The extraordinary mechanical properties and unique electrical properties of carbon nanotubes (CNT... more The extraordinary mechanical properties and unique electrical properties of carbon nanotubes (CNTs) have stimulated extensive research activities across the world since their discovery by Sumio Iijima of the NEC Corporation in the early 1990s. Although early research focused on growth and characterization, these interesting properties have led to an increase in the number of investigations focused on application development in the past 5 years. The breadth of applications for carbon nanotubes is indeed wide ranging: nanoelectronics, quantum wire interconnects, field emission devices, composites, chemical sensors, biosensors, detectors, etc. There are no CNT-based products currently on the market with mass market appeal, but some are in the making. In one sense, that is not surprising because time-to-market from discovery typically takes a decade or so. Given that typical time scale, most current endeavors are not even halfway down that path. The community is beginning to move beyond the wonderful properties that interested them in CNTs and are beginning to tackle real issues associated with converting a material into a device, a device into a system, and so on. At this point in the development phase of CNT-based applications, this book attempts to capture a snap shot of where we are now and what the future holds. Chapter 1 describes the structure and properties of carbon nanotubes — though well known and described in previous textbooks — both as an introduction and for the sake of completeness in a book like this one. In understanding the properties, the modeling efforts have been trailblazing and have uncovered many interesting properties, which were later verified by hard characterization experiments. For this reason, modeling and simulation are introduced early in Chapter 2. Chapter 3 is devoted to the two early techniques that produced single-walled nanotubes, namely, arc synthesis and laser ablation. Chemical vapor deposition (CVD) and related techniques (Chapter 4) emerged later as a viable alternative for patterned growth, though CVD was widely used in early fiber development efforts in the 1970s and 1980s. These chapters on growth are followed by a chapter devoted to a variety of imaging techniques and characterization (Chapter 5). Important techniques such as Raman spectroscopy are covered in this chapter. The focus on applications starts with the use of single-walled and multiwalled carbon nanotubes in scanning probe microscopy in Chapter 6. In addition to imaging metallic, semiconducting, dielectric, and biological surfaces, these probes also find applications in semiconductor metrology such as profilometry and scanning probe lithography. Chapter 7 summarizes efforts to date on making CNT-based diodes and transistors and attempts to explain the behavior of these devices based on well-known semiconductor device physics theories explained in undergraduate and graduate textbooks. It is commonly forecast that silicon CMOS device scaling based on Moore’s law may very well end in 10 or 15 years. The industry has been solving the technical problems in CMOS scaling impressively even as we embark on molecular electronics, as has been the case with the semiconductor industry in the past 3 decades. Therefore, for those pursuing alternatives such as CNT electronics and molecular electronics, the silicon electronics is a moving target and the message is clear: replacing silicon-conducting channel simply with a CNT-conducting channel in a CMOS may not be of much value — alternative architectures;different state variable (such as spin)-based systems; and coupling functions such as computing, memory, and sensing are what can set the challengers apart from the incumbent. Unfortunately, at the writing of this book, there is very little effort in any of these directions, and it is hoped that such alternatives emerge, succeed, and flourish. Field emission by carbon nanotubes is very attractive for applications such as flat panel displays, x-ray tubes, etc. The potential for commercial markets in television and computer monitors, cell phones, and other such displays is so enormous that this application has attracted not only much academic research but also substantial industrial investment. Chapter 8 discusses principles of field emission, processes to fabricate the emitters, and applications. One application in particular, making an x-ray tube, is covered in great detail from principles and fabrication to testing and characterization. With every atom residing on the surface in a single-walled carbon nanotube, a very small change in the ambient conditions can change the properties (for example, conductivity) of the nanotube. This change can be exploited in developing chemical sensors. The nanotubes are amenable to functionalization by attaching chemical groups, DNA, or proteins either on the end or sidewall. This also allows developing novel sensors using nanotubes. Chapter 9 discusses principles and development of chemical and physical sensors. Likewise, Chapter 10 describes biosensor development. The mechanical, thermal, and physical properties of carbon nanotubes have resulted in numerous studies on conducting polymer films, composites, and other structural applications. Chapter 11 captures these developments. Finally, all other applications that elude the above prime categories are summarized in Chapter 12. This is an edited volume, and various authors who practice the craft of carbon nanotubes day to day have contributed to this volume. I have made an effort to make this edited volume into a cohesive text. I hope that the readers — students and other researchers getting into this field, industry, and even the established experts — find this a valuable addition to the literature in carbon nanotubes. I would like to thank Nora Konopka of the CRC Press for her support throughout this work. Finally, this book would not have been possible without the help and skills of my assistant Amara de Keczer. I would like to thank her also for the cover design of the book.
