Research Express@NCKU - Articles Digest Research Express@NCKU Volume 5 Issue 2 - July 4, 2008 [ http://research.ncku.edu.tw/re/articles/e/20080704/5.html ] Growth of CNTs on Fe-Si catalyst prepared on Si and Al coated Si substrate F.-Y. Teng, Jyh-Ming Ting * , Sahendra P. Sharma, Kun-Hou Liao Department of Materials Science and Engineering, College of Engineering, National Cheng Kung University * Corresponding Author. Email address: jting@mail.ncku.edu.tw Nanotechnology 19, 095607 (6pp) Issue 9 (2008) Carbon nanotubes (CNTs) continue to draw tremendous attentions from the entire research community since its discovery in 1991 [1]. These fascinating properties of CNTs depend on their structures, which are strongly influenced by the synthesis methods and parameters. Among the parameters, characteristics of the catalyst play a key role in controlling the structure of CNTs at molecular or nano scale. Typical catalysts that are widely employed in CNT synthesis include transition metals such as Co, Fe, Ni, Mo, and their combination such as Fe/Ni, Co/Ni, Y/Ni [2-4]. It is also known that when the formation of silicide between a catalyst and Si substrate, e.g., iron silicide, is highly undesirable. Various types of thin film materials have therefore used as an interlayer to prevent silicide formation [5-8]. In this paper, the use of a thin Al layer, ranging from 2 nm to 12 nm, between a 24-nm thick Fe-Si catalyst and a silicon substrate is reported. We show that the Al interlay not only prevents the silicide formation but also greatly enhanced the CNT growth rate at growth temperature of only 370 ℃ in a microwave plasma enhanced chemical vapor deposition (MPCVD) reactor. Furthermore, the use of such an Al interlayer is so effective as normally required catalyst etching prior to the growth is waived. Fig. 1. TEM cross sectional image of an etched Fe-Si catalyst. Fig. 1 shows a TEM cross sectional image of an etched Fe-Si catalyst which is bounded by the two dotted lines. It is seen that only the region near the surface become particles, adjacent to which there is a flat region. It is noted that the thickness of the catalyst layer increases from 24 nm for its as-deposited state 1 of 4