David Kirkpatrick

September 3, 2010

Graphene transistors hit 300 GHz

Via KurzweilAI.net — Great news, but as always I’d love to see a market-ready application come out of this research in the near future. Blogging about nanotech breakthroughs is all well and good, but it is excellent when I get the chance to blog about a real-world application of said breakthroughs.

From the link:

High-speed graphene transistors achieve world-record 300 GHz

September 3, 2010 by Editor

UCLA researchers have fabricated the fastest  graphene transistor to date, using a new fabrication process with a  nanowire as a self-aligned gate.

Self-aligned gates are a key element in modern transistors, which are semiconductor devices used to amplify and switch electronic signals.  Gates are used to switch the transistor between various states, and self-aligned gates were developed to deal with problems of misalignment encountered because of the shrinking scale of electronics.

“This new strategy overcomes two limitations previously encountered in graphene transistors,” professor of chemistry and biochemistry Xiangfeng Duan said. “First, it doesn’t produce any appreciable defects in the graphene during fabrication, so the high carrier mobility is retained. Second, by using a self-aligned approach with a nanowire as the gate, the group was able to overcome alignment difficulties previously encountered and fabricate very short-channel devices with unprecedented performance.”

These advances allowed the team to demonstrate the highest speed graphene transistors to date, with a cutoff frequency up to 300 GHz — comparable to the very best transistors from high-electron mobility materials such gallium arsenide or indium phosphide.

Graphene, a one-atom-thick layer of graphitic carbon, has great potential to make electronic devices such as radios, computers and phones faster and smaller. With the highest known carrier mobility — the speed at which electronic information is transmitted by a material — graphene is a good candidate for high-speed radio-frequency electronics. High-speed radio-frequency electronics may also find wide applications in microwave communication, imaging and radar technologies.

Funding for this research came from the National Science Foundation and the National Institutes of Health.

More info: UCLA news

June 4, 2010

A cyborg transistor

Via KurzweilAI.net — Interesting, if not a little bit creepy.

Part-human, part-machine transistor devised
Discovery News, June 2, 2010

University of California, Merced scientists have embedded a carbon nanotube-based transistor inside a lipid bilayer (cell-like membrane) and powered it with an ion pump and a solution of adenosine triphosphate (ATP) to fuel the ion pump.

Artist’s representation of a new transistor that’s contained within a cell-like membrane (Scott Dougherty, LLNL)

The research could lead to new types of man-machine interactions where embedded devices could relay information about the inner workings of disease-related proteins or toxins inside the cell membrane, and eventually even treat diseases. It could also lead to new ways to read, and even influence, brain or nerve cells.

The headline is misleading — the device is simply biomimetic. – Ed.
Read Original Article>>

May 25, 2010

A seven atom transistor

Via KurzweilAI.net — We are heading toward the terminus of physical computing components. Can’t get a whole lot smaller than seven atoms.

Quantum leap: World’s smallest transistor built with just 7 atoms
PhysOrg.com, May 24, 2010

The world’s smallest precision-built transistor — aquantum dot of just seven phosphorus atoms in a single silicon crystal — has been created by scientists from the UNSW Centre for Quantum Computer Technology and the University of Wisconsin-Madison.

At present, the length of a commercial transistor gate is about 40 nanometers (billionths of a metet). The new device has features about 10 times smaller at 4 nanometers.

Template of the quantum dot device showing a central hole where seven phosphorus atoms are incorporated
Read Original Article>>

May 12, 2010

Graphene transistor

Filed under: Science, Technology — Tags: , , , , , — David Kirkpatrick @ 12:23 am

One step toward nanoelectronics.

From the link:

For years, scientists and researchers have been looking into the properties of carbon nanotubes and graphene for use in nanoelectronics. “There is no real mass application of devices based on graphene and carbon nanotubes,” Zhenxing Wang tells PhysOrg.com. “This is really an opportunity for them to show their capabilities.”

