CVD Growth, Optical and Thermal Characterization of Vertically Aligned Single-Walled Carbon Nanotubes
CVD Growth, Optical and Thermal Characterization of Vertically Aligned Single-Walled Carbon Nanotubes
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垂直排列单壁碳纳米管的 CVD 生长、光学和热表征
DOI：
10.1115/1.4005713
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
S. Maruyama and R. Xiang
中科院分区：
文献类型：
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作者：
Hamed Dalir;Fumio Koyama;S. Maruyama and R. Xiang
垂直排列单壁碳纳米管（VA-SWNT）有望成为各种光学、电学、能源和热学器件的特殊材料。将讨论生长控制和表征技术的最新进展。基于 CVD 过程中激光吸收的原位生长监测，研究了 VA-SWNT 的化学气相沉积 (CVD) 生长机制。生长曲线的特征是生长速率从乙醇压力确定的初始速率开始呈指数衰减。用金属催化剂上的碳涂层和前体乙醇的气相热分解讨论了它的初始生长速率和衰减。为了实现单壁碳纳米管的精确图案化生长，我们最近提出了一种表面能差驱动的选择性沉积催化剂，用于单壁碳纳米管的局部生长。对于自组装单层（SAM）图案化的硅表面，催化剂颗粒沉积并且单壁碳纳米管仅在亲水区域生长。与最先进的技术相比，所提出的全液体方法在可扩展性和分辨率方面具有显着的优势，我们相信这可以极大地推进使用高质量生长的单壁碳纳米管纳米器件的制造。将讨论使用偏振吸收、偏振拉曼和光致发光光谱对 VA-SWNT 薄膜进行光学表征。从顶部垂直排列薄膜的激光激发意味着每个纳米管垂直于其轴被激发。由于这种主要的垂直激发，观察到有趣的交叉偏振吸收和令人困惑且实际上重要的拉曼特征。通过非平衡分子动力学模拟方法探索了单壁碳纳米管极高且奇特的导热率。基于热导率和热边界热阻的分子动力学输入，通过多种实验技术和蒙特卡罗模拟研究了垂直排列薄膜和复合材料的热性能。讨论了目前对薄膜热性能的理解。
Vertically aligned single-walled carbon nanotubes (VA-SWNTs) is expected to be an extra-ordinal material for various optical, electrical, energy, and thermal devices. The recent progress in growth control and characterization techniques will be discussed. The chemical vapor deposition (CVD) growth mechanism of VA-SWNTs is studied based on the in situ growth monitoring by laser absorption during CVD. The growth curves are characterized by an exponential decay of the growth rate from the initial rate determined by ethanol pressure. The initial growth rate and decay of it are discussed with carbon over-coat on metal catalysts and gas phase thermal decomposition of precursor ethanol. For the precisely patterned growth of SWNTs, we recently propose a surface-energy-difference driven selective deposition of catalyst for localized growth of SWNTs. For a self-assembled monolayer (SAM) patterned Si surface, catalyst particles deposit and SWNTs grow only on the hydrophilic regions. The proposed all-liquid-based approach possesses significant advantages in scalability and resolution over state-of-the-art techniques, which we believe can greatly advance the fabrication of nanodevices using high-quality as-grown SWNTs. The optical characterization of the VA-SWNT film using polarized absorption, polarized Raman, and photoluminescence spectroscopy will be discussed. Laser-excitation of a vertically aligned film from top means that each nanotube is excited perpendicular to its axis. Because of this predominant perpendicular excitation, interesting cross-polarized absorption and confusing and practically important Raman features are observed. The extremely high and peculiar thermal conductivity of single-walled carbon nanotubes has been explored by nonequilibrium molecular dynamics simulation approaches. The thermal properties of the vertically aligned film and composite materials are studied by several experimental techniques and Monte Carlo simulations based on molecular dynamics inputs of thermal conductivity and thermal boundary resistance. Current understanding of thermal properties of the film is discussed.