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1.
叙述了宽带半导体材料ＳｉＣ、ＧａＮ的主要特性和生长方法,并对其发展动态和存在问题进行了简要评述。  相似文献   

2.
    
A new series of wide‐bandgap materials, 4‐dipenylphosphine oxide‐4′‐9H‐carbazol‐9‐yl‐tetraphenylsilane (CSPO), 4‐diphenylphosphine oxide‐4′,4″‐di(9H‐carbazol‐9‐yl)‐tetraphenylsilane (pDCSPO), 4‐diphenylphosphine oxide ‐4′‐[3‐(9H‐carbazol‐9‐yl)‐carbazole‐9‐yl]‐tetraphenylsilane (DCSPO), 4‐diphenylphosphine oxide‐4′,4″,4″′‐tri(9H‐carbazol‐9‐yl)‐tetraphenylsilane (pTCSPO) and 4‐diphenylphosphine oxide ‐4′‐[3,6‐di(9H‐carbazol‐9‐yl)‐9H‐carbazol‐9‐yl]‐tetraphenylsilane (TCSPO), containing different ratios and linking fashions of p‐type carbazole units and n‐type phosphine oxide units, are designed and obtained. DCSPO is the best host in FIrpic‐doped devices for this series of compounds. By utilizing DCzSi and DPOSi as hole‐ and electron‐transporting layers, a high EQE of 27.5% and a maximum current efficiency of 49.4 cd A?1 are achieved in the DCSPO/FIrpic doped device. Even at 10 000 cd m?2, the efficiencies still remain 41.2 cd A?1 and 23.0%, respectively.  相似文献   

3.
    
Electronics implemented on biocompatible ultrathin substrates like polyethylene terephthalate, polyimide, or parylene enabled a wide range of conformable, lightweight smart wearables and implantables. However, applications in such dynamic environments require robust devices that adjust and stretch while maintaining their functionality. Universal approaches that unite scalable, low-cost fabrication with high performance and versatile, space-efficient design are sparse. Here, stretchable architectures of parylene enabled by Origami-inspired folds at the micrometer scale are demonstrated. Parylene is directly deposited onto anisotropically etched silicon molds to greatly reduce bending stress, allowing folds with bending radii of a few micrometers. 50-nm-thick gold conductors fabricated on the folded parylene facilitate electronics with a stretchability of up to 55% tensile strain. The conductors sustain a resistance below 20 Ω during reversible stretching of more than 10 000 cycles, enabling long-term operation in practical settings. This method presents a versatile tool for the microfabrication of stretchable devices with tunable properties.  相似文献   

4.
    
Soft, elastically deformable composites can enable new generations of multifunctional materials for electronics, robotics, and reconfigurable structures. Liquid metal (LM) droplets dispersed in elastomer matrices represent an emerging material architecture that has shown unique combinations of soft mechanical response with exceptional electrical and thermal functionalities. These properties are strongly dependent on the material composition and microstructure. However, approaches to control LM microdroplet morphology to program mechanical and functional properties are lacking. Here, this limitation is overcome by thermo‐mechanically shaping LM droplets in soft composites to create programmable microstructures in stress‐free materials. This enables LM loadings up to 70% by volume with prescribed particle aspect ratios and orientation, enabling control of microstructure throughout the bulk of the material. Through this microstructural control in soft composites, a material which simultaneously achieves a thermal conductivity as high as 13.0 W m?1 K?1 (>70 × increase over polymer matrix) with low modulus (<1.0 MPa) and high stretchability (>750% strain) is demonstrated in stress‐free conditions. Such properties are required in applications that demand extreme mechanical flexibility with high thermal conductivity, which is demonstrated in soft electronics, wearable robotics, and electronics integrated into 3D printed materials.  相似文献   

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6.
    
