[Cyborg] New wonder material (MoS2) replaces graphene for future electronic devices - including eFabrics

Brad Neiman brad.neiman at gmail.com
Sun Aug 26 21:54:01 UTC 2012


Last section talks about possible applications

 New wonder material replaces graphene for future electronic devices
Entirely new kinds of devices --- entire walls of light, smart windows,
eyeglass displays, complex electronic circuits --- from new 2D molybdenum
disulfide: MIT researchers
August 23, 2012
 *[+]*[image: molybdenum_disulfide]<http://www.kurzweilai.net/images/molybdenum_disulfide.jpg>

This diagram shows the flat-sheet structure of molybdenum disulfide —
molybdenum atoms shown in teal, sulfur atoms in yellow (credit:  Han Wang
et al.)

MIT <http://web.mit.edu/> researchers — who struggled for several years to
build electronic circuits out of graphene with very limited results (except
for radio-frequency applications) — have now
succeeded<http://web.mit.edu/newsoffice/2012/graphene-molybdenum-sulfite-flat-materials-0823.html>
in
making a variety of electronic components from an amazing new material: a
2D version of molybdenum disulfide (MoS2).

The MIT researchers say the material could help usher in radically new
products, from whole walls that glow to clothing with embedded electronics
to glasses with built-in display screens.

Tomás Palacios <http://web.mit.edu/tpalacios/>, the Emmanuel E. Landsman
Associate Professor of EECS says he thinks graphene and MoS2 are just the
beginning of a new realm of research on two-dimensional materials. “It’s
the most exciting time for electronics in the last 20 or 30 years,” he
says. “It’s opening up the door to a completely new domain of electronic
materials and devices.”

A report on the production <http://pubs.acs.org/doi/abs/10.1021/nl302015v> of
complex electronic circuits from the new material was published online this
month in the journal *Nano Letters, *authored by Han Wang and Lili Yu,
graduate students in the Department of Electrical Engineering and Computer
Science (EECS); Palacios; and others at MIT and elsewhere.

*Promises to replace graphene*

Like graphene, itself a 2-D form of graphite, molybdenum disulfide has been
used for many years as an industrial lubricant. But it had never been seen
as a 2-D platform for electronic devices until last year, when scientists
at the Swiss university EPFL produced a transistor on the material.

Yi-Hsien Lee, a postdoc in associate professor Jing Kong’s group in EECS,
found a good way to make large sheets of the material using a chemical
vapor deposition process. Lee came up with this method while working with
Lain-Jong Li at Academia Sinica in Taiwan and improved it after coming to
MIT. Palacios, Wang and Yu then set to producing building blocks of
electronic circuits on the sheets made by Lee, as well as on MoS2 flakes
produced by a mechanical method, which were used for the work described in
the new paper.

Wang had been struggling to build circuits on graphene for his doctoral
thesis research, but found it much easier to do with the new material.
There was a “hefty bottleneck” to making progress with graphene, he
explains, because that material lacks a
bandgap<http://web.mit.edu/newsoffice/2010/explained-bandgap-0723.html>
—
the key property that makes it possible to create transistors, the basic
component of logic and memory circuits. While graphene needs to be modified
in exacting ways in order to create a bandgap, MoS2 just naturally comes
with one.

The lack of a bandgap, Wang explains, means that with a switch made of
graphene, “you can turn it on, but you can’t turn it off. That means you
can’t do digital logic.” So people have for years been searching for a
material that shares some of graphene’s extraordinary properties, but also
has this missing quality — as molybdenum disulfide does.

Because it already is widely produced as a lubricant, and thanks to ongoing
work at MIT and other labs on making it into large sheets, scaling up
production of the material for practical uses should be much easier than
with other new materials, Wang and Palacios say.

*Logic elements, memory fabricated*

Wang and Palacios were able to fabricate a variety of basic electronic
devices on the material: an inverter, which switches an input voltage to
its opposite; a NAND gate, a basic logic element that can be combined to
carry out almost any kind of logic operation; a memory device, one of the
key components of all computational devices; and a more complex circuit
called a ring oscillator, made up of 12 interconnected transistors, which
can produce a precisely tuned wave output.

Palacios says one potential application of the new material is large-screen
displays such as television sets and computer monitors, where a separate
transistor controls each pixel of the display. Because the material is just
one molecule thick — unlike the highly purified silicon that is used for
conventional transistors and must be millions of atoms thick — even a very
large display would use only an infinitesimal quantity of the raw
materials. This could potentially reduce cost and weight and improve energy
efficiency.

*Entirely new kinds of devices: entire wall of light, smart windows,
eyeglass displays*

In the future, it could also enable entirely new kinds of devices. The
material could be used, in combination with other 2-D materials, to make
light-emitting devices. Instead of producing a point source of light from
one bulb, an entire wall could be made to glow, producing softer, less
glaring light. Similarly, the antenna and other circuitry of a cellphone
might be woven into fabric, providing a much more sensitive antenna that
needs less power and could be incorporated into clothing, Palacios says.

The material is so thin that it’s completely transparent, and it can be
deposited on virtually any other material. For example, MoS2 could be
applied to glass, producing displays built into a pair of eyeglasses or the
window of a house or office.

Ali Javey, an associate professor of electrical engineering and computer
science at the University of California at Berkeley, who was not involved
in this research, says layered materials such as MoS2 are “a promising
class of materials for future electronics,” but cautions that while “the
future looks bright for layered semiconductors, still work needs to be done
to better understand their performance limits and large-scale
manufacturing.”

Overall, Javey says, the MIT team’s research is “elegant” work that “takes
an important step forward in advancing the field of layered semiconductors.”

Researchers at the U.S. Army Research Laboratory researchers  and Academia
Sinica in Taiwan were also involved. The work was funded by the U.S. Office
of Naval Research, the Microelectronics Advanced Research Corporation Focus
Center for Materials, the National Science Foundation and the Army Research
Laboratory.
 REFERENCES:

   - Han Wang, Lili Yu, Yi-Hsien Lee, Yumeng Shi, Allen Hsu, Matthew L.
   Chin, Lain-Jong Li, Madan Dubey, Jing Kong, Tomas Palacios, Integrated
   Circuits Based on Bilayer MoS2 Transistors, *Nano Letters*, 2012, DOI:
   10.1021/nl302015v <http://dx.doi.org/10.1021/nl302015v>

*Topics:* Computers/Infotech/UI | Electronics | Nanotech/Materials Science
| VR/Augmented Reality/Computer Graphics
*---—---—---–---–------—---—---–---–------—---—---–---–---
Brad Jeffrey Neiman
Principal - Agile Project Manager/ ScrumMaster for Product Development
NeīMan Technical Services
San Francisco  CA 94110
USA
Brad.Neiman at gmail.com
+1 415 990-8249

> LinkedIn: http://www.linkedin.com/in/bradneiman
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wearable technology & sensor systems, startup, synergizing leadership/ team
effectiveness, et. al.*
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