SiAlCN前驱体低温陶瓷化过程研究

采用异丙醇铝改性氨解制备的聚甲基乙烯基硅氮烷来制备聚铝硅氮烷,研究其在200～800℃下的陶瓷化过程中所发生的结构变化.采用红外光谱(IR)、气相色谱(GC)和耦合热重/差热分析(TG/DTA)对陶瓷化过程的键变化、挥发物、热失重和差热分析进行表征.结果表明:200℃之前有吸热峰是溶剂和低聚物挥发所致,此时只有1％的质量损失;质量损失主要发生在200～600℃之间,可达28％,进一步交联成键,大量CH4,H2和NH3放出;600℃到800℃只有3％的失重,陶瓷化过程基本结束.通过IR,GC和DTA推测出陶瓷化过程可能发生的变化,XRD结果表明800℃裂解产物是非晶态物质.     

Effect of carrier screening on ZnO-based resistive switching memory devices

The carrier screening effect occurs commonly in dielectric materials. It reduces the electric potential gradient, thus negatively affecting the functionality of resistive random access memory (RRAM) devices. An Au/ZnO film/Al-doped ZnO device fabricated in this work exhibited no resistive switching (RS), which was attributed to the carrier screening effect. Therefore, annealing was used for alleviating the screening effect, significantly enhancing the RS property. In addition, different on/off ratios were obtained for various bias values, and the screening effect was accounted for by investigating electron transport mechanisms. Furthermore, different annealing temperatures were employed to modulate the free carrier concentration in ZnO films to alleviate the screening effect. The maximal on/off ratio reached 10⁵ at an annealing temperature of 600 °C, yielding the lowest number of free carriers and the weakest screening effect in ZnO films. This work investigates the screening effect in RS devices. The screening effect not only modulates the characteristics of memory devices but also provides insight into the mechanism of RS in these devices.

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High Phase Purity of Large‐Sized 1T′‐MoS2 Monolayers with 2D Superconductivity

The development of transition metal dichalcogenides has greatly accelerated research in the 2D realm, especially for layered MoS₂. Crucially, the metallic MoS₂ monolayer is an ideal platform in which novel topological electronic states can emerge and also exhibits excellent energy conversion and storage properties. However, as its intrinsic metallic phase, little is known about the nature of 2D 1T′‐MoS₂, probably because of limited phase uniformity (<80%) and lateral size (usually <1 µm) in produced materials. Herein, solution processing to realize high phase‐purity 1T′‐MoS₂ monolayers with large lateral size is demonstrated. Direct chemical exfoliation of millimeter‐sized 1T′ crystal is introduced to successfully produce a high‐yield of 1T′‐MoS₂ monolayers with over 97% phase purity and unprecedentedly large size up to tens of micrometers. Furthermore, the large‐sized and high‐quality 1T′‐MoS₂ nanosheets exhibit clear intrinsic superconductivity among all thicknesses down to monolayer, accompanied by a slow drop of transition temperature from 6.1 to 3.0 K. Prominently, unconventional superconducting behavior with upper critical field far beyond the Pauli limit is observed in the centrosymmetric 1T′‐MoS₂ structure. The results open up an ideal approach to explore the properties of 2D metastable polymorphic materials.     

主动磁悬浮轴承支承旋转机械的减振性能研究

针对旋转机械的振动噪声问题,在对轴承工作特性及系统振动传递特性进行理论分析的基础上,提出了采用新型主动磁悬浮轴承取代传统机械轴承以实现整机减振降噪的设想.以某工程试验样机为研究对象,利用有限元软件考察了轴承的刚度变化对该样机轴承座机脚振动不平衡响应的影响,进而开展了专门的振动对比实验来对主动磁悬浮轴承的减振性能进行实际评估.结果表明:减小轴承刚度的思路对于降低旋转机械的机脚振动确实可行;相比于机械轴承,采用主动磁悬浮轴承支承对于减小整机振动水平具有显著实际效果.相关结论可为拓展主动磁悬浮轴承技术的应用领域和场合提供重要思路及数据支持,同时也为其今后的工程化实用奠定研究基础.     