Origami offers a distinct approach for designing and engineering new material structures and properties. The folding and stacking of atomically thin van der Waals (vdW) materials, for example, can lead to intriguing new physical properties including bandgap tuning, Van Hove singularity, and superconductivity. On the other hand, achieving well‐controlled folding of vdW materials with high spatial precision has been extremely challenging and difficult to scale toward large areas. Here, a deterministic technique is reported to fold vdW materials at a defined position and direction using microfluidic forces. Electron beam lithography (EBL) is utilized to define the folding area, which allows precise control of the folding geometry, direction, and position beyond 100 nm resolution. Using this technique, single‐atomic‐layer vdW materials or their heterostructures can be folded without the need for any external supporting layers in the final folded structure. In addition, arrays of patterns can be folded across a large area using this technique and electronic devices that can reconfigure device functionalities through folding are also demonstrated. Such scalable formation of folded vdW material structures with high precision can lead to the creation of new atomic‐scale materials and superlattices as well as opening the door to realizing foldable and reconfigurable electronics.  相似文献   

7.
    
Facing the future development trend of miniaturization and intelligence of electronic devices, solar-blind photodetectors based on ultrawide-bandgap 2D semiconductors have the advantages of low dark current, and high signal-to-noise ratio, as well as the features of micro-nanometer miniaturization and multi-functionalization of 2D material devices, which have potential applications in the photoelectric sensor part of high-performance machine vision systems. This study reports a 2D oxide semiconductor, AsSbO3, with an ultrawide bandgap (4.997 eV for monolayer and 4.4 eV for multilayer) to be used to fabricate highly selective solar-blind UV photodetectors, of which the dark current as low as 100 fA and rejection ratio of UV-C and UV-A reaches 7.6 × 103. Under 239 nm incident light, the responsivity is 105 mA W−1 and the detectivity is 7.58 × 1012 Jones. Owing to the remarkable anisotropic crystal structure, AsSbO3 also shows significant linear dichroism and nonlinear optical properties. Finally, a simple machine vision system is simulated by combining the real-time imaging function in solar-blind UV with a convolutional neural network. This study enriches the material system of ultrawide-bandgap 2D semiconductors and provides insight into the future development of high-performance solar-blind UV optoelectronic devices.  相似文献   

8.
    
Here, a novel and facile method is reported for manufacturing a new stretchable conductive material that integrates a hybrid three dimensional (3D) carbon nanotube (CNT)/reduced graphene oxide (rGO) network with a porous poly(dimethylsiloxane) (p‐PDMS) elastomer (pPCG). This reciprocal architecture not only alleviates the aggregation of carbon nanofillers but also significantly improves the conductivity of pPCG under large strains. Consequently, the pPCG exhibits high electrical conductivity with a low nanofiller loading (27 S m?1 with 2 wt% CNTs/graphene) and a notable retention capability after bending and stretching. The simulation of the mechanical properties of the p‐PDMS model demonstrates that an extremely large applied strain (εappl) can be accommodated through local rotations and bending of cell walls. Thus, after a slight decrease, the conductivity of pPCG can continue to remain constant even as the strain increases to 50%. In general, this architecture of pPCG with a combination of a porous polymer substrate and 3D carbon nanofiller network possesses considerable potential for numerous applications in next‐generation stretchable electronics.  相似文献   

9.
    
The remarkable success of lead halide perovskites (LHPs) in photovoltaics and other optoelectronics is significantly linked to their defect tolerance, although this correlation remains not fully clear. The tendency of LHPs to decompose into toxic lead-containing compounds in the presence of humid air calls for the need of low-toxicity LHP alternatives comprising of cations with stable oxidation states. To this aim, a plethora of low-dimensional and wide-bandgap perovskite-inspired materials (PIMs) are proposed. Unfortunately, the optoelectronic performance of PIMs currently lags behind that of their LHP-based counterparts, with a key limiting factor being the high concentration of defects in PIMs, whose rich and complex chemistry is still inadequately understood. This review discusses the defect chemistry of relevant PIMs belonging to the halide elpasolite, vacancy-ordered double perovskite, pnictogen-based metal halide, Ag-Bi-I, and metal chalcohalide families of materials. The defect-driven optical and charge-carrier transport properties of PIMs and their device performance within and beyond photovoltaics are especially discussed. Finally, a view on potential solutions for advancing the research on wide-bandgap PIMs is provided. The key insights of this review will help to tackle the commercialization challenges of these emerging semiconductors with low toxicity and intrinsic air stability.  相似文献   

10.
    
