The bilocal approximation for the effective dielectric constant of an isotropic random medium

The bilocal approximation in strong fluctuation theory leads to an expression for the effective dielectric constant of a random medium. A detailed study of this expression is made for the case of a medium characterized by an isotropic correlation function. The effective dielectric constant is shown to obey an equation involving an integral containing the correlation function, the free space propagation constant, the quasistatic dielectric constant, and the effective dielectric constant itself, Numerical methods for solution are suggested. The low frequency behavior is also examined. The leading correction term to the quasistatic dielectric constant is shown to be different than previously deduced expressions.     

Variation of lange-coupler geometry with dielectric constant

Geometry of the ?3 dB, 50? Lange coupler is presented as a continuous function of dielectric constant, between ?r=2 and 12. Corresponding even- and odd-mode phase velocities are also given, allowing the length of coupled section to be calculated.     

Resonant modes of a concentric spherical cavity with conicallystratified medium

An analysis on electromagnetic fields of a cavity formed by two concentric conducting spheres with a conically stratified medium is presented in this paper. Angular transmission formulation and the radial eigenfunction expansion are used to formulate the field components. Boundary matching methods are applied to obtain the characteristic equations containing various infinite series of spherical Hankel functions and Legendre functions of complex order for resonant frequencies. The first two resonant frequencies and field expansion coefficients are determined numerically. The distribution pattern of angular field components and the forms of typical electric field lines and magnetic field lines for the first resonant fields are also indicated     

Waveguide-fed spherical dielectric antennas

The results of an experimental investigation into the radiation properties of circular waveguide excited dielectric sphere antennas are reported. The input waveguide had a plain end without a flange or ground plane. The input voltage standing-wave ratio varied from about 1.1 to 2.5 for the sphere sizes used but can usually be reduced to about 1.25 over the 8-12 GHz band by separating the sphere from the waveguide. Separation increases the on-axis gain by 1-3 dB and produces nearly equal beamwidths in bothE- andH- planes. Phase front measurements located a fixed phase center near the end of the waveguide.     

Waveguide-fed dielectric spherical antennas

A theoretical method is presented for obtaining the far-field patterns of a feed structure consisting of a homogeneous dielectric sphere placed in front of, but displaced from, the open end of a circular waveguide carrying the TE11 mode. Such a feed, for an optimum value of the sphere offset, has a reduced input v.s.w.r., as indicated experimentally elsewhere. Theoretical expressions are derived for the radiated far-field components of this type of a feed and the results are compared with the experimental data obtained from the test feeds     

Low dielectric constant materials

The more advanced an integrated circuit becomes, the more stringent are the demands for certain properties of a dielectric or insulating material. In addition, it is essential that the layer maintain its specific electrical, physical, and chemical properties after incorporation in the device structure and during subsequent processing. Due to temperature budget constraints and the accelerated decrease of feature sizes below 0.25 μm, one can no longer rely on traditional choices but has to search for alternatives, both for low and high permittivity replacements. In this article we survey currently used low dielectric constant materials and future trends for microelectronic applications.     

Theory of Fabry-Perot resonators with dielectric medium

A Fabry-Perot resonator filled with a dielectric slab is investigated using the Vainshtein method. Simple and explicit formulas are obtained for the diffraction loss, phase shift, and field distributions for both strip and circular mirrors. It is found that the presence of the dielectric reduces the diffraction loss, and causes mode confinement to certain degrees.     

Effective conductivity of a polycrystalline medium with weak macroscopic anisotropy

In the effective medium approximation, an analytical solution is obtained for calculating the tensor of the effective conductivity of a polycrystalline medium with weak uniaxial texture. The medium is assumed to consist of a single type of biaxial spherical crystallites. The orientation of the crystallites is taken into account by means of the theory of rotation group representations. A solution generalized to triaxial textures is obtained.     

A spherical scatterer inside a circular hollow dielectric waveguide

A theoretical investigation is presented of scattering characteristics of a perfectly conducting spherical object placed inside a quasi-optical transmission line of the millimeter and submillimeter waves in the form of a circular hollow dielectric waveguide (HDW). From the analytical expressions obtained, backscattering and extinction cross sections of this object are derived via the excitation coefficient of the dominantHE ₁₁ mode of the circular HDW and the HDW geometrical parameters. The agreement of the results with the corresponding data for the scattering of a plane homogeneous wave is shown.     

中等电压透射电镜的球差矫正

20世纪末中等电压透射电镜的物镜球差矫正获得成功,这是上世纪80年代世界第一台电子显微镜创制者获得诺贝尔物理奖以来电镜发展史上迄今取得的最重大成就.本文简要回顾了球差矫正研究的历史,重点介绍Scherzer,Rose,Haider等关于球差矫正的观点、理论和实验研究所取得的成果,详细讨论了六极消球差系统的工作原理以及对中合轴的原理和方法.     

