Elucidating Electron Kinetics in Low Temperature Plasmas with Non-Invasive Optical Diagnostics

通过非侵入性光学诊断阐明低温等离子体中的电子动力学

• 批准号: 1068670
• 负责人: Amy Wendt
• 金额: $ 39万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-01 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1068670&HistoricalAwards=false
• 关键词: Elucidating; Electron; Kinetics; Low; Temperature

Low-temperature plasmas (LTP) have had a tremendous societal impact by enabling a wide range of technologies that improve quality of life, such as computer chips, energy efficient light sources and wear-resistant artificial joints. Fundamental plasma science is instrumental in continued LTP application development for meeting basic human needs in domains including energy, materials and healthcare. Specifically, many applications rely on manipulation of energy flow and particle fluxes in the plasma, an area lacking a complete science foundation. The quantities of ions, neutral radicals, and photons, which all play central roles in technological outcomes, depend on reactions in the plasma driven by collisions involving energetic electrons. Process results are thus critically sensitive to the spectrum of electron energies, known as the "electron energy distribution function" (EEDF), which in turn depends on pressure, power, gas mixture,flow rates, system geometry and method of power input. "Predictive plasma design" is an as yet unfulfilled goal of LTP modeling with transformational potential for emerging applications. Diagnostics play an essential role in identifying the physical processes that dominate plasma behavior, and in confirming that models accurately represent that behavior. We bring the field closer to the goal of predictive plasma design by applying a new method to experimentally capture electron kinetics using non-invasive optical diagnostics to address fundamental science questions for LTP systems. Intellectual Merit- Electron collisions are responsible for the electronic excitation leading to the plasma glow, and the spectrum of emitted light carries an encoded mapping of the EEDF. Probing the EEDF from the spectrum of the light emitted by the plasma is thus possible, but only with a thorough understanding of processes leading to the excitation and de-excitation of photon emitting species. The efficiencies of the electron-driven excitation processes are expressed as "cross sections," and a set recently measured at UW forms the foundation of an emission model to probe the EEDF using the recorded plasma optical emission spectrum. Here we apply the non-invasive optical technique to examine fundamental behavior of two or more of the following types of radio frequency (rf) LTPs, each of which is distinguished by phenomena involving the high energy region of the EEDF: 1) rf LTPs augmented with dc power, 2) rf LTPs in electronegative gases, and 3) dual-frequency rf capacitively-coupled plasmas. EEDF characterization in space and time will target pecific science questions about the form of the high energy region of the EEDF and its impact on discharge properties. Broader Impacts- The potential impact of the proposed research has several distinct components. 1) If successful, research outcomes will advance understanding in an area critical to establishing predictive and control capabilities for LTP technological applications. 2) The diagnostic approach is widely applicable and easily implemented by others. 3) The interdisciplinary nature of this research effort (PIs from Physics and Engineering) will provide a wide range of teaching and learning experiences and will provide excellent training in both basic and applied physics for the students involved. 4) Plasma technology will also be highlighted in a new program designed to introduce the "grand challenges" in middle school science and math courses, an effort to increase interest in engineering careers among a more diverse student population through an emphasis on humanitarian applications.

低温等离子体（LTP）通过实现各种提高生活质量的技术，如计算机芯片，节能光源和耐磨人工关节，产生了巨大的社会影响。基础等离子体科学有助于持续的LTP应用开发，以满足能源，材料和医疗保健等领域的基本人类需求。具体而言，许多应用依赖于操纵等离子体中的能量流和粒子通量，这是一个缺乏完整科学基础的领域。离子、中性自由基和光子的数量都在技术成果中发挥着核心作用，它们取决于高能电子碰撞驱动的等离子体反应。因此，工艺结果对电子能量谱（称为“电子能量分布函数”（EEDF））非常敏感，而电子能量分布函数又取决于压力、功率、气体混合物、流速、系统几何形状和功率输入方法。“预测等离子体设计”是LTP建模的一个尚未实现的目标，具有新兴应用的转型潜力。诊断在识别主导等离子体行为的物理过程以及确认模型准确地表示该行为方面发挥着至关重要的作用。我们使该领域更接近预测等离子体设计的目标，通过应用一种新的方法来实验捕获电子动力学，使用非侵入性光学诊断来解决LTP系统的基本科学问题。智能优点-电子碰撞负责电子激发导致等离子体辉光，发射光的光谱携带EEDF的编码映射。因此，从等离子体发射的光的光谱探测EEDF是可能的，但只有在彻底理解导致光子发射物质的激发和去激发的过程的情况下。电子驱动的激发过程的效率表示为“横截面”，最近在UW测量的一组形成了发射模型的基础，使用记录的等离子体光发射光谱探测EEDF。在这里，我们应用非侵入性的光学技术来检查两个或更多的以下类型的射频（rf）LTP的基本行为，其中每一个是由涉及的EEDF的高能量区域的现象区分：1）射频LTP与直流电源增强，2）射频LTP在电负性气体，和3）双频射频电容耦合等离子体。EEDF在空间和时间上的表征将针对关于EEDF的高能区域的形式及其对放电特性的影响的具体科学问题。更广泛的影响-拟议研究的潜在影响有几个不同的组成部分。1)如果成功，研究成果将促进对建立LTP技术应用的预测和控制能力至关重要的领域的理解。2)这种诊断方法适用广泛，易于其他人实施。3)这项研究工作的跨学科性质（物理学和工程学的PI）将提供广泛的教学和学习经验，并将为相关学生提供基础和应用物理学方面的优秀培训。4)等离子体技术也将在一个新的计划中得到强调，该计划旨在在中学科学和数学课程中引入“重大挑战”，旨在通过强调人道主义应用，提高更多样化学生对工程职业的兴趣。