nanotechnologie,nanoteknologi,nanotecnologia,
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Sumio IIJIMA

Professor, Meijo University and Director, Research
Center for Advanced Carbon Materials, National Institute of Advanced
Industrial Science and Technology (AIST

Nanotube and nanohorn
Future real key player of nanotechnology

"I really don't want people to exaggerate carbon nanotubes too much. I want them to leave the tubes alone a little more," says Prof. Iijima, the discoverer of carbon nanotubes. He now thinks that commercial applications of carbon nanohorns will be realized much earlier than those of carbon nanotubes.

Unlike carbon nanotubes, carbon nanohorns can be made simply without the use of a catalyst. Carbon nanohorn aggregates can be produced with a yield of more than 90% through laser vaporization of carbon at room temperature. These aggregates have a dahlia-like shape with a large number of horn-shaped short single-layered nanotubes that stick out in all directions. The tips of these short nanotubes are capped with five-membered rings. Carbon nanohorns' key characteristic is high adsorbability, due to their large surface area -- about 400 square meters per gram, but as Prof. Iijima says, "Adsorbed atoms tend to slip easily from the surface of the carbon nanohorns because of their complete graphite surface structure. To hold atoms on the carbon nanohorn surface, either the carbon nanohorns must be modified chemically or their structures must be partially damaged. Various potential characteristics of carbon nanohorns can be displayed by modifying their surface."

Researchers have high expectations for applying carbon nanohorns to fuel cells as their electrode material, among other applications under consideration. Fuel cell electrodes made of carbon nanohorns are expected to help improve the cells' power-generation capacity and extend their lifetime because platinum catalyst nanoparticles disperse among carbon nanohorns and do not aggregate. Carbon nanohorns are also expected as gas storage material, making use of their high adsorbability. Carbon nanohorns have for the first time cleared the United States Department of Energy threshold of commercial reality as methane gas storage material. Carbon nanohorns have also been found to selectively adsorb DNA fractions. Inorganic materials are now used in selecting DNA fractions. However, it is believed that carbon with a high biocompatibility may be a better material than inorganic substances. The Japan Science and Technology Agency (JST) has adopted a project to promote the application of carbon nanohorns in the biotechnology field as one of its "Solution Oriented Research and Technology" projects. This project started in January 2003 for a better understanding of the adsorption to carbon nanohorns, as well as for studying surface modification methods for controlling their selective adsorbability.

Prof. Iijima has not forgotten carbon nanotubes entirely; he has been studying how they grow. Carbon nanotubes will not be used commercially unless they can be mass-produced. He says, "Real nanotechnological progress is to develop nanomaterials, which can be used in fuel cells, field effect transistors and other useful products." Such developments have not been achieved yet at this stage. Prof. Iijima says, "People are exaggerating carbon nanotubes too much. However, I can say with confidence that carbon nanotubes have made great contributions to basic science." They do play a significant role in verifying the quantum effect. Prof. Iijima thinks that the real value of carbon nanotubes is their contribution to basic science.

He does not want to hear that what he has achieved in his research is the discovery of carbon nanotubes. He says, "I had conducted research using electron microscopy for 30 years before I discovered carbon nanotubes, so discovering them is just one of the results of my research based on electron microscopy." He obtained a Ph.D. in studying filament-shaped silver bromide. His experience conducting structural analyses at that time helped him find carbon nanotubes. He says, "When you do not have any clue as to how to start new research, you cannot rely on anyone but yourself. What you can rely on when you face a serious difficulty is nothing but your experience." This is his empirical rule.
(Interviewer: Kuniko Ishiguro, Cosmopia Inc.)

For more information,
http://www.nanonet.go.jp/english/mailmag/2004/023a.html

 

Tsukasa TORIMOTO

Associate Professor, Catalysis Research Center,
Hokkaido University and Researcher, Precursory Research for
Embryonic Science and Technology (PRESTO), Japan Science and
Technology Agency (JST)

Fabrication of novel core-shell nanostructured materials using the size-selective photoetching technique

Surface coating of nanoparticles with different materials to produce
core-shell structures is currently an active area of research, because
such coating allows modification and tailoring of physical and
chemical properties of core materials depending on synthetic
conditions. Furthermore, core-shell nanoparticles are expected to have
unique properties that are not originally present in either core or
shell materials. In the present study, we attempt to fabricate the
novel core-shell structure of semiconductor nanocomposites using the
size-selective photoetching technique and apply them to develop new
catalysts, optoelectronic devices and sensors.

We have recently developed the size-selective photoetching technique
as a means of preparing monodisperse semiconductor nanoparticles. The
principle of this technique relies on two facts -- that metal
chalcogenide semiconductor particles are photocorroded, and that the
energy gap of size-quantized semiconductor nanoparticles increases
with a decrease in the particle size. If the irradiation is performed
with use of monochromatic light that can photoexcite the large
particles alone, these nanoparticles are selectively photoetched to
smaller ones until the irradiated photons are not absorbed in the
nanoparticles due to the size quantization effect.

With irradiation of monochromatic light, the diffuse reflectance
spectra of silica-coated CdS nanoparticles were blue-shifted, and
finally the absorption onset agreed well with the wavelength of
irradiation light. These results indicated that the large CdS
particles were photoetched to smaller ones until the irradiated
photons were not absorbed in nanoparticles. TEM observation revealed
that the monochromatic light irradiation caused a decrease in the size
of the CdS core particles but the shell structure seemed to be
unchanged, resulting in a void space formation between the photoetched
core particle and the shell. The void space could be adjusted by
choosing the wavelength of irradiation light. We call this structure a
"jingle-bell" nanostructure.

The void space in the core-shell nanostructure will be useful for the
purpose of applications, such as novel catalytic reaction sites and
fabrication of metal-semiconductor nanojunctions. Work in this
direction is currently in progress.

