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中国物理学会期刊

射频容性耦合等离子体中下极板凹槽对尘埃颗粒集体行为的影响

CSTR: 32037.14.aps.74.20251047

Influence of lower electrode plate grooves on collective behavior of dust particles in radio-frequency capacitively coupled plasma

CSTR: 32037.14.aps.74.20251047
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  • 在射频容性耦合尘埃等离子体放电中, 下极板凹槽通过影响鞘层里的电势分布, 进而对尘埃颗粒的集体行为产生显著影响. 实验中通过在腔室内撒入微米级直径的尘埃颗粒, 观察到其在下电极凹槽势阱上方分层出现, 整体呈“碗状”云分布. 尘埃云的体积大小随射频功率和放电气压的变化而变化. 尘埃空洞在每层尘埃颗粒的中心出现, 其直径大小和变化受尘埃颗粒数量、射频功率和放电气压影响. 此外, 基于流体模型和尘埃粒子模型建立混合模型, 模拟发现尘埃颗粒的集体行为主要由其所受的轴向合力(考虑轴向电场力、离子拖拽力和重力)和径向合力(考虑径向电场力和离子拖拽力)决定. 实验发现, 通过在射频电极施加负直流偏压, 尘埃颗粒悬浮高度先增大后减小, 悬浮高度的变化能够较直观地反映等离子体放电从α-γ模式的转变.

     

    In radio-frequency capacitively coupled dusty plasma discharge, the grooves on the lower electrode plate significantly modify the electric potential distribution in the sheath region, thereby influencing the collective dynamic behavior of dust particles. Experimentally, when micrometer-sized dust particles are injected into the discharge chamber, a distinct layer of dust particles forms above the groove-induced potential well, exhibiting a characteristic bowl-shaped cloud structure. The volume of the dust cloud shows a strong dependence on RF power and discharge pressure. As power increases or pressure decreases, the dust cloud moves upward due to the influence of axial force on the particles. Besides, dust voids form in the middle of each dust layer, and their diameter evolution is influenced by particle number, RF power, and pressure. Particularly, when the diameters of the electrode grooves are small, the diameters of the dust voids first increase, then decrease and finally disappear as discharge pressure increases. Furthermore, a hybrid model is theoretically established. This model couples a fluid model with a dust particle model to explain the collective behavior of dust particles. This behavior is governed by the resultant axial force which includes axial electric field force, ion drag force, and gravity, as well as the resultant radial force, which considers radial electric field force and ion drag force. It is also found that in the DC-overlapped RF plasma, the suspension height of dust particles first increases and then decreases as the negative DC bias is increased. The change in dust particle height can reflect the transition of plasma discharge from α -mode to γ -mode.

     

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