Nanotechnology/Perspective

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A perspective on Nanotechnology

Nanotechnology in the Middle Ages?

The Duke TIP eStudies Nanotechnology course will be adding more to this section (this will be completed by 22 Jun 08)

One of the first uses of nanotechnology was in the Middle Ages. It was done by using gold nanoparticles to make red pigments in stained glass showing that nanotechnology has been around for centuries. The gold when clumped together appears gold, but certain sized particles when spread out appear different colors. Reference: The Nanotech Pioneers Where are they taking us? By Steven A Edwards

In the year 1974 at the Tokyo Science University, Professor Norio Taniigrichi came up with the term nanotechnology.

Nanotechnology was first used to describe the extension of traditional silicon machining down into regions smaller than one micron (one millionth of a meter) by Tokyo Science University Professor Norio Taniguchi in 1974. It is now commonly used to describe the engineering and fabrication of objects with features smaller than 100 nanometers (one tenth of a micron).

Nanotechnology has been used for thousands of years, although people did not know what they were doing. For example, stained glass was the product of nanofabrication of gold. Medieval forgers were the first nanotecnologists in a sense, because they, by accident, found out a way to make stained glass.

Reference Nanotechnology A GENTLE INTRODUCTION TO THE NEXT BIG IDEA By Mark Ratner & Daniel Ratner

In 2001, the federal government announced the National Nanotechnology Intiative to coordinate the work of different U.S. agencies and to provide funds for research and accelerate development in nanotechnology. This was spearheaded by Mahail Roco and supported by both president Clinton and Bush.

References The Nanotech Pioneers Where are they taking us? By Steven A. Edwards http://www.nano.gov/html/about/docs/20070521NNI_Industrial_Nano_Impact_NSTI_Carim.pdf

A Vision

Richard Feynman was a man of great importance to the field of nanotechnology. He was a man with a vision. He believed that with research we could change things on a small scale. In his famous speech There's Plenty of Room at the Bottom in 1959, Richard Feynman discussed the possibility of manipulating and controlling things on a molecular scale in order to achieve electronic and mechanical systems with atomic sized components. He concluded that the development of technologies to construct such small systems would be interdisciplinary, combining fields such as physics, chemistry and biology, and would offer a new world of possibilities that could radically change the technology around us.

Miniaturization

A few years later, in 1965, Moore noted that the number of transistors on a chip had roughly doubled every other year since 1959, and predicted that the trend was likely to hold as each new generation of microsystems would help to develop the next generation at lower prices and with smaller components. To date, the semiconductor industry has been able to fulfill Moore's Law, in part through the reduction of lateral feature sizes on silicon chips from around 10 micrometers in 1965 to 45-65 nm in 2007 via changing from the use of optical contact lithography to deep ultraviolet projection lithography.

In 1974 in Japan, Norio Taniguchi coined the word "nano-technology" to describe semiconductor processes such as thin film deposition and ion beam milling exhibiting characteristic control on the order of a nanometer: "‘Nano-technology’ mainly consists of the processing of separation, consolidation, and deformation of materials by one atom or one molecule."

Since Feynman's 1959 speech the arts of "seeing" and "manipulation" at the nanoscale have progressed from transmission electron microscopy (TEM) and scanning electron microscopy (SEM) to various forms of scanning probe microscopy including scanning tunneling microscopy (STM) developed by Binnig and Rohrer at IBM Zurich and atomic force microscopy (AFM) developed by (Binnig and Quate?) The STM, in particular, is capable of single-atom manipulation on conducting surfaces and has been used to build "quantum corrals" of atoms in which quantum mechanical wave function phenomena can be discerned. These atomic-scale manipulation capabilities prompt thoughts of building up complex atomic structures via manipulation rather than traditional stochastic chemistry. (Note: this paragraph is still rough and references are needed.)

Motivated by Feynman’s beliefs building things nanoscale top-down, Eric Drexler devoted much of his research to making a universal assembler. The American engineer Eric Drexler has speculated extensively about the laboratory synthesis of machines at the molecular level via manipulation techniques, emulating biochemistry and producing components much smaller than any microprocessor via techniques which have been called molecular nanotechnology or MNT.