The selective removal of structural elements plays a decisive role in 3D printing applications enabling complex geometries. To date, the fabrication of complex structures on the microscale is severely limited by multistep processes. Herein, a subtractive photoresist platform technology that is transferable from microscopic 3D printing via direct laser writing to macroscopic structures via stereolithography is reported. All resist components are readily accessible and exchangeable, offering fast adaptation of the resist's property profile. The micro‐ and macroprinted structures can be removed in a facile fashion, without affecting objects based on standard photoresists. The cleavage is analyzed by time‐lapse optical microscopy as well as via in‐depth spectroscopic assessment. The mechanical properties of the printed materials are investigated by nanoindentation. Critically, the power of the subtractive resist platform is demonstrated by constructing complex 3D objects with flying features on the microscale.  相似文献   

11.
    
This study demonstrates UV‐sensing semitransparent organic field‐effect transistors (OFETs) with wide bandgap small molecular channel and polymeric gate‐insulating layers. N,N′ ‐di(1‐naphthyl)‐N,N′ ‐diphenyl‐(1,1′‐biphenyl)‐4,4′‐diamine (NPB) is employed as the wide bandgap channel layer, while poly(methyl methacrylate) is introduced as the wide bandgap gate‐insulating layer. The performance of OFETs is optimized by NPB thickness control and thermal treatment. Results show that the best device performance (on/off ratio = 4.7 × 106 and hole mobility = 4.2 × 10−5 cm2 V−1 s−1) is achieved by thermal treatment of the 130 nm thick NPB layers at 70 °C for 30 min leading to a noticeably changed surface morphology in the NPB layers. The optimized OFETs exhibit excellent operation stability without hysteresis, while those with semitransparent silver electrodes deliver quite a good transparency. The semitransparent OFETs can sensitively detect a UV light with high stability even though no photoresponse is measured under a visible light.  相似文献   

12.
The fabrication of a three-dimensional (3D) metallic mold for multi-production of microstructures was studied to settle the problem of long processing time and efforts in 3D fabrication based on the accumulation of layer-by-layer. Even though two-photon induced polymerization (TPP) has been considered as a unique way for fabrication of precise real 3D microstructures such as 3D filters, 3D photonic crystals, microlens arrays, it required considerable effort and much processing time inevitably for these fabrications. Therefore, a simple and effective method was proposed using a metallic mold in this work. 3D micro-master patterns were prepared using TPP, and then counter-shaped Ni molds were created using an electroforming process. With this hybrid approach, 3D microstructures were much more easily and quickly reproduced by hot-forming compared to the TPP approach was used only. In this work, we report on the processing parameters used to fabricate a metallic mold and reproduce 3D microstructures using the mold.  相似文献   

13.
    
Origami is a topic of rapidly growing interest in both the scientific and engineering research communities due to its promising potential in a broad range of applications. Previous assembly approaches for origami structures at the micro/nanoscale are constrained by the applicable classes of materials, topologies, and/or capability for reversible control over the transformation process. Here, a strategy is introduced that exploits mechanical buckling for autonomic origami assembly of 3D structures across material classes from soft polymers to brittle inorganic semiconductors, and length scales from nanometers to centimeters. This approach relies on a spatial variation of thickness in the initial 2D structures as a means to produce engineered folding creases during the compressive buckling process. The elastic nature of the assembly scheme enables active, deterministic control over intermediate states in the 2D to 3D transformation in a continuous and reversible manner. Demonstrations include a broad set of 3D structures formed through unidirectional, bidirectional, and even hierarchical folding, with examples ranging from half cylindrical columns and fish scales, to cubic boxes, pyramids, starfish, paper fans, skew tooth structures, and to amusing system‐level examples of soccer balls, model houses, cars, and multifloor textured buildings.  相似文献   

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15.
阐述了碳化硅（SiC）材料的优异特性,并在此基础上,针对目前处于商业化热点的SiC整流器件,进行了重点介绍,分析了国内外发展现状,并对未来发展趋势做出展望。  相似文献   

16.
    
