High-Resolution Laser Diagnostics and Modeling of Single-Walled Carbon Nanotube Synthesis by Plasma-Enhanced CVD

CBET-0828165本研究旨在为发展等离子体增强化学气相沉积(PECVD)可控合成单壁碳纳米管(SWCNTs)奠定基础。碳纳米管已被证明具有广泛的优异物理性能，具有重要的技术和社会意义。然而，一些重要的性质强烈依赖于材料参数，到目前为止，这些参数在合成过程中基本上是无法控制的。碳纳米管的良好控制制造可以使其在广泛的应用领域取得突破，包括超快场效应晶体管和纳米电子电路、直接能量转换工艺、场发射设备、高温超导体、纺织纤维和高导热薄膜。此外，微波等离子体具有潜在的非常高浓度的物种，如CH3和C原子。这些物种在燃烧化学中非常重要，但对这些物种的诊断技术还不是很发达。因此，H2/CH4等离子体作为开发新的光学诊断技术的试验台引起了极大的兴趣。研究团队开创的一项技术通过降低生长表面的原子氢浓度来帮助合成，即使在室温下，它们也会在生长表面刻蚀SWCNT。关键是在生长表面施加正电偏压，以排斥H离子。尽管氢原子在这些新过程中的作用似乎很关键，但人们对生长表面附近等离子体的组成知之甚少。将在这项工作中应用和开发的空间分辨光学测量和互补模型对于理解原子H和含碳前体等物种在碳纳米管合成中的作用至关重要。在这项工作中获得的知识有望使合成方案和模型的建立成为可能，而合成方案和模型反过来将有助于控制合成碳纳米管材料、结构和器件的长期目标。拟议的计划将通过与电气工程师、材料科学家、物理学家和化学家的现有合作，使机械工程研究生接触到更多的科学和工程领域，如分子电子学和等离子体物理。此外，在纳米技术和激光诊断学方面令人兴奋的新研究将通过参加普渡大学夏季本科生研究奖学金(SURF)计划，有力地吸引国内学生进入科学和技术研究职业。

CBET-0828165LuchtThis research aims to develop key science for developing controlled synthesis of single-wall carbon nanotubes (SWCNTs) by plasma-enhanced chemical vapor deposition (PECVD). Carbon nanotubes have been shown to produce a wide range of outstanding physical properties with important technical and societal implications. However, some crucial properties depend strongly on material parameters that, to date, have been largely uncontrollable in the synthesis process. Well controlled fabrication of carbon nanotubes could enable breakthroughs across a vast range of applications, including ultrafast field-effect transistors and nanoelectronic circuits, direct energy-conversion processes, field-emission devices, high-temperature superconductors, textile fibers, and high-thermal-conductivity films. In addition, the microwave plasma has potentially very high concentrations of species such as CH3 and C-atom. These species are very important in combustion chemistry, but diagnostic techniques for these species are not well developed. The H2/CH4 plasma is thus of great interest as a testbed for the development of new optical diagnostic techniques.A technique pioneered by the research team aids synthesis by reducing concentration of atomic hydrogen from the growth surface, where they etch SWCNTs even at room temperature. The key is applying a positive electrical bias to the growth surface to repel H+ ions from it. Although the role of atomic H appears to be critical in these new processes, very little is known about the composition of the plasma near the growth surface. Spatially resolved optical measurements and complementary models, to be applied and developed in this work, are critical to understanding the role of species such as atomic H and carbon-containing precursors to CNT synthesis. The knowledge gained in this work is expected to enable the creation of synthesis protocols and models that in turn will aid the longer-term goal of controlled synthesis of CNT materials, structures, and devices. The proposed program will expose mechanical engineering graduate students to additional areas of science and engineering, such as molecular electronics and plasma physics, through existing collaborations with electrical engineers, material scientists, physicists, and chemists. In addition, exciting new research on nanotechnology and laser diagnostics will strongly attract domestic students into science and technology research careers through participation in Purdue's Summer Undergraduate Research Fellowship (SURF) program.