For more information,
http://www.nanonet.go.jp/english/mailmag/2004/023b.html

 

Koji KAYA

Director-General/Professor, Institute for Molecular
Science, Okazaki National Research Institutes
Currently, Director,Wako Institute and Discovery Research Institute,
The Institute of Physical and Chemical Research (RIKEN)

Discovery of organic-metallic
multiple-decker sandwich clusters
" Opening up cluster chemistry "

Prof. Koji Kaya, says, "I heard later that when I sent my first paper on this study to a scientific journal, the comments of the referees were divided. Some of them said it was a great work, while the others called it completely wrong." He looked back at the reaction when he announced his discovery of benzene-vanadium sandwich clusters.

At that time, an established theory in this field was that benzene with a stable molecular structure does not react with transitional metal, and therefore does not form any chemical bonds with such metals.

His new discovery completely overturned this theory. He was originally a chemist. He used to synthesize binary metal clusters, dimers and polymers. He started studying combinations of transitional metals and benzene with a simple molecular structure, believing that bonding organic chemicals and metals could create new, unique compounds. He began this research with studying the reaction between transitional metals with 3d-electrons and benzene through gas phase reactions. As a result, he discovered that sandwich clusters of benzene and a metal could be synthesized with metal atoms belonging to the scandium to chrome groups in the periodic table. He says, "When a transitional metal with d-electrons reacted with an aromatic compound, d-electrons and pi-electrons created bonding orbits, and these electrons moved freely within the orbits. This indicates that metal atoms and aromatic molecules became a single molecule. I was really excited about proving this phenomenon. When the magnetism of vanadium atoms inside the sandwich clusters was measured, their magnetic moment was found to have increased linearly as the number of metal atom is increased. When moveable electrons exist around a metal atom, these electrons interact with electrons of the next metal atom as if they are chatting with each other in the cluster. As a result, the spins of the metal atoms' electrons align in the same direction." Prof. Kaya's discovery that benzene-vanadium clusters have magnetism surprised researchers around the world.

Prof. Kaya started his career as a chemist by measuring the potential curve between mercury and rare gas atoms by bombarding mercury atoms with those of the rare gases. Since he has considered that periodicity is the basis of chemistry, he focused his attention on the magic number of valence electrons, and discovered metal clusters of NaAl13, which has an electronically stable structure. These clusters were formed by combining aluminum tridecamer having 39 valence electrons with sodium having a single valence electron, to bring the total amount of valence electrons to the magic number of 40.

He developed the so-called soft-landing technique, through which metal clusters can be piled up on a substrate without any fragmentation. He has been researching methods to put these clusters to practical use.

For him, metal clusters are now going from materials for clarifying properties to materials toward new catalysts and realization of novel optical properties.

Prof. Kaya is continually working to create new ideas. He says, "What I think I really need to do is to investigate what functions compounds associated with weak interactions will show in solution under certain conditions." His goal beyond this is to understand the mystery of life and contribute it to human happiness. He says, "I want to clarify theoretically information transmission, energy transfer and other mechanisms occurring continuously inside the human body through cooperation among researchers in physics, chemistry, biology and other fields." He adds that this kind of effort may in the long run lead to new cures for diseases. He says that nanotechnology should be used for human happiness in the 21st century.
(Interviewer: Shiro Saito, Cosmopia Inc.)

For more information,
http://www.nanonet.go.jp/english/mailmag/2004/021a.html

 

Xiaobing REN

Senior Researcher, Materials Physics Group, National
Institute for Materials Science and Researcher, Precursory Research
for Embryonic Science and Technology (PRESTO),
Japan Science and Technology Agency (JST)

Exotic multiscale phenomena associated with nano-order of point defects

A huge class of materials exhibits spontaneous (automatic) ordering
with respect to atomic/ionic displacement or spin below a
characteristic temperature (Currie temperature); they are called
ferroic materials. Such ordering transitions (called ferroic
transitions) result in very interesting phenomena at three different
length scales simultaneously, from nano scale (atomic/ionic
displacement, spin, etc.), mesoscopic scale (domain), to macroscopic
scale (strain, electric effects, magnetic effects). On the other hand,
point defects (such as vacancies, impurities, doping elements, etc.)
are inevitable in these materials. Recently we found that the nano-
range distribution of these point defects possesses a general symmetry
property. This nano-ordering is expected to generate a wide range of
exotic multiscale phenomena in these transforming materials, such as
huge response in elasticity, piezoelectricity, and magnetism.

Recently, we clarified that the exotic multiscale phenomena exist in
martensitic alloys by observing the process of martensitic/reverse
transformation. However, it is not known whether these phenomena exist
in other materials, or whether novel properties predicted by the
phenomena will be discovered. If novel properties are discovered,
potential applications in various fields of science and engineering
are greatly expected.

Our present project is aimed at discovering these novel phenomena and
their underlying physical mechanisms. These new effects are also of
significant technological importance and may have potential
applications in novel actuators and sensors as well as magneto-electro
-mechanical devices.

For more information,
http://www.nanonet.go.jp/english/mailmag/2004/021b.html

Hideyo KODAMA

Executive Vice President,
Research and DevelopmentGroup, Hitachi Ltd.
(Currently, Chief Technical Officer, Automotive Systems, Hitachi, Ltd.)

Bridging the gap between technological
seeds and needs.

Devising a strategy to cross technology's death valley

Japan is thought to be a world leader in the field of nanotechnology.

But even in Japan, the so-called "Death Valley of Technology" lies between results of research and their commercialization. Hitachi Ltd. is devising various strategies to cross this abyss. Leading such efforts is the executive vice president of Hitachi's Research and Development Group, Dr. Hideyo Kodama, the company's chief strategist in the nanotechnology field.

