
Carbon nanotube transistors outperform silicon - ccozan
http://news.wisc.edu/for-first-time-carbon-nanotube-transistors-outperform-silicon/
======
skywhopper
I'm glad researchers are making progress on figuring out how to surpass the
limitations of silicon. But best to take PR articles like this with a grain of
salt of course.

"Carbon nanotube transistors should be able to perform five times faster or
use five times less energy than silicon transistors, according to
extrapolations from single nanotube measurements."

Well, that's the real trick isn't it? Other factors will come into play when
you scale from one transistor to a billion. Heat dissipation, physical size,
and practicality of manufacture are all open questions. This technology is
still many many years away.

------
omosubi
"Carbon Nanotube Valley" doesn't have quite the same ring to it

~~~
smb06
Let's just call it "Group 14 Valley"

~~~
goldenkey
Monster Group (formerly the Baby Monster)

------
prewett
This is a pretty vacuous article, definitely recommend tl;dr this one (or a
better headline by wisc.edu). They claim to outperform silicon, but there are
basically no actual numbers for feature size, leakage current, voltage,
switching speed, yield, or anything.

tl;dr: they developed a process that separates out the semiconducting
nanotubes from the metalic ones, and coated a 1x1 inch area in 5 minutes. They
achieved a current 1.9 times that of silicon. There were no specifics beyond
that, including what kind of "current" this was or the technique used to
create the transistors.

~~~
VygmraMGVl
Paper is here:
[http://advances.sciencemag.org/content/2/9/e1601240](http://advances.sciencemag.org/content/2/9/e1601240)

I don't know a whole lot about transistor characteristics, but their process
is debatably scalable (specifically the 5mm/min draw rate for the CNT
alignment).

------
marcosdumay
So, outperform silicon on conductivity?

The article isn't any clear about switching frequency. Does anybody know about
it?

Also, is that a multi-layer FET like VSLI FETs? The article implies so, but
isn't stated anywhere.

~~~
Tuna-Fish
Switching frequency of a single transistor is essentially the channel current
divided by the gate capacitance. If their gates are of similar size than
silicon transistors, 1.9 times greater channel current means 47% less time to
switch.

------
Symmetry
There isn't any doubt that nanotube transistors can ultimately be higher
performing than silicon. The problem is getting yon nanotubes to stick to more
than 70% of the pads that they're supposed to be sticking to. Even modern
silicon processes have the occasional bad transistor but with those it's 1 in
10 million or so, not 1 in ten. For VLSI we really need breakthroughs in
getting the nanotubes to go where we want them to.

~~~
InclinedPlane
Not even that, it's how to max produce them. Today transistors are made in
batches of trillions with hundreds of billions per silicon wafer and up to
billions per chip. Scaling up to that level of mass production, let alone
reliability, is a huge leap from where we are today and most likely will
require decades of work.

~~~
sevenless
The key advantage of silicon, as I understand it, is that we can mass produce
ICs on wafers via light-directed etching and epitaxy. I don't know of an
equivalent process for carbon that's been proposed yet.

~~~
Symmetry
The way that people currently plan to incorporate carbon into ICs is to create
a traditional silicon chip with a number of special pads. When a solution of
carbon nanotubes is washed over the chip the tubes stick to the pads and
create a connection there. So you would be leveraging all the current silicon
technology. The problem is getting an economical source of nanotubes and
getting them to stick to the damn pads reliably

------
mtgx
Too bad they could also become 21st century's asbestos problem.

[http://www.scientificamerican.com/article/carbon-nanotube-
da...](http://www.scientificamerican.com/article/carbon-nanotube-danger/)

~~~
vorotato
Sure if we develop some kind of voracious habit of cracking processors open.

~~~
mtgx
Maybe we will, if we do start putting a chip in everything around us
(including our clothes). Then we'd also be more vulnerable to those chips
potentially breaking around us, too. It probably still wouldn't be quite as
bad as asbestos, though, as that's much more frail.

~~~
vorotato
Well and we were using a LOT of abestos, not a few grams here and there but
kilos of the stuff.

------
yigitdemirag
I wonder how hyped carbon nanotube technology is. In case of graphene, lots of
groups had wonderful results on the theory, on simulations but when it comes
to nanofabrication or mass-scale production no much progress is done.

~~~
StreamBright
It is like saying that nuclear fusion is wonderful in theory but not so much
in practice, while we know that the biggest energy source of our galaxy is
coming from a thing that uses fusion to generate its energy. We are at the
beginning of the technical era, that first needs to revolutionise energy
production and storage that will be required for space travel. I have high
hopes in graphene and carbon nanotube tech.

~~~
rw
> biggest energy source of our galaxy

You meant the Sun, of course. However, your phrasing sent me on a quest to
answer the galactic question. From the following article, I learned that the
"supermassive black hole at the centre of the Milky Way" emits "cosmic
radiation at petaelectronvolt energies", which fits the bill for largest
energy source of our galaxy.

[https://www.mpg.de/10390310/acceleration-petaelectronvolt-
pr...](https://www.mpg.de/10390310/acceleration-petaelectronvolt-protons)

~~~
Retric
On the other hand if your looking at energy by type, fusion wins hands down.

------
the8472
They compare it to silicon. But what about other semiconductors like SiGe,
InGaAs, etc.

As far as I know intel&co already aim to integrate some of those into future
processes.

~~~
mtgx
IBM/Samsung/GloFo consortium has already demonstrated a 7nm SiGe chip. IBM is
also heavily researching carbon-nanotubes transistors, but I doubt we'll see
those before 5nm, or even later (so potentially 2025+).

[http://arstechnica.com/gadgets/2015/07/ibm-unveils-
industrys...](http://arstechnica.com/gadgets/2015/07/ibm-unveils-industrys-
first-7nm-chip-moving-beyond-silicon/)

[https://www-03.ibm.com/press/us/en/pressrelease/39250.wss](https://www-03.ibm.com/press/us/en/pressrelease/39250.wss)

------
faragon
How much will cost to manufacture chips with that technology? Current silicon
lithography is a photograph superposition process. Will be "drawing" with
carbon nanotubes as cheap, or will require per-transistor "drawing" instead of
per-layer lithography?

------
jacquesm
Performance is complex, in this case the performance is measured in computing
capacity for a $ or computing capacity per Watt, and all that at yields not
substantially worse than what Silicon can already do.

Just size, clock frequency or any other single parameter does not indicate
viability of a technology.

------
legohead
No mention of the performance increase? Are they 10x faster, or .001% faster?

~~~
oh_sigh
They say they could be 5x faster or use 5x less energy, based on
extrapolations of a single transistor in the article

~~~
rpwverheij
yes, which still leaves me wondering. the latest silicon transistors also use
a lot less energy then they did just a few years ago right. So in what way
does it compare to silicon transistors. Compared to 14nm? 10nm? Or in general?
For transisters of the same size?