NMOB与花生酸的组装多层膜及其非线性光学性质

利用与花生酸交替的方法，制备了2－硝基－5（N－甲基－N－十八烷基）氨基苯甲酸（NMOB）非中心对称多层膜，研究了它的非线性光学性质，结果表明，该多层膜的二次谐波强度与NMOB层数平方基本成正比。X－射线小角衍射测定结果再次表明，多层膜的排列相当有序，NMOB单层膜厚度为2．76nm.NMOB有良好的二阶非线性光学性质和出色的成膜性质，是一种很好的非线光学LB膜材料，可望用于制作光波导。     

Grain‐Boundary “Patches” by In Situ Conversion to Enhance Perovskite Solar Cells Stability

The power conversion efficiency of organic–inorganic hybrid perovskite solar cells has increased rapidly, but the device stability remains a big challenge. Previous studies show the grain boundary (GB) can facilitate ion migration and initiate device degradation. Herein, methimazole (MMI) is employed for the first time to construct a surface “patch” by in situ converting residual PbI₂ at GBs. The resultant MMI–PbI₂ complex can effectively suppress ion migration and inhibit diffusion of the metal electrodes. The origin of the surface “patch” effect and their working mechanisms are investigated experimentally and theoretically at the microscopic level. It hence demonstrates a simple and effective method to prolong the device stability in the context of GB engineering, which could be extensively applied to perovskite‐based optoelectronics.     

非对称电阻场板场效应器件击穿特性仿真分析

利用TCAD仿真研究一种二维紧耦合电阻场板电流调制原理下的物理模型与最优化结构。通过优化关键工艺与材料参数,改善器件漂移区尖峰电场,最终在相同漂移区掺杂下击穿电压较一维PN结理论击穿电压提升273%,相同归一化击穿电压10%变化范围下,漂移区电荷变化允许冗余范围比现有传统PN超结拓宽15倍。相较于对称电阻场板场效应器件,在现有工艺下非对称优化电阻场板场效应器件能够更好的实现结构小型化与高密度的设计。     

构建警务技能虚拟学习社区研究

当今的公安进修体制,已经无法跟上日益增长的公安工作要求,并且侧重于理论研究的课程内容,让公安民警无法将所学知识运用在工作实践中.因此模拟的真实执法情景,让公安民警将理论与实际相结合,将理论真正的运用于警务执勤中,并且可以促进公安民警提升自身解决警务工作的能力与应变能力.文章构建出一个以案例为核心,借助网络交流虚拟社区为基础的公安专业发展空间,为提升民警的专业技能和基础知识的奠定,并促进公安专业深化改革与发展.     

基于注意力机制的自监督图卷积会话推荐

为了解决会话推荐系统中数据稀疏性问题, 提出了一种基于注意力机制的自监督图卷积会话推荐模型(self-supervised graph convolution session recommendation based on attention mechanism, ATSGCN). 该模型将会话序列构建成3个不同的视图: 超图视图、项目视图和会话视图, 显示会话的高阶和低阶连接关系; 其次, 超图视图使用超图卷积网络来捕获会话中项目之间的高阶成对关系, 项目视图和会话视图分别使用图卷积网络和注意力机制来捕获项目和会话级别局部数据中的低阶连接信息; 最后, 通过自监督学习使两个编码器学习到的会话表示之间的互信息最大化, 从而有效提升推荐性能. 在Nowplaying和Diginetica两个公开数据集上进行对比实验, 实验结果表明, 所提模型性能优于基线模型.     

Ultra-thin Body Buried In0.35Ga0.65As Channel MOSFETs with Extremely Low Off-current on Si Substrates

In this paper, we investigated the electrical properties of the Metal-oxide-semiconductor gate stack of Ti/Al2O3/InP under different annealing conditions. A min...