Tailoring of Photoluminescence Properties in All-Vacuum Deposited Perovskite via Ruddlesden–Popper Faults

Ruddlesden–Popper (RP) faults are well known in oxide perovskites, and are also observed in promising metal halide perovskites. However, the effect of RP faults on optical properties of perovskite has not been systematically investigated. In this study, it is found that RP faults are common planar faults in all-vacuum deposited CsPbBr₃-based perovskite polycrystal thin films, and the density of RP planar faults can be greatly increased by non-stoichiometric composition (Cs-rich) as well as reduced dimensionality (quasi-2D) strategies. The photoluminescence (PL) measurement reveals monotonically increasing peak intensities with higher densities of RP planar faults from Cs-rich, quasi-2D to Cs-rich & quasi-2D samples. The corresponding atomic-scale differential phase contrast maps indicate strongly confined charges within the RP planar fault network, which explains well the relationship between PL enhancement and the density of RP planar faults, and offers an alternative pathway for tailoring the optoelectronic properties of perovskite.     

A Stable Polymer-based Solid-State Lithium Metal Battery and its Interfacial Characteristics Revealed by Cryogenic Transmission Electron Microscopy

Solid-state lithium metal batteries (SSLMBs) are a promising candidate for next-generation energy storage systems due to their intrinsic safety and high energy density. However, they still suffer from poor interfacial stability, which can incur high interfacial resistance and insufficient cycle lifespan. Herein, a novel poly(vinylidene fluoride‑hexafuoropropylene)-based polymer electrolyte (PPE) with LiBF₄ and propylene carbonate plasticizer is developed, which has a high room-temperature ionic conductivity up to 1.15 × 10⁻³ S cm⁻¹ and excellent interfacial stability. Benefitting from the stable interphase, the PPE-based symmetric cell can operate for over 1000 h. By virtue of cryogenic transmission electron microscopy (Cryo-TEM) characterization, the high interfacial compatibility between Li metal anode and PPE is revealed. The solid electrolyte interphase is made up of an amorphous outer layer that can keep intimate contact with PPE and an inner Li₂O-dominated layer that can protect Li from continuous side reactions during battery cycling. A LiF-rich transition layer is also discovered in the region of PPE close to Li metal anode. The feasibility of investigating interphases in polymer-based solid-state batteries via Cryo-TEM techniques is demonstrated, which can be widely employed in future to rationalize the correlation between solid-state electrolytes and battery performance from ultrafine interfacial structures.     

A Hybrid Strategy-Based Ultra-Narrow Stretchable Microelectrodes with Cell-Level Resolution

Stretchable ultra-narrow (e.g., 10 µm in width) microelectrodes are crucial for the electrophysiological monitoring of single cells providing the fundamental understanding to the working mechanism of neuro network or other electrically functional cells. Current fabrication strategies either focus on the preparation of normal stretchable electrodes with hundreds of micrometers or millimeters in width by using inorganic conductive materials or develop conductive organic polymer gel for ultra-narrow electrodes which suffer from low stretchability and instability for long-term implantation, therefore, it is still highly desirable to explore bio-interfacial ultra-narrow stretchable inorganic electrodes. Herein, a hybrid strategy is reported to prepare ultra-narrow multi-channel stretchable microelectrodes without using photolithography or laser-assisting etching. A 10 µm × 10 µm monitoring window is fabricated with enhanced interfacial impedance by the special rough surface. The stretchability achieves to 120% for this 10 µm-width stretchable electrode. Supported by these superior properties, it is demonstrated that the stretchable microelectrodes can detect electrophysiological signals of single cells in vitro and collect electrophysiological signals more precisely in vivo. The reported strategy will open up the accessible preparation of the fine-size stretchable microelectrode. It will significantly improve the resolution of monitoring and stimulation of inorganic stretchable electrodes.     

Direct Observation of Oxygen Ion Dynamics in a WO3-x based Second-Order Memristor with Dendritic Integration Functions

Direct observation of oxygen dynamics in an oxide-based second-order memristor can provide the valid evidence to clarify the memristive mechanism, however, which is still limited for now. In this study, the migration and diffusion of oxygen ions in the region of Pt/WO_3-x Schottky interface are observed in the WO_3-x second-order memristor by using the technique of in situ transmission electron microscopy (TEM) and the electron energy loss spectroscopy. Interestingly, the coexistence of memristive and memcapacitive switching can be implemented in this memristor. Combined with the analysis of depth-profile X-ray photoelectron spectroscopy (XPS), an interface-barrier-modulation second-order memristive model is proposed based on the above results. Notably, temporally correlative oxygen dynamics in the memristor offers the platform to integrate signals from multiple inputs, enabling the realization of the dendritic functions of synchronous and asynchronous integration for the application of logic operations with fault-tolerance capability and associative learning. These findings provide the experimental evidence to in-depth understanding of oxygen dynamics and switching mechanism in second-order memristor, which can support the optimization of memristive performance and the achievement of biorealistic synaptic functions.     

