A completely iterative method for the infinite domain electrostatic problem with nonlinear dielectric media

We present an iterative method for the solution of the exterior all-space electrostatic problem for nonlinear dielectric media. The electric potential is specified on interior boundaries and the electric field decays at infinity. Our approach uses a natural variational formulation based on the total energy of the nonlinear dielectric medium subject to boundary conditions. The problem is decomposed into an exterior calculation and an interior calculation with the boundary-specified electric potentials imposed as constraints between them. Together, these enable an iterative method that is based on the variational formulation. In contrast to direct solution of the electrostatic problems, we avoid the construction, storage and solution of dense and large linear systems. This provides important advantages for multiphysics problems that couple the linear electrostatic Poisson problem to nonlinear physics: the latter necessarily involves iterative approaches, and our approach replaces a large number of direct solves for the electrostatics with an iterative algorithm that can be coupled to the iterations of the nonlinear problem. We present examples applying the method to inhomogeneous, anisotropic nonlinear dielectrics. A key advantage of our variational formulation is that we require only the free-space, isotropic, homogeneous Greens function for all these settings.     

Equivalence of the Abraham momentum and the Minkowski momentum of photons in media

The century-long debate on the momentum of light in a medium involves two rival forms of momentum, namely those of Abraham and Minkowksi. In this Letter, we analyze this dilemma from the view of the quantum theory of light, the result of which can be easily extended to the classical level. It is found that the Abraham momentum of one polariton mode in linear and dispersive dielectrics differs from its Minkowski momentum, by a considerable factor. However, after taking all branches into consideration, we find the two lead to the same end, which unifies the two rival forms of momentum. The sum rule is traditional, but our conclusion provides a new perspective on the Abraham-Minkowski dilemma, and is consistent with existing experiments including a recent measurement of recoil momentum of atoms using an atom interferometer with Bose-Einstein Condensates [G. K. Campbell et al. Phys. Rev. Lett. 94, 170403 (2005).], the Cerenkov effect, the Doppler effect and the phase matching conditions in nonlinear optical processes.     

Incorporating the Havriliak–Negami dielectric model in the FD-TD method

We derive and analyze an efficient algorithm to incorporate the anomalously dispersive Havriliak–Negami dielectric model of induced polarization in the Finite-difference time-domain (FD-TD) method. Our algorithm implements this dielectric model, which in the time-domain involves fractional derivatives and fractional differential operators, with a preset error over the desired computational time interval [0,T_comp] and correctly takes into account the singularity at t = 0⁺ of the corresponding time-domain dielectric susceptibility. The overall algorithm is shown to be second-order accurate in space and time, and to obey the standard FD-TD stability condition. Numerical experiments confirm our analysis.     

Enhanced mobility and environmental stability in all organic field‐effect transistors: The role of high dipole moment solvent

Low‐operating voltage, high mobility, and stable organic field‐effect transistors (OFETs) using polymeric dielectrics such as pristine poly(4‐vinyl phenol) (PVP) and poly(methyl methacrylate) (PMMA), dissolved in solvents of high dipole moment, have been achieved. High dipole moment solvents such as propylene carbonate and dimethyl sulfoxide used for dissolving the polymer dielectric enhance the charge carrier mobilities by three orders of magnitude in pentacene OFETs compared with low dipole moment solvents. Fast switching circuits with patterned gate PVP‐based pentacene OFETs demonstrated a switching frequency of 75 kHz at input voltages of |5 V|. The frequency response of the OFETs is attributed to a high degree of dipolar‐order in dielectric films obtained from high‐polarity solvents and the resulting energetically ordered landscape for transport. Remarkably, these pentacene‐based OFETs exhibited high stability under bias stress and in air with negligible shifts in the threshold voltage. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1533–1542     

The oxidation of GaAs(1 0 0) surfaces under atmospheric pressure conditions studied in real time using dynamic reflectance anisotropy spectroscopy at 2.6 and 4 eV

Using real-time, dynamic reflectance anisotropy spectroscopy (RAS) at both 2.6 eV and 4.0 eV, we demonstrate that an anisotropic oxide will form on As rich c(4 × 4)/d(4 × 4) GaAs surfaces when exposed to moisture- free air diluted in inert gases in a metal organic chemical vapour deposition (MOCVD) reactor, and that the initial c(4 × 4)/d(4 × 4) structure effects the resulting optical anisotropy of the oxide. This was achieved by investigating how the RA signals at 2.6 eV and 4 eV of annealed GaAs (1 0 0) surfaces evolve relative to the as-etched and as-annealed signals when exposed to oxygen. It is found that while the 2.6 eV response, which is known to be associated with the As dimers, degrades to pre-process levels indicating their destruction, the 4 eV signal, stabilizes at an intermediate, permanent level, suggesting the formation of an anisotropic oxide film whose structure is determined at least in part, by the initial c(4 × 4)/d(4 × 4) surface.     