In 2001, Nanotechnology R&D Promotion Center for the Hitachi Group was established by over ten Hitachi Group companies, and Dr. Kodama has since been general manager of the center. He explained the reasons for establishing the center by saying, "There are both potential users and developers of new nanotechnologies within the Hitachi group because group members include manufacturers and users of industrial materials.

The group established the R&D promotion center to strengthen its nanotechnology sector." Some Hitachi group laboratories have cooperated special projects being carried out in the fields of information technology/electronics, environment/energy, and medicine/ welfare. Researchers and other staff members participating in such projects use an effective information-sharing system designed to match technological "seeds" developed by project participants with technological needs of other participants. Developers of seeds usually cannot imagine all their potential applications. In the system, the seeds are spread by their developers to other participants by e-mail.

These messages stimulate project members to find potential applications of the new seeds. This system has greatly shortened the time needed between the development of technological seeds and the
realization of trial products based on the seeds.

Dr. Kodama says he plans to establish a technology platform. In April, 2003, his center established a platform for computational science designed in combination with measurement technologies to strengthen the group's computer-based simulation capability for developing new materials. The center has also been very active in forming partnerships with national laboratories and universities. It has already established such partnerships with 14 research bodies, to which Hitachi researchers are sent to discuss their projects.

Dr. Kodama says, "I think there used to be the idea among both university professors and companies that professors create new ideas and companies commercialize them. But now, both sides need to get closer to each other. I think this is the simplest approach for crossing the 'Death Valley.'" His center signed a partnership agreement with the Nanotechnology Research Center of Hokkaido University in April, 2003 as its latest cooperation with an outside research organization. They have kicked off a project to develop periodic nano-structures based on self-organization.

What specific areas is Dr. Kodama paying attention to in the widely diversifying nanotechnology field? "I'm interested in the environment.

When we think about the so-called 'Hydrogen Society' in 10 years, what technological problems related to industrial materials will we face and what kinds of materials will enable us to solve such problems? We have been discussing these issues." He says his center is studying a method to improve sharply the power generation efficiency of fuel cells by applying nanotechnology. He has confidence in the method, saying that he and his colleagues at the center will astonish the world when they unveil a trial product in fall, 2003.

(Interviewer: Kuniko Ishiguro, Cosmopia Inc.)

For more information,
http://www.nanonet.go.jp/english/mailmag/2004/020a.html

Tsutomu FURUZONO

Division Head, Department of Bioengineering,
National Cardiovascular Center Research Institute and Researcher,
Precursory Research for Embryonic Science and Technology (PRESTO),
Japan Science and Technology Agency (JST)

Development of a bioactive-material consisting of an inorganic nanoparticle-organic-cell composite

Germ infection through a percutaneous device has been very serious issue for long-term implantation in the body for such applications as artificial hearts, peritoneal dialysis and tube feeding. In this study, we are developing a percutaneous device for preventing germ infection by strong adhesion in the body.

The concept of the material is based on three elements:

I. Sintered hydroxyapatite (HAp) nano-crystal controlled the morphology: this shows high bioactivity and actual clinical results in dental and orthopedic fields.

II. Silk fiber: this has good mechanical strength, good stability in the living body, good molderability, and an actual clinical result as a surgical suture.

III. Fibroblast: this secretes collagen to construct an extra cellular matrix.There are covalent bonds between I and II, an anchoring effect between II and III, and good compatibility between III and I. The elements are in good harmony in thecomposite.

A novel inorganic-organic composite was developed consisting of HAp nanoparticles showing 50-200 nm prepared by an emulsion system and silk fiber with graft-polymer having the functional groups reacting covalently toward the HAp surface. The composite fiber showed good mechanical properties, just like non-treated fiber, and fibroblasts strongly adhered on the material.

We are trying to increase the collagen secretion from the cells on the material. The research is progressing with medical doctors in my facility, aimed at clinical application.

For more information,
http://www.nanonet.go.jp/english/mailmag/2004/020b.html

Chris Phoenix

CRN Director of Research

The Bugbear of Entropy

Entropy and thermodynamics are often cited as a reason why diamondoid mechanosynthesis can't work. Supposedly, the perfection of the designs violates a law of physics that says things always have to be imperfect and cannot be improved.

It has always been obvious to me why this argument was wrong. The argument would be true for a closed system, but nanomachines always have an energy source and a heat sink. With an external source of energy available for their use, they can certainly build near-perfect structures without violating thermodynamics. This is clear enough that I've always assumed that people invoking entropy were either too ignorant to be critics, or willfully blind.

It appears I was wrong. Not about the entropy, but about the people. Consider John A. N. (JAN) Lee. He's a professor of computer science at Virginia Tech, has been vice president of the Association for Computing Machinery, has written a book on computer history, etcetera. He's obviously intelligent and well-informed. And yet, he makes the same mistake about entropy--not in relation to nanotech, but in relation to Babbage, who designed the first modern computer in the early 1800's.

In Lee's online history of Babbage, he asserts, "the limitations of Newtonian physics might have prevented Babbage from completing any Analytical Engine." He points out that Newtonian mechanics has an assumption of reversibility, and it wasn't until decades later that the Second Law of Thermodynamics was discovered and entropy was formalized. Thus, Babbage was working with an incomplete understanding of physics.

Lee writes, "In Babbage's design for the Analytical Engine, the discrete functions of mill (in which 'all operations are performed') and store (in which all numbers are originally placed, and, once computed, are returned) rely on this supposition of reversibility." But, says Lee, "information cannot be shuttled between mill and store without leaking, like faulty sacks of flour. Babbage did not consider this, and it was perhaps his greatest obstacle to building the engine."

