Interview
Interview with Professor Sumio Iijima. He discovered carbon nanotubes in 1991.

‘HOW I FOUND CARBON NANOTUBES AND WHAT THEY CAN DO IN THE FUTURE’

P rofessor Sumio Iijima,

first discovered, the electron microscopy com-the trend, hoping to discover something asso-

Meijo University, NEC
Laboratories, JST, Japan

munity was still very small worldwide. So only

ciated with superconductivity.

Interviewer: Masakazu Ichikawa, JSAP
International Editor-in-Chief

Ichikawa: First of all, I would like you to talka handful of people heard about the discovery

But I was really studying something elseof C60 initially. And C60 remained relatively un-at that time - the so-called onion structure of

known until 1990, when it was first mass-pro-graphites. You could say it was an accident

duced. The mass-production of C60 brought athat I found that structure. In 1990, when C60

whole host of physicists into this realm of re-

was first mass-produced, we used arc dis-search and it then became a popular subject ofcharges to create the C60: Kroto and Smalley

study.

had used laser ablation to produce smoke in achamber and it was in the smoke that a lot of

about your discovery of the carbon nanotube.

You should bear in mind that those physi-

The topic is being studied extensively all overcists had not previously been a part of the small

the world, but I have yet to find anything incommunity of microscopists. But when C60 is

In the arc discharge process, carbon isprint explaining how it was first discovered or

crystallized in large quantities and put throughmelted and evaporated in a gas stream. When

how it has been developed. Perhaps you would

a process called doping, the material becomes

you do this, some carbon gets deposited ontell us how it was discovered in the first place?

superconducting - that is why so many physi-

the electrodes but, because there was no C60

Iijima: The discovery itself was really a bitcists were attracted to C60. And around thatin the deposits, no one paid any attention toaccidental, but the path that led to it was nottime, another interesting thing happened.

them. Well, I examined the deposits on the elec-

so accidental. You see, I had been conducting

Oxides were also found to be superconductors

trodes - and under my microscope I saw the

research and development into the technology

at very high temperatures in 1988. That dis-carbon nanotubes.

required for high-resolution transmission elec-

covery, too, was a very exciting and significant

tron microscopy on both the hardware and soft-

event for physicists.

C60 was found.

Now, the objective of the arc discharge
process was to make super-small clusters. Thisware sides for some years. As a matter of fact,

Now, remember, I was still studying elec-

was what I had been doing for around for five

I was already working in this area in the 1970s

tron microscopy. The knowledge and experi-

years, beginning around 1982; I was involved- developing the technology for these incred-ence I had gained in microscopy somehow led

in a project under Professor Ryozi Ueda of theibly powerful microscopes. By the early 1980’s,

me to believe my field could perhaps be linked

Science and Technology Agency (STA). We

the technology was pretty much ready.

to this new area of superconductivity research.

were studying all sorts of smoke, putting all

So the 80’s saw the developed technol-

So my dream was that one day I would do somemanner of stuff into an arc discharge and mak-ogy being put to practical use in finding new

good work on superconductivity. Well, on re-ing it evaporate. You can make silicon clusters

and extremely small structures in the micro-

flection, I can’t say I contributed very much atwith arc discharges, you know. So this was a

scopic world - after all, the goal of microscopy

all to the concept of superconductivity. To tell

technology I was very familiar with.

is to see things that are very small. With the

you the truth, I was more than a little disap-

From that standpoint, it was like goingnecessary technology in place, the 1980s waspointed at not having made any significant

back to my old trick. By the time C60 camea decade when scientists were enthusiasticallycontribution. It turned out to be just a pipealong, I had already seen practically everything

trying to discover new things with the newly

dream and nothing more. I had hoped to come- most of the metals and semiconductors in theavailable microscopes. It was actually the high-across some very tiny particle one day that was

periodic table. I had seen all kinds of smoke

resolution transmission electron microscope

essential to superconductivity - but it never

and the clusters they produced. But the onethat made it possible to examine objects on

happened.

thing I hadn’t looked at was carbon. Imagine!

the nanometer-scale for the first time.

You see, when you don’t know what you

Everything except carbon! Well, I did see sili-

Well, perhaps a little more explanation isare looking for, you can waste a lot of timecon carbide - but that’s the closest I ever got todue about the discovery of the carbon

and energy... then you look back and say,carbon. So you could say my discovery was

nanotube. Back in the 1980s, when I was look-“What have I achieved in all those years?”

both fortuitous and coincidental. If you don’t

ing intensively at a bunch of clusters - in 1985

However, I finally succeeded with C60, althoughlook in the right place, you won’t find the rightto be precise - C60 was discovered by three sci-

I was only looking at it, observing it under myanswer... And that is how I got to see carbon

entists, Kroto, Smalley, and Curl. When I was

high-resolution transmission electron micro-

nanotubes - just by pure luck. (laughs)

looking at these clusters, and when C60 was

scope. As a microscopist, I was just following

Ichikawa: When you first saw the carbon

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JSAP International No.3 (January 2001)

Interview‘HOW I FOUND CARBON NANOTUBES AND WHAT THEY CAN DO IN THE FUTURE’nanotubes, did you find them exciting?

discovered in 1991 - and after that, wheneverof investigating the properties of nanotubes

Iijima: Yes, indeed! To the electron micros-

I went overseas to attend conferences every-

and they certainly have all the right equipment

copist, shape is everything, be it a circle, a

one was still talking about C60. I was one of- you need scanning transmission microscopessquare or a triangle. Whiskers are one-dimen-

the few giving lectures on the tube structures.