面向电子战射频光传输的宽带射频信号杂散产生机理及优化方法

针对电子战系统的宽带射频信号波分复用传输,通过理论分析给出了微波光子链路中各关键参量对杂散信号的影响规律,提出了非均匀信道间隔分配的除杂优化方法。该方法通过微调各通道的波长,使四波混频产生的杂散频率超过电子战接收机带宽,从而降低杂散对系统的影响。该方案实现简单,且无需改变现有电子战系统架构,具有较好的工程实现性。实验结果表明:与等波长间隔相比,5通道非均匀波分复用信号传输1 km时,在接收机带宽内四波混频引起的杂散得到了显著优化,动态范围提升了26 dB以上。     

InPBi薄膜材料的结构性能和光学性能研究

室温下,InPBi表现出强而宽的光致发光光谱,其宽光谱特性来自于材料中的PIn反位深能级和与Bi相关的深能级。该特性使得InPBi有希望应用于制备光学相干层析扫描系统中的超辐射光源。文章利用透射电子显微镜和三维原子探针研究了InPBi薄膜材料的结构性能,发现Bi原子在InPBi薄膜中的分布极不均匀,在InPBi/InP界面出现了Bi的富集区,从该区域沿[001]方向出现了Bi的纳米面,此纳米面位于(110)平面上。这种Bi原子的富集分布阻碍了PIn反位参与的载流子复合过程,对InPBi的光学性能有显著的影响。研究结果可为制造光学相干层析扫描系统的超辐射发光二极管提供一定的理论基础。     

相位调制微波光传输链路特性分析（特邀）

常规的微波光子系统采用强度调制方式实现微波信号的电光转换,由于调制器采用马赫-曾德尔干涉结构(MZI),系统性能不仅受到自身正弦响应特性的制约,而且需要进行偏置点控制,因此存在动态范围受限、系统控制复杂以及3 dB固有损耗带来的效率不足的问题,而采用相位调制可避免该问题。围绕相位调制光传输链路,为了完成相位调制信号的光电解调,文章提出采用薄膜滤波器通过边带抑制与边带选通两种方式实现相位调制到强度调制的转换,并分析了链路射频性能与器件参数之间的映射关系。实测对比了相位调制与常规强度调制链路之间的传输特性,通过分析可知,在相同链路配置条件下,相位调制链路具有更高的传输效率,而且光滤波带来的均衡作用,使得相位调制链路的3 dB带宽比强度调制链路大两倍。     

太赫兹带阻滤波器工艺研究

以中心工作频率130 GHz、衰减深度为-40 dB的太赫兹带阻滤波器为制备对象,介绍了其在制备过程中蒸镀、光刻、显影及湿法刻蚀等工艺步骤中的一些技术细节。制备得到的太赫兹滤波器加工误差<±3 μm,考察了加工误差对滤波器传输性能的影响,该加工误差在可接受范围。为进一步验证工艺的可靠性,使用空间测量装置获得了滤波器样品传输性能,测试结果与设计值吻合度较好。最后,探讨了本工艺推广至更高频率器件的适用性及需要改进之处。文中介绍的硅基太赫兹器件加工工艺适用于电子器件与光子器件的融合发展。     

Help from space: grant-free massive access for satellite-based IoT in the 6G era

The Sixth-Generation (6G) standard for wireless communications is expected to realize ubiquitous coverage for massive Internet of Things (IoT) networks by 2030. Satellite-based communications are recognized as a highly promising technical enabler to satisfy IoT service requirements in the 6G era. This study analyzes multiple access technologies, which are essential for the effective deployment of satellite-based IoT. First, we thoroughly investigate the existing research related to massive access, including information-theory considerations as well as Non-Orthogonal Multiple Access (NOMA) and Random Access (RA) technologies.Then, we explore the influence of the satellite transmission environment on multiple access technologies. Based on this study, a Non-orthogonal Massive Grant-Free Access (NoMaGFA) scheme, which reaps the joint benefits of RA and NOMA, is proposed for asynchronous transmissions in satellite-based IoT to achieve improved system throughput and enhance the system robustness under varying traffics. Finally, we identify some important and interesting future developments for satellite-based IoT, including waveform design, transceiver design, resource allocation, and artificial intelligence-enhanced design.     

基于约束空间光谱联合的亚像素定位方法北大核心CSCD

针对高光谱遥感图像,提出了一种约束空间光谱的亚像素定位方法。传统的亚像素定位方法以解混的结果作为输入,可能无法充分利用高光谱图像丰富的光谱信息。本文所提出的基于约束空间光谱联合的亚像素定位方法(constraint spatial-spectral subpixel mapping,CSSSM),利用下采样将像素丰度与亚像素丰度显式联系起来,代入线性解混模型得到亚像素丰度求解的新模型。在求解过程中,通过添加稀疏性约束与平滑性约束,以限制亚像素丰度的解空间,亚像素丰度求解更精确。其中,针对亚像素丰度稀疏性先验采用重加权1范数作为新的约束,并自适应地更新权重;针对亚像素丰度空间先验信息则采用全变分(total variational,TV)正则化作为约束,然后使用乘法迭代算法求解亚像素丰度,最后利用赢者通吃的策略进行类别确定。在两个合成数据集上进行了实验,结果表明,本方法能够进一步提高亚像素定位的精度。