High-density, spatially defined multicolor emitters are key building blocks for ultrahigh-resolution displays. However, monolithic integration of such emitters on the same chip remains difficult as the pixel size is reduced to the submicrometer scale. Here, we demonstrate diameter-controlled, wavelength-tunable GaN-based core–shell nanowire (NW) emitters through direct epitaxial growth. By optimizing the selective area growth (SAG) conditions, highly ordered and vertically well-aligned n-GaN core NW arrays are obtained. Subsequent growth of InGaN/GaN multiple quantum wells and p-GaN shells yields core–shell NW arrays with strong luminescence. By engineering the SAG opening size and utilizing the diameter-dependent indium incorporation mechanism, the emission wavelength of the core–shell nanowires is continuously tuned from blue to green. These results provide a viable route toward monolithic multicolor integration for ultrahigh-resolution display applications.

The ability to perceive three-dimensional spatial positions is critical for smart human–machine interaction in immersive environments such as the metaverse. Conventional position sensors are typically limited to detecting lateral movements and cannot capture vertical displacement, restricting the richness of user input. Here we introduce a body-induced electroluminescence device and use it to realize a three-dimensional spatial position sensing system, inspired by caterpillars’ ability to sense surrounding electric fields. This system detects finger positions both on the device surface and above it, whereas the underlying electroluminescence mechanism is characterized to explain its optoelectronic behaviour. We further demonstrate the three-dimensional spatial position sensing system in diverse applications, including non-contact keyboards, remote-control interfaces and virtual reality systems, providing a versatile platform that enhances user experience and offers a new route for advancing human–machine interaction technologies. A body-induced electroluminescence device enables three-dimensional finger tracking, providing a versatile platform for human–machine interaction that senses motion both on and above the device surface.

Nitride materials, renowned for their unique polarity properties, underpin modern electronics and photonics. In particular, the polarity discontinuity is expected to form two-dimensional electron gases (2DEGs), which are highly desirable for many applications, such as high-electron-mobility transistors (HEMTs). However, traditional epitaxial growth methods face challenges in achieving controllable and high polarization difference 2DEG interfaces. Here, we report the wafer-scale bonded fabrication of a polarity inversion aluminum nitride (AlN) interface, achieving a high-quality 2DEG with the mobility of ∼1.7× 103 cm2 V-1 s-1 and average sheet charge density of 3.3 × 1013 cm-2 at room temperature. We find the evidence of oxygen at the interface, and the unique Al-O bonding structure at the polarity inversion interface is confirmed by atomic-scale electron microscopy and spectroscopy, combined with first-principles calculations, to account for the formation of 2DEG. Furthermore, distinct ultraviolet luminescence at ∼3.8 eV is observed, originating from the oxygen defects at the interface. These findings deepen our understanding of polarity inversion in nitrides and provide new strategies for designing advanced semiconductor devices via polarity engineering.

The substitutional doping of two-dimensional (2D) transition metal dichalcogenides (TMDs) is essential for tuning their electronic and optoelectronic properties. However, conventional doping methods often suffer from the edge enrichment by dopant atoms, particularly for rare-earth dopants with large ionic radii, owing to their tendency to migrate toward high-energy edge sites during growth. Herein, we present a seed-mediated, self-driven nucleation strategy that leverages the high surface energy of stepped sapphire substrates to pre-adsorb dopant atoms at the step edges. These sites guide the localized nucleation and incorporation of the dopants, thereby effectively suppressing edge segregation. Using this approach, we synthesized centimeter-scale monolayer Yb-doped WS2 films with incorporated substitutional atoms, along with other metal-doped WS2 films. The introduction of mid-gap states near the conduction band in monolayer Yb-doped WS2 films was further demonstrated by the characterization of the bound exciton emission and electronic density of states. This study broadens the pathways for the controllable synthesis of substitutional 2D materials and extends the potential for developing novel 2D optoelectronic devices.image

