The Casimir Effect in Dielectrics

Abstract

The Casimir force in one dimension between two dielectrics with arbitrary position-dependent refractive index is calculated. A numerical procedure is developed, including renormalization and regularization, to calculate this force and the temperature correction. The force is directly derived from the electromagnetic mode structure and the corresponding eigenenergy spectrum. Some essential differences between one- and three-dimensional results are discussed.     

Charge-Formation Processes in Liquid Dielectrics

On the basis of the results of analytic investigation of the processes of charge formation in weakly conducting liquids in the presence of associations of ions, we make the following conclusions: The bulk concentration of charges increases if we take into account the process of formation of complex ions. The qualitative influence of this process is observed if the discharge rate is constant. It is shown the density of heterocharges on the electrodes undergoes abrupt jumps and is proportional to the concentration of admixtures N ₀ ^3/2. For a liquid dielectric with dissociation–injection conductivity, the sign of charges on the anode changes for a certain value of the electric-field intensity, which is higher than the corresponding value observed in the absence of complex formation.     

Polarization of Dielectrics by Acceleration

We argue that acceleration induces electric polarization in usual dielectrics. Both accelerations in superfluid ( and ) participate in the medium polarization. Excitations contribution to the polarization is calculated at low temperatures. Estimates of the effect show order of magnitude agreement with recent experimental results on electric effect of superflow.     

Dielectrics for Field Effect Technology

The availability of stable MOS gate systems and high density storage capacitors is an essential requirement for the development of the field effect storage technology. For standard MOSFET gates this role has been fulfilled by SiO₂ grown by thermal oxidation of the Si substrate. Improved insight into the properties of the Si/Si0₂ system and perfection of its growth technology will secure its role in Si MOSFET memories for the future. For charge storage application the stability requirements are less demanding. However, here SiO₂ is not able to provide sufficient capacity. In this case higher dielectric constant materials (Si₃N₄ or Ta₂O₅) have to take over. Particularly attractive appears the use of ferroelectrics. These dielectric materials not only offer a high dielectric constant, but also the perspective of providing non-volatile storage in capacitor structures.     

Propagation of Squeezed Light in Dielectrics

Abstract

We model the propagation of squeezed light through a dielectric medium. Frequency-dependent absorption reduces the level of squeezing and may decrease the squeezing bandwidth. Dispersion dephases the squeezing at different frequencies within the spectrum.     

Flexible Temperature-Invariant Polymer Dielectrics with Large Bandgap

Flexible dielectrics operable under simultaneous electric and thermal extremes are critical to advanced electronics for ultrahigh densities and/or harsh conditions. However, conventional high-performance polymer dielectrics generally have conjugated aromatic backbones, leading to limited bandgaps and hence high conduction loss and poor energy densities, especially at elevated temperatures. A polyoxafluoronorbornene is reported, which has a key design feature in that it is a polyolefin consisting of repeating units of fairly rigid fused bicyclic structures and alkenes separated by freely rotating single bonds, endowing it with a large bandgap of ≈5 eV and flexibility, while being temperature-invariantly stable over −160 to 160 °C. At 150 °C, the polyoxafluoronorbornene exhibits an electrical conductivity two orders of magnitude lower than the best commercial high-temperature polymers, and features an unprecedented discharged energy density of 5.7 J cm⁻³ far outperforming the best reported flexible dielectrics. The design strategy uncovered in this work reveals a hitherto unexplored space for the design of scalable and efficient polymer dielectrics for electrical power and electronic systems under concurrent harsh electrical and thermal conditions.     

钛酸锆固溶体微波介电瓷的制备与性能

用共沉淀的方法制备了一系列ZrxTi1-xO4(0.4≤x≤0.6）纳米粉，XRD物相分析为ZrTiO4固溶体，TEM观察粒子粒径为20～30nm。通过制陶实验对该系列固溶体的烧结特性，形貌及介电性能进行了研究。结果表明，TiO2含量影响固溶体的最佳烧结温度，在相同的烧结温度下，TiO2含量越高，瓷体的相对密度越低，晶粒越大。该材料有很好的频率、温度稳定性，其介电性能与组成和瓷体的相对密度有关。介电常数和品质因数随瓷体相对密度增大而增大。当材料的相对密度高于90%时，随着TiO2含量增加，其介电常数增大，而品质因数降低。     

Hf基高K栅介质材料研究进展

随着微电子技术的不断发展,MOSFET的特征尺寸已缩小至100nm以下,SiO2作为栅介质材料已不能满足技术发展的需求,因此必须寻求一种新型高K的介质材料来取代SiO2.当今普遍认为Hf基栅介质材料是最有希望取代SiO2而成为下一代MOSFET的栅介质材料.综述了高K栅介质材料的意义、Hf基高K栅介质材料的最新研究进展和Hf基高K栅介质材料在克服自身缺陷时使用的一些技术;介绍了一款由Hf基高K介质材料作为栅绝缘层制作的MOSFET.     

聚合物电介质的击穿与空间电荷的关系

空间电荷是聚合物在交流或直流高压作用下发生老化和击穿的主要原因之一,以往的研究基本认为由于空间电荷的注入并集聚使介质内部电场严重畸变,从而使介质老化最终引起击穿,相应的解释模型都是在有外加电场作为前提建立的.但是,根据最新的实验研究发现,外加电场并不是介质击穿的必要条件,介质的击穿可以发生在空间电荷的脱阱过程中而与外加电场无关.本文阐述了空间电荷与绝缘高聚物的老化和击穿的关系,并且结合最新的研究成果,揭示了介质内部空间电荷的存在是击穿的重要条件,而且击穿是发生在空间电荷的脱阱过程中.     

