Nanotechnology Global Strategies, Industry Trends and Applications phần 8 pot

Frontier Nanotechnology for the Next Generation Tsuneo Nakahara and Takahiro Imai Sumitomo Electric Industries Ltd This chapter proposes how to select unique research targets of frontier

For better or worse, venture capitalists need to acknowledge that they have leadership responsibilities to society at large The power of the capital formation is one aspect The power of the intellectual capital formation is even greater 6.6 Summary

Life is definitely more complicated than ever before, regardless of what aspect we look at Business is more challenging; there are more dimensions, more factors to consider, more unknowns that need to be addressed More knowledge is required; more people of diverse backgrounds need to participate in the creation of value

Question: How is market value created out of innovation?

Answer: To direct and manage this process, an effective approach is to use of selected human resource teams

The teams will include multiple points of view from a cross section of human society, to assess common needs and expectations Representatives from the following areas are encouraged to participate actively in the process:

Public relations people deal with issues of visibility, credibility and desirability

Creative translators can translate innovation to different venues or contexts

Business people can only make money when people or customers acknowledge some benefit to them Their commitment to buy determines value

Legal experts protect the intrinsic value of the innovation

Government agencies may regulate or promote certain kinds of innovation The successful articulation and communication of a business concept that integrates all of these points of view will be the basis of a humanistic approach to building a business with true long-term value

Need for a New Type of Venture Capital 125

Part Three

Frontiers of

Nanotechnology

Frontier Nanotechnology for the Next Generation

Tsuneo Nakahara and Takahiro Imai

Sumitomo Electric Industries Ltd

This chapter proposes how to select unique research targets of frontier nanotech-nology fields by considering the small size effect and the nano size effect Examples are given for each size effect

At the Asia-Pacific Nanotech Forum held in Tsukuba, Japan, in February 2002 more than ten policymakers from various industrialized countries delivered speeches about national strategy together with budgetary plans for frontier nano-technology In particular, speakers from newly industrialized countries in Asia strongly insisted that they would put the greatest emphasis on nanotechnology and increase their budget rapidly as much as possible And they said they were quite sure they would catch up the US and Japan by the time of mass-produced nanotechnology products, as they did in the semiconductor and electronics industries

All the policymakers said that they planned a large budget for research and development on frontier nanotechnology for several years starting in 2001 Almost all of their budgets were allocated to very similar projects previously proposed

by Japan and the US, such as nanocarbon materials, nanoelectronics and nanobio-materials Consequently, there will be a fear that too many budgets for very similar projects will create a nanotechnology bubble that will eventually burst It

is strongly recommended that they adopt different approaches from each other so

Nanotechnology: Global Strategies, Industry Trends and Applications Edited by J Schulte

# 2005 John Wiley & Sons, Ltd ISBN: 0-470-85400-6 (HB)

that they may be able to reach unique and complementary achievements in frontier nanotechnology

How can we select unique and original research themes in the field of frontier nanotechnology? We need to consider the original target of the nanotechnology 7.1 What is the Target of Nanotechnology?

Figure 7.1 illustrates a beneficial way of selecting innovative themes in frontier nanotechnology The left-hand graph shows resistivity change of various wires as a function of temperature The resistivity of ordinary metallic wire such as copper wire decreases linearly as temperature goes down The resistivity of cryogenic wire such as highly purified aluminium wire exhibits a step change at a specific low temperature but never becomes zero, even at 0 K Notice that the resistivity of superconductor wire decreases as temperature goes down and abruptly becomes zero at a certain low temperature, TC, called the Curie temperature

The right-hand graph illustrates change in a certain physical parameter as a function of size, assuming that the phenomenon is similar to change in resistivity as

a function of temperature With ordinary materials the parameter may change linearly as size becomes small With some extraordinary materials the parameter may exhibit a step change at a certain small size as in the cryogenic wire Let us call this the small size effect Notice that with some revolutionary materials the para-meter may change surprisingly at a certain critical nanosize, as in the superconductor wire Let us call this the nano size effect

Figure 7.2 shows an example of the small size effect This is the case of compressed ferrous alloy powder developed by Sumitomo Electric in 2001 The compressed alloy powder shaped like a coin shows high electromagnetic wave absorption in the microwave frequency region this is due to resonance By gluing

Temperature (K)

