Collaborative Research: Plasma-Surface Interactions in Hydrogen Plasma-Induced Transitions from Carbon Nanotubes to Diamond Nanostructures

摘要国家科学基金项目编号：CTS-0613629 /0613501主要研究者： Aydil，E.S. / Maroudas，D. 明尼苏达大学/马萨诸塞大学阿默斯特分校提案标题：合作研究：从碳纳米管到金刚石纳米结构的氢等离子体诱导转变中的等离子体-表面相互作用IV族材料的纳米结构薄膜，例如碳纳米管（CNT）、硅、锗和金刚石，在太阳能电池、生物或化学传感器、过滤器、散热器、高功率半导体器件和分子电子学。 所有这些薄膜都是由SiH 4、CH 4和GeH 4等气体通过等离子体沉积生长的;等离子体是由电子、离子和反应性自由基组成的电离气体，通过将射频电场应用于低压气体而产生。纳米结构的Si，Ge和C膜仅当相应的进料气体在H2中被严重稀释时才产生，其中等离子体中存在大量的原子H。等离子体表面的相互作用，支配这些薄膜的成核和生长的基本理解是必不可少的定制他们的属性。 因此，所提出的研究的目标是调查等离子体表面相互作用的作用，特别是H的作用，在等离子体沉积的CNT和在H2等离子体诱导的CNT到金刚石过渡。 我们问是否碳纳米管，碳纳米纤维，和氢化的无定形碳等离子体沉积产生的可以转化为金刚石在低温下暴露于氢原子形成的等离子体解离的H2。 为了实现这一目标，我们提出了一个研究计划，集成等离子体和表面表征实验与原子尺度的模拟。计算结果将与实验数据进行比较，从模拟中获得的见解将用于指导新的实验研究。等离子体-表面相互作用以及这些相互作用对膜性质的影响是等离子体处理中最不了解的方面。有一个关键的需要，以补充经验的过程开发和定性与关键的基本过程的系统分析。为此，拟议的研究旨在将等离子体和表面诊断测量和结构表征与化学反应和结晶机制的计算原子尺度研究联系起来，以解决技术上重要和科学上有趣的现象，即CNT的生长和CNT和其他碳形式向金刚石的结构转变。拟议的项目跨越物理，化学，化学工程，材料科学以及应用和数值数学之间的传统界限。 因此，它提供了理想的手段，培养学生使用综合的，最先进的实验和计算方法来解决技术上的重要问题。PI让本科生参与研究，特别是鼓励在科学和工程领域代表性不足的学生，并广泛传播物理，化学，电子材料和等离子体工程社区的研究成果。 我们预计我们的研究策略、方法和结果将适用于研究其他IV族材料及其合金（例如Ge、Si/Ge和SiC）的生长和加工，并可能实现低温等离子体沉积的技术进步IV族薄膜，在我们的日常生活中有各种各样的应用。这个项目是由NSF/DOE基础等离子体科学和工程合作伙伴资助的。

ABSTRACTNational Science FoundationProposal Number: CTS-0613629 / 0613501Principal Investigator: Aydil, E.S. / Maroudas, D.Affiliation: University of Minnesota / University of Massachusetts-AmherstProposal Title: Collaborative Research: Plasma-Surface Interactions in Hydrogen Plasma-Induced Transitions from Carbon Nanotubes to Diamond Nanostructures Nanostructured thin films of group IV materials, such as carbon nanotubes (CNTs), silicon, germanium, and diamond have a broad range of existing and potential applications in solar cells, biological or chemical sensors, filters, heat sinks, high-power semiconductor devices, and molecular electronics. All of these films are grown by plasma deposition from gases such as SiH4, CH4 and GeH4; a plasma is an ionized gas consisting of electrons, ions, and reactive radicals and is created by application of radio-frequency electric fields to low-pressure gases. Nanostructured Si, Ge, and C films are produced only when the corresponding feed gases are heavily diluted in H2 with copious amounts of atomic H present in the plasma. Fundamental understanding of the plasma-surface interactions that govern the nucleation and growth of these films is essential for tailoring their properties. Accordingly, the goal of the proposed research is to investigate the role of plasma-surface interactions, and specifically the role of H, in the plasma deposition of CNTs and in the H2 plasma-induced CNT-to-diamond transition. We ask whether CNTs, carbon nanofibers, and hydrogenated amorphous carbon produced by plasma deposition can be transformed into diamond at low temperatures by exposure to H atoms formed by plasma dissociation of H2. Toward this goal, we propose a research plan that integrates plasma and surface characterization experiments with atomic-scale simulations. The computational results will be compared with the experimental data and the insights gained from the simulations will be used to guide new experimental studies. Plasma-surface interactions and the effects of these interactions on the film properties are among the least understood aspects of plasma processing. There is a crucial need to complement empirical process development and characterization with systematic analysis of the key fundamental processes. To this end, the proposed research aims to link plasma and surface diagnostic measurements and structural characterization with computational atomic-scale studies of chemical reactions and crystallization mechanisms to address technologically important and scientifically interesting phenomena, namely, growth of CNTs and structural transitions to diamond of CNTs and other carbon forms. The proposed project cuts across traditional boundaries between physics, chemistry, chemical engineering, materials science, as well as applied and numerical mathematics. Thus, it provides ideal means for training students to address technologically important problems using an integrated, state-of-the-art experimental and computational approach. The PIs involve undergraduate students in research, particularly encouraging students who are underrepresented in science and engineering, and disseminate broadly the research results in the physics, chemistry, electronic materials, and plasma engineering communities. We expect that our research strategy, methodology, and results will be applicable to studying the growth and processing of other group IV materials and their alloys, such as Ge, Si/Ge, and SiC,and potentially enable technological advancements in low-temperature plasma deposition of group IV films, which have a variety of applications in our daily lives.This project was funded through the NSF/DOE Partnership in Basic Plasma Science and Engineering.