Successful realization of the MNT dream would comprise a collection of technologies which are not currently practical, and the dream has resulted in considerable hyperbolic description of the resulting capabilities. While realization of these capabilities would be a vindication of the hype associated with MNT, concrete plans for anything other than computer modeling of finished structures are scant. Somehow, a means has to be found for MNT design evolution at the nanoscale which mimics the process of biological evolution at the molecular scale. Biological evolution proceeds by random variation in ensemble averages of organisms combined with culling of the less-successful variants and reproduction of the more-successful variants, and macroscale engineering design also proceeds by a process of design evolution from simplicity to complexity as set forth somewhat satirically by John Gall: "A complex system that works is invariably found to have evolved from a simple system that worked. . . . A complex system designed from scratch never works and can not be patched up to make it work. You have to start over, beginning with a system that works." A breakthrough in MNT is needed which proceeds from the simple atomic ensembles which can be built with, e.g., an STM to complex MNT systems via a process of design evolution. A handicap in this process is the difficulty of seeing and manipulation at the nanoscale compared to the macroscale which makes deterministic selection of successful trials difficult; in contrast biological evolution proceeds via action of what Richard Dawkins has called the "blind watchmaker" comprising random molecular variation and deterministic survival/death.

Technological development and limits

The impact on society and our lives of the continuous downscaling of systems is profound, and continues to open up new frontiers and possibilities. However, no exponential growth can continue forever, and the semiconductor industry will eventually reach the atomic limit for downsizing the transistor. Atoms in solid matter are typically one or two hundred picometers apart so nanotechnology involves manipulating individual structures which are between ten and ten thousand atoms across; for example, the gate length of a 45 nm transistor is about 180 silicon atoms long. Such very small structures are vulnerable to molecular level damage by cosmic rays, thermal activity, and so forth. The way in which they are assembled, designed and used is different from prior microelectronics.

New ways

Today, as that limit still seems to be some 20 years in the future, the growth is beginning to take new directions, indicating that the atomic limit might not be the limiting factor for technological development in the future, because systems are becoming more diverse and because new effects appear when the systems become so small that quantum effects dominate. The semiconductor devices show an increased diversification, dividing for instance processors into very different systems such as those for cheap disposable chips, low power consumption portable devices, or high processing power devices. Microfabrication is also merging with other branches of science to include for instance chemical and optical micro systems. In addition, microbiology and biochemistry are becoming important for applications of all the developing methods. This diversity seems to be increasing on all levels in technology and many of these cross-disciplinary developments are linked to nanotechnology.

Diversification

As the components become so small that quantum effects become important, the diversity will probably further increase as completely new devices and possibilities begin to open up that are not possible with the bulk materials of today's technology.

The nanorevolution?

The visions of Feynman are today shared by many others: when nanotechnology is seen as a general cross disciplinary technology, it has the potential to create a coming "industrial" revolution that will have a major impact on society and everyday life, comparable to or exceeding the impact of electricity and information technology.

Nanocomponents, Tools, and Methods

A positive spiral

As an emerging technology, the methods and components of nanotechnology are under continuous development and each generation is providing a better foundation for the following generation.

Seeing 'nano'

With regards to the methods, the Scanning tunneling microscope (STM) and Atomic Force Microscope (AFM) were developed in the 1980s and opened up completely new ways to investigate nanoscale materials. An important aspect was the novel possibility to directly manipulate nanoscale objects. Transmission and scanning electron microscopes (TEM and SEM) had been available since the 30s, and offered the possibility to image as well as create nanodevices by electron beam lithography.

New nanomaterials

Several unique nanoscale structures were also discovered around 1990: the Carbon-60 molecule and later the carbon nanotubes. In recent years, more complex nanostructures such as semiconductor nanowire heterostructures have also proven to be useful building blocks or components in nanodevices.

So what can I use this 'nano' for?

The applications of such nanocomponents span all aspects of technology: Electronics, optics/photonics, medical, and biochemical, as well as better and smarter materials. But to date few real products are available with nanoscale components, apart from traditional nanoscale products, such as paint with nanoparticles or catalytic particles for chemical reactors.

Prototype devices have been created from individual nanocomponents, but actual production is still on the verge. As when integrated electronics were developed, nanotechnology is currently in the phase where component production methods, characterization methods, tools for manipulation and integration are evolving by mutual support and convergence.

