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JAPAN NANONET BULLETIN
-- 86th Issue -- December 21, 2006
Nanotechnology Researchers Network Center of Japan
Ministry of Education, Culture, Sports, Science and Technology (MEXT)
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JAPAN NANO 2007: Call for Registration
-Nanotechnology, Progress for Five Years and Expectation to The Future-
The Nanotechnology Researchers Network Center of Japan (nanonet), MEXT
organizes the 5th International Symposium on Nanotechnology (JAPAN
NANO 2007) on February 20 - 21, 2007, at Tokyo Big Sight (Ariake,
Tokyo).
The constitution of JAPAN NANO 2007 is : Plenary lectures, symposia on
nano-IT devices, nano-physics, nano-materials, nano-biology, nano-
process, metrology and nano-implications and the oral presentation &
poster session.
Lectures will be given by the world-leading researchers on the state-
of-the-art nano science and technology. Posters will be introduced by
the best young researchers who will lead the next generation of this
area. JAPAN NANO 2007 provides you the current topics and future
perspective of nano science and nanotechnology.
For more information,
http://www.nanonet.go.jp/english/event/japannano2007/index.html
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IN THIS ISSUE
Nanonet Interview:
"New development of a focused ion beam
-- Fabricating desired three-dimensional nanostructures --"
Shinji MATSUI, Professor, Laboratory of Advanced Science and
Technology for Industry and Graduate School of Material Science,
University of Hyogo
Young Researchers' Introduction:
"Development of novel "size-effect free" high permittivity thin film"
Hiroshi FUNAKUBO, Associate Professor, Department of Innovative and
Engineered Materials, Interdisciplinary Graduate School of Science and
Engineering, Tokyo Institute of Technology
-- NANO CALENDAR --
For information on nanotechnology related symposiums and conferences
held in the world,
http://www.nanonet.go.jp/english/calendar/
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NANONET INTERVIEW
New development of a focused ion beam
-- Fabricating desired three-dimensional nanostructures --
(Issued in Japanese: October 5, 2005)
Shinji MATSUI, Professor, Laboratory of Advanced Science and
Technology for Industry and Graduate School of Material Science,
University of Hyogo
Prof. Matsui made a jungle gym of wires that is 80 nm wide on a human
hair using focused ion beams (FIBs). Previously, FIBs had only limited
uses, such as experimental fabrication of quantum effect devices and
sample preparation for defect analysis, but now they can be used for
three-dimensional nanofabrication.
Prof. Matsui thought that, with the current technology, only two-
dimensional structures could be fabricated on the nanoscale. Then, he
happened to see a picture of bovine Achilles tendon. "Bovine Achilles
tendon is a coil with a 68 nm pitch. 'This is it!' I thought of
fabricating three-dimensional structures," says Prof. Matsui. In FIB-
chemical vapor deposition (FIB-CVD), the pressure of phenanthrene
(C14H10) gas is 5x10^-6 Torr in the specimen chamber, and the mean free
path of a gas molecule is several tens of centimeters in the chamber
filled with a gas of 5x10^-6 Torr. This means that the probability of
ions colliding with gas molecules in the chamber is almost zero.
However, the entire surface area of the substrate is covered with
adsorbed gas molecules. This is the key to fabricating three-
dimensional structures. Irradiation with a Ga^+ FIB that has a beam
diameter of 5 nm operating at 30 keV of the substrate results in the
scattering of a certain amount of incident ions within a 20 nm radius
from the beam position, while secondary electrons are emitted within
the area of a 40 nm radius. The secondary electrons are captured by
adsorbed gas molecules with high probability because of their low
energy of a few electron volts. This leads gas molecules to decompose,
and then, diamond-like carbons (DLC) are likely to deposit within an 80
nm diameter region on the surface of the substrate.
"When the beam position is moved by 20 nm, gas molecules are adsorbed
and decomposed again within a 40 nm radius from the new beam position.
This results in the creation of an off-positioned deposited terrace
with a diameter of 80 nm," says Prof. Matsui. Gallium ions that are
accelerated with a voltage of 30 keV are injected as deep as 20 nm into
a graphite substrate surface. Thus, when the beam position is moved
after depositing DLC thicker than 20 nm, DLC can be deposited again in
the adjacent region without ions penetrating the terrace and a new
terrace is formed. As a result, desired three dimensional shapes can be
fabricated. He says, "However, there was no three dimensional CAD
system that turns a desired structure into voxel data with angstrom
accuracy and draws the structure in a proper order." Then, his student
made it possible. "Hoshino, who liked robots, had knowledge about
electronics, mechanics and software. He made the most important part of
a three dimensional fabrication system involving FIB-CVD," says Prof.
