Local in situ Raman analysis of the gas and solid phase for understanding the catalytic growth process of carbon nanotubes by chemical vapor deposition (CVD)

在第一个项目阶段，开发了一种策略，并成功地应用于在线监测在Si/SiO_2晶片上化学气相沉积(CVD)中碳纳米管(CNTs)的气相组成和气相温度，该晶片携带有铁纳米颗粒来催化碳纳米管的形成。通过应用气相线性拉曼光谱，这是可能的。通过扫描电子显微镜(SEM)和固相拉曼光谱对碳纳米管进行了非原位表征。第二个项目期的目标是继续研究不同参数对碳源分解动力学的影响。根据到目前为止的结果，需要改变的参数包括衬底材料(应该用Al_2O_3和MgO代替Si/SiO_2)、氢浓度和碳源(乙炔和酒精)。最终的目标是将基于线性拉曼光谱的测量技术结合起来，在CVD过程中对碳纳米管的气相和固相进行同时分析。这使得以高时间和空间分辨率同时在线测量沉积的碳纳米管的气相组成、气相温度和微结构成为可能，从而最终可以跟踪碳源的分解及其对气体温度和对碳纳米管生长的影响。此外，还将通过扫描电子显微镜和拉曼光谱对生成的碳纳米管进行表征，以进行异地验证。这些对碳纳米管形成的全面研究将提供对碳纳米管成核和生长机制的持续了解，这将首次在实验上考虑发生在碳纳米管反应器内的中间反应步骤。

In the first project period a strategy was developed and successfully applied to in situ monitor the gas phase composition and the gas phase temperature during the chemical vapor deposition (CVD) of carbon nanotubes (CNTs) on a Si/SiO2-wafer, which was carrying iron nanoparticles to catalyze the CNT formation. This was possible by applying gas phase linear Raman spectroscopy. The resulting CNTs were characterized ex situ via scanning electron microscopy (SEM) and solid phase Raman spectroscopy. The goal of the second project period is to continue the investigations in exploring the influence of different parameters on the decomposition kinetics of the carbon source. In accordance with the results so far achieved, the parameters to be changed comprise the substrate material (Si/SiO2 should be replaced by Al2O3 and MgO), the hydrogen concentration and the carbon source (acetylene and alcohol). The final goal is to combine the measurement technique based on linear Raman spectroscopy for the simultaneous analysis of the gas and the solid phase in situ during the CVD of CNTs. This makes possible the simultaneous in situ measurement of the gas phase composition, the gas phase temperature and the microstructure of the deposited CNTs with high temporal and spatial resolution, such that finally the decomposition of the carbon source and its effect on the gas temperature and on the CNTs growth can be followed as a function of time. Additionally, the characterization of the resulting CNTs via SEM and Raman spectroscopy will be carried out ex situ for validation. These comprehensive investigations into the CNT formation will provide a sustained understanding of the CNTs nucleation and growth mechanism, which for the first time will experimentally consider the intermediate reactions steps taking place inside the CNT reactor.