Difficult nanointegration

A main problem is reliable integration of the nanoscale components into microsystems, since the production methods are often not compatible. For fabrication of devices with integrated nanocomponents, the optimal manipulation technique is of course to have the individual components self-assembling or growing into the required complex systems. Self assembly of devices in liquids is an expanding field within nanotechnology but usually requires the components to be covered in various surfactants, which usually also influence the component properties. To avoid surface treatments, nanotubes and whiskers/wires can be grown on chips and microsystems directly from pre-patterned catalytic particles. Although promising for future large scale production of devices, few working devices have been made by the method to date.

The prevailing integration technique for nanowire/tube systems seems to be electron beam lithography (EBL) of metal structures onto substrates with randomly positioned nanowires deposited from liquid dispersions. By using flow alignment or electrical fields, the wire deposition from liquids can be controlled to some extent. The EBL method has allowed for systematic investigations of nanowires' and tubes' electrical properties, and creation of high performance electronic components such as field-effect transistors and chemical sensors. These proof-of-principle devices are some of the few but important demonstrations of devices nanotechnology might offer. In addition, nanomechanical structures have also recently been demonstrated, such as a rotational actuator with a carbon nanotube axis built by Fennimore et al.

A more active approach to creating nanowire structures is to use Scanning probe microscopy(SPM) to push, slide and roll the nanostructures across surfaces. SPM manipulation has been used to create and study nanotube junctions and properties. The ability to manipulate individual nanoscale objects has hence proven very useful for building proof-of-principle devices and prototypes, as well as for characterizing and testing components.

Top-down manufacturing takes bulky products and shrinks them to the nano scale, vs. bottom-up manufacturing is when individual molecules are placed in a specific order to make a product. The bottom-up self-assembly method may be important for future large scale production as well as many of the different approaches to improve the top-down lithographic processes. Such techniques could hence become important factors in the self-sustaining development of nanotechnology.

Hot and hyped

Suddenly everything is 'nano'

There's no question that the field of nanotechnology has quite a sense of hype to it - many universities have created new nanotech departments and courses. But there is also a vision behind the hype and emerging results - which are truly very few in industrial production, but nevertheless hold promise for a bright future. In the hype, many things that were once chemistry, microtechnology, optics, mesoscopic or cluster physics, have been reborn as nanotechnology.

Nanotech is old

You can find nanotechnology in the sunscreen you use in the summer, and some paints and coatings can also be called nanotech since they all contain nanoparticles with unique optical properties. In a way, nanoparticles have been known in optics for hundreds of years if you like to take a broad perspective on things, since they have been used to stain and color glasses, etc. since the middle ages. Nano-size particles of gold were used to create red pigments.

Catalysis is a major industrial process, without which not many of the materials we have around us today would be possible to make, and catalysis is often highly dependent on nanoscale catalytic particles. In this way thousands of tons of nanotechnology have been used with great benefit for years.

Nanoscale wires and tubes have only recently really been given attention with the advent of carbon nanotubes and semiconductor nanowires, while nanoscale films are ever present in antireflection coatings on your glasses and binoculars, and thin metal films have been used for sensitive detection with surface plasmons for decades. Surface plasmons are excitations of the charges at a surface. Nanowires actually were observed in the middle ages - well, they did not have the means to observe them, but saw whiskers grow from melted metals.

The better control over the nanostructure of materials has led to optimization of all these phenomena - and the emergence of many new methods and possibilities.

An example

Take for instance nano-optics: The surface plasmons turn out to be very efficient at enhancing local electrical fields and work as a local amplifier for optical fields, making a laser seem much more powerful to atoms in the vicinity of the surface plasmon. From this comes the surface enhanced raman spectroscopy which is increasingly used today because it makes it possible to do sensitive raman spectroscopy on the large majority of samples that would otherwise be impossible to make such spectra on. In addition, photonic crystals, fancy new quantum light sources that can make single photons on demand and other non-classical photon states are being developed, based on nanotechnology.

The future

There are definitely future scientific applications and commercial potential of all these new methods to handle light, use it for extremely sensitive detection and control its interaction with matter - and so it seems nanotechnology, being about making smaller versions of existing technology as well as new technology, is worth a bit of hype.

References

See also notes on editing this book Nanotechnology/About#How_to_contribute. .

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