Translated into modern computer terms, Lee's statement reads, "Information cannot be shuttled between CPU and RAM without leaking, like faulty sacks of flour." The fact that my computer works as well as it does shows that there's something wrong with this argument.
In a modern computer, the signals are digital; each one is encoded as a voltage in a wire, above or below a certain threshold. Transistors act as switches, sensing the incoming voltage level and generating new voltage signals. Each transistor is designed to produce either high or low voltages. By the time the signal arrives at its destination, it has indeed "leaked" a little bit; it can't be exactly the same voltage. But it'll still be comfortably within the "high" or "low" range, and the next transistor will be able to detect the digital signal without error.
This does not violate thermodynamics, because a little energy must be spent to compensate for the uncertainty in the input signal. In today's designs, this is a small fraction of the total energy required by the computer. I'm not even sure that engineers have to take it into account in their calculations, though as computers shrink farther it will become important.

In Babbage's machine, information would move from place to place by one mechanism pushing on another. Now, it's true that entropy indicates a slightly degraded signal--meaning that no matter how precisely the machinery was made, the position of the mechanism must be slightly imprecise. But a fleck of dust in a bearing would degrade the signal a lot more. In other words, it didn't matter whether Babbage took entropy into account or even knew about it, as long as his design could tolerate flecks of dust.

Like a modern computer, Babbage's machine was designed to be digital. The rods and rotors would have distinct positions corresponding to encoded numbers. Mechanical devices such as detents would correct signals that were slightly out of position. In the process of correcting the system, a little bit of energy would be dissipated through friction. This friction would require external energy to overcome, thus preserving the Second Law of thermodynamics. But by including mechanisms that continually corrected the tiny errors in position caused by fundamental uncertainty (along with the much larger errors caused by dust and wear), Babbage's design would never lose the important, digitally coded information. And, as in modern computers, the entropy-related friction would have been vastly smaller than friction from other sources.

Was Babbage's design faulty because he didn't take entropy into account? No, it was not. Mechanical calculating machines already existed, and worked reliably. Babbage was an engineer; he used designs that worked. There was nothing very revolutionary in the mechanics of his design. He didn't have to know about atoms or quantum mechanics or entropy to know that one gear can push another gear, that there will be some slop in the action, that a detent can restore the signal, and that all this requires energy to overcome friction. Likewise, the fact that nanomachines cannot be 100% perfect 100% of the time is no more significant than the quantum-mechanical possibility that part of your brain will suddenly teleport itself elsewhere, killing you instantly.

Should Lee have known that entropy was not a significant factor in Babbage's designs, nor any kind of limitation in their effectiveness? I would have expected him to realize that any digital design with a power supply can beat entropy by continually correcting the information. After all, this is fundamental to the workings of electronic computers. But it seems Lee didn't extend this principle from electronic to mechanical computers.

The point of this essay is not to criticize Lee. There's no shame in a scientist being wrong. Rather, the point is that it's surprisingly easy for scientists to be wrong, even in their own field. If a computer scientist can be wrong about the effects of entropy on an unfamiliar type of computer, perhaps we shouldn't be too quick to blame chemists when they are likewise wrong about the effects of entropy on nanoscale machinery. If a computer scientist can misunderstand Babbage's design after almost two centuries, we shouldn't be too hard on scientists who misunderstand the relatively new field of molecular manufacturing.

But by the same token, we must realize that chemists and physicists talking about molecular manufacturing are even more unreliable than computer scientists talking about Babbage. Despite the fact that Lee knows about entropy and Babbage did not, Babbage's engineering was more reliable than Lee's science. How true it is that "A little learning is a dangerous thing!"

There are several constructive ways to address this problem. One is to continue working to educate scientists about how physics applies to nanoscale systems and molecular manufacturing. Another is to educate policymakers and the public about the limitations of scientific practice and the fundamental difference between science and engineering. CRN will continue to pursue both of these course
http://crnano.org/index.html

Masatsugu SHIMOMURA

Director/Professor, Nanotechnology Research
Center, Research Institute of Electronic Science, Hokkaido
University and Team Leader, Frontier Research System, The Institute
of Physical and Chemical Research (RIKEN)

Fabrication of patterned film by self-organization -Utilization of the bottom-up approach
dependent on natural phenomena-

The regular convection seen in a hot miso soup (Benard convection), wine droplets forming on the edge of a wine glass (fingering instability), stains formed in concentric layers in a coffee cup that was purposely allowed to sit for several days (stick-slip motion)_$B!D_(Ball of these patterns form on their own. Prof. Shimomura directed his attention to the fact that in complex systems, these patterns are self -organized based on the rules of non-equilibrium thermodynamics.

By simply evaporating polymer solutions on a substrate, Prof.
Shimomura succeeded in fabricating films that have ordered structures such as dot, line-patterned or honeycomb structure. For this purpose, two glass plates were first set one on top of the other. By putting a polymer solution with a constant concentration into the space between the two plates, a uniform pattern can be formed. Because self- organization in dissipative structures is not so dependent on molecular structure, it can be applied to various polymeric materials to form patterns. The biggest benefit of this patterning technology is that compared to lithography, the process of creating the patterns can be greatly simplified. The process is also energy- and cost-efficient.

Currently, the minimum unit size of the patterned films is around 200 to 300nm. For Prof. Shimomura, the target is to reduce this to less than 100nm. "If we can reduce the unit size to less than 100nm, the scope of application of this technology will be significantly expanded, " says Prof. Shimomura. He now faces the challenge of making a completely uniform pattern along with enhancing the reproducibility and also miniaturizing the patterns. The honeycomb-patterned polymer film fabricated using this method is expected to have potential applications in regenerative medicine. "When liver cells are cultured on a flat film, the cells also tend to flatten. Cells in this form do not function properly. However, when liver cells are cultured on a honeycomb-patterned film made by utilizing self-organization, a number of the cells assemble, take on a spherical shape, and come to express the function of the liver." Even when using films made from the same material, the form and the function of the cultured cells can be altered depending on the structure of the film.

