale GaN single-crystal integrated electrodes applied in the energy storage field. Herein, Si-doped GaN nanochannel with gallium oxynitride (GaON) layer on a centimeter scale (denoted by GaN NC) is reported. The Si atoms modulate electronic redistribution to improve conductivity and drive nanochannel formation. Apart from that, the distinctive nanochannel configuration with a GaON layer provides adequate active sites and extraordinary structural stability. The GaN-based supercapacitors are assembled and deliver outstanding charge storage capabilities at 140 °C. Surprisingly, 90% retention is maintained after 50 000 cycles. This study opens the pathway toward wafer-scale GaN single-crystal integrated electrodes with self-powered characteristics that are compatible with various (opto)-electronic devices.

In this work, it is reported that CuIn₅Se₈ is born to possess all-scale hierarchical architectures covering the ranges from atomic-scale cation disorder in the tetragonal phase and nanoscale diversified stacking units and stacking sequences in the hexagonal phase, to mesoscale grain boundaries between tetragonal phase and hexagonal phase to scatter phonons with different mean free paths, which are responsible for the intrinsically ultralow κ _L of CuIn₅Se₈.

Abstract

Copper (Cu)-based thermoelectric (TE) materials have attracted great attention from both scientific and industrial societies, but for a long time, their real applications are greatly limited by the lack of high-performance n-type Cu-based TE materials. Most recently, the novel n-type Cu-based TE material, CuIn₅Se₈, has been discovered to show a record-high TE figure-of-merit (zT) to match the state-of-the-art p-type Cu-based TE materials. However, the physical origin of such high zT is still unclear due to its complex phase compositions and crystal structures. In this work, it is revealed that the excellent TE performance is mainly contributed by the intrinsically ultralow lattice thermal conductivity originating from the unique all-scale hierarchical architecture. It covers the ranges from atomic-scale cation disorder in the tetragonal CuIn₅Se₈ phase and nanoscale diversified stacking units and stacking sequences in the hexagonal CuIn₅Se₈ phase, to mesoscale grain boundaries between the tetragonal phase and hexagonal phase. Doping Br at the Se-sites can largely tune the electrical transports of CuIn₅Se₈ while maintaining the ultralow lattice thermal conductivity, leading to high zT reaching the optimal value predicted by the single parabolic model. This work will guide the investigation of n-type Cu-based TE materials in the future.

Energy is pivotal for microrobotic functions, yet a gap exists in integrating energy devices into microrobots. This Perspective proposes a three-level development, advocating for moving material-centric approaches to device design and even swarm energy management. Only then can advanced energy materials contribute to microrobotic field. Evaluating social and environmental impacts is crucial for the safe implementation of microrobotic swarms.

Abstract

Energy serves as the foundational element for all active functions within microrobots. Harvesting devices, such as photovoltaic cells and coils, play a crucial role in converting diverse forms of energy into electricity, while energy storage devices enable uninterrupted operation and liberate microrobots from dependence on external sources. Despite the evident importance of energy, there exists a significant disconnect between the development of energy devices and their integration into microrobotic systems, hampering the deployment of microrobots across diverse fields from agriculture to microsurgery. Here, for transcending the “material for material's sake” focus on simple generic metrics for material optimization, such as energy density, advocating attention to the higher tier transformation of material metrics that determine device-level performance and so make a meaningful contribution to microrobotic technology is argued. Appropriate metrics for microrobotic swarms challenge the stereotype that tiny energy supplies are impractical; instead, swarms simplify individual microrobotic functions, reducing single energy supply requirements and utilizing swarm energy distribution and management. In addition to essential evaluations of the environmental and social impacts of intelligent microrobotic swarms for their safe and beneficial implementation, research targeting these higher-tier metrics is crucial to connecting energy material research and microrobot developments effectively.