Controllable growth of single wall carbon nanotubes by pyrolizing acetylene on the ¯oating iron catalysts Lijie Ci, Sishen Xie * , Dongsheng Tang, Xiaoqin Yan, Yubao Li, Zuqin Liu, Xiaoping Zou, Weiya Zhou, Gang Wang Institute of Physics, Center for Condensed Matter Physics, Chinese Academy of Science, Group 412, P.O. Box 603-92#, Beijing 100080, PR China Received 7 August 2001; in ®nal form 12 September 2001 Abstract Single wall carbon nanotubes SWNTs) without amorphous carbon coating were prepared by thermally decom- posing acetylene C 2 H 2 ) at the temperature range 750±1200 °C in a ¯oating iron catalyst system. The C 2 H 2 partial pressure was controlled to make a carbon supply limiting growth of SWNTs. The higher reaction temperature above 1100 °C seemed not to favor the SWNT production due to the quick thermal decomposition of C 2 H 2 . Ó 2001 Elsevier Science B.V. All rights reserved. 1. Introduction Single wall carbon nanotubes SWNTs) exhibit many exceptional and useful electronic and me- chanical properties and will be a promising can- didate for application in nano-scale technologies [1,2]. The most established methods to produce SWNTs currently include laser-ablation method [3] and carbon arc method [4]. By pyrolizing car- bon-containing molecules such as CO [5], CH 4 [6] and C 2 H 4 [7] on supported nanometer-sized metal particles, chemical vapor deposition CVD) method can be a promising way to up-scale the production of SWNTs. During the past three years, a continuous CVD synthetic method, in which SWNTs are grown in a ¯owing gaseous feedstock mixture, was developed to provide a mass-production method of SWNTs [8±11]. Cheng et al. [8] ®rst reported that they obtained ropes of SWNTs in high yield by pyrolizing a benzene± ferrocene±thiophene mixture at a temperature of 1200 °C. After that, Rao and coworkers [9], Nikolaev et al. [10] and Bladh et al. [11] also demonstrated that SWNTs could be produced in similar experiments by pyrolyzing other carbon- containing gases C 2 H 2 , CO and CH 4 ) at a tem- perature range 800±1200 °C. In those studies, CO was shown to be a better carbon feedstock to produce clean SWNTs with- out amorphous carbon coating [10]. In contrast, SWNTs produced from hydrocarbon sources such as C 2 H 2 [9] and C 6 H 6 [8] often suer from amor- phous carbon coating due to their self-pyrolysis at the reaction temperature. However, the reaction 30 November 2001 Chemical Physics Letters 349 2001) 191±195 www.elsevier.com/locate/cplett * Corresponding author. Fax: +86-10-82-64-95-31. E-mail address: ssxie@aphy.iphy.ac.cn S. Xie). 0009-2614/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII:S0009-261401)01098-3