(STM) to measure nanotubes and study them,sional and are naturally very interesting to a

Of course, the trend has now been reversed.

since STMs are the essential tools for the job -microscopist. When I first saw carbon and saw

But it took ten long years!

but they lack the motivation. Only recently,

those whiskers, I knew right away I was on to

Curiously enough, the initial reaction of

only since the start of the new millennium, havesomething very different. Of course, I was stillscientists in Japan was quite different from thatJapanese scientists begun to do that kind ofinterested in the onion structure of graphites -of foreign scientists. The problem was thatwork. It seems that until now Japanese scien-

I was motivated by the idea that right in theJapanese scientists were reluctant to accept its

tists have been much more interested in mak-middle of the onion structure was a nucleus

importance, would you believe. That was be-

ing nanotubes than in learning about theirabout the size of C60 and around it there mustcause everyone here was interested in nothingproperties.

exist some other interesting structure.

but C60 and generating high-temperature su-

The very first group to study the proper-Now, for a microscopist, if you see C60,

perconductivity. So when something looking

ties of nanotubes was led by Professor Cees

just one molecule of it, it’s not such a big deal.

like a tube or a whisker turned up, hardly any-

Dekker of the Delft University of Technology in

You see it and that’s the end of the matter. But

one cared about it at all. And that was true

the Netherlands, where his group studied thewhen you see multiple layers of C60, then you’reeven in my own research group! There wasproperties of individual tubes. Dekker’s previ-

really talking. I thought if I could understandhardly any interest in nanotubes in Japan at allous experience lay in the fields of STM and or-

the onion structure and the mechanism of for-- and that came as a total surprise to me. I felt

ganic molecules, in which he was an expert, so

mation of the C60 molecule it might lead tokind of offended, thinking, “These nanotubes

he has used his expertise to apply STM tech-something significant. That was why I was at-

are absolutely fascinating. Why is no one else

nology to the study of various kinds oftracted to the C60 molecule - I had hoped to

paying any attention to them?”

nanotubes. He himself joined this research areasolve the mystery of the formation of C60 by

On the other hand, the reaction from sci-

fairly recently, much later than others, but he isstudying the growth of the onion structure. So

entists outside Japan was completely different

already one of the world’s leading authorities

when I discovered the carbon nanotubes, it was- perhaps because there are many more re-in the field and is doing excellent work.

like stumbling on hidden treasure.

searchers overseas, but maybe for other rea-

If we had people like him in Japan, it

The only appropriate term is “serendip-sons, too. The discovery of C60 was certainly

would be tremendous. We need more goodity”. I think serendipity is crucial in scientificheralded in Japan as a significant event, butscientists who are excited by nanotubes andresearch: if you look at the history of science, I

the early Japanese reaction to carbon

are highly motivated to do creative research.

dare say you’ll find more than half of all the

nanotubes was mild in the extreme.

Japan was a tad slow to enter the field, but

truly great discoveries were serendipitous. My

Perhaps the difference is that scientists inthere are some encouraging signs. One sign isprofessor used to tell me that being aggressive

foreign countries study a lot of different top-that the number of Japanese scientists enter-in research is not necessarily a good thing: “We

ics, but in Japan it is not like that... not all thating the field recently and doing good work

scientists study the physical world - you must

many research topics are studied in Japan. In

seems to be growing quite fast. I am looking

approach natural phenomena with humility,

fact, for about five years, no one here studied

forward to the future!

hoping to be privileged to see just a glimpse ofanything but C60. And then, gradually, with

Ichikawa: Would you now peer into thatthe truth of our physical world, because thethe help of new physicists who joined the com-future and tell us what you hope to see comeobject of our studies is Mother Nature herself.”munity, people in Japan also began studyingout of all this R&D?

Professor Ueda used to say that very often, andtubes.

Iijima: Nanotubes are getting quite close to

My own main interest in nanotubes nowa-

a number of practical applications, I think. For

Ichikawa: Nanotubes are now being inves-

days is to produce them and study the growth

example, field emission electrons are used intigated in Japan and overseas, too. Would you

mechanisms. So far, I have not studied theirlarge two-dimensional screens and displays, so

tell us about the current status of research andproperties very much - their properties are notperhaps these will be made with nanotubes. I

development in this area?

being studied very extensively in Japan.

believe many Japanese companies are work-

I believe it with all my heart.

Iijima: As I have said, carbon nanotubes were

I think Japanese scientists are very capableing on this type of product.