Flexoelectricity in Solid Dielectrics: From Theory to Applications

Flexoelectricity phenomenologically describes the universal electromechanical coupling effect between electric polarization and strain gradient, and electric field gradient and elastic strain. In contrast to piezoelectricity which is invalid in materials with inversion symmetry, flexoelectricity exists, commonly, in all solid dielectrics. In this paper, a summary of the research on flexoelectricity is presented to illustrate the development of this topic. Flexoelectricity still have many open questions and unresolved issues in the developing field, although it has attracted a surge of attention recently. Here we review the theoretical investigations and experimental studies on flexoelectricity, and the aim of the current paper is to look into the potential applications of this electromechanical coupling effect.     

高K栅介质材料的研究现状与前景

论述了45～32nm技术节点下高K材料取代SiO2的必要性和基本要求,综述了高K栅介质中极具代表性的Hf基材料.研究表明,向HfO2中分别掺杂Al、si、Ta、N等形成的复合Hf基高K栅介质材料具备较Hfo2更加优异的物理结构、晶化温度、热力学稳定性以及电学特性,但与此同时也存在如何优化掺杂量、沟道载流子迁移率下降以及中间层引起的界面退化等难题.针对这些挑战,探讨了新型"堆垛结构"和引起载流子迁移率下降的物理机制,展望了高K材料在未来先进COMS器件中的应用.     

固态电介质的物理特性及其应用前景

本文综述了固态电介质的特征、极化的基本过程、极化弛豫过程中的表征及其各种物理特性和相关的技术应用，介绍了固态电介质介电特性研究的最新进展，明确指出开发性能优异的铁电器件关键在于设法获得具有高介电特性、低损耗、高稳定性和抗疲劳等综合物理特性的固态电介质材料。     

Dielectrics of lead zirconate bonded with barium borate glass

Dielectric constant variation with temperature and frequency is reported for barium-borate glass-bonded lead zirconate. Lowering of the relative permittivity of the ceramic is attributed to the presence of the glass.     

On the Working Mechanisms of Molecules-Based Van der Waals Dielectrics

Sb₂O₃ molecules offer unprecedented opportunities for the integration of a van der Waals (vdW) dielectric and a 2D vdW semiconductor. However, the working mechanisms underlying molecules-based vdW dielectrics remain unclear. Here, the working mechanisms of Sb₂O₃ and two Sb₂O₃-like molecules (As₂O₃ and Bi₂O₃) as dielectrics are systematically investigated by combining first-principles calculations and gate leakage current theories. It is revealed that molecules-based vdW dielectrics have a considerable advantage over conventional dielectric materials: defects hardly affect their insulating properties. This shows that it is unnecessary to synthesize high-quality crystals in practical applications, which has been a long-standing challenge for conventional dielectric materials. Further analysis reveals that a large thermionic-emission current renders Sb₂O₃ difficult to simultaneously satisfy the requirements of dielectric layers in p-MOS and n-MOS, which hinders its application for complementary metal-oxide-semiconductor (CMOS) devices. Remarkably, it is found that As₂O₃ can serve as a dielectric for both p-MOS and n-MOS. This work not only lays a theoretical foundation for the application of molecules-based vdW dielectrics, but also offers an unprecedentedly competitive dielectric (i.e., As₂O₃) for 2D vdW semiconductors-based CMOS devices, thus having profound implications for future semiconductor industry.     

Mechanical and Electric Control of Photonic Modes in Random Dielectrics

Random dielectrics defines a class of non‐absorbing materials where the index of refraction is randomly arranged in space. Whenever the transport mean free path is sufficiently small, light can be confined in modes with very small volume. Random photonic modes have been investigated for their basic physical insights, such as Anderson localization, and recently several applications have been envisioned in the field of renewable energies, telecommunications, and quantum electrodynamics. An advantage for optoelectronics and quantum source integration offered by random systems is their high density of photonic modes, which span a large range of spectral resonances and spatial distributions, thus increasing the probability to match randomly distributed emitters. Conversely, the main disadvantage is the lack of deterministic engineering of one or more of the many random photonic modes achieved. This issue is solved by demonstrating the capability to electrically and mechanically control the random modes at telecom wavelengths in a 2D double membrane system. Very large and reversible mode tuning (up to 50 nm), both toward shorter or longer wavelength, is obtained for random modes with modal volumes of the order of few tens of (λ/n)³.     

Rational Co‐Design of Polymer Dielectrics for Energy Storage

Although traditional materials discovery has historically benefited from intuition‐driven experimental approaches and serendipity, computational strategies have risen in prominence and proven to be a powerful complement to experiments in the modern materials research environment. It is illustrated here how one may harness a rational co‐design approach—involving synergies between high‐throughput computational screening and experimental synthesis and testing—with the example of polymer dielectrics design for electrostatic energy storage applications. Recent co‐design efforts that can potentially enable going beyond present‐day “standard” polymer dielectrics (such as biaxially oriented polypropylene) are highlighted. These efforts have led to the identification of several new organic polymer dielectrics within known generic polymer subclasses (e.g., polyurea, polythiourea, polyimide), and the recognition of the untapped potential inherent in entirely new and unanticipated chemical subspaces offered by organometallic polymers. The challenges that remain and the need for additional methodological developments necessary to further strengthen the co‐design concept are then presented.