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

这些研究将系统地调查在气体等离子体放电和包含等离子体的反应堆壁面之间发生的选定化学物质。等离子体-壁边界的这种基本知识在等离子体科学中是缺乏的，对于等离子体工艺的控制是至关重要的，例如硅集成电路中用于细线图案转移的刻蚀以及其他未来的纳米技术。为了接近等离子体-壁边界，等离子体室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。以前，我们用的是这个？旋转墙？方法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，以及氧和氯混合物等离子体中生成二氧化氯和氧化氯的表面反应。新的研究将集中在四个对理解和控制等离子体中表面化学至关重要的主题上：1)弱结合的稳定吸附物，如Cl2，在氯原子的复合中起什么作用？我们先前发现，物理吸附的Cl2阻止了Cl2的重组。我们将把研究扩展到更广泛的情况，并调查其他疑似病例，如溴2和氟碳化合物。2)我们最近发现，在铜的亚单分子层存在的情况下，O被痕量金属催化的复合有多普遍，其机制是什么？提出的铜的氧化还原机理将与其他金属和重组原子一起进行测试。3)对于选定的原子和小分子，将确定两种主要的表面反应机制(所谓的朗缪尔-辛舍伍德反应或延迟反应与埃利理想或快速反应)的相对重要性。除了原始表面上的氢原子，这些信息几乎完全缺乏。4)离子和电子轰击对表面化学反应的作用是什么？正离子轰击表面会产生或破坏反应中心，而电子轰击会导致吸附层的分解，以及产生负离子，降低痕量金属较高氧化态的催化活性。拟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，重点是用于刻蚀集成电路和其他未来器件中纳米级特征的等离子体。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的表面反应的理解，但它也将有助于空间物理、燃烧化学、催化和大气非均相反应等多个领域。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影响和潜在的影响。计划了几项外展活动，包括让一名高中教师参与研究，以及本科生通过UH本科生研究体验(REU)等项目参与。最后，将争取代表人数不足的学生(休斯顿大学超过一半的本科生是少数族裔)的参与。

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.