Environmental barrier coatings (EBCs) enable SiCf/SiC ceramic matrix composites (CMC) to operate under high-temperature combustion conditions. They reduce the oxidation rate of SiC f/SiC, the volatilization of the composites due to reaction with water vapor, and the surface temperature of the composites. Rare-earth monosilicates (RE2SiO5), owing to their excellent high-temperature durability, low thermal conductivity, and good phase stability, are used as the top layer of EBCs. However, they exhibit a high coefficient of thermal expansion (CTE), leading to thermal mismatch and inducing tensile residual stress (with a magnitude of several hundred MPa) in the coating, resulting in the formation of vertical cracks, which act as extremely-high-diffusivity paths for oxidation species transportation and silica volatilization. Therefore, regulating the CTE of RE2SiO5 EBCs and minimizing the CTE mismatch among constituent RE2SiO5 layers with SiC f/SiC CMCs are critical for multilayered EBCs. Through atmospheric plasma spraying, a typical Yb2SiO5/Yb 2Si2O7/Si coating system and a tri-layer structured multicomponent (Y1/4Ho1/4Er1/4Yb1/4)(2)SiO5/Yb2Si2O7/Si coating system with better matched CTEs were manufactured. Both the coatings remained adhered to the substrate during deposition and after annealing, and no mud cracks that would compromise the coating gas-tightness quality and delamination cracks were observed at any of the coating interfaces. In thermal cycling tests, (Y1/4Ho1/4Er1/4Yb1/4)(2)SiO5/Yb2Si2O7/Si coatings showed a lifetime that is three times longer than that of conventional Yb2SiO5/Yb2Si2O7/Si coatings. The failure mechanisms in thermal cycling were investigated via the finite element simulation of stress. It was found that the stress in the substrate was low, and the residual thermal stress was mainly concentrated on the top, inter, and bond layers and increased with an increase in temperature. Compared with that of the (Y1/4Ho1/4Er1/4Yb1/4)(2)SiO5 top coat, the Yb2SiO5 top coat showed obviously higher residual tensile stress, which contributed to a higher tendency for mud-crack formation and higher energy release rate, substantially reducing the coating.. s thermal cycling lifetime. Through neutron powder diffraction and pair distribution function (PDF) analysis, the average and local structures of RE2SiO5 were studied. Overall, the average and local structures did not differ significantly, both of which can be described using the C2/c structure. Nevertheless, the PDF results demonstrated some differences in the disorder degree of Si-O and RE-O coordination environments. In particular, Rietveld refinement results of the PDF showed lower local distortion degree of [ORE4] tetrahedrons when compared with that of the average structure. It is effective to reduce the distortion degree of [ORE4] tetrahedrons by introducing Y3+, Ho3+, and Er3+ into the Yb3+ sites of Yb2SiO5, and smaller distortion degrees lead to lower CTE values. Coordinative local disturbances introduced by strategic high-entropy design have been proposed as the key method for CTE regulation.

The majority of dislocations in nitride epilayers are edge threading dislocations (TDs), which diminish the performance of nitride devices. However, it is extremely difficult to reduce the edge TDs due to the lack of available slip systems. Here, we systematically investigate the formation mechanism of edge TDs and find that besides originating at the coalescence boundaries, these dislocations are also closely related to geometrical misfit dislocations at the interface. Based on this understanding, we propose a novel strategy to reduce the edge TD density of the GaN epilayer by nearly 1 order of magnitude via graphene-assisted remote heteroepitaxy. The first-principles calculations confirm that the insertion of graphene dramatically reduces the energy barrier required for interfacial sliding, which promotes a new strain release channel. This work provides a unique approach to directly suppress the formation of edge TDs at the source, thereby facilitating the enhanced performance of photoelectronic and electronic devices.