MICROWAVE MEASUREMENT OF COMPLEX DIELECTRIC CONSTANT

In this paper,the formula given by S.Roberts and A.Von Hippel (1946) has been extended.We make a program for calculating the phase transmission constant of the tested material which is put into thewavegoide and for obtaining the multi-value solutions.Tbe method for,determining ε_r and tanδ of a testedmaterial does not need special equipments,but it can meet the accuracy requirement for testing ordinarymaterials.     

Guided optical waves in fibers with negative dielectric constant

We classify and discuss all optical guided modes able to propagate in ideal metallic-dielectric structures having the symmetry of a step index fiber. The cases of a metallic core with a dielectric cladding and a dielectric core with a metallic cladding are considered. In each case, the intensity profile of the allowed guided modes is shown. The geometric and frequency dispersion of the effective index of the modes is discussed as a function of the optogeometrical parameters of the fibers     

Effective permittivity of dielectric mixtures

General mixing formulas are derived for discrete scatterers immersed in a host medium. The inclusion particles are assumed to be ellipsoidal. The electric field inside the scatterers is determined by quasi-static analysis, assuming the diameter of the inclusion particles to be much smaller than one wavelength. The results are applicable to general multiphase mixtures, and the scattering ellipsoids of the different phases can have different sizes and arbitrary ellipticity distribution and axis orientation, i.e. the mixture may be isotropic or anisotropic. The resulting mixing formula is nonlinear and is suitable for iterative solutions. The formula contains a quantity called the apparent permittivity, and with different choices of this quantity, the result leads to the generalized Lorentz-Lorenz formula, the generalized Polder-van Santen formula, and the generalized coherent potential-quasicrystalline approximation formula. The results are applied to calculating the complex effective permittivity of dry and wet snow, and sea ice     

ULSI低介电常数材料制备中的CVD技术

综述了制备ULSI低介电常数材料的各种CVD技术。详细介绍了PCVD技术淀积含氟氧化硅薄膜、含氟无定型碳膜与聚酰亚胺类薄膜的工艺,简要介绍了APCVD技术淀积聚对二甲苯类有机薄膜及RTCVD技术淀积SiOF薄膜的工艺。     

Propagation of TM modes in a circular dielectric waveguide filled with a medium with Kerr nonlinearity

Eigenmodes propagating in a cylindrical dielectric waveguide of circular cross section filled with a nonlinear medium whose nonlinearity is described by the Kerr law are analyzed. The nonlinear eigenvalue boundary problem for the nonlinear Helmholtz equation is considered. An iterative numerical method for obtaining the approximate solutions is developed. Numerical results are presented.     

Convergence of FDTD and wavelet-collocation modeling of curved dielectric interface with the effective dielectric constant technique

The convergence of the effective dielectric constant (EDC) model of curved dielectric surfaces has been investigated precisely for the finite-difference time-domain (FDTD) as well as for the interpolet-collocation time-domain (ICTD) methods. The EDC is computed by solving the Laplace equation of static electric potential by a finite-difference (FD) method for each cell located on the interface of arbitrary dielectric media. The FD solution of the Laplace equation provides an accurate EDC for arbitrary curved interface with even high contrast of the dielectric constants. It has been demonstrated in this paper that the precisely chosen EDC allows both the FDTD and the wavelet-collocation methods to exhibit second-order convergence for the analysis of not only planar but also curved dielectric interfaces.     

电子的介电常数研究

提出了电子介电常数的计算模型,从不同的角度得到了电子的非相对论散射截面,进一步得到了电子的非相对论性介电常数,发现电子是一色散介质,介电常数是波粒二象性的统一;得到了导体的等效介电常数,验证了所得电子介电常数的有效性;填补了此项研究的空白。     

Static dielectric constant of heavily doped semiconductors

One of the major effects of heavy doping in semiconductors is that the dielectric constant κ changes with impurity density and thus with position. The change is significant for impurity densities N greater than 10¹⁷ cm^?3. The low temperature classical relation of Castellan and Seitz is modified by including the contribution to the local field at the atomic site by the polarization of the host atoms due to an electric field. This correction makes an appreciable difference in κ(N). A new model for the polarizability of the impurity atoms is also developed. It is found that there is good agreement between the values of the dielectric constant of Si doped with As, P and Sb predicted by this theory and those found experimentally by Bethin et al. The critical impurity concentration for the metal-nonmetal transition found from this theory is however higher than that given by Castner et al. Reasons for this discrepancy are given.     

介质表面颗粒膜介电常数分析

假设材料表面极性棒状分子为取向分布,采用取向序参数,考虑局域场对有极分子、固有偶极矩的作用及基底材料表面和分子之间相互作用能,计算了材料表面颗粒膜的介电常数。计算结果表明：颗粒膜的介电常数依赖于基底材料相对介电常数和棒状分子之间的距离;其次还发现在分子面积和分子临界面积接近的范围内,分子和材料表面之间的相互作用能使之成为单一的贡献。反之,分子面积与分子临界面积相差较大时,局域场的相互作用是主要的贡献。