In 2002, the Hokkaido University Nanotechnology Research Center was established. Prof. Shimomura, who played a role in its opening, is now the center's director. Says Prof. Shimomura, "In order to further proceed with the research on nanotechnology, we need to have a global vision and realize collaborations that go beyond the boundaries of the current academic fields. In order to do this, we need to develop a good system." The Nanotechnology Research Center was completed on November 27, 2003 on the northern campus of Hokkaido University. The site was originally appointed as a place to promote the Joint Research Project and is now being developed to become the center of intelligence for the creation of a new industry. Furthermore, the Nanotechnology Research Center is a key member of the 21st Century Center of Excellent Project for Advanced Life Science on the Base of Bioscience and Nanotechnology, meaning that an environment for developing young researchers is about to be created.

"The research on nanotechnology is not just a one-time trend,"
emphasizes Prof. Shimomura. "The European researchers are describing nanotechnology as a 'renaissance in science technology.'" In this so- called renaissance, Prof. Shimomura points out that a strict definition of terminology is necessary. "Originally, there was no discipline in the world of science, but then it gradually got more and more subdivided. In the nano world, researchers talk to each other going beyond the walls of discipline. However, we sometimes find out that same words are used differently depending on the research field you are in. For instance, there is a slight difference in the nuance when I use the word 'self-organization' and when a researcher in physics uses it. By clarifying what the difference is, we should be able to get new inspirations and findings." Prof. Shimomura expects younger generations of researchers to overcome the boundaries between different fields and cultivate a new domain. "I want the young people to be flexible in their way of thinking and act as interpreters between the different fields."
(Interviewer: Yu Tatsukawa, Cosmopia Inc.)

For more information,
http://www.nanonet.go.jp/english/mailmag/2004/019a.html

Seigi MIZUNO

Associate Professor, Department of Molecular and
Material Sciences, Kyushu University and Researcher, Precursory
Research for Embryonic Science and Technology (PRESTO), Japan
Science and Technology Agency (JST)

Surface structure determination
and development of low-energy electron
diffraction for small surface regions

Determination of surface structures is the initial stage in
understanding surface properties. I have studied relatively complex
structures, including the surface reconstruction of substrates by low-
energy electron diffraction (LEED) and scanning tunneling microscopy
(STM). Cu(001)-(4x4)-Li is one of the typical structures. We have
determined atomic positions with an accuracy of better than 0.01 nm
using LEED analysis. The best-fit model consists of four Li adatoms
and six substituting Li atoms. In an STM image, although we could not
distinguish individual Li atoms, we could observe four Li adatoms as
one protrusion. Since we know the surface crystal structure in the
unit cell, we could make a detailed atomic arrangement, including
steps and defects. Recently we have been studying mixed ordered
structures formed by coadsorption of two different elements.

On the other hand, the usual diffraction method cannot be used to
study nanometer-scale structures or small domain structures, which
makes it very difficult to learn the atomic arrangements of such
structures. Convergent-beam electron diffraction in transmission
electron microscopy has great potential for use in determining the
structures of small regions, but it is applicable only to thin films.
Low-energy electron microscopy is also a marvelous technique. It can
be used to obtain diffraction patterns from regions as small as 100 nm.
I would like to obtain LEED patterns from even smaller regions, for
instance 10 nm, and I am trying to develop a new LEED apparatus using
STM tips as a field emission gun. Although certain diffraction
patterns have not been obtained yet, elastically scattered electrons
have been detected. To obtain sharper electron beams, improvement of
the tips is being planned.

For more information,
http://www.nanonet.go.jp/english/mailmag/2004/019b.html

 

Yoshio BANDO

Director, Advanced Materials Laboratory, National
Institute for Materials Science (NIMS)

Exploring new nanoscale materials
The world's smallest thermometer brought by serendipity and an inquisitive spirit

The "carbon nanothermometer" that Dr. Bando discovered is ranked as the "smallest thermometer" in the Guinness Book of Records. A gallium filling in a carbon nanotube of 85 nm in diameter expands in proportion to temperature. Dr. Bando's enthusiasm for studying new nano structures led to the accidental discovery that was destined to happen.

Initially, he focused on making nanotubes from GaN as a blue LED material. The idea was to grow the nanotubes out of GaN produced by flowing nitrogen gas at 1360 degree C over amorphous carbon particles and gallium oxide, but in fact the carbon nanotubes grew on the gallium particles. "When I observed them with an electron microscope, I found that depending on how the electron beam was irradiated, the gallium in the carbon nanotube expanded or shrank." This phenomenon is explained by the change in the temperature of the gallium. The possibility of measuring temperature over a range from 50 degree C to 500 degree C with an accuracy of 0.25 degree by maximizing the resolution of an electron microscope has since been confirmed. The technique was first made public in the February 2002 issue of "Nature"
and was recognized as the world's smallest thermometer.

Dr. Bando specializes in electron microscopy. When he started off as a scientist around 1975, he came across the most-advanced ultra-high voltage electron microscope. He says, "It might have been the best electron microscope at the time, but it was only being used to observe atomic arrangements. It was more important to identify atoms and analyze the bonding states of atoms." He went to the U.S. where research on analytical electron microscopes was just beginning, and developed his first analytical electron microscope in 1984.
Furthermore, he developed a field-emission electron microscope with improved spatial resolution of electron spectrometry by reducing the diameter of the beam spot to 0.4 nm in 1993.

In the year 2000, he developed the world's most powerful atom- discriminating electron microscope, which is now used to identify atoms and analyze electron states by separating electrons that have lost energy (inelastically scattered electrons) and electrons that have retained energy (elastically scattered electrons) by using an omega-type energy filter in the microscope cylinder. By using such spectrometry to achieve atom discrimination with the spatial resolution of 0.5 nm, he was the first to observe the periodic structure of oxygen atoms in AlN.

Currently, his research using electron microscopes is mainly focused on BN nanotubes. He initially succeeded in creating nanocables with metallic nanowires in BN nanotubes, and discovering BN nanocones with the tip angle of 39 degree and BN fullerene cages. He has found that the BN fullerenes consist of five-membered rings and four-membered rings so far.

