航天器内部充电效应及典型事例分析

航天器内部充电效应是由空间高能电子诱发的,通常发生在航天器内部以及表面绝缘材料深层,所产生的放电击穿及静电放电脉冲干扰较表面充电更为严重. 对内部充放电的一般规律进行了总结,并就一次典型的航天器异常事件,从异常的时空表现特征及其与高能电子环境扰动的相关性角度进行了深入分析和定量计算,得出了高能电子产生的内部充电引起的卫星异常的结论,为卫星异常诊断提供了范例. 关键词： 高能电子 内部充电 静电放电 空间环境     

航天器内部充电效应及典型事例分析

航天器内部充电效应是由空间高能电子诱发的,通常发生在航天器内部以及表面绝缘材料深层,所产生的放电击穿及静电放电脉冲干扰较表面充电更为严重. 对内部充放电的一般规律进行了总结,并就一次典型的航天器异常事件,从异常的时空表现特征及其与高能电子环境扰动的相关性角度进行了深入分析和定量计算,得出了高能电子产生的内部充电引起的卫星异常的结论,为卫星异常诊断提供了范例.     

Computer simulation of charging the silicon dioxide surface and subsurface layers by electron bombardment

A physical model and program of calculating the parameters of charging dielectrics by electron bombardment is described. A method of computer simulation is used to investigate the main processes of charging the subsurface silicon dioxide layers. Dependences of the current density, volume charge density, and electric field strength on the material layer depth are calculated for variable electron beam parameters, irradiation time, and grid potential near the sample surface.     

Charging Dielectrics when Bombarded with Ar+ Ions of Medium Energies

Physics of the Solid State - A complex facility for measuring the kinetics of high-voltage charging potentials of the surface of massive dielectrics when irradiated with medium-energy Ar+ ions has...     

电子辐照下聚合物介质内部放电模型研究

空间电子辐照环境中,聚合物介质充放电现象是威胁航天器安全的重要因素. 传统航天器介质充放电模型仅能分析材料充电过程,缺乏对放电前后介质电位残余情况与放电脉冲强弱的评估. 本文通过引入介质放电电导率,在数值积分 充电模型基础上建立同时描述航天器介质内部充电和放电过程的新模型,并将模型计算结果与实验数据进行比较,验证了所构建的模型. 模型分析结果表明,聚合物介质放电残余电位与放电电流脉冲宽度随着样品电阻率的增加而增大,放电电流强度随着临界电场强度和充电时间的增加而增强,其增幅随着辐照电子束流强度的增加而增大. 关键词： 放电模型 内部放电 电子辐照 航天器介质     

Charging of Ion-Implanted Dielectrics by Electron Irradiation

Technical Physics - The charging kinetics of Al2O3 (sapphire) and SiO2 (α-quartz) dielectrics irradiated by inert gas ions (Ar+), metal ions (Ga+), and protons (H+) has been studied. It has...     

Time variation of the concentration of excess carriers in dielectrics under irradiation

In this paper, a theoretical analysis is performed of charge carriers in dielectrics which are irradiated by electrons. A phenomenological model of a uniform bulk charging is used in the approximation of unipolar conductivity. It is shown that the process consists of two or three stages, corresponding to a certain accumulation regime of excess charge. Using the results of the analysis, the time dependence of the equilibrium parameter is calculated for certain numerical values of the model parameters. It turns out that this dependence consists of a fast and a slow component; moreover, thermodynamic equilibrium between free and captured carriers exists only for the slow component. Results of experiments on the bulk charging of polymers, described in the paper, confirm the obtained theoretical conclusions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 47–52, March, 1990.     

Some kinetic aspects of the charging of dielectric targets by a (1–50)-keV electron beam

The electron-emission characteristics of dielectrics irradiated with electron beams with a current density of about 10^?5 A cm^?2 have been experimentally investigated. An ambiguous relationship between the secondary electron-emission properties, the charged-surface potential, and the positive and negative charges accumulated in the surface region of dielectric targets is demonstrated. The character and values of various experimentally observed time charging constants, inconsistent with a number of theoretical models and estimates, are qualitatively explained.     

一种新的航天器外露介质充电模型

为综合考虑高能电子辐射与周围等离子体对航天器外露介质充电的影响,在航天器内带电模型的基础上,通过添加边界充电电流来考虑等离子体与航天器介质表面的相互作用,并统一参考电位为等离子体零电位,建立了航天器外露介质充电模型,给出了新模型的一维稳态解法,并与表面充电模型和深层充电模型进行了对比分析.结果表明:新建模型能够综合考虑表面入射电流、深层沉积电流和传导电流对充电的耦合作用过程,实现外露介质表面和深层耦合充电计算,有利于全面评估航天器外露介质的充电问题.     

