以熱化學氣相沉積在不同緩衝層合成奈米碳管之參數研究

Abstract

本文主要研究如何以不同緩衝層(buffer layer)的選擇，以物理氣相沉積 ( PVD ) 得到鎳為觸媒及利用熱裂解化學氣相沉積法的方式，再加入甲烷、乙烯等碳氫化合物為碳源，合成奈米碳管，並探討不同參數對奈米碳管的合成影響。 實驗中主要以TiN、TaN、SiO2為緩衝層，鎳層為觸媒層，實驗發現不同參數條件合成之奈米碳管具有不同的形態與品質，因此在掃瞄電子顯微鏡 ( SEM )、拉曼光譜儀觀察之下，分析碳管成長的差異，藉以研究緩衝層與奈米碳管間的影響，並由穿透電子顯微鏡 ( TEM )探討其微結構特性。 實驗結果顯示，由熱裂解方式合成的碳管其方向性較不好，在高熱下成長機構易受凡得瓦力（Van der Waals Forces）或空間阻礙 （Steric Hindrance），使造成碳管隨意成長，結構缺陷較多，若以緩衝層作為防止擴散之功能，可以在更低溫下(450~500度)提升準直性與增加碳管之數量與密度。

This thesis mainly devoted to study the growth of the carbon nanotubes (CNTs) using different buffer layers include TiN、TaN and SiO2. In the experiment, nickel was act as catalyst for grown CNTs. The nanostructures have been synthesized from hydrocarbon from the mixture of methane and ethylene by thermal chemical vapor deposition. The effect of experimental parameters on the growth characteristics of CNTs were evaluated by Scanning Electron Microscope (SEM). The qualities of CNTs were measured by Raman spectroscope and the characteristic of carbon lattice was analyzed using Transmission Electron Microscope (TEM). The experimental results show that the size of the catalyst and the quality of CNTs can be controlled by appropriate pretreatments. The CNTs were non-aligned grown by Thermal-CVD due to the Van der Waals forces and steric hindrance, which were elevated the defect at the microstructure. The relationship between of CNTs and the catalyst were demonstrated by TiN and TaN buffer layers at low-temperature (450~500). TiN or TaN buffer layer can act an important roles to decrease process temperature and use as barrier to avoid diffusion between catalyst and silicon substrate.