Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Beyond Silicon: Transistors without Semiconductors

24.06.2013
For decades, electronic devices have been getting smaller, and smaller, and smaller. It’s now possible—even routine—to place millions of transistors on a single silicon chip.

But transistors based on semiconductors can only get so small. “At the rate the current technology is progressing, in 10 or 20 years, they won’t be able to get any smaller,” said physicist Yoke Khin Yap of Michigan Technological University. “Also, semiconductors have another disadvantage: they waste a lot of energy in the form of heat.”


Electrons flash across a series of gold quantum dots on boron nitride nanotubes. Michigan Tech scientists made the quantum-tunneling device, which acts like a transistor at room temperature, without using semiconducting materials. Yoke Khin Yap graphic

Scientists have experimented with different materials and designs for transistors to address these issues, always using semiconductors like silicon. Back in 2007, Yap wanted to try something different that might open the door to a new age of electronics.

“The idea was to make a transistor using a nanoscale insulator with nanoscale metals on top,” he said. “In principle, you could get a piece of plastic and spread a handful of metal powders on top to make the devices, if you do it right. But we were trying to create it in nanoscale, so we chose a nanoscale insulator, boron nitride nanotubes, or BNNTs for the substrate.”

Yap’s team had figured out how to make virtual carpets of BNNTs,which happen to be insulators and thus highly resistant to electrical charge. Using lasers, the team then placed quantum dots (QDs) of gold as small as three nanometers across on the tops of the BNNTs, forming QDs-BNNTs. BNNTs are the perfect substrates for these quantum dots due to their small, controllable, and uniform diameters, as well as their insulating nature. BNNTs confine the size of the dots that can be deposited.

In collaboration with scientists at Oak Ridge National Laboratory (ORNL), they fired up electrodes on both ends of the QDs-BNNTs at room temperature, and something interesting happened. Electrons jumped very precisely from gold dot to gold dot, a phenomenon known as quantum tunneling.

“Imagine that the nanotubes are a river, with an electrode on each bank. Now imagine some very tiny stepping stones across the river,” said Yap. “The electrons hopped between the gold stepping stones. The stones are so small, you can only get one electron on the stone at a time. Every electron is passing the same way, so the device is always stable.”

Yap’s team had made a transistor without a semiconductor. When sufficient voltage was applied, it switched to a conducting state. When the voltage was low or turned off, it reverted to its natural state as an insulator.

Furthermore, there was no “leakage”: no electrons from the gold dots escaped into the insulating BNNTs, thus keeping the tunneling channel cool. In contrast, silicon is subject to leakage, which wastes energy in electronic devices and generates a lot of heat.

Other people have made transistors that exploit quantum tunneling, says Michigan Tech physicist John Jaszczak, who has developed the theoretical framework for Yap’s experimental research. However, those tunneling devices have only worked in conditions that would discourage the typical cellphone user.

“They only operate at liquid-helium temperatures,” said Jaszczak.

The secret to Yap’s gold-and-nanotube device is its submicroscopic size: one micron long and about 20 nanometers wide. ”The gold islands have to be on the order of nanometers across to control the electrons at room temperature,” Jaszczak said. “If they are too big, too many electrons can flow.” In this case, smaller is truly better: “Working with nanotubes and quantum dots gets you to the scale you want for electronic devices.”

“Theoretically, these tunneling channels can be miniaturized into virtually zero dimension when the distance between electrodes is reduced to a small fraction of a micron,” said Yap.

Yap has filed for a full international patent on the technology.

Their work is described in the article “Room Temperature Tunneling Behavior of Boron Nitride Nanotubes Functionalized with Gold Quantum Dots,” published online on June 17 in Advanced Materials. In addition to Yap and Jaszczak, coauthors include research scientist Dongyan Zhang, postdoctoral researchers Chee Huei Lee and Jiesheng Wang, and graduate students Madhusudan A. Savaikar, Boyi Hao, and Douglas Banyai of Michigan Tech; Shengyong Qin, Kendal W. Clark and An-Ping Li of the Center for Nanophase Materials Sciences at ORNL; and Juan-Carlos Idrobo of the Materials Science and Technology Division of ORNL.

The work was funded by the Office of Basic Energy Sciences of the US Department of Energy (Award # DE-FG02-06ER46294, PI:Y.K.Yap) and was conducted in part at ORNL (Projects CNMS2009-213 and CNMS2012-083, PI: Y.K.Yap).

Michigan Technological University (www.mtu.edu) is a leading public research university developing new technologies and preparing students to create the future for a prosperous and sustainable world. Michigan Tech offers more than 130 undergraduate and graduate degree programs in engineering; forest resources; computing; technology; business; economics; natural, physical and environmental sciences; arts; humanities; and social sciences.

Marcia Goodrich | EurekAlert!
Further information:
http://www.mtu.edu

More articles from Physics and Astronomy:

nachricht Significantly more productivity in USP lasers
06.12.2016 | Fraunhofer-Institut für Lasertechnik ILT

nachricht Shape matters when light meets atom
05.12.2016 | Centre for Quantum Technologies at the National University of Singapore

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Silicon solar cell of ISFH yields 25% efficiency with passivating POLO contacts

08.12.2016 | Power and Electrical Engineering

NTU scientists build new ultrasound device using 3-D printing technology

07.12.2016 | Health and Medicine

The balancing act: An enzyme that links endocytosis to membrane recycling

07.12.2016 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>