Page 9 - Carbon Nanotubes

PREFACE

Since the start of this decade (the 1990's), fullerene efficiency and smaller nanotubes are discussed in
research has blossomed in many different directions, the article by Ivanov and coworkers. The quantum
and has attracted a great deal of attention to Carbon aspects of carbon nanotubes, stemming from their
Science. It was therefore natural to assemble, under small diameters, which contain only a small number
the guest editorship of Professor Harry Kroto, one of carbon atoms (< lo2), lead to remarkable sym-
of the earliest books on the subject of fullerenes 111, metries and electronic structure, as described in the
a book that has had a significant impact on the articles by Dresselhaus, Dresselhaus and Saito and
subsequent developments of the fullerene field. by Mintmire and White. Because of the simplicity
Stemming from the success of the first volume, it is of the single-wall nanotube, theoretical work has
now appropriate to assemble a follow-on volume on focussed almost exclusively on single-wall nanotubes.
Carbon Nanotubes. It is furthermore fitting that The remarkable electronic properties predicted for
Dr Sumio Iijima and Professor Morinobu Endo serve carbon nanotubes are their ability to be either con-
as the Guest Editors of this volume, because they are ducting or to have semiconductor behavior, depending
the researchers who are most responsible for opening on purely geometrical factors, namely the diameter
up the field of carbon nanotubes. Though the field and chirality of the nanotubes. The existence of
is still young and rapidly developing, this is a very conducting nanotubes thus relates directly to the
appropriate time to publish a book on the very active symmetry-imposed band degeneracy and zero-gap
topic of carbon nanotubes. semiconductor behavior for electrons in a two-dirnen-
The goal of this book is thus to assess progress in sional single layer of graphite (called a graphene
the field, to identify fruitful new research directions, sheet). The existence of finite gap semiconducting
to summarize the substantial progress that has thus behavior arises from quantum effects connected with
far been made with theoretical studies, and to clarify the small number of wavevectors associated with
some unusual features of carbon-based materials that the circumferential direction of the nanotubes. The
are relevant to the interpretation of experiments on article by Kiang et al. reviews the present status of the
carbon nanotubes that are now being so actively synthesis of single-wall nanotubes and the theoretical
pursued. A second goal of this book is thus to implications of these single-wall nanotubes. The geo-
stimulate further progress in research on carbon metrical considerations governing the closure, helicity
nanotubes and related materials. and interlayer distance of successive layers in multi-
'The birth of the field of carbon nanotubes is layer carbon nanotubes are discussed in the paper by
marked by the publication by Iijima of the observation Setton.
of multi-walled nanotubes with outer diameters as Study of the structure of carbon nanotubes and
small as 55 A, and inner diameters as small as 23 A, their common defects is well summarized in the
and a nanotube consisting of only two coaxial review by Sattler, who was able to obtain scanning
cyknders [2]. This paper was important in making tunneling microscopy (STM) images of carbon nan-
the connection between carbon fullerenes, which are otube surfaces with atomic resolution. A discussion
quantum dots, with carbon nanotubes, which are of common defects found in carbon nanotubes,
quantum wires. Furthermore this seminal paper [2] including topological, rehybridization and bonding
has stimulated extensive theoretical and experimental defects is presented by Ebbesen and Takada. The
research for the past five years and has led to the review by Ihara and Itoh of the many helical and
creation of a rapidly developing research field. toroidal forms of carbon nanostructures that may be
The direct linking of carbon nanotubes to graphite realized provides insight into the potential breadth
and the continuity in synthesis, structure and proper- of this field. The joining of two dissimilar nanotubes
ties between carbon nanotubes and vapor grown is considered in the article by Fonseca et al., where
carbon fibers is reviewed by the present leaders of this these concepts are also applied to more complex
area, Professor M. Endo, H. Kroto, and co-workers. structures such as tori and coiled nanotubes. The role
Further insight into the growth mechanism is pre- of semi-toroidal networks in linking the inner and
sented in the article by Colbert and Smalley. New outer walls of a double-walled carbon nanotube is
synthesis methods leading to enhanced production discussed in the paper by Sarkar et al.

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