Resistivity

0

Ordinary wire

ex Cu

Superconductive

Wire ex Bi system

TC

Cryogenic wire

ex pure Al

Size

Parameter

Ordinary Extraordinary

Small size effect

Critical size

Revolutionary Nano size effect

Figure 7.1 What is the target of nanotechnology?

these coins together, excellent performance has been obtained for thin and large-area electromagnetic wave absorbing sheets These electromagnetic wave absorbing sheets are especially suitable for small and precise communication and for electronic equipment such as cellphones and personal computers

Figure 7.3 shows carbon allotropes to explain an example of the nano size effect Note the significant difference between a single crystal such as a diamond and a

Feature

Particle shape is controlled at the nano-level,

giving high magnetic absorption characteristics

Adjustable particle shape and metal

composition giving optimized absorption peak

from 0.5 to 5 GHz

Application

Cell phones Game consoles BS/CS converters VTRs digital cameras Personal computers

Electromagnetic waves absorber Compressed ferrous alloy powder

Figure 7.2 An example of the small size effect

Graphite Fullerene

Diamond

Merit:

Hardness,

Thermal conductivity,

Chemical inertness,

Wide band gap

semiconductor,

Transparent,

Low dielectricity

Demerit:

Hard to machine, Small Size, Expensive

Laser machining, High speed growth, Film deposition, Dry etching

Overcome

Eco-material Varied Chemical Bond

Graphite Fullerene

Diamond

Graphite Fullerene

Diamond

Graphite

Nanotube

Fullerene Diamond

Carbyne

Merit

Hardness

Thermal conductivity

Chemical inertness

Wide band gap

semiconductor

Transparent

Low dielectric constant

Demerit

Hard to machine Small size Expensive

Laser machining High speed growth Film deposition Dry etching

Overcome

Eco-material

nanostructure Eco-material

Varied Chemical Bond

Varied chemical bond

Figure 7.3 An example of the nano size effect Frontier Nanotechnology for the Next Generation 131

uniform cluster molecule such as a fullerene Fullerenes are characterized by their atomically uniform size, autonomous formation for synthesis and quantum effective functions Diamond is entirely different A detailed explanation will be given below 7.2 Diamond Nanotechnology Is a Good Illustration

Diamond has many excellent properties as a semiconductor and it can be precisely machined into a nanostructure Diamond is not a substantially self-structured nano-material, unlike fullerene so Nevertheless, there are three reasons why diamond can

be considered as one of the best nanomaterials The first is its rigid atomic structure that gives diamond an extremely high hardness, very high thermal conductivity and high acoustic velocity The second is its properties as a semiconductor, which suggest applications for semiconductor devices, optical devices and electron emis-sion devices The third is the recent advanced developments in diamond fabrication and synthesis technology

One of the most outstanding advantages of diamond as a nanomaterial is that

it can be manufactured very precisely in a controlled manner This is particularly important during precision industrial mass production such as for nanoelectronics Sometimes the precision of products made from self-structured material like fuller-enes and carbon nanotubes is very sensitive to the conditions in the manufacturing environment, just as with agricultural products

Diamond has many distinctive properties as a semiconductor and can be extremely precisely machined on a nanometre scale compared with other materials Even now,

Figure 7.4 A diamond nanoemitter of size 2 nm

machined nanoscale diamond is at least comparable to self-structured nanomaterials such as carbon nanotubes Figure 7.4 shows a photograph of nanostructured dia-mond This is a steeple diamond single crystal made by reactive ion etching using patterned aluminium sacrificial masks The aluminium mask disappears after pre-cisely guiding the position of the steeple on the diamond surface

The radius is 2 nm at the top of the steeple in Figure 7.4 This is nearly equal to the radius of a carbon nanotube The size 2 nm can be considered as one of the most advanced examples of top-down nanotechnology Figure 7.5 shows the measured electron emission from the diamond tips made by this method as compared with tips made from flat diamond It is surprising that the electron emission from the tips was increased by almost 1 million times at the applied electric field of 1.0 V/mm as compared with that from the flat diamond surface This can be called the nano size effect

Many years ago the triode vacuum tube was developed and was used industrially for a long time Then it was necessary to prepare very high temperatures of over

