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)

在第一个项目期间，开发了一种策略，并成功地应用于原位监测碳纳米管（CNT）在Si/SiO2-晶片上的化学气相沉积（CVD）过程中的气相组成和气相温度，该晶片携带铁纳米颗粒以催化CNT的形成。通过应用气相线性拉曼光谱法，这是可能的。通过扫描电子显微镜（SEM）和固相拉曼光谱对所得碳纳米管进行了表征。项目第二阶段的目标是继续研究不同参数对碳源分解动力学的影响。根据迄今为止获得的结果，待改变的参数包括衬底材料（Si/SiO2应当由Al 2 O3和MgO代替）、氢浓度和碳源（乙炔和醇）。最终目标是将基于线性拉曼光谱的测量技术联合收割机用于在CNT的CVD过程中原位同时分析气相和固相。这使得可以以高的时间和空间分辨率同时原位测量气相组成、气相温度和沉积的CNT的微结构，使得最终可以随时间而变化地跟踪碳源的分解及其对气体温度和CNT生长的影响。此外，将通过SEM和拉曼光谱对所得CNT进行非原位表征以进行验证。这些对CNT形成的全面调查将提供对CNT成核和生长机制的持续理解，这将首次在实验上考虑CNT反应器内发生的中间反应步骤。

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.