Systematic Studies of Plasma Reactions on Dynamic Surfaces, Using a Novel Rotating Substrate

[09:66967]这些研究将系统地研究发生在气态等离子体放电和包含等离子体的反应器壁之间边界上的选定化学反应。等离子体科学缺乏等离子体壁边界的基本知识，而这对于控制等离子体加工至关重要，例如硅集成电路中精细线图案转移的蚀刻和其他未来的纳米技术。为了进入等离子体壁边界，等离子体腔壁内的圆柱形衬底将快速旋转，允许部分表面周期性地暴露在等离子体中，然后进行分析。之前，我们用过这个？旋转的墙?研究氧等离子体中氧原子和氯等离子体中氯原子的表面复合反应，以及氧和氯的混合物在等离子体中形成氧化氯和二氧化氯的表面反应。新的研究将集中在四个对理解和控制等离子体表面化学至关重要的主题上：1)弱结合稳定吸附剂（如Cl2）在Cl原子重组中的作用是什么？我们之前发现物理吸附的Cl2阻断了Cl重组的位点。我们将把研究范围扩大到更广泛的情况，并调查其他疑似病例，如Br2和氟碳化合物。2)我们最近在铜的亚单层覆盖层中发现了O，微量金属催化重组的范围有多广，机制是什么？提出的铜的氧化还原机制将与其他金属进行测试，并重新组合原子。3)对于选定的原子和小分子，将确定两种流行的表面反应机制（所谓的Langmuir-Hinshelwood或延迟反应与Eley理想反应或迅速反应）的相对重要性。除了原始表面上的氢原子，这些信息几乎是完全缺乏的。4)离子轰击和电子轰击在表面化学反应中的作用是什么？正离子轰击表面可以产生或破坏反应位点，而电子轰击可以引起吸附层的分解，也可以产生负离子，降低痕量金属高氧化态的催化活性。这项提议的工作将是一项极具挑战性的基础研究项目，对于提高我们对等离子体表面相互作用的理解至关重要，重点是等离子体用于集成电路和其他未来设备中纳米级特征的蚀刻。更广泛的影响拟议的工作将为两名研究生和一名或多名本科生提供具有挑战性的项目，具有丰富的科学和教育回报，以及技术进步。虽然它将提高我们对复杂等离子体条件下表面反应的理解，但它也将有助于不同的领域，如空间物理学，燃烧化学，催化和大气非均相反应。此外，分离这种复杂反应的新方法对这些不同的领域以及基础表面科学具有广泛的意义和潜在的影响。计划开展几项外展活动，包括让一名高中教师参与研究，以及让本科生通过诸如休斯敦大学本科生研究体验（REU）等项目参与研究。最后，未被充分代表的学生（超过一半的休斯敦大学本科生是少数民族）的参与将被追求。

0966967DonnellyIntellectual MeritThese studies will systematically investigate selected chemistry occurring at the boundary between a gaseous plasma discharge and the walls of the reactor that contains the plasma. Such basic knowledge of the plasma-wall boundary is lacking in plasma science and is critically needed for control of plasma processing such as etching for fine-line pattern transfer in silicon integrated circuits and other future nano-technology. To gain access to the plasma-wall boundary, a cylindrical substrate within the plasma chamber wall will be rapidly rotated, allowing portions of the surface to be periodically exposed to the plasma and then analyzed. Previously, we used this ?spinning wall? method to investigate surface recombination reactions of oxygen atoms in an oxygen plasma and chlorine atoms in a chlorine plasma, and as well as surface reactions that form chlorine oxide and chlorine dioxide in plasmas with mixtures of oxygen and chlorine. The new studies will focus on four topics of critical importance to understanding and controlling chemistry at surfaces immersed in plasma: 1) What is the role of weakly bound stable adsorbates such as Cl2 on recombination of Cl atoms? We previously found that physisorbed Cl2 blocks sites for Cl recombination. We will extend the study to a much wider range of conditions and investigate other suspected cases such as Br2 and fluorocarbons. 2) How widespread is, and what is the mechanism for, catalyzed recombination by trace metals, as we recently discovered for O in the presence of sub-monolayer coverages of copper? The oxidation-reduction mechanism proposed for copper will be tested with other metals, and recombining atoms. 3) The relative importance of the two prevailing mechanisms for surface reactions (the so-called Langmuir-Hinshelwood or delayed reaction vs. the Eley Rideal or prompt reaction) will be determined for selected atoms and small molecules. Except for hydrogen atoms on pristine surfaces, such information is almost completely lacking. 4) What are the roles of ion and electron bombardment on surface chemical reactions? Positive ions bombarding the surface can create or destroy reaction sites, while electron bombardment can cause decomposition of adsorbed layers, as well as create negative ions and reduce catalytic activity of higher oxidation states of trace metals. The proposed work will be an extremely challenging, basic research project that is critical for improving our understanding of plasma-surface interactions with an emphasis on plasmas used for etching of nano-scale features in integrated circuits and other future devices. Broader ImpactsThe proposed work will provide challenging projects for two graduate student and one or more undergraduates, with rich scientific and educational payoffs, as well as technological advances. While it will improve our understanding of surface reactions under complex plasma conditions, it will also contribute to diverse areas such as space physics, combustion chemistry, catalysis, and atmospheric heterogeneous reactions. In addition, the new methods for isolating such complex reactions have broad implications for and potential impact on these diverse areas, as well as basic surface science. Several outreach activities are planned, including involving a high school teacher in the research, and the participation by undergraduate students through programs such as the Research Experience for Undergraduates (REU) at UH. Finally, the participation of underrepresented students (more than half of the University of Houston undergraduate students are minorities) will be pursued.