Wang is part of a group at the Key Laboratory for the Physics and Chemistry of  at Peking University in Beijing. Along with Zhiyong Zhang, Huilong Xu, Li Ding, Sheng Wang, and Lian-Mao Peng, Wang tested a top-gate  field-effect transistor based frequency doubler in order to gauge its performance. They were able to show that a graphene based frequency doubler can provide more than 90% converting efficiency, while the corresponding value is not larger than 30% for conventional frequency doubler. Their work is published in : “A high-performance top-gate graphene field-effect transistor based frequency doubler.”

April 23, 2009

Nanotech improves transistor chips

Nanotechnology offers fairly regular breakthroughs in chip tech. Here’s the latest.

The release:

Self-assembled nanowires could make chips smaller and faster

CHAMPAIGN, Ill. — Researchers at the University of Illinois have found a new way to make transistors smaller and faster. The technique uses self-assembled, self-aligned, and defect-free nanowire channels made of gallium arsenide.

In a paper to appear in the IEEE (Institute of Electrical and Electronics Engineers) journal Electron Device Letters, U. of I. electrical and computer engineering professor Xiuling Li and graduate research assistant Seth Fortuna describe the first metal-semiconductor field-effect transistor fabricated with a self-assembled, planar gallium-arsenide nanowire channel.

Nanowires are attractive building blocks for both electronics and photonics applications. Compound semiconductor nanowires, such as gallium arsenide, are especially desirable because of their better transport properties and versatile heterojunctions. However, a number of challenges – including integration with existing microelectronics – must first be overcome.

“Our new planar growth process creates self-aligned, defect-free gallium-arsenide nanowires that could readily be scaled up for manufacturing purposes,” said Li, who also is affiliated with the university’s Micro and Nanoelectronics Laboratory and the Beckman Institute. “It’s a non-lithographic process that can precisely control the nanowire dimension and orientation, yet is compatible with existing circuit design and fabrication technology.”

The gallium-arsenide nanowire channel used in the researchers’ demonstration transistor was grown by metal organic chemical vapor deposition using gold as a catalyst. The rest of the transistor was made with conventional microfabrication techniques.

While the diameter of the transistor’s nanowire channel was approximately 200 nanometers, nanowires with diameters as small as 5 nanometers can be made with the gold-catalyzed growth technique, the researchers report. The self-aligned orientation of the nanowires is determined by the crystal structure of the substrate and certain growth parameters.

In earlier work, Li and Fortuna demonstrated they could grow the nanowires and then transfer-print them on other substrates, including silicon, for heterogeneous integration. “Transferring the self-aligned planar nanowires while maintaining both their position and alignment could enable flexible electronics and photonics at a true nanometer scale,” the researchers wrote in the December 2008 issue of the journal Nano Letters.

In work presented in the current paper, the researchers grew the gallium-arsenide nanowire channel in place, instead of transferring it. In contrast to the common types of non-planar gallium arsenide nanowires, the researchers’ planar nanowire was free from twin defects, which are rotational defects in the crystal structure that decrease the mobility of the charge carriers.

“By replacing the standard channel in a metal-semiconductor field-effect transistor with one of our planar nanowires, we demonstrated that the defect-free nanowire’s electron mobility was indeed as high as the corresponding bulk value,” Fortuna said. “The high electron mobility nanowire channel could lead to smaller, better and faster devices.”

Considering their planar, self-aligned and transferable nature, the nanowire channels could help create higher performance transistors for next-generation integrated circuit applications, Li said.

The high quality planar nanowires can also be used in nano-injection lasers for use in optical communications.

The researchers are also developing new device concepts driven by further engineering of the planar one-dimensional nanostructure.




The work was supported by the National Science Foundation.

December 19, 2008

Nanotech transistor from IBM to improve cell phone

Filed under: Business, Technology — Tags: , , , , , , , — David Kirkpatrick @ 11:11 am

I’ve done some recent blogging on nanotech transistors (this post is on the very subject of the post you’re reading) and it looks like IBM has something gearing up for market-ready to improve cell phone range and battery life.