Whether time-modulated pulsed-electron imaging in ultrafast electron microscopy (UEM) can mitigate the electron radiation damage that occurs to samples, is still controversial. The effectiveness of such mitigation effect and relevant potential application in cryo-EM remain to be explored. Herein, we built an ultrafast cryo-EM (cryo-UEM) device based on an ultrafast laser system. Using such equipment and the saturated aliphatic hydrocarbon compounds (C44H90), the fading curves of diffraction intensity and corresponding critical electron doses (Ne) of the samples were carefully measured under different imaging modes, temperatures, imaging dose rates and pulsed repetition rates. Our experimental results show that, the fading curves and Ne values of the C44H90 crystals are uncorrelated with the imaging electron dose rates and do not show dependence on the dose-rate effect. As the temperature decreased, the Ne values of the sample increased, indicating the cryoprotective effect on radiation damage to the samples. Surprisingly, at a constant temperature, the fading curves and Ne values of the sample in multi-electrons-packet and near-single-electron-packet pulsed modes are all approximately the same as those in conventional continuous electron-beam mode, even when the results are obtained at different pulsed repetition rates. These results show that the time-modulated pulsed electron beam does not seem to mitigate the electron radiation damage that occurs on samples. Our findings offer new insights and experimental basis for the radiation damage behavior of samples under electron beams, and provide guidance and inspiration for elucidating the fundamental principles of radiation damage. ### Competing Interest Statement The authors have declared no competing interest.

2D Buffer Strategy In article number 2209880, Zhiqiang Liu, Jinmin Li, Xiaoyan Yi, and co-workers review the progress, challenges, and prospects of mechanically transferable III-nitride based on a 2D buffer strategy and its applications in transferable nitride electronic and optoelectronic devices. This 2D buffer strategy provides a new paradigm for semiconductor preparation and a new dimension for novel device design.

Group III-nitrides have attracted significant attention in recent years for their wide tunable band-gaps and excellent optoelectronic capabilities, which are advantageous for several applications including light-emitting diodes, lasers, photodetectors, and large-size low-cost power electronic devices. However, conventional epitaxy accompanied by the covalent bond formation renders the transfer of nitride epilayers difficult, thereby limiting the application potential of nitrides in wearable and flexible electronics. Furthermore, interfacial covalent bonds also limit substrate selection and hinder the development of heterogeneous integration between nitrides and other material systems. 2D materials can mitigate these problems significantly. On the one hand, due to the weak van der Waals forces between the layers of 2D materials, influences of lattice mismatch can be avoided to improve crystal quality. On the other hand, delamination and transfer of nitride epilayers can be achieved easily. Therefore, this study focuses on providing comprehensive guidelines regarding the exfoliation of epitaxial layers using 2D materials to provide new design freedoms for nitride devices. Different 2D buffers and release layers have also been discussed. Furthermore, the limitations, promising solutions, future directions, and applicability of this strategy to flexible nitride devices are presented.

Data security is a major concern in digital age, which generally relies on algorithm-based mathematical encryption. Recently, encryption techniques based on physical principles are emerging and being developed, leading to the new generation of encryption moving from mathematics to the intersection of mathematics and physics. Here, device-level encryption with ideal security is ingeniously achieved using modulation of the electron-hole radiative recombination in a GaN-light-emitting diode (LED). When a nano-LED is driven in the non-carrier injection mode, the oscillation of confined electrons can split what should be a single light pulse into multiple pulses. The morphology (amplitude, shape, and pulse number) of those history-dependent multiple pulses that act as carriers for transmitted digital information depends highly on the parameters of the driving signals, which makes those signals mathematically uncrackable and can increase the volume and security of transmitted information. Moreover, a hardware and software platform are designed to demonstrate the encrypted data transmission based on the device-level encryption method, enabling recognition of the entire ASCII code table. The device-level encryption based on splitting electroluminescence provides an encryption method during the conversion process of digital signals to optical signals and can improve the security of LED-based communication.

Achieving high precision in the fabrication of electronic circuits through additive manufacturing requires breaking the resolution limit of traditional printing processes. To address this challenge, we have developed a novel approach that involves preparing a heterogeneous wetting surface using a light-sensitive NBE-acrylate resin. By creating differences in surface energy on the substrate, we can limit the spread of the ink and surpass the limitations of conventional processes, achieving a printing resolution of 5 μ m. The NBE-acrylate resin can be cross-linked under white LED light illumination (with λ > 400 nm) to yield a hydrophobic surface, which can be converted to a hydrophilic surface by UV light illumination ( λ = 254 nm). The photochemical reaction of the NBE-acrylate resin under different light irradiation was confirmed by Fourier transform infrared spectroscopy (FTIR) and atomic force microscope (AFM) microforce measurements. In combination with a photomask, patterned heterogeneous wettability surfaces were prepared, which can be utilized for printing precision electronic circuits. Micrometer-scale printed circuits with a low line-to-space (L/S) of 5/50 and 10/10 μ m were successfully achieved by optimizing the ink formulation, which is significantly beyond the printing resolution. In the end, fully printed thin film transistor arrays based on semi-conducting carbon nanotubes were achieved, which showed higher charge carrier mobilities of 1.89–4.31 cm 2 s −1 V −1 depending on the channel width, demonstrating the application of this precision printed technique.

