Scanning Probe Microscopy Studies of Carbon Nanotubes

Teri Wang Odom1, Jason H. Hafner1, and Charles M. Lieber1'2

1 Department of Chemistry, Harvard University Cambridge, MA 02138, USA {teri,jason,cml}@cmliris.harvard.edu

2 Division of Engineering and Applied Sciences, Harvard University Cambridge, MA 02138, USA

Abstract. This paper summarizes scanning probe microscopy investigations of the properties and manipulation of carbon nanotubes, and moreover, the fabrication and utilization of nanotubes as novel tips for probe microscopy experiments. First, scanning tunneling microscopy and spectroscopy measurements that elucidate (1) the basic relationship between Single-Walled Carbon Nanotube (SWNT) atomic structure and electronic properties, (2) the one-dimensional band structure of nanotubes, (3) localized structures in SWNTs, and (4) the electronic behavior of finite-size SWNTs are discussed. Second, atomic force microscopy investigations of the manipulation of nanotubes on surfaces to obtain information about nanotube-surface interactions and nanotube mechanical properties, and to create nanotube device structures are reviewed. Lastly, the fabrication, properties and application of carbon nanotube probe microscopy tips to ultrahigh resolution and chemically sensitive imaging are summarized. Prospects for future research are discussed.

Carbon nanotubes are currently the focus of intense interest worldwide. This attention to carbon nanotubes is not surprising in light of their promise to exhibit unique physical properties that could impact broad areas of science and technology, ranging from super strong composites to nanoelectron-ics [1,2,3]. Recent experimental studies have shown that carbon nanotubes are the stiffest known material [4,5] and buckle elastically (vs. fracture) under large bending or compressive strains [5,6]. These mechanical characteristics suggest that nanotubes have significant potential for advanced composites, and could be unique force transducers to the molecular world. Moreover, the remarkable electronic properties of carbon nanotubes offer great intellectual challenges and the potential for novel applications. For example, theoretical calculations first predicted that Single-Walled Carbon Nanotubes (SWNTs) could exhibit either metallic or semiconducting behavior depending only on diameter and helicity [7,8,9]. This ability to display fundamentally distinct electronic properties without changing the local bonding, which was recently experimentally demonstrated through atomically resolved Scanning Tunneling Microscopy (STM) measurements [10,11] sets nanotubes apart from all other nanowire materials [12,13].

M. S. Dresselhaus, G. Dresselhaus, Ph. Avouris (Eds.): Carbon Nanotubes, Topics Appl. Phys. 80, 173-211 (2001) © Springer-Verlag Berlin Heidelberg 2001

Scanning probe microscopies, such as STM and Atomic Force Microscopy (AFM), have been exploited to interrogate the electrical and mechanical properties of individual 1D nanostructures such as carbon nanotubes, and moreover, nanotubes have been incorporated as tips in scanning probe microscopies to enable these techniques to image with unprecedented sensitivity. In this paper, we will review scanning probe microscopy investigations of the fundamental properties and manipulation of carbon nanotubes, and the fabrication and use of nanotubes as novel probe tips. The basic structure of the review is as follows. First, we discuss scanning tunneling microscopy and spectroscopy measurements addressing (1) the basic relationship between SWNT atomic structure and electronic properties, (2) the one-dimensional band structure of nanotubes, (3) localized structures in SWNTs, and (4) the electronic behavior of finite size SWNTs. Second, we review AFM investigations of the manipulation of nanotubes on surfaces to obtain information about nanotube-surface interactions and nanotube mechanical properties, and to create nanotube device structures. Lastly, we discuss the fabrication and properties of carbon nanotube probe microscopy tips and the application of this new generation of probes to ultrahigh resolution and chemically sensitive imaging. Prospects for future research are discussed.

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