塑封硅器件中介电薄膜的温湿效应分析(英文)

随着铜互连以及low-k电介质在超大规模集成电路中地广泛使用,low-k电介质的机械完整性及其对互连可靠性变得更加重要。影响介电膜的机械完整性和互连可靠性的因素包括介电膜的工艺制程,芯片与封装材料的相互影响,以及环境温度和湿度的影响。本文研究集中于了解环境温度和湿度对塑封硅器件中介电薄膜的可靠性影响。采用快速温度和湿度实验条件,对塑封硅器件中介电薄膜受水分和温度损伤的敏感性进行了分析。运用商业有限元(FEA)分析软件,对水分在塑封材料和硅器件中的扩散过程进行了建模及仔细分析。并对硅器件周边密封圈的防水分扩散效力进行了研究。通过这一系列实验与分析,对塑封硅器件中介电薄膜的温湿效应有了完整地了解,并提出和建立了相关的物理模型和经验公式。运用这物理模型和经验公式可对在各种使用环境温度和湿度条件下,塑封硅器件中介电薄膜的可靠性进行评估及分析。     

迭代正则化方法求解电介质中空间电荷分布

首先介绍了迭代正则化方法的理论基础,建立了含有空间电荷密度分布的Fredholm第一类积分方程的反卷积算法,利用数值实验研究了加性高斯白噪声对迭代反卷积算法的影响,以及迭代停止标准对非适定问题的数值解的影响,最后使用该方法求解电介质样品中的空间电荷分布.结果表明,在无噪或者低噪环境下,反卷积算法能够非常好地计算出非适定问题的解.当噪声影响增大,信噪比降低时,反卷积的计算结果受到明显的影响.迭代停止标准对数值解的计算精度起着明显的作用.对实际测量数据进行处理表明,迭代正则化反卷积算法能够计算出固体电介质中的空间电荷分布.     

Dielectric spectroscopy and calorimetry during postcuring of a linear chain polymer thermoset formed from a diepoxide and cyclohexylamine,and the nature of the products

The dielectric permittivity and loss spectra of an equimolar liquid mixture of diglycidyl ether of bisphenol-A and cyclohexylamine have been studied during the liquid's isothermal polymerization or curing in separate experiments at different temperatures and thereafter during the postcuring, both on rate-heating and isothermally. The spectra obtained during the growth of the linear chain polymer during the curing and postcuring show the evolution of an intermediate relaxation process whose position in the frequency plane remains relatively insensitive to the decrease in the configurational entropy during the postcuring, but whose strength increases. Postcuring ceases to occur once the calorimetric glass-liquid transition temperature of 345 K, corresponding to the ultimately formed polymeric state, has been reached. The increase in the number of covalent bonds, n, formed during curing and postcuring decreased the equilibrium dielectric permittivity, ε_s, and increased the characteristic relaxation time, τ₀, for all curing and postcuring conditions. For a fixed temperature and n, (dε_s/dT) and (dτ₀/dT), as well as the values ε_s and τ₀ of the ultimately formed state of the polymers differ significantly when the thermal history of polymerization differs. The slow dynamics in the glass-liquid transition region were analyzed in terms of the enthalpy relaxation and fictive temperature concepts. The distribution of relaxation times for these dynamics correspond to the stretched exponential parameter of 0.6, which is significantly greater than 0.39 determined for the dielectric α-relaxation spectra measured at a temperature 30 K higher. The enthalpy relaxation involves a narrower distribution of intermolecular barriers than dielectric relaxation. The results also show that the recently proposed method for determining the gelation time from the plots of the imaginary component of electrical impedance lacks scientific merit. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 303–318, 1998     

Calorimetric and dielectric effects during polymerization of an elastomer‐containing mixture and liquid‐liquid phase separation

Calorimetry and dielectric spectroscopy of an elastomer, amine terminated butadiene acrylonitrile (ATBN), dissolved in a stoichiometric mixture of ethylene diamine and diglycidyl ether of bisphenol‐A, were studied in real time during the polymerization and phase separation of the mixture. In the two polymer compositions containing 8 w/w % ATBN and 20 w/w % ATBN, the total enthalpy released per mole of DGEBA's reaction was the same, indicating indetectably small changes in molecular interactions before and after the phase separation. The dielectric relaxation spectra showed no evidence for phase separation, which indicated a gradual phase separation with time and the extent of polymerization, and relatively small differences in the permittivity and conductivity between the ATBN particles and the network matrix at the time of phase separation. The equilibrium permittivity and dc conductivity showed a nonideal mixing of ATBN. The stretched exponential relaxation parameter remained at 0.36, but the characteristic dielectric relaxation time and the dc conductivity increased on addition of ATBN. An increase in the temperature had a greater effect on the relaxation time than the increase in the extent of polymerization. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1911–1919, 1999     

Transfer-Free Graphene Growth on Dielectric Substrates: A Review of the Growth Mechanism

Ever since the more-than-decade-old discovery of application of mechanical exfoliation to obtain graphene, this 2-dimensional material was known for its soaring promise in various applications, owing to its excellent properties. Graphene, most popularly grown on metallic substrates by chemical vapour deposition, needs to be transferred onto dielectric substrates for multiple optical and electronic applications. During such complex and expensive transfer steps, defects are introduced into graphene, which deteriorates the quality and thus, properties of graphene. An alternative approach to surmount these problems is the elimination of the transfer process and to directly grow graphene on dielectric substrates, for future electronic and optical applications. This review presents a comprehensive and an up-to-date account of the development of synthesis methods, challenges and future directions for transfer-free graphene growth on dielectric substrates. Special emphasis is given on the fundamentals of growth mechanisms of various transfer-free graphene synthesis processes on dielectric materials.