Shape memory polymers (SMPs) respond to heat by generating programmable movement in devices that require substantial deformation and operate at transient temperatures, including stents and embolization coils. To enable their use in small-scale applications like retinal vasculature stenting, shape transformations must occur in SMPs with complex 3D geometries with nanoscale features. This work describes the synthesis and sculpting of a benzyl methacrylate-based SMP into 3D structures with <800 nm characteristic critical dimensions via two photon lithography. Dynamic nanomechanical analysis of 8 µm-diameter cylindrical pillars reveal the initiation of this SMP's glass transition at 60 °C. Shape memory programming of the characterized pillars as well as complex 3D architectures, including flowers with 500 nm thick petals and cubic lattices with 2.5 µm unit cells and overall dimensions of 4.5 µm × 4.5 µm × 10 µm, demonstrate an 86 +/− 4% characteristic shape recovery ratio. These results reveal a pathway toward SMP devices with nanoscale features and arbitrary 3D geometries changing shape in response to temperature.  相似文献   

17.
    
Stretchable electronics have the unique capability of 3D (three dimensional) deformation, overcoming the brittleness of traditional inorganic electronics. However, during large deformations, different scale strains between the rigid and stretchable components lead to mismatch, causing interconnect failures. Therefore, the development of the rigidity-programmable substrate with effective strain shielding capabilities has become a research hotspot. Furthermore, the exponential growth in electronic density presents challenges in the circuit design of stretchable electronics. The urgent need is to develop highly integrated stretchable electronic systems. In this study, a highly integrated stretchable pulse sensor with effective strain shielding capabilities using hybrid 3D printing technology is developed, which comprises electronic chips, a rigidity-programmable substrate/encapsulation layer printed by using PSC (polydimethylsiloxane/silica-nanoparticles composite)-based ink, and LM (liquid metal)-based 3D circuits. First, the PSC-based ink is optimized to enhance the strain shielding effectiveness of the rigidity-programmable substrate. Meanwhile, 3D printing parameters are optimized to achieve high printing precision with minimum line widths below 100 µm. The resulting stretchable pulse sensor demonstrated good mechanical and electrical stability under complex 3D deformations, including bending, twisting, and stretching. The PSC region strain of the sensor is only ≈2% when the global strain is up to ≈65%, which exhibited effective strain shielding capabilities.  相似文献   

18.
本文介绍了基于新型GaN宽禁带半导体材料的大功率器件的特点和优势,采用微波仿真软件ADS对一款S波段的GaNMOSFET进行优化仿真设计,得到了良好的仿真结果,并给出了该功放的实物和测试数据。测试结果表明,该功放适用于2．1～2．7GHz,功率量级为IOOW,连续波和脉冲制式均可工作,对GaNMOSFET功率器件高增益...  相似文献   

19.
    
Modulating electronic structure of monolayer transition metal dichalcogenides (TMDCs) is important for many applications, and doping is an effective way toward this goal, yet is challenging to control. Here, the in situ substitutional doping of niobium (Nb) into TMDCs with tunable concentrations during chemical vapor deposition is reported. Taking monolayer WS2 as an example, doping Nb into its lattice leads to bandgap changes in the range of 1.98–1.65 eV. Noteworthy, electrical transport measurements and density functional theory calculations show that the 4d electron orbitals of the Nb dopants contribute to the density of states of Nb-doped WS2 around the Fermi level, resulting in an n- to p-type conversion. Nb-doping also reduces the energy barrier of hydrogen absorption in WS2, leading to an improved electrocatalytic hydrogen evolution performance. These results highlight the effectiveness of controlled doping in modulating the electronic structure of TMDCs and their use in electronic related applications.  相似文献   

20.
    
Patterning customized arrays of microscale Galinstan or EGaIn liquid metals enables the creation of a variety of microfabricated systems. Current techniques for creating microsized 3D structures of liquid metals are limited by the large dimension or low aspect ratio of such structures, and time‐consuming processes. Here, a novel technique for creating 3D microstructures of Galinstan using dielectrophoresis is introduced. The presented technique enables the rapid creation of Galinstan microstructures with various dimensions and aspect ratios. Two series of proof‐of‐concept experiments are conducted to demonstrate the capabilities of this technique. First, the 3D Galinstan microstructures are utilized as 3D microelectrodes to enhance the trapping of tungsten trioxide (WO3) nanoparticles flowing through a microfluidic channel. Second, the patterned Galinstan microstructures are utilized as microfins to improve the dissipation of heat within a microfluidic channel that is located onto a hot spot. The presented technique can be readily used for creating customized arrays of 3D Galinstan microstructures for a wide range of applications.  相似文献   

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