High-energy passive-ionization electrons and holes in dielectrics with pulsed irradiation by high-density electron beams

This article is a survey of works by the author and colleagues on the investigation of charging and discharging dynamics in solid dielectrics exposed to dense electron beams with subnanosecond resolution. Small high-current electron accelerators of theDzhin type, which were developed and fabricated at the Nonlinear Physics Laboratory, were used as the source of the primary electron beam. The primary electron beam parameters were: 0.25–0.45 MeV, 1–30 nsec, 0.1–10,000 A/cm³. The dielectric is investigated experimentally with its surface covered by a metallic electrode and with critical electron emission into the vacuum eliminated. In this case, the total current in the dielectric consists of three components: the primary beam current, the displacement current, and the conduction current. The first and last are responsible for charging and discharging of the dielectric volume. It is shown that the bulk nonequilibrium radiation conduction mechanism depends greatly on the dose intensity. For small dose intensities, the principal current carriers are the low-energy electrons of the conduction band and holes of the valence band, which are in quasi-equilibrium with the lattice phonon field before capture by defects or merging into excitons preceding recombination. This type of conduction has been well studied in the physics of semiconductors and dielectrics. However, over a broad interval of intermediate and high dose intensities, another type of nonequilibrium conduction dominates — the high-energy, which was discovered and studied by the author and colleagues. The principal carriers are then passive-ionization electrons and holes with energies of 0.1–10 eV in the process of phonon relaxation in which phonon emission dominates absorption. The high-energy conduction differs considerably from the low-energy in many properties, which determines the unusual dynamics of dielectric charging and discharging with irradiation by the dense electron beam of a high-current accelerator. Institute of High-Current Electronics, Siberian Section, Russian Academy of Sciences. Tomsk Polytechnic University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 109–119, November, 1996.     

A general continuum approach to describe fast electronic transport in pulsed laser irradiated materials: The problem of Coulomb explosion

We present a continuum model, based on a drift-diffusion approach, aimed at describing the dynamics of electronic excitation, heating, and charge-carrier transport in different materials (metals, semiconductors, and dielectrics) under femtosecond and nanosecond pulsed laser irradiation. The laser-induced charging of the targets is investigated at laser intensities above the material removal threshold. It is demonstrated that, for near-infrared femtosecond irradiation, charging of dielectric surfaces causes a sub-picosecond electrostatic rupture of the superficial layers, alternatively called Coulomb explosion (CE), while this effect is strongly inhibited for metals and semiconductors as a consequence of superior carrier transport properties. On the other hand, application of the model to UV nanosecond pulsed laser interaction with bulk silicon has pointed out the possibility of Coulomb explosion in semiconductors. For such regimes a simple analytical theory for the threshold laser fluence of CE has been developed, showing results in agreement with the experimental observations. Various related aspects concerning the possibility of CE depending on different irradiation parameters (fluence, wavelength and pulse duration) and material properties are discussed. This includes the temporal and spatial dynamics of charge-carrier generation in non-metallic targets and evolution of the reflection and absorption characteristics. PACS  79.20.Ds, 52.50.Jm     

Effect of electron drift and emission on the surface potential of an irradiated dielectric

A mathematical model is proposed for the steady-state charging of dielectrics with an open surface under bombardment with a nonpenetrating electron beam. The model is based on inclusion of the emission and drift mechanisms of the leakage of charge injected into the dielectric. Charge transfer through the unirradiated layer of dielectric adjacent to the grounded substrate is assumed to occur in a space-charge-limited current mode. As a result of this the strength in the unirradiated layer is of sufficient strength to make a certain contribution to the surface potential of the dielectric. The steady-state surface potential on the electron-beam parameters and the characteristics of the sample are studied by analyzing the proposed model. We consider the irradiation conditions under which one of the charge-leakage mechanisms dominates.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 5–10, November, 1990.     

Self-consistent charging in dielectric films under defocused electron beam irradiation

We clarify the transient and equilibrium charging characteristics of grounded dielectrics due to low-energy defocused electron beam irradiation by a three-dimensional self-consistent simulation model. The model incorporates the electron scattering, transport and trapping. Results show that some electrons can arrive at the grounded substrate due to the internal field and density gradient, forming the leakage current. The transient charging process tends to equilibrium as the surface potential decreases and the leakage electron current increases. The positive and negative space charges are distributed alternately along the beam incident direction. In the equilibrium state, the surface potential and leakage electron current decrease to stable values with increasing film thickness and the trap density, but with decreasing electron mobility. Moreover, the surface potential of the dielectric thin film exhibits a maximum negative value with variation of the beam energy; for example, under the condition of the film thicknesses 0.5 μm and 2 μm, the maximum negative values of surface potentials are -13 V and -98 V in beam energies 2 keV and 3.5 keV, respectively. However, for the thick film, the surface potential decreases with the increase in beam energy.     

