Carbon nanotubes are unique nanostructures with remarkable electronic and mechanical properties, some stemming from the close relation between carbon nanotubes and graphite, and some from their one-dimensional aspects. Initially, carbon nanotubes aroused great interest in the research community because of their exotic electronic structure. As other intriguing properties have been discovered, such as their remarkable electronic transport properties, their unique Raman spectra, and their unusual mechanical properties, interest has grown in their potential use in nanometer-sized electronics and in a variety of other applications, as discussed in this volume.

An ideal nanotube can be considered as a hexagonal network of carbon atoms that has been rolled up to make a seamless hollow cylinder. These hollow cylinders can be tens of micrometers long, but with diameters as small as 0.7 nm, and with each end of the long cylinder "capped with half a fullerene molecule, i.e., 6 pentagons". Single-wall nanotubes, having a cylindrical shell with only one atom in thickness, can be considered as the fundamental structural unit. Such structural units form the building blocks of both multi-wall nanotubes, containing multiple coaxial cylinders of ever-increasing diameter about a common axis, and nanotube ropes, consisting of ordered arrays of single-wall nanotubes arranged on a triangular lattice.

The first reported observation of carbon nanotubes was by Iijima in 1991 for multi-wall nanotubes. It took, however, less than two years before singlewall carbon nanotubes were discovered experimentally by Iijima at the NEC Research Laboratory in Japan and by Bethune at the IBM Almaden Laboratory in California. These experimental discoveries and the theoretical work, which predicted many remarkable properties for carbon nanotubes, launched this field and propelled it forward. The field has been advancing at a breathtaking pace ever since with many unexpected discoveries. These exciting developments encouraged the editors to solicit articles for this book on the topic of carbon nanotubes while the field was in a highly active phase of development.

This book is organized to provide a snapshot of the present status of this rapidly moving field. After the introduction in Chap. 1, which provides some historical background and a brief summary of some basic subject matter and definitions, the connection between carbon nanotubes and other carbon materials is reviewed in Chap. 2. Recent developments in the synthesis and purification of single-wall and multi-wall carbon nanotubes are discussed in Chap. 3. This is followed in Chap. 4 by a review of our present limited understanding of the growth mechanism of single-wall and multi-wall carbon nanotubes. Chapter 5 demonstrates the generality of tubular nanostructures by discussing general principles for tubule growth, and providing the reader with numerous examples of inorganic nanotube formation. The unique electronic structure and properties of perfect and defective carbon nanotubes are reviewed from a theoretical standpoint in Chap. 6. The electrical properties, transport, and magneto-transport measurements on single-wall nanotubes and ropes, as well as simple device structures based on carbon nanotubes are presented in Chap. 7. Scanning tunneling microscopy is used to study that nanotube electronic structure and spectra. The use of nanotubes as atomic force microscope tips for ultra-high resolution and chemically sensitive imaging is also discussed in Chap. 8. The application of optical spectroscopy to nanotubes is presented in Chap. 9. In this chapter, the discussion of the optical properties focuses on the electronic structure, the phonon structure, and the coupling between electrons and phonons in observations of resonance Raman scattering and related phenomena. The contribution made by electron spectroscopies to the characterization of the electronic structure of the nanotubes is discussed in Chap. 10, in comparison with similar studies devoted to graphite and Ceo. This is followed in Chap. 11 by a brief review of the phonon and thermal properties, with emphasis given to studies of the specific heat and the thermal conductivity, which are both sensitive to the low-dimensional aspects of carbon nanotubes. Chapter 12 discusses experiments and theory on the mechanical properties of carbon nanotubes. Linear elastic parameters, non-linear instabilities, yield strength, fracture and supra-molecular interactions are all reviewed. Chapter 13 discusses transport measurements, magnetotransport properties, electron spin resonance, and a variety of other exotic properties of multiwall nanotubes. The volume concludes in Chap. 14 with a brief review of the present early status of potential applications of carbon nanotubes.

Because of the relative simplicity of carbon nanotubes, we expect them to play an important role in the current rapid expansion of fundamental studies on nanostructures and their potential use in nanotechnology. This simplicity allows us to develop detailed theoretical models for predicting new phenomena connected with these tiny, one-dimensional systems, and then look for these phenomena experimentally. Likewise, new experimental effects, which have been discovered at an amazingly rapid rate, have provided stimulus for further theoretical developments, many of which are expected to be broadly applicable to nanostructures and nanotechnology research and development.

Cambridge, Massachusetts Yorktown Heights, New York January 2001

Mildred S. Dresselhaus Gene Dresselhaus Phaedon Avouris

0 0

Post a comment