Matsui.
Prof. Matsui's goal is to fabricate electronic devices and biodevices.
He first wants to fabricate free-space nanowiring. When a beam is
scanned at 20 nm/sec, wiring with a width of 100 nm at desired
positions is possible. C14H10 is mainly used as the source gas because
its deposition rate is ten times faster than other carbon-based gases.
He says, "Although DLC is usually not conductive, it shows conductivity
of 100 ohm cm because the DLC contains gallium because of the Ga^+ FIB."
When tungsten carbonyl (W(CO)6) gas is added to C14H10, the
conductivity of the DLC increases and shows semiconductive properties,
which usually cannot be observed in W(CO)6. "DLC has unique properties
because it is a kind of composite material. I would like to research
thoroughly basic material properties and mechanisms of deposition and
then fabricate three dimensional wiring systems, such as a cranial
nerve system, into which light emitting devices and p-n junctions are
incorporated."
Prof. Matsui has been focusing on the mechanical properties of three-
dimensional structures made of DLC. The elastic coefficient of a DLC
coil with a diameter of 400 nm is 85 GPa, which is the same value as
that of an iron coil spring. Nanoscale electromagnetic induction
experiments were also conducted using two coils. Prof. Matsui says,
"When a sine wave voltage is applied to a coil, cosine wave induction
current is generated in the other coil. The two coils may become a nano
-transformer, which leads to ultraminiturization of NMR equipment and
speakers."
For biological devices, Prof. Matsui has fabricated cell wall cutting
tools and nanomanipulators. He says, "Currently, organelles in cells
are extracted after disrupting the cells with a mixer. I wanted to
extract organelles from an individual cell by removing the cell
membrane without damaging organelles." He adds, "However, pinching
something soft with a manipulator causes damage. So, I have fabricated
a net." He was able to capture polystyrene beads that are 2 microns in
diameter in water with a nano-net that is 7 microns in diameter attached
at the tip of a commercially available manipulator.
Prof. Matsui came up with the idea of fabricating three-dimensional
structures with FIB-CVD when he saw the three-dimensional structure of
bovine Achilles tendon. He says, "It seems as if I am making something
small and playing with it. However, I feel that I have made
technological progress. I had thought that there was nothing left to
research in the field of FIB, but FIB was what made the fabrication of
three-dimensional structures possible. I have been told that a man
succeeds in completing three tasks in his life. Fabricating three-
dimensional structures using a FIB was my second task. There may be one
more left."
(Interviewer: Kuniko Ishiguro, Cosmopia Inc.)
For more information including figures,
http://www.nanonet.go.jp/english/mailmag/2006/086a.html
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YOUNG RESEARCHERS' INTRODUCTION
Development of novel "size-effect free" high permittivity thin film
(Japanese Issue: July 21, 2006)
Hiroshi FUNAKUBO, Associate Professor, Department of Innovative and
Engineered Materials, Interdisciplinary Graduate School of Science
and Engineering, Tokyo Institute of Technology
Dielectric materials with a high dielectric constant are important for
the development of high density capacitors for the development of
highly integrated devices. However, the dielectric constant of these
materials, especially having perovskite type of structure, is widely
known to decrease as the film thickness decreases, which is widely
known as "size effect in dielectric thin film". Because of this, it
has been difficult to prepare high density capacitors.
In this study, I focused on c-axis-oriented thin films of bismuth layer
-structured dielectrics (BLD) having a natural superlattice structure
made of the alternating stacks of the bismuth oxide layers and
pseudoperovskite layers along c-axis orientation (Fig. 1). We found
that c-axis-oriented BLD films had dielectric constants above 200 and
were "size effect free" (Fig. 2). In addition, they had good
insulating characteristics and had stable dielectric constants
independent of the applied voltage and the strain from the substrate.
These unique characteristics are considered to occur because of the
stacked structure.
I am now trying to develop novel characteristics by exploiting the
advanced stack structure.
For more information including figures,
http://www.nanonet.go.jp/english/mailmag/2006/086b.html
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