ION AND NEUTRAL VELOCITY DISTRIBUTIONS IN MULTI-ION PLASMA SHEATHS

该提案旨在研究多离子鞘层的物理性质，自发形成双层（鞘层）的高能离子的超音速通量的产生，以及可用于等离子体辅助蚀刻的高能中性通量的产生。中性蚀刻避免了在微电子工业中使用高能离子蚀刻晶圆时发生的衬底充电问题。离子在多离子等离子体中通过鞘层的加速是一个基本的等离子体物理学问题，对从空间等离子体到聚变等离子体的系统都有重要的影响。这项提议有两个主要目标。首先是确定附加离子种类对膨胀螺旋等离子体双层形成的影响，其次是测量由于电荷交换过程导致的层中离子与中性原子之间的动量耦合。所提出的活动的基本智力价值将是第一次详细测量等离子体鞘中两种不同离子和单一中性离子的流速。多离子等离子体中通过预鞘层和鞘层的离子加速尚未完全了解，本项目将对这一活跃的基础等离子体科学研究领域做出重大贡献。这项工作的更广泛影响包括在一个强调基础和应用等离子体物理学之间协同作用的研究环境中培养研究生；提高获得物理学高级学位的妇女比例；并通过参与前沿研究活动吸引高素质的本科生进入物理学领域。对半导体等离子体刻蚀领域的影响也很可能，因为通过电荷交换产生大量的高能中性原子，双层加速离子的中和作用将提供一种新的方法，在小于10纳米的尺度上刻蚀硅的特征。考虑到等离子体从等离子体推进器中分离是一个重要且尚未解决的问题，等离子体推进领域也可能受到影响。

The proposal is directed at investigating the physics of multi-ion sheaths, the generation of supersonic fluxes of energetic ions in spontaneously forming double layers (sheaths), and the creation of fluxes of energetic neutrals that could be used for plasma-aided etching. Neutral etching avoids the problem of substrate charging that occurs when energetic ions are used to etch wafers in the microelectronics industry. The acceleration of ions through sheaths in multi-ion plasmas is a fundamental plasma physics question with important ramifications for systems ranging from space plasmas to fusion plasmas. There are two primary objectives of this proposal. First is the determination of the effect of additional ion species on double layer formation in expanding helicon plasmas, and second, the measurement of the momentum coupling between ions and neutral atoms in the layer due to charge exchange processes. The essential intellectual merit of the proposed activity will be the first detailed measurement of the flow velocities of two different ion species and a single neutral species in a plasma sheath. Ion acceleration through pre-sheaths and sheaths in multi-ion plasmas is not fully understood and this project will make a significant contribution to this active area of fundamental plasma science research. The broader impact of the work involves the training of graduate students in a research environment that emphasizes the synergy between basic and applied plasma physics; improvement of the percentage of women obtaining advanced degrees in physics; and attracting high quality undergraduates into physics through involvement in cutting-edge research activities. Impact on the field of plasma etching of semiconductors is also likely since production of significant fluxes of energetic neutral atoms through charge exchange neutralization of the double layer accelerated ions would provide a new means of etching features in silicon at scales of less than ten nanometers. Impact on the field of plasma propulsion is also likely given that plasma detachment from plasma-based thrusters is an important and unresolved question.