Studies of CNTs grown on Si substrate by thermal CVD

• Main Authors: Chou-Chin Chang, 張朝欽
• Other Authors: Tzay-Shing Lai
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/4pmgzk

碩士 === 中原大學 === 應用物理研究所 === 91 === Abstract Growth and characteristics of carbon nanotubes (CNTs) on Ni-sputtered substrates Via the pyrolysis of methane by thermal CVD are studied in this thesis. The growth of CNTs was conducted with and without the introduction of NH3. Pure silicon and 200nm-Si3N4-coated silicon were used as our substrates. In all cases CH4 was used as carbon source. In the first part, the growth of CNTs without the use of NH3, by the observations of SEM, we studied the effect of temperature, CH4/Ar flow-rate ratio, and the thickness of the catalyst on the characteristics of the grown CNTs. In the second part, the growth of CNTs with the use of NH3 on the three growing stages of CNTs. We first studied the effect of the pretreatment of NH3 on the nucleation of the catalyst, by the use of AFM and SEM to observe the surface morphology and particle size of the catalyst. We then studied the effect of NH3 on the growth of CNTs, by the use of SEM and TEM to observe the surface morphology and structure of the grown CNTs. Finally we studied the growth mechanism and the vertical alignment of the grown CNTs. Ours results show that, under the pretreatment of NH3, the nucleation of the catalyst is more uniform in particle size, and the diameter of the CNTs is proportional to the particle size of the catalyst. We found that there is a critical thickness after the nucleation of the catalyst. Beyond the critical thickness of the catalyst, carbon nanoparticles are apt to be formed; under the critical thickness of the catalyst, CNTs are apt to be grown and, the thicker the catalyst, the bigger the tubes, the slower the growth rate. The growth rate of our CNTs ranges from 1μm/min for the bigger ones to 2.4μm/min for the smaller ones. The TEM observations of our bamboo-like CNTs show that, the CNTs growth on the Si3N4 substrate are shorter and thicker than those.