From the second link:

Researchers at the company are using nanotechnology to build a future generation of wireless transceivers that are much more sensitive than the ones found in phones today. They’ll also be made with a less expensive material, according to IBM. The catch is that the new chips probably won’t make it into consumers’ hands for another five or ten years.

The scientists, sponsored by DARPA (the U.S. Defense Advanced Research Projects Agency), have built prototype transistors with the new material, called graphene. It is a form of graphite that consists of a single layer of carbon atoms arranged in a honeycomb pattern. Graphene’s structure allows electrons to travel through it very quickly and gives it greater efficiency than existing transceiver chip materials, said Yu-Ming Lin, a research staff member at IBM in Yorktown Heights, New York. The project is part of DARPA’s CERA (Carbon Electronics for radio-frequency applications) program.

December 17, 2008

More nanotech transistor news

Just blogged on a Technology Review story a few minutes ago, and here’s a press release on another nanotech transistor breakthrough. Bonus because this one even involves LEDs.

The release:

USC researchers print dense lattice of transparent nanotube transistors on flexible base

Low-temperature process produces both n-type and p-type transistors; allows embedding of LEDs

IMAGE: See-through circuit makers: Hsaioh-Kang Chang, left, and Fumiaki Ishikawa, with their transparent, flexible transistor array.

Click here for more information. 

It’s a clear, colorless disk about 5 inches in diameter that bends and twists like a playing card, with a lattice of more than 20,000 nanotube transistors capable of high-performance electronics printed upon it using a potentially inexpensive low-temperature process.

Its University of Southern California creators believe the prototype points the way to such long sought after applications as affordable “head-up” car windshield displays. The lattices could also be used to create cheap, ultra thin, low-power “e-paper” displays.

They might even be incorporated into fabric that would change color or pattern as desired for clothing or even wall covering, into nametags, signage and other applications.

A team at the USC Viterbi School of Engineering created the new device, described and illustrated in a just-published paper on “Transparent Electronics Based on Printed Aligned Nanotubes on Rigid and Flexible Structures” in the journal ACS Nano.

Graduate students Fumiaki Ishikawa and Hsiaoh-Kang Chang worked under Professor Chongwu Zhou of the School’s Ming Hsieh Department of Electrical Engineering on the project, solving the problems of attaching dense matrices of carbon nanotubes not just to heat-resistant glass but also to flexible but highly heat-vulnerable transparent plastic substrates.

The researchers not only created printed circuit lattices of nanotube-based transistors to the transparent plastic but also additionally connected them to commercial gallium nitrate (GaN) light-emitting diodes, which change their luminosity by a factor of 1,000 as they are energized.

“Our results suggest that aligned nanotubes have great potential to work as building blocks for future transparent electronics,” say the researchers.

The thin transparent thin-film transistor technology developed employs carbon nanotubes – tubes with walls one carbon atom thick – as the active channels for the circuits, controlled by iridium-tin oxide electrodes which function as sources, gates and drains.

Earlier attempts at transparent devices used other semiconductor materials with disappointing electronic results, enabling one kind of transistor (n-type); but not p-types; both types are needed for most applications.

The critical improvement in performance, according to the research, came from the ability to produce extremely dense, highly patterned lattices of nanotubes, rather than random tangles and clumps of the material. The Zhou lab has pioneered this technique over the past three years.

The paper contains a description of how the new devices are made.

“These nanotubes were first grown on quartz substrates and then transferred to glass or PET substrates with pre-patterned indium-tin oxide (ITO) gate electrodes, followed by patterning of transparent source and drain electrodes. In contrast to random networked nanotubes, the use of massively aligned nanotubes enabled the devices to exhibit high performance, including high mobility, good transparency, and mechanical flexibility.