As an emerging single crystals growth technique, the 2D-material-assisted epitaxy shows excellent advantages in flexible and transferable structure fabrication, dissimilar materials integration, and matter assembly, which offers opportunities for novel optoelectronics and electronics development and opens a pathway for the next-generation integrated system fabrication. Studying and understanding the lattice modulation mechanism in 2D-material-assisted epitaxy could greatly benefit its practical application and further development. In this review, we overview the tremendous experimental and theoretical findings in varied 2D-material-assisted epitaxy. The lattice guidance mechanism and corresponding epitaxial relationship construction strategy in remote epitaxy, van der Waals epitaxy, and quasi van der Waals epitaxy are discussed, respectively. Besides, the possible application scenarios and future development directions of 2D-material-assisted epitaxy are also given. We believe the discussions and perspectives exhibited here could help to provide insight into the essence of the 2D-material-assisted epitaxy and motivate novel structure design and offer solutions to heterogeneous integration via the 2D-material-assisted epitaxy method.

Beyond traditional heteroepitaxy, 2D-materials-assisted epitaxy opens opportunities to revolutionize future material integration methods. However, basic principles in 2D-material-assisted nitrides' epitaxy remain unclear, which impedes understanding the essence, thus hindering its progress. Here, the crystallographic information of nitrides/2D material interface is theoretically established, which is further confirmed experimentally. It is found that the atomic interaction at the nitrides/2D material interface is related to the nature of underlying substrates. For single-crystalline substrates, the heterointerface behaves like a covalent one and the epilayer inherits the substrate's lattice. Meanwhile, for amorphous substrates, the heterointerface tends to be a van der Waals one and strongly relies on the properties of 2D materials. Therefore, modulated by graphene, the nitrides' epilayer is polycrystalline. In contrast, single-crystalline GaN films are successfully achieved on WS2 . These results provide a suitable growth-front construction strategy for high-quality 2D-material-assisted nitrides' epitaxy. It also opens a pathway toward various semiconductors heterointegration.

III-Nitrides, especially InGaN, are promising for high-efficiency thermoelectric (TE) components operating at high temperatures (HTs), playing a critical role in the recovery of waste heat for sustainable energy development. However, the performance of InGaN TE materials is limited by the high thermal conductivity (k) and the conflict coupling between the power factor (PF) and the k. Here, the previously unstudied two-dimensional InGaN/GaN SL structured TE device with a high In composition of 31% was developed and demonstrated to improve the TE figure of merit (ZT, Z = PF/k) by reducing the k value without deteriorating the PF. The Seebeck coefficient (S) exhibited a value of -365 mu V/K due to the increased density of electron states near the Fermi level by the low dimensional construction. Simultaneously, a relatively low k was obtained as 7.7 W/m.K, benefitting from the alloying and SL interface scattering effect of high energy phonons. Moreover, enhancement of the Umklapp process by the space confinement effect further lowers the k. Accordingly, a record ZT value of 0.089 at 300 K was achieved, which was better than previously reported values for GaN-based TE film materials. This work provides a new material system for improving the performance of nitride TE materials at HTs and extends the fields of application in electricity harvesting from waste heat.

