PDF《Vapor Deposition》

以常压热化学气相沉积法由乙炔成长?米碳管之研究 韩世泽 ?竞荣 姚品全 大?大学电机工程系 彰化县大村乡山脚?

112 号摘要本研究以溶胶―凝胶法(sol-gel method)制备之镍触媒,旋转涂布於矽基板上,经线上还 原后,以常压热化学气相沉积法(atmospheric thermal CVD)由乙炔成长?米碳管(carbon nanotubes, CNT).

研究结果发现:1. 触媒前处?时间、气体??、温?、气体种?、混合比 等制程??,可用以控制 CNT 之直径.前处?温?为 800o C,添加氢气最适作用时间约 10~20 分钟;

2. 沉积反应条件之掌控对 CNT 产物的形态至为关键.成长温?为

800 o C,此时成长速 ?最快,CNT 在基板分布密?最高;

成长 CNT 时,添加氢气有助於 CNT 管径的控制,避免过 多的竹节与弯曲形态产物发生;

碳源与氢气(C2H2/H2)最适比?约为 0.1,如欲以 thermal CVD 系统达成?米碳管的准直成长(aligned growth),则必须?精确掌控?属触媒的分散?态(颗 ?大小、分布均匀性等)及控制 CNT 的成长速?.所成长之?米碳管,以?曼光谱分析,显 示?个峰值,分别是

1305 cm-1 与1560 cm-1 ,证明产物为多壁?米碳管,含有多?的石墨态非 晶形沉积物. 关键词:溶胶-凝胶法,触媒,化学气相沉积法,?米碳管 Synthesis of Carbon Nanotubes over Sol-Gel Deposited Substrates from Acetylene by Thermal Chemical Vapor Deposition SHIH-TSE HANG, CHIN-YUNG YEH and PIN-CHUAN YAO Department of Electrical Engineering, DaYeh University No. 112, Shanjiao Rd., Dacun, Changhua, Taiwan 51591, R.O.C. ABSTRACT Nickel nanoparticles synthesized by a sol-gel process were spin-coated over silicon substrates as catalysts for the growth of a carbon nanotube (CNT) by atmospheric thermal chemical vapor deposition. The as-deposited Ni film exhibited relatively good activity for the growth of CNTs. On the basis of the results obtained, several characteristics of CNT growth were observed: I. Pretreatment stage: Parameters including the reduction temperature, composition and flow rate of ambient gases had a prominent effect on the diameter and morphology of the as-grown carbon nanotube. A pretreatment temperature of 800o C for 10~20 minutes seems adequate for CNT growth. II. CNT growth stage: The temperature range for CNT growth extends from

700 o to 900o C. For intensive growth and better quality control of the nanotube, it was beneficial to introduce a reduction ambient such as hydrogen flow. The optimal ratio of H2/C2H2 extends to within 0.1 under which CNT was grown at a considerable rate. Meanwhile, it took about 10~20 minutes for complete CNT growth under an ambient containing H2. For better control of the orientation of the as-grown CNTs (vertically aligned growth), information about the catalysts dispersion, growth rate control and how to prevent the deactivation of active sites during the growth stage would be necessary and vital. The Raman spectroscopy has strong bands at

1305 and

1560 cm-1 , respectively, thus providing definite evidence that the CNTs are multi-walled with a graphitic structure. Key Words: sol-gel method, chemical vapor deposition, carbon nanotubes

一、前言 ?米碳管(carbon nanotube)拥有各种优?的特性,可 ?是迈入

21 世纪的关键材?之一 [3].在电性上,?同管径 及旋角(chiral angle)的?米碳管可具有?属导体或半导体 的特性 [14],前者之导电?可高达铜的十倍,其一维 (one-dimension)结构可应用作?子导线 [11].?米碳管在 电子产业的应用之一为场发射(field emission)元件 [19], 其典型的研究有场电子发射显示器 [2],目前已有概?产品 上市 [1].在机械性质方面,具有极强的结构和目前已知材 ?最高的杨氏系?(~1.3 GPa)[15],因此可用以制作防弹 衣等.此外,可?用?米碳管发展气体储存,?如储氢材? 及作为电极材?,用於二次锂?子充放电效?之改进等?域 [9]. 合成?米碳管的方法包括:电弧放电法(carbon arc discharge)[3]、?射剥?法(laser ablation)[18] 以及化学 气相?积法(chemical vapor deposition, CVD)[7].其中以 CVD 法最常用?合成?米碳管,因为具有成本低?、可大 面积及?规则表面成长 , 同时可选择性成长於特定区域等优 点[5-8, 12, 13, 17]. ?同结构与形态的?米碳管,具有迥?的的电性、物性、化性等,因而影响最终应用.藉由?同的合成方法及合 成条件,可以调控?同种?之?米碳管及其尺寸与形态,因 此可知制程掌控之重要性.本研究以溶胶-凝胶法(sol-gel method)合成?属触媒先驱物,以旋转涂布(spin-coating) 法将其均匀涂布於单晶矽基板上 , 置於二际?管中成长 ?米碳管.使用溶胶-凝胶法具有以下优点:1. 触媒薄膜 ?均匀涂布在基板上;