尘埃颗粒在射频等离子体鞘层中的非线性共振现象的理论研究

The oretical study on nonlinear resonances of a charged micro-particle in a RF sheath

一种自洽的理论模型用于研究尘埃颗粒在射频鞘层中垂直方向的非线性共振现象 .利用射频鞘层动力学模型 ,研究了鞘层电场和尘埃颗粒的充电过程 .考虑作用在尘埃颗粒上的各种作用力 (如重力、电场力、离子拖拽力、中性气体摩擦力及探针的扰动力 ) ,并通过数值求解颗粒运动方程 ,模拟了该尘埃颗粒在探针扰动下的非线性振荡过程 .所得结果不仅很好地再现了最近的实验观察 ,同时还发现这种非线性振动过程与等离子体参数、施加的射频偏压的功率、探针的扰动电位和位置等有着密切的联系 .

A self-consistent model is proposed here to study the nonlinear resonance and the hysteresis phenomena in the vertical oscillations of a charged micro-particle in a RF sheath. In this model, the charging process of the micro-particle and the sheath dynamics is considered self-consistently. And also, various forces acting on the particle are fully taken into account in the Newton' s equations of the micro-particle. By solving the equation, we simulate the motions of the micro-particle in the sheath, under the excitations of the probe. Numerical results reproduce well the recent experimental observations; at the same time, we find that these nonlinearities are not only due to the structure of the sheath, but also due to the charging process of the micro-particle, ion drag force, neutral gas friction and the excitation of the probe.