Although he describes his great discoveries as "unexpected discoveries, true serendipity", they were the direct result of his efforts. "Only a researcher with appropriate knowledge and experience can see through a phenomenon. A researcher's capability should be judged by his ability to see through things."
(Interviewer: Shiro Saito, Cosmopia Inc.)

For more information,
http://www.nanonet.go.jp/english/mailmag/2004/018a.html

Kazuki NAKANISHI

Associate Professor, Department of Material
Chemistry, Graduate School of Engineering,
Kyoto University and Researcher,
Precursory Research for Embryonic Science and Technology
(PRESTO), Japan Science and Technology Agency (JST)

Design and application of materials
with hierarchical pore structure
via liquid phase process

Supramolecular templating of nano-pores in inorganic-based materials
has been becoming popular recently. There exists, however, a difficult
step if one tries to construct macroscopic devices that make the best
use of such templated pores. The author and his colleagues have
developed a so-called "top-down" liquid phase processing of
hierarchical pores consisting of well-defined macropores and templated
(not yet highly ordered) nano-pores.

When the polymerization-induced phase separation and sol-gel
transition take place concurrently, spinodal decomposition may occur,
generating a transient multiphase structure characterized by "co-
continuity" of the respective phases. By freezing the transient co-
continuous structure within the gel through the irreversible sol-gel
transition, a well-defined macroporous structure can be easily
obtained after the removal of the volatile components. The median pore
size can be controlled by adjusting the onsets of phase separation and
sol-gel transition.

Surfactants that have supramolecular templating ability can be used to
induce the phase separation in the sol-gel process based on the
hydrolysis of metal alkoxides. The co-continuous gel skeletons then
contain a sub-structure consisting of templated structural units of
the gel phase. Upon removal of the templating molecules by thermal
decomposition or solvent extraction, sharply distributed nano-pores
are obtained without influencing the pre-formed macroporous framework.

Materials with such hierarchical pore structures exhibit a superior
efficiency and lower pressure resistance than those of conventional
particle-packed devices. Pure silica gels with hierarchical macropores
and nano-pores have been applied to the highly efficient monolithic
HPLC column, and its capillary version also appears on the market.
Catalyst-loaded columns that polymerize monomers and in parallel
partition the products by molecular mass are now under investigation.
Widespread possibilities of the monolithic highly efficient support
material are to be found in every industrial field that has utilized
solid-liquid contact devices consisting of particle-packed structures.

For more information,
http://www.nanonet.go.jp/english/mailmag/2004/018b.html

 

Kazunobu TANAKA

Board trustee, National Institute of Advanced Industrial Science
and Technology (AIST)

Four suggestions for developing nanotechnology
as a key industry in Japan
Based on experience conducting atom technology project

A project initiated in 1992 was carried out for the upcoming era of nanotechnology in Japan. The project focused on atom technology, a type of nanotechnology with emphasis on the bottom-up approach. This project, whose aim was partially to merge semiconductor technology and biotechnology, was conducted at the Joint Research Center for Atom Technology (JRCAT), where about 100 researchers from the business, academic and government sectors were brought. Dr. Tanaka was responsible for this project and served as a project leader for 1997- 2002.

This project comprised four focused areas. -- identification and manipulation of atoms and molecules; formation and control of nanostructures on the surface and at the interface of materials; spin electronics; and theoretical analysis of the dynamic processes of atoms and molecules. Completed in March 2002, the project generated many results that have contributed significantly to the establishment of the present nanotechnological foundation in Japan.

Dr. Tanaka strongly requested universities to participate in the project. Behind his strong desire was his successful experience as the leader of an earlier research project in which his project group developed amorphous silicon solar cells. Dr. Tanaka attributed one of the reasons for the success of the project to the participation of university teams.

In the atom technology project, he also wanted to conduct research at a single laboratory at which many researchers from various fields could gather. He says, "All research groups of the project not only worked closely with each other in the facility but also shared the same cafeteria and relaxation room. This sounds like a very simple child's play. But the effectiveness of this method, designed to promote the integration of groups from various research fields at a faster pace, has been proved at the Max Planck Institute for Solid State Physics, Stuttgart, Germany and other research institutes."

Dr. Tanaka has made four suggestions for the successful consolidation of research from different fields, as follows:

1) "A higher investment priority should be put on research proposals that appear to help develop a new research field based on a wide range of the present sectors," he says. He adds that it is important to encourage researchers to integrate their own expertise with that of their counterparts in different fields. Inter-ministry joint research projects being studied by the Council for Science and Technology Policy, Japan, are examples of his suggestion and will start from the coming FY 2004.

2) It is important to create an environment in which -- more than in other research circumstances -- researchers are highly likely to meet each other. Namely, researchers from different fields should have their own offices closely located on the same floor of the same building or share the same office. It effectively accelerates cross- disciplinary interaction between researchers and groups, which has been historically evidenced by several institutes as mentioned above.
Dr. Tanaka also created such an environment in JRCAT, as he has explained.

3) Active use of sabbatical leaves. Dr. Tanaka says it is important to provide researchers with a period of six months to one year during which they can reconfirm the positioning of their own studies in society. Such a break is necessary once for every six to seven years to give researchers a "bird's eye view" of their work.

4) University curriculums should be flexible enough to respond quickly to changing times and to meet current social needs.

Dr. Tanaka says nanotechnology in Japan will not make any progress unless project leaders and researchers with a wide outlook are brought up. He adds that the master plan for developing nanotechnology in Japan should be discussed from the mid- and long-term viewpoint by young researchers with strong physical and intellectual ability.

(Interviewer: Kuniko Ishiguro, Cosmopia Inc.)