JSAP International No.3 (January 2001)23

Interview‘HOW I FOUND CARBON NANOTUBES AND WHAT THEY CAN DO IN THE FUTURE’And extremely fine carbon fibers - fibers

be effective as a reservoir for storing hydrogen.

because they see things. A lot of things, toothat were once considered to be merely very

That is only conjecture. If there was any way

many things... All that glisters is not gold!

small carbon fibers - are now expected to be

to confirm my conjecture, it would make an

Young researchers need to learn how to distin-very useful. Maybe the current research in thisexcellent research project. But, for the moment,

guish between what really matters and whatarea is too theoretical or fundamental. After

I will content myself with large 2-dimensional

doesn’t.

all, for me at any rate, it is when applications

displays.

like this materialize that the work becomes ex-

Ichikawa: So, for the human race, would

is important? One way is to develop the ability

citing and fun. Remember, until recently car-the most important application of carbon be

to observe things around us in nature, and tobon was simply called “the black stuff”! Thereas a hydrogen reservoir to help solve the en-study what’s out there... to learn the joy of dis-

was not much to study in it, or so it was widely

ergy crisis?

covery. I believe it is important to nurture thisheld. Of course, there was the obvious excep-

Iijima: Yes, that is undoubtedly the case. But

type of natural curiosity and the fun of discov-tion of activated carbon. And carbon was al-

there is something else. Even though we are

ery and learning from an early age. It should

ways a very important element from a chemical

speaking of a miniscule tube with a diameterstart from very early childhood. I grew up in

standpoint. But, apart from activated carbon,of only one nanometer, the tube might provethe countryside, in a small town, and I think I

there was nothing interesting about carbon...

to possess transistor-like properties or sharefirst learnt the joy of discovery as a child.

As far as carbon itself is concerned, it may

some other useful properties with metals or

Nowadays, though, a lot of people arestill be the “black stuff”, but the more recently

semiconductors. In theory, at least, it should

growing up in cities with no natural environ-studied forms of carbon - or even some of thethen be possible to make transistors and di-ment to learn from. My theory is that it is more

more conventional forms like carbon fibers, forodes as small as a single molecule. So silicondifficult for children growing up in big cities tothat matter - are really important. For example,

chips could be made much smaller - that is quite

become good scientists... That’s my view.

carbon fibers have recently come into use for mak-a possibility... The 21st century would then

Learning to discriminate - it’s like the man ining the positive terminals of lithium batteries.

become an era of transition from silicon to car-the antique shop who can judge whether anbon, and I don’t exclude biotechnology.

objet d’art is real or fake. Can you tell the dif-coming up almost every day. Perhaps in the

Ichikawa: Finally, Professor Iijima, you haveference between a forgery and a real work of

21st century, the coming energy revolution will

done a great deal of important and successful

art? Mother Nature can train your eyes... The

be initiated by utilizing hydrogen. Since hydro-

research. Do you have any secrets to share withnature that surrounds us - I think that’s essential.

gen is a dangerously inflammable gas that must

us in that regard?

Ichikawa: So when you saw nanotubes forbe stored safely in some way, well, activatedIijima: Yes, I think I can shed some light on it.

the first time, did you have this feeling thatcarbon is known to absorb gases and other el-

First of all, arbitrary discrimination against in-

you are talking about?

ements and is often used in bathrooms, kitch-

dividuals and groups worries me. National labo-

Iijima: Yes, I did! You know, there is treasureens and so forth to absorb bad smells. If car-ratories in Japan often impose unnecessary andeverywhere, whether it be lying just over there

bon can absorb hydrogen, which is dangerous

inappropriate age limits on research projector under your very nose. The key question lies

but is also likely to be central to energy pro-leaders and I am very much against that. I don’t

in which direction you should look. Is that in-duction, that would be great, and perhaps

believe age has anything at all to do with re-tuition? Well, you certainly can’t just bend

these tubes can contribute in some way, too.

search. It may be true in physics that young

down and try to look everywhere. It was Pas-

So maybe more fundamental research really is

researchers originate new theories more often

teur, I think, who said, “To find something sig-

necessary, since we don’t even know if it isthan old researchers. But in the kind of re-nificant, you must have a heart prepared to takepossible yet.

search I am doing, age is completely irrelevant.

good care of that discovery.” And it was

Ichikawa: Now, speaking about yourself,

What is important above all else is motivation

Einstein who said, “Imagination is more impor-have you a personal goal you want to pursue,and zeal. As long as a researcher is highly

tant than knowledge.” I believe those are say-a direction you want to take?

motivated, he or she should be encouraged toings worth thinking about. Creativity and imagi-

Iijima: Regarding the energy revolution thiskeep on doing research.

nation are vitally important in science. The fu-

In fact, new applications of carbon are

coming century, I would like to make a positive

Concerning younger researchers, youcontribution in a related area - perhaps by iden-must first consider their potential, especially intifying a specific structure of carbon that could

the experimental arena. They will often struggle

24

JSAP International No.3 (January 2001)

And how can you develop an eye for whatture of Japanese science and technology depends
on how carefully we nurture those qualities.