“In addition, these aligned nanotube transistors are easy to fabricate and integrate, as compared to individual nanotube devices. The transfer printing process allowed the devices to be fabricated through low temperature process, which is particularly important for realizing transparent electronics on flexible substrates. … While large manufacturability must be addressed before practical applications are considered, our work has paved the way for using aligned nanotubes for high-performance transparent electronics ”




Ishikawa and Chang are the principal authors of the paper. Viterbi School graduate students Koungmin Ryu, Pochiang Chen, Alexander Badmaev, Lewis Gomez De Arco, and Guozhen Shen also participated in the project. Zhou, an associate professor, holds the Viterbi School’s Jack Munushian Early Career Chair.

The Focus Center Research Program (FCRP FENA) and the National Science Foundation supported the research. The original article can be read at: http://pubs.acs.org/doi/abs/10.1021/nn800434d


Graphene improving transistors

Haven’t blogged about the nanotech material graphene in a while. Here’s some exciting news from Technology Review.

From the link:

A pair of research groups, working independently, report making graphene-based transistors that work at the highest frequencies reported to date. The new transistors are a promising first step toward ultrahigh radio-frequency (RF) transistors, which could be useful for wireless communications, remote sensing, radar systems, and weapons imaging systems.

The reports come from researchers at the IBM T. J. Watson Research Center in Yorktown Heights, NY, and at the HRL Laboratories in Malibu, CA. The IBM transistors work at frequencies up to 26 gigahertz. Both the IBM and HRL work was funded by the U.S. military’s Defense Advanced Research Projects Agency (DARPA). Kostya Novoselov, a physicist and graphene researcher at the University of Manchester, in the U.K., says that the results are “a really big step forward to demonstrating that high-frequency graphene transistors should work.”

Graphene, a flat sheet of carbon atoms, is a promising material for RF transistors. Typical RF transistors are made from silicon or more expensive semiconductors like indium phosphide. In graphene, for the same voltage, electrons zip around 10 times faster than in indium phosphide, or 100 times faster than in silicon.

Graphene transistors will also consume less power and could turn out to be cheaper than those made from silicon or indium phosphide. Yu-Ming Lin, who led the work at IBM, says that silicon technology is extremely mature, but graphene could “achieve device performance that may never be obtained with conventional semiconductors.”

Jeong-Sun Moon, HRL Laboratories

Speedy carbon devices: Researchers at HRL Laboratories create high-frequency transistors on top of two-inch-wide graphene pieces by patterning metal electrodes and depositing insulating aluminum oxide on top of the graphene. Credit: Jeong-Sun Moon, HRL Laboratories

July 23, 2008

Paper-based transistors

Filed under: Science, Technology — Tags: , , , — David Kirkpatrick @ 4:55 pm

Very interesting tech news on the first paper-based transistors:

Portuguese researchers have created the first paper-based transistors. To be more precise, they’ve made the first field effect transistors (FET) with a paper interstrate layer. According to the research team, these new transistors offer the same level of performance as ’state-of-the-art oxide based thin film transistors (TFTs) produced on glass or crystalline silicon substrates.’ Possible applications for these paper-based transistors include new disposable electronics devices, such as paper displays, smart labels, bio-applications or RFID tags. But read more…

First paper interstrate thin film transistors

You can see above the first paper interstrate thin film transistors developed by the Portuguese team. (Credit: CENIMAT) Here is a link to a larger version of this picture.

(Hat tip: KurzweilAI.net)


April 18, 2008

Single atom thick graphene transistors

Filed under: Science, Technology — Tags: , , , , , — David Kirkpatrick @ 2:48 pm

From KurzweilAI.net:

Atom-thick material runs rings around silicon
NewScientist.com news service, April 17, 2008

University of Manchester researchers have used graphene to make some of the smallest transistors ever, at one atom thick and ten atoms wide.

credit: MU Mesoscopic Physics Group

They found that cutting small quantum dots of graphene gave the material switchable conductivity. Dots just a few nanometers across trap electrons due to quantum effects, and applying a magnetic field to the smallest dots lets current flow again, making a switchable transistor. The smallest dots that worked as transistors contained as few as five carbon rings–around 10 atoms or 1 nm wide.

Previous graphene transistors were significantly bigger–ribbons 10 nm across and many times longer.

Read Original Article>>