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have stimulated extensive research activities across the world since their discovery by Sumio Iijima of the
NEC Corporation in the early 1990s. Although early research focused on growth and characterization,
these interesting properties have led to an increase in the number of investigations focused on application
development in the past 5 years. The breadth of applications for carbon nanotubes is indeed wide ranging:
nanoelectronics, quantum wire interconnects, field emission devices, composites, chemical sensors, biosensors,
detectors, etc. There are no CNT-based products currently on the market with mass market
appeal, but some are in the making. In one sense, that is not surprising because time-to-market from
discovery typically takes a decade or so. Given that typical time scale, most current endeavors are not
even halfway down that path. The community is beginning to move beyond the wonderful properties
that interested them in CNTs and are beginning to tackle real issues associated with converting a material
into a device, a device into a system, and so on. At this point in the development phase of CNT-based
applications, this book attempts to capture a snap shot of where we are now and what the future holds.
Chapter 1 describes the structure and properties of carbon nanotubes — though well known and
described in previous textbooks — both as an introduction and for the sake of completeness in a book
like this one. In understanding the properties, the modeling efforts have been trailblazing and have
uncovered many interesting properties, which were later verified by hard characterization experiments.
For this reason, modeling and simulation are introduced early in Chapter 2. Chapter 3 is devoted to the
two early techniques that produced single-walled nanotubes, namely, arc synthesis and laser ablation.
Chemical vapor deposition (CVD) and related techniques (Chapter 4) emerged later as a viable alternative
for patterned growth, though CVD was widely used in early fiber development efforts in the 1970s and
1980s. These chapters on growth are followed by a chapter devoted to a variety of imaging techniques
and characterization (Chapter 5). Important techniques such as Raman spectroscopy are covered in this
chapter.
The focus on applications starts with the use of single-walled and multiwalled carbon nanotubes in
scanning probe microscopy in Chapter 6. In addition to imaging metallic, semiconducting, dielectric,
and biological surfaces, these probes also find applications in semiconductor metrology such as profilometry
and scanning probe lithography. Chapter 7 summarizes efforts to date on making CNT-based
diodes and transistors and attempts to explain the behavior of these devices based on well-known
semiconductor device physics theories explained in undergraduate and graduate textbooks. It is commonly
forecast that silicon CMOS device scaling based on Moore’s law may very well end in 10 or 15
years. The industry has been solving the technical problems in CMOS scaling impressively even as we
embark on molecular electronics, as has been the case with the semiconductor industry in the past 3
decades. Therefore, for those pursuing alternatives such as CNT electronics and molecular electronics,
the silicon electronics is a moving target and the message is clear: replacing silicon-conducting channel
simply with a CNT-conducting channel in a CMOS may not be of much value — alternative architectures;different state variable (such as spin)-based systems; and coupling functions such as computing, memory,
and sensing are what can set the challengers apart from the incumbent. Unfortunately, at the writing of
this book, there is very little effort in any of these directions, and it is hoped that such alternatives emerge,
succeed, and flourish.
Field emission by carbon nanotubes is very attractive for applications such as flat panel displays, x-ray
tubes, etc. The potential for commercial markets in television and computer monitors, cell phones, and
other such displays is so enormous that this application has attracted not only much academic research
but also substantial industrial investment. Chapter 8 discusses principles of field emission, processes to
fabricate the emitters, and applications. One application in particular, making an x-ray tube, is covered
in great detail from principles and fabrication to testing and characterization.
With every atom residing on the surface in a single-walled carbon nanotube, a very small change in
the ambient conditions can change the properties (for example, conductivity) of the nanotube. This
change can be exploited in developing chemical sensors. The nanotubes are amenable to functionalization
by attaching chemical groups, DNA, or proteins either on the end or sidewall. This also allows developing
novel sensors using nanotubes. Chapter 9 discusses principles and development of chemical and physical
sensors. Likewise, Chapter 10 describes biosensor development.
The mechanical, thermal, and physical properties of carbon nanotubes have resulted in numerous
studies on conducting polymer films, composites, and other structural applications. Chapter 11 captures
these developments. Finally, all other applications that elude the above prime categories are summarized
in Chapter 12.
This is an edited volume, and various authors who practice the craft of carbon nanotubes day to day
have contributed to this volume. I have made an effort to make this edited volume into a cohesive text.
I hope that the readers — students and other researchers getting into this field, industry, and even the
established experts — find this a valuable addition to the literature in carbon nanotubes. I would like to
thank Nora Konopka of the CRC Press for her support throughout this work. Finally, this book would
not have been possible without the help and skills of my assistant Amara de Keczer. I would like to thank
her also for the cover design of the book.