2000C in order to get electron emission from the cathode of the triode vacuum tube Therefore the size of the triode vacuum tube was of order several centimetres Because of its large size and its poor reliability, due to the high temperature, it was replaced by solid-state semiconductors in many places Now, with this diamond nanoemitter, the required temperature for reasonable electron emission becomes 30C, which is almost room temperature The size of the triode vacuum tube can be squeezed down to a few micrometres Figure 7.6 shows a design example of such a micro vacuum triode Let us call this a vacuum microelectronic device (VMD)

10 –12

10 –11

10 –10

10 –9

10 –8

10 –7

10 –6

10 –5

10 –4

Without tip

Emission Current

With tips

Electric field (V/ µm)

Figure 7.5 Electron emission characteristics Frontier Nanotechnology for the Next Generation 133

Figure 7.7 shows estimated potential properties of the VMD as compared with other conventional semiconductor devices Because the electrons in the VMD travel

in the vacuum space, their mobility and their velocity will be much larger than in any other semiconductor materials Therefore the frequency limit for the VMD will

be much higher than for the other semiconductor devices, as shown in Figure 7.7 Also, performance of the VMD under a high-power applied environment is expected to be excellent because of the nature of diamond

The diamond nanoemitter explained above was one result of work undertaken by Sumitomo Electric Industry, Ltd and its partners under the auspices of METI and NEDO in Japan The project extended from this work is now a new Japanese national project that was begun in fiscal year 2003 by METI and NEDO

Anode Gate

e e

Centimetres

Micrometres

Advantage are

high speed and

high breakdown

voltage

e e

e e

e e

Vacuum tube

e

e

VMD

Using diamond we can achieve smaller size and power Loss

Emitter Hot cathode

Figure 7.6 Schematic diagram of a vacuum microdevice

Longer transmission

distance

InP

SiC

Si

Larger information

GaN

SiC

Si

Diamond emitter

(Vac Device)

Power Controlled Device

Base Station

Satellite Station

GaAs

InP

SiC

Si

109 1010 1011 1012

SiC

Si

Diamond emitter

(VMD)

Power controlled device

Base station

Satellite Station

Frequency (Hz)

DC

GaN

10−1

101

105

103

GaAs

Wireless network

Figure 7.7 Potential functions of semiconductor and vacuum device

7.3 Conclusion

In the field of frontier nanotechnology, there will be a tremendous number of opportunities for selecting research and development programmes from top down to bottom up Also, there will be a considerable variety of research and development fields classified by various materials, structures and processes Among these frontier nanotechnology projects, projects on the nano size effect discussed here will be most effective in creating the next generation of industry A diamond nanoemitter project was explained as an example

If huge sums of money are invested in very similar projects worldwide, there will

be fear that a bubble may be created and then collapse, as happened a few years ago with information technology It is recommended that each research institute and each industry around the world should make an independent plan for the frontier nanotechnology with their own unique programmes and perform research and development work aimed at original achievements in order to avoid duplication When, in the near future, these achievements are integrated worldwide, the next-generation industries will be created more efficiently

Frontier Nanotechnology for the Next Generation 135

Next-Generation Applications for Polymeric Nanofibres

Teik-Cheng Lim and Seeram Ramakrishna

Nanoscience and Nanotechnology Initiative, National University of Singapore

8.1 Background

Polymeric fibres that possess a high degree of molecular orientation along the fibre longitudinal axis can be formed from a solution or melt of the polymer via various techniques that involve a number of molecular processes These processes involve time- and temperature-dependent molecular motions, phase transitions under high stress, entanglement constraints and various intermolecular reactions As a result, the final state of molecular order in a fibre depends on the process variables These variables are stress, strain, time-dependent temperature and the length distribution

of the molecules These polymer microfibres (of diameter in the range1–100 mm) can be obtained using spinning or drawing techniques

Investigation into the structure of polymeric microfibres has brought about the ability to manipulate structural formation, that has resulted in fibres of high tensile modulus and tensile strength These high-strength high-modulus fibres are used in producing ropes, satellite tethers and high-performance sails and in polymer composites for applications such as aircraft, boats, automobiles, sporting goods and biomedical implants In addition, a number of remarkable fibre properties include UV resistance, electrical conductivity and biodegradability This ability to engineer properties of microfibres to meet specific requirements has resulted in

Nanotechnology: Global Strategies, Industry Trends and Applications Edited by J Schulte

# 2005 John Wiley & Sons, Ltd ISBN: 0-470-85400-6 (HB)