共查询到18条相似文献,搜索用时 125 毫秒
1.
在流体力学方程的基础上建立了一种自洽的无碰撞射频等离子体鞘层动力学模型.这种自洽性包含两个方面:一方面,由于考虑了瞬时鞘层电场对离子运动的影响,因此该模型适用于描述任意频率段的射频鞘层演化过程;另一方面,在模型中采用等效电路方法来自洽地确定极板上的瞬时电位与瞬时鞘层厚度之间的关系.采用数值方法模拟出鞘层的瞬时厚度及极板的瞬时电位变化、鞘层内离子密度和电场强度等物理量的时空变化.结果表明,当射频场的频率小于或等于离子等离子体频率时,离子流密度明显地随时间变化
关键词:
射频
离子
鞘层
流体力学 相似文献
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离子引出的研究在AVLIS工程中有重要的意义,离子引出量和引出时间直接关系到整个系统 的离子收集效率. 在静电场中,由于等离子体屏蔽效应的存在,等离子体电位要高于正、负 极板的电位,而且在靠近正、负极板的两侧均存在鞘层. 理论模拟表明在正极板一边也可以 引出离子. 选取铯(Cs)作为实验对象,研究静电场对Cs等离子体的离子引出,使用安装在 两个极板上的法拉第筒收集离子引出信号. 实验结果表明,正极板确实可以引出离子,随着 外加电压的升高,从正极板一边引出离子的比率降低.
关键词:
AVLIS
离子引出
等离子体 相似文献
4.
采用相分辨发射光谱法, 对双频容性耦合纯Ar和不同含O2量的Ar-O2混合气体放电等离子体的鞘层激发模式进行了探究. 在射频耦合电源上极板的鞘层区域处观察到两种电子激发模式: 鞘层扩张引起的电子碰撞激发模式和二次电子引起的电子碰撞激发模式; 并发现这两种激发模式均受到低频射频电源周期的调制. 在纯Ar放电等离子体中, 两种激发模式的激发轮廓相似; 而在Ar-O2混合气放电等离子体中, 随着含O2量的增加, 二次电子的激发轮廓变弱. 此外, 利用相分辨发射光谱法对不同含O2量的Ar-O2混合气放电下Ar的 750.4 nm谱线的平均低频电源周期轴向分布进行了研究, 得到了距耦合电源上极板约3.8 mm处为双频容性耦合射频等离子体的鞘层边界.
关键词:
双频容性耦合等离子体
等离子体鞘层
发射光谱 相似文献
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本文从离子动力学方程出发,利用LB碰撞模型研究了离子-离子碰撞效应对前鞘等离子体输运的影响。电子分布假定为等温麦克斯韦-玻耳兹曼分布。结果表明,在低碰撞频率和高碰撞频率下,LB碰撞模型都能较好地描述前鞘等离子体中的离子-离子碰撞行为。离子-离子碰撞对表面等离子体的输运行为有较大影响。 相似文献
7.
为了研究尘埃等离子体中尘埃颗粒以及鞘层中粒子密度分布等特性,对尘埃颗粒存在条件下等离子体鞘层结构的采取数值模拟.采用稳态无碰撞的尘埃等离子体鞘层模型,对玻姆判据、尘埃颗粒的荷电性质、平板鞘层区域的电势分布及鞘层内粒子分布特性进行了系统的数值模拟研究.计算结果显示,鞘层边缘尘埃颗粒数密度的增加、尘埃温度的升高,将引起孤立尘埃颗粒对电子吸附能力的减弱,集体效应也受到一定程度的影响;二者同时对离子玻姆速度以及鞘层厚度的增加都有着极大的促进作用.鞘层电势在靠近下极区处降落迅速,主要聚集在接近阴极极板的鞘层区域,各种微粒数密度的空间分布满足准中性条件. 相似文献
8.
建立一个一维坐标空间、三维速度空间的斜磁场作用下的射频等离子体平板鞘层模型,讨论了磁场对射频鞘层结构及其参数特性的影响.研究结果表明:磁场对鞘层结构有不可忽略的影响,特别是能够使鞘层边界附近的离子速度分布和密度分布产生明显的变化.此外,虽然磁场不能改变离子总的能量密度分布,却能改变离子的运动状态,并同时影响着基板上离子在各个方向上的能量分布和入射偏移角度.
关键词:
射频
鞘层
磁场 相似文献
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建立包括两种正离子的电负性磁鞘的流体模型,利用四阶龙格库塔法数值求解描述一维稳态等离子体鞘层的方程组,考察离子与中性粒子碰撞对一维稳态等离子体鞘层的影响.结果表明:鞘边Ar+与He+的含量比值与碰撞参数对离子马赫数的取值范围都有影响.鞘边负离子含量越少,碰撞对鞘层中带电粒子密度的影响越明显.并且随碰撞参数的加大,鞘层中电子、负离子的密度下降越快,两种正离子的密度则呈现不同的波动变化.鞘边负离子含量越多,碰撞对鞘层中两种正离子的速度影响就越明显.此外,碰撞参数越大对鞘边δ越大的鞘层中的带电粒子密度影响越大. 相似文献
11.
