Patterning of Single-Wall Carbon Nanotubes via a Combined Technique (Chemical Anchoring and Photolithography) on Patterned Substrates Myung-Sup Jung, †,‡ Sung-Ouk Jung, ‡ Dae-Hwan Jung, † Young Koan Ko, † Yong Wan Jin, ‡ Jongmin Kim, ‡ and Hee-Tae Jung* ,† Department of Chemical and Biomolecular Engineering, Korea AdVanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea, and Materials and DeVices Research Center, Samsung AdVanced Institute of Technology, P.O. Box 111, Suwon 440-600, Korea ReceiVed: February 16, 2005; In Final Form: April 7, 2005 Single-walled carbon nanotubes (SWNTs) have been chemically attached with high density onto a patterned substrate. To form the SWNT pattern, the substrate was treated with acid-labile group protected amine, and an amine prepattern was formed using a photolithographic process with a novel polymeric photoacid generator (PAG). The polymeric PAG contains a triphenylsulfonium salt on its backbone and was synthesized to obtain a PAG with enhanced efficiency and ease of spin-coating onto the amine-modified glass substrate. The SWNT monolayer pattern was then formed through the amidation reaction between the carboxylic acid groups of carboxylated SWNTs (ca-SWNTs) and the prepatterned amino groups. A high-density multilayer was fabricated via further repeated reaction between the carboxylic acid groups of the ca-SWNTs and the amino groups of the linker with the aid of a condensation agent. The formation of covalent amide bonding was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. Scanning electron microscopy and UV-vis-near-IR results show that the patterned SWNT films have uniform coverage with high surface density. Unlike previously reported patterned SWNT arrays, this ca-SWNT patterned layer has high surface density and excellent surface adhesion due to its direct chemical bonding to the substrate. 1. Introduction Carbon nanotubes (CNTs) have attracted much attention in recent years because of their remarkable physical and chemical properties. Their potential applications include flat panel displays, logic gates, sensors, and energy storage, which all require that the CNTs be patterned at defined positions with large-scale control of location and orientation. 1-3 Many efforts have been made to pattern CNTs on a large scale. According to previous reports, CNT patterns on substrates have been fabricated with various selective growth and self- assembly methods. To prepare for the selective growth of CNTs, various technologies such as plasma patterning 3 as well as soft- lithographic 4 and photolithographic methods 2,5-7 have been applied to the prepatterning of metal catalysts. By growing multiwalled carbon nanotubes (MWNTs) on these prepatterned metal catalysts, well-defined MWNT patterns have been pro- duced with high resolution and density. However, the patterned growth method is difficult to apply for SWNT patterning and always requires the use of high processing temperatures. As a result, the application of this method has been limited. Self- assembly methods have also been applied to the patterning of SWNTs and have proved to be especially powerful for patterning at low temperatures. Several self-assembly methods, including adsorption onto prepatterned substrates 8-11 as well as chemical assembly onto various surfaces, 12-14 have been used to pattern SWNT films. Although this method has great potential for the modification and functionalization of surfaces, the adhesion between the resulting SWNT patterns and substrates is not sufficient for practical applications, which results in low surface density. In this paper we report a novel fabrication method for patterning of SWNTs with high density and excellent surface adhesion by the covalent attachment of ca-SWNTs onto an amine prepatterned glass with the aid of a condensation agent. To prepare the amine prepatterned glass, a glass plate was treated with aminosilane compound and acid-labile group protected amine, and the acid-labile group was then selectively deprotected with a photolithographic process. We also show that a novel polymeric PAG with triphenylsulfonium salt on its backbone has the enhanced ease of spin coating onto the acid-labile group modified glass substrate. The SWNT monolayer pattern was formed by the reaction between the carboxylic acid groups of the ca-SWNTs and the prepatterned amino groups, and a multilayer pattern with high density was fabricated via further repeated reactions between the carboxylic acid groups of the ca-SWNTs and the amino groups of the linker with the aid of the condensation agent. The variation of the surface density of the ca-SWNT multilayer film with respect to the number of reaction cycles was monitored. The resulting ca-SWNT pat- terned layer was found to have high density and excellent surface adhesion due to its direct chemical bonding with the substrate surface. 2. Experimental Sections 2.1. Synthesis of the Polymeric Photo Acid Generator. Scheme 1 has described the synthesis of the monomer and the subsequent polymerization of the polymeric PAG. A mixture of 2,6-dimethylanisole (0.213 mol) and 4,4′-hydroxyphenylsul- * Corresponding author. Telphone: +82-42-869-3931. Fax: +82-42- 869-3910. E-mail: heetae@kaist.ac.kr. † Korea Advanced Institute of Science and Technology. ‡ Samsung Advanced Institute of Technology. 10584 J. Phys. Chem. B 2005, 109, 10584-10589 10.1021/jp0508103 CCC: $30.25 © 2005 American Chemical Society Published on Web 05/11/2005