For more information,
http://www.nanonet.go.jp/english/mailmag/2004/017a.html

 

 

Tadaaki NAGAO

Masayoshi ESASHI

Professor, New Industry Creation Hatchery Center,
Tohoku University

Creating next generation industry
based on 'NEMS technology'
Combining micromachining with nanomachining.

A slender catheter equipped with a sensor at its tip is inserted through a blood vessel to measure the pH of blood. Development of this semiconductor ion sensor for medical use by Prof. Esashi opened up a new world of micromachining research in Japan.

In the mid 70s, Prof. Esashi was a graduate student at Tohoku University when he developed a semiconductor ion sensor (ISFET) for medical use, using MOS transistors that were used for electric calculators. He was working with Prof. Jun-ichi Nishizawa who was a leader of Japanese semiconductor researches at that time. Later, he developed miniaturized technology for pressure and acceleration
sensors and advanced technology in packaging that was important for devices applicable to practical uses. Prof. Esashi also developed original micromachining equipment and has been leading a way in pioneering research in the micromachining field. Micromachining is the technology based on silicon microfabrication technology and a combination of various technologies such as electronics, mechanics, optics, and material science. This technology has been utilized for the production of various microelectromechanical systems (MEMS) that
are key components for information/communication systems, electric appliances for automobile/home, and medical/biological devices. Currently, Prof. Esashi is making efforts to combine micromachining with nanomachining because "The combination of micromachining and nanomachining will enable us to construct sensors and systems with higher performance and better quality than the existing MEMS." He aims at developing MEMS into NEMS (nanoelectromechanical systems) by applying nanomachining.

One of his remarkable achievements is the electron beam source for a lithography system that enables the fabrication of high performance VLSIs: it allows direct and maskless patterning narrower than 100 nm. It consists of deposited carbon nanotubes with nanomachining at the tips of a silicon needle array that has been prepared with micromachining. Another one is the next generation high-density data storage device with multi-nanoprobes. The device consists of 32 x 32 arrayed probes with nano heater tips each. A recording media is heated by the tips and data is written onto the medium at a density of as high as 1 Tb / inch^2. The stored data are read out by using the conductivity difference of a single digit between the heated portions and unheated portions.

Prof. Esashi's research theme, researches toward practical use, is based on the Tohoku University's traditional philosophy, "Jitsugaku" or practical science. He suggests "the small volume production of multiple kinds of high-value-added products using high technologies" to utilize our own technological skills and know-how for national industrial recovery. He also suggests the joint industry-university
research based on "open collaboration" to make our industries more internationally competitive. Nanomachining can be applied in various fields.

Prof. Esashi always makes his standpoint clear by saying; "Providing industry with 'NEMS technologies' information that industry needs is the role of university researchers." Indeed, there are many visitors from private companies to share information with him. "Our job is to open up a new field into which no one has been. Therefore, our efforts could go wrong. What is important here is to find out what went wrong. Learning from failure will lead you to further research." adds Prof. Esashi.

(Interviewer: Shin Chikushi)

For more information

Satoshi KAWATA

Professor, Applied Physics, Graduate School of
Engineering, Osaka University
and Chief Scientist, Nanophotonics Laboratory,
The Institute of Physical and Chemical Research (RIKEN)

Beyond the diffraction limit
Photonics explores the nano world

The world's smallest bull, which will appear in next year's Guinness Book of World Records, is 8 mm in length and 5mm in height. The legs, horns, and the tail are so small as to be beyond the diffraction limit and can not be imaged by visible light. The bull's body is made from photopolymerizable resin, a polymer that solidifies by absorption of light. Prof. Kawata has developed a nanophotonics method to manipulate nanoscale structures using an ultrafast femtosecond laser of several
hundred nm wavelength.

When photons are strongly confined both temporally and spatially, two photons can simultaneously excite an electron in a target. The femtosecond laser has made this strong confinement possible. A 1kW peak power femtosecond laser compresses energy into a 100fs pulse so that strong confinement is achieved with an exposure of only 1mW near infrared light for 10ns. When this compressed pulse meets the resin target, the multiphoton process is confined to the region of high
photon density and solidification occurs only at the focal point. Nanodevices can be developed from this new method, completely different from the conventional method of "cutting". The micro-bull is proof indeed.

Femtosecond lasers have also proved to be very powerful as a tool for biology. Since a cell is transparent, a femtosecond laser beam can propagate through the interior of a cell without damaging the surface and manipulate only the subcellular organelles at the focal point. Photonics is becoming indispensable in the field of biology, as well as the more conventional semiconductor applications.

Another field of photonics research that Prof. Kawata is active in is the optical near-field. He has observed DNA and carbon nanotubes by near-field microscopy based on Raman scattering where the light spectra is shifted by molecular vibrations in the sample. The ability to simultaneously observe and analyse the sample is one primary aim of photonics. Prof. Kawata aims to develop optical microscopy that can observe the vibrations of single molecules. "I am still in the world of 10nm; I intend to go into the world smaller than 1nm to really see what is there. I intend to observe DNA in its natural state, without cutting or using chemical preparations. I have the ideas for how to get there and I think I will be able to reach it within a few years."

Prof. Kawata has been the Director of the Handai Frontier Research Center (FRC) at Osaka University since October 2001. The FRC has established the e-learning nano-engineering program within FRe-University for people who are now working in related fields. "Those with science or engineering degrees have never taken nanotechnology class at university before, and even people with non-science or engineering degrees can now learn nanotechnology. Take DNA as an example; it cannot be categorized precisely as biology, chemistry or physics. Nanotechnology explores not just a single field but a combination of cutting-edge science." Along with pursuing great advances in science, he also realizes the necessity of bringing
nanotechnology to the wider society.

(Interviewer: Kuniko Ishiguro, Cosmopia Inc.)