Experiments on collisional ion sheaths are carried out by applying a pulsed negative bias on a disc electrode immersed in
a collisional plasma. The pulse is characterized by a linear rise, followed by a constant voltage phase and then exponential
decay. The measured currents to the electrode are compared to predictions from a dynamic collisional ion sheath model which
is developed from the basic two fluid equations. The parameter determining the degree of collisionality is also defined. The
agreement between the two in the rising and the flat top phases of the pulse is found to be good. Some residual discrepancies
as well as the disagreement in the decay phase are discussed. 相似文献
12.
Effects of gas pressure on plasma characteristics in dual frequency argon capacitive glow discharges at low pressure by a self-consistent fluid model
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A self-consistent fluid model for dual radio frequency argon capacitive glow discharges at low pressure is established.Numerical results are obtained by using a finite difference method to solve the model numerically, and the results are analyzed to study the effect of gas pressure on the plasma characteristics. It shows that when the gas pressure increases from 0.3 Torr(1 Torr = 1.33322×10~2 Pa) to 1.5 Torr, the cycle-averaged plasma density and the ionization rate increase;the cycle-averaged ion current densities and ion energy densities on the electrodes electrode increase; the cycle-averaged electron temperature decreases. Also, the instantaneous electron density in the powered sheath region is presented and discussed. The cycle-averaged electric field has a complex behavior with the increasing of gas pressure, and its changes take place mainly in the two sheath regions. The cycle-averaged electron pressure heating, electron ohmic heating, electron heating, and electron energy loss are all influenced by the gas pressure. Two peaks of the electron heating appear in the sheath regions and the two peaks become larger and move to electrodes as the gas pressure increases. 相似文献
13.
Chandhok M. Grizzle J.W. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1998,26(2):181-189
A semianalytical model for capacitively coupled radio frequency (RF) sheaths of asymmetric (unequal electrode area) systems has been developed. It can be applied in the high-frequency (ω > ω pi) regime at different pressures. An analytical approximation to the pressure-dependent ion density profile is used. The time-varying electric field and potential within the sheath are obtained by solving Poisson's equation. The current balance and zero net DC current conditions are applied to solve for the RF sheath parameters and DC bias voltage. The DC voltage ratio between the powered and grounded electrode sheaths increases as the pressure decreases, which results in a larger DC bias voltage at lower pressures 相似文献
14.
The impact of a secondary electron beam, generated at the electrodes and accelerated in the sheaths, on the self-consistent treatment of the electron behaviour in an rf bulk plasma has been investigated by a parametric study. Source of electrons in the plasma are collisional ionization and secondary electron injection. Electrons are lost by ambipolar diffusion to the electrodes of a parallel plate rf discharge configuration. The non-stationary Boltzmann equation is used to determine self-consistently the rf field amplitude necessary for maintaining the steady-state rf bulk plasma as well as the time resolved behaviour of the electron energy distribution function and of all contributions to the electron particle and power balance, at given source rate and energy distribution of secondary electron injection. 相似文献
15.
A simple analytical model is presented making it possible to determine the amplitudes and phases of the rf field in the electrode
sheaths and quasineutral plasma of an rf discharge in the presence of electronneural collisions. The collisional case ω≪ν
is considered in detail. Measurements are also made of the electron temperature, plasma density, thickness of the electrode
sheaths, and rf field amplitude in the quasineutral plasma of an rf discharge in argon. The rf field amplitudes predicted
by this model are in satisfactory agreement with both our experimental data and the results of theoretical calculations of
other authors.
Kharkov State University, Kharkov. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 41, No. 12, pp. 31–38,
December, 1998. 相似文献
16.
Jong-Chul Park Bongkoo Kang 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(3):499-506
Magnetic and collisional effects on capacitive radio frequency (RF) discharges for magnetically enhanced reactive ion etching (MERIE) are investigated. Using simplified plasma and sheath models, a collisional magnetic-sheath equation that governs the sheath dynamics under a de magnetic field crossed with a sinusoidal RF electric field is obtained. The sheath equation includes global effects of the bulk plasma. Together with the power-balance equation and the particle-conservation equation, the sheath equation is used to extract a circuit model and predict the electrical behavior of MERIE reactors. Numerical results on the plasma density and the power in MERIE reactors agree well with reported experimental results and the circuit model describes the repeated discharge properties well 相似文献
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The characteristics of radio-frequency (RF) plasma sheaths have been topics of much scientific study for decades, and have
also been of great importance in the manufacture of integrated circuits and fabricating microelectromechanical systems (MEMS),
as well as in the study of physical phenomena in dusty plasmas. The sheaths behave special properties under various situations
where they can be treated as collisionless or collisional, single-or dual-RF, one-or two-dimensional (1D or 2D) sheaths, etc.
This paper reviews our recent progress on the dynamics of RF plasma sheaths using a fluid method that includes the fluid equations
and Poission’s equation coupled with an equivalent circuit model and a hybrid method in which the fluid model is combined
with the Monte-Carlo (MC) method. The structures of RF sheaths behave differently in various situations and plasma parameters
such as the ion density, electron temperature, as well as the external parameters such as the applied frequency, power, gas
pressure, magnetic field, are crucial for determining the characteristics of plasma sheaths. 相似文献