Graphene (Gr)-assisted epitaxy of semiconductors has been demonstrated as a revolutionary strategy for the fabrication of nitride materials and flexible devices. However, till now, most of the GaN epitaxy assisted by Gr is performed on thermally stable foreign substrates because Gr suffers obvious deterioration due to the decomposition of GaN substrate. Thus, large lattice and thermal mismatches still exist and inevitably lead to a high density of dislocations in nitrides. To address this issue, here, the Gr-assisted epitaxy of high-quality GaN films on GaN templates is demonstrated by constructing specially designed self-organized defective (SOD) Gr as a buffer layer. The SOD Gr allows for the spontaneous relaxation of strain in GaN epilayers by weakening the interfacial interactions; and thus, blocks the upward spread of threading dislocations in GaN templates. Therefore, screw and edge dislocation densities in GaN epilayers show reductions of 51% and 62%, respectively, compared to that in homoepitaxy. Based on the GaN film grown on SOD Gr, the as-fabricated blue light-emitting diode exhibits a 17% enhancement of light output power and a better emission wavelength stability than that without Gr. This work opens a practical pathway for the growth of high-quality nitrides and manufacturing of high-performance nitride-based devices.

Semiconductors In article number 2202529, Tongbo Wei, Zhongfan Liu, Peng Gao, Zhiqiang Liu, and co-workers find that geometry matched WS2 can provide a proper lattice potential field for nitrides epitaxial growth. By using a transferred WS2 buffer layer, a single-crystalline GaN epilayer can be obtained on an amorphous quartz glass by heterogenous epitaxy.

The structure and morphology of the substrate surface play critical roles in tuning the properties of the supported two-dimension materials (2DM). In this work, a simple strategy to engineer the SrTiO3 single crystal into a trenched structure which is composed of atomically flat terraces and high steps of several nanometers is developed. Through the conventional chemical vapor deposition method, high quality single-layered MoS2 nanosheets are successfully fabricated directly on the trenched SrTiO3 (Tr-STO) substrate, which thus result in a heterostructure with well-defined interface and controllable corrugated morphology. The corrugated MoS2/Tr-STO sample displays a drastically suppressed photoluminescence as compared to those grown on atomically flat substrates. Detailed scanning probe microscopy in combination with optical spectroscopy measurements demonstrates that the photoluminescence quenching occurs exclusively in the MoS2 area carpeting the high SrTiO3 steps, which can be attributed to the significantly reduced bandgaps hence massively enriched free charges in these regions. This work not only provides a new strategy to tailor the 2DM properties by simply engineering the substrate surface corrugations, but also brings deep insights into the dependence of properties of the hybridized system on the interface morphologies.

Superconducting nanowire single photon detectors (SNSPDs) have been extensively investigated due to their superior characteristics, including high system detection efficiency, low dark count rate and short recovery time. The polarization sensitivity introduced by the meandering-type superconductor nanowires is an intrinsic property of SNSPD, which is normally measured by sweeping hundreds of points on the Poincaré sphere to overcome the unknown birefringent problem of the SNSPD's delivery fiber. In this paper, we propose an alternative method to characterize the optical absorptance of SNSPDs, without sweeping hundreds of points on the Poincaré sphere. It is shown theoretically that measurements on the system detection efficiencies (SDEs) subject to cases of four specific photon polarization states are sufficient to reveal the two eigen-absorptances of the SNSPD. We validate the proposed method by comparing the measured detection spectra with the spectra attained from sweeping points on the Poincaré sphere and the simulated absorption spectra.

传统L1惩罚序列凸规划算法(LPSCP)在进行制导炮弹弹道规划时,线性近似误差大,导致目标函数曲线震颤,难以收敛到最优解.针对此问题提出了一种改进的L1惩罚序列凸规划算法(ILPSCP).ILPSCP算法引入指数衰减的相对信赖域宽度和带上界的惩罚系数,消除了目标函数的震颤.以一般化控制能量最优轨迹规划模型为研究对象,利用Radau伪谱法离散连续变量,线性凸化非线性动态方程,建立标准凸优化模型.以制导炮弹纵向平面内滑翔弹道模型为仿真实例,分别采用传统的LPSCP算法、提出的ILPSCP算法和非线性最优化通用工具箱GPOPS23种方法进行仿真对比.结果表明:ILPSCP算法成功解决了传统LPSCP算法震颤和不稳定等问题;同时ILPSCP算法的仿真结果与GPOPS2的仿真结果高度重合,证明了提出的算法对求解复杂弹道规划问题的有效性.