For more information

Takaaki KOGA

Researcher, Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST) and Visiting Scientist, Materials Science Research Laboratory, NTT Basic Research Laboratories

Control and applications of novel spin
properties found in
semiconducting nano structures

Researcher, Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST) and Visiting Scientist, Materials Science Research Laboratory, NTT Basic Research Laboratories

Electrons have spin degree of freedom in addition to charge degree of freedom. It is the charge degree of freedom that various conventional electronic devices to date have been based on. The ultimate purpose in the new research area of semiconductor spintronics is the development of electronic devices that actively utilize the spin degree of freedom of electrons in order to realize functionalities
that have never been realized in conventional electronic devices.

What I specially focus on in my PRESTO research is the gate-control of the spin properties in semiconductor heterostructures. Electron spins, which areexemplified by small magnets, have conventionally been controlled by externally applied magnetic fields. Although it had also been proposed that electron spins could be controlled by an electric field (via so-called Rashba spin-orbit interaction) instead
of a magnetic field, the main accomplishment in my PRESTO research includes the quantitative clarification of the gate-controlled Rashba spin-orbit coupling using the weak antilocalization analysis as itemized below:

(1) We performed a quantitative analysis on the weak antilocalization phenomena that are observed in a magneto-resistance at low temperatures in the InAlAs/InGaAs/InAlAs quantum well system. We then discovered an existence of zero-field spin-splitting in this system, which should be caused by the asymmetry in the potential shape of the quantum wells. The magnitudes of the spin splitting energies turned out to be consistent with those predicted in theory.

(2) We showed, theoretically, that a spin filter device can be realized using a triple barrier resonant tunneling structure. This spin device is composed of InGaAs and InAlAs for the well and barrier layers, respectively. These are both nonmagnetic materials, hence proposing a spin filter device without the use of any magnetic
materials.

(3) We examined a spin interference effect in a square loop array that is nanolithographically fabricated on an InAlAs/InGaAs/InAlAs quantum well heterostructure.

Regarding the above item (3), recent experimental results showed that the magnitude of the self-interference of the electron wave function varies as a function of the gate voltage. This result indicates that the electron wave function interferes with itself constructively or destructively depending on the value of the applied gate voltage, which supports the fact that spin precession angle is controlled by the magnitude of the spin-orbit interaction.

For future projects, I would like to make every effort, on the basis of the academic results accumulated to date, in experimental realization of the proposed spin filter device that utilizes resonant tunneling structure, as well as exploration of new research areas such as the examination of the relation between spin-orbit effect and phase relaxation time in a two-dimensional electron gas system.

For more information

Chris Phoenix

Director of Research CRN

Akihisa INOUE

Director/Professor, Institute for Materials Research,
Tohoku University

Yasunori TODA

Associate Professor, Department of Applied Physics,
Hokkaido University and Researcher, Precursory Research for
Embryonic Science and Technology (PRESTO), Japan Science and
Technology Agency (JST)

Quantum mechanical control of quantum dots by using coherently controlled light

One of the fascinating characteristics of quantum dots is their atomic-like discrete density of states with large energy-level spacing, in which acoustic phonon-mediated scattering should be suppressed compared with higher-dimensional structures. As a consequence, excitons in quantum dots are expected to exhibit long coherence time, which is advantageous for application of quantum information
processing. In such quantum logic devices, it is important to coherently control quantum units individually.

Our research aims at quantum mechanical control of exciton wavefunctions by using coherently controlled light. Because laser light exhibits high coherence, we can easily manipulate its waveform by a dispersion-free 4-f optical system in conjunction with a spatial light modulator (SLM), which alters the spectral phase of the pulse. By optimizing the excitation pulse, we can address the exciton
wavefunctions in individual self-assembled quantum dots (SAQDs).

We here used the sample of SAQDs. In a photoluminescence (PL) spectrum of the sample, several sharp emission lines originating from different SAQDs are observed. For the selective excitation, we optimized the excitation pulse based on the photoluminescence excitation (PLE) resonances. A contour plot of the PL spectra as a function of the phase of SLM shows normalized PL intensities at two peaks with fitting of the data by a sinusoidal function. Both peaks show oscillatory
behavior as a consequence of the quantum interference of the wavefunctions in each excited states. Furthermore we can address the exciton wavefunctions even in the collective excitation. This indicates the feasibilities for selective coherent control of individual exciton wavefunctions.

For more information,

Chihaya ADACHI

Associate Professor, Department of Photonics Materials Science,
Chitose Institute of Science and Technology and Leader,
"Construction of organic semiconductor laser and clarification of
device physics," Core Research for Evolutional Science and
Technology (CREST) Project "Construction of super high-speed, super
power-saving, high-performance nanodevice system," Japan Science and
Technology Agency (JST)

Organic electronics and photonics

Since the 1980's, research on organic semiconductors, both low molecular materials and polymers, has progressed, because of their unique electronic properties different from those of inorganic semiconductors, leading to novel optoelectronic applications.

Our research is now focused on electronic and optical properties of organic semiconductors that are open to novel optoelectronic applications, Organic LED, FET, solar cells and laser diodes. Through material design and synthesis, and new device architectures, we are aiming at realizing new organic devices and establishing device physics of organic semiconductors.

Recently, we clarified detailed exciton decay processes of electrophosphorescence. Photoluminescence of Ir(ppy)3 shows unique emission characteristics due to strong interaction between the central Ir and the ligands. It is independent of temperature, suggesting internal phosphorescence efficiency of 100%. We have also realized
injection of very high current density over 1000A/cm^2 into organic thin films. While it has been considered hard to inject high current density exceeding 1000A/cm^2, we have demonstrated that the injection of high current density is possible for organic thin films, which will open a way to realize organic laser diodes in the near future.

We are also interested in annihilation processes of molecular excitons, Triplet-Triplet, Singlet-Single and Exciton-Charge carrier under high current density.

...read the wave

Toshio KIMURA,

Fellow and General Manager, Central Research
Institute, Mitsubishi Materials Corporation