Experimental modeling of the electric potential decay at the surface of polypropylene films (PP)

Surface potential decay (SPD) measurements have been considered as the most appropriate technique for the investigation of the corona charging of dielectrics. The aim of the present paper is to point out the interactions between three factors namely: grid potential, grid current and sample size (length), by taking advantage of the experimental design methodology. The experiments were performed on 0.08 mm – thick samples of PP films, in ambient air (temperature: 20 °C–22 °C; relative humidity: 56 %–62 %), The domains of variation of the three factors considered in the experiments were as follows: – 8 to – 12 kV, for grid potential – 50 to – 90 μA for grid current and 70–150 mm, for sample length. The relative SPD after 300 s and 900 s were considered as output variables of the process. The models that express these variables as quadratic polynomial functions of the three factors were obtained using the Design of Experiments methodology and the commercial software MODDE 5.0. They point out that the surface potential decay is faster at higher applied voltages, lower grid currents and smaller sample areas. The grid voltage has a stronger effect at lower values of the grid current. Both the grid voltage and the corona current have a stronger effect of the SPD in the case of the samples of smaller areas. These observations suggest the optimal operating conditions of the corona charging devices for this kind of dielectric materials.     

刻槽绝缘子真空表面闪络光学特性

利用超高速相机Hsfc-Pro对绝缘子真空表面闪络光学特性进行了研究,重点分析了平板和刻槽结构圆盘形介质样品在指状电极下闪络通道的差异以及刻槽结构对材料绝缘强度的提升。实验结果表明:槽纹的引入改变了闪络通道的形成位置,平板结构介质样品的表面闪络一般是沿两电极中心连线发展,而刻槽结构介质样品的表面闪络则是沿介质边缘发展。这导致后者的闪络时延至少是前者的/2倍,证明了刻槽结构可以在不增加器件尺寸的前提下有效提高介质材料的绝缘强度。     

Fabrication and characteristics of high-K HfO2 gate dielectrics on n-germanium

This paper reports that the high-K HfO2 gate dielectrics are fabricated on n-germanium substrates by sputtering Hf on Ge and following by a furnace annealing. The impacts of sputtering ambient, annealing ambient and annealing temperature on the electrical properties of high-K HfO2 gate dielectrics on germanium substrates are investigated. Experimental results indicate that high-K HfO2 gate dielectrics on germanium substrates with good electrical characteristics are obtained, the electrical properties of high-K HfO2 gate dielectrics is strongly correlated with sputtering ambient, annealing ambient and annealing temperature.     

Casimir stress in an inhomogeneous medium

The Casimir effect in an inhomogeneous dielectric is investigated using Lifshitz’s theory of electromagnetic vacuum energy. A permittivity function that depends continuously on one Cartesian coordinate is chosen, bounded on each side by homogeneous dielectrics. The result for the Casimir stress is infinite everywhere inside the inhomogeneous region, a divergence that does not occur for piece-wise homogeneous dielectrics with planar boundaries. A Casimir force per unit volume can be extracted from the infinite stress but it diverges on the boundaries between the inhomogeneous medium and the homogeneous dielectrics. An alternative regularization of the vacuum stress is considered that removes the contribution of the inhomogeneity over small distances, where macroscopic electromagnetism is invalid. The alternative regularization yields a finite Casimir stress inside the inhomogeneous region, but the stress and force per unit volume diverge on the boundaries with the homogeneous dielectrics. The case of inhomogeneous dielectrics with planar boundaries thus falls outside the current understanding of the Casimir effect.     

CVD-derived Hf-based High-k Gate Dielectrics

Hf-based high-k gate dielectric has been recently highlighted as the most promising high-k dielectrics for the next-generation CMOS devices with high performance due to its excellent thermal stability and relatively high dielectric constant. This article provides a comprehensive view of the state-of-the-art research activities in advanced Hf-based high-k gate dielectrics grown by chemical-vapor-deposition-based method, including metal-organic-chemical-vapor-deposition (MOCVD), atomic-layer-chemical-vapor-deposition (ALCVD), and plasma-enhanced- chemical-vapor-deposition (PECVD), in CMOS device. We begin with a survey of methods developed for generating Hf-based high-k gate dielectrics. After that, most attention has been paid to the detailed discussion of the latest development of novel Hf-based high-k gate dielectrics grown by CVD. Finally, we conclude this review with the perspectives and outlook on the future developments in this area. This article explores the possible influences of research breakthroughs of Hf-based gate dielectrics on the current and future applications for nano-MOSFET devices.     

电子经过介质由于介质被极化影响能量损失的研究

电子经过介质时,将介质极化,本工作的目的是研究较低能量的电子经过不同介质时,由于这种极化效应对于电子能量损耗的影响。利用灌氢气的膨胀式云雾室测量了能量为0.3—1.0Mev的电子经过铍、炭及铝片的平均能耗及最大可几能耗。实验指出:在此能量范围内的电子,经过某些介质,它们的传导电子数与全部电子数的比值f₀以及电阻系数ρ都大,如铍及炭,其能量损耗由于介质被极化而显著减少。电子经过铍的能耗实验结果显著比考虑了介质极化影响的Helpern及Hall与电子能量损耗有显著减少Sterneimer的理论为小;电子经过炭的能耗实验结果是介于此二理论之间。