Featured Research

from universities, journals, and other organizations

Real-world graphene devices may have a bumpy ride

Date:
January 24, 2011
Source:
National Institute of Standards and Technology (NIST)
Summary:
New measurements by researchers may affect the design of devices that rely on the high mobility of electrons in graphene -- they show that layering graphene on a substrate transforms its bustling speedway into steep hills and valleys that make it harder for electrons to get around.

Electronics researchers love graphene. A two-dimensional sheet of carbon one atom thick, graphene is like a superhighway for electrons, which rocket through the material with 100 times the mobility they have in silicon. But creating graphene-based devices will be challenging, say researchers at the National Institute of Standards and Technology (NIST), because new measurements show that layering graphene on a substrate transforms its bustling speedway into steep hills and valleys that make it harder for electrons to get around.

In a new article in Nature Physics, NIST scientists also say that graphene may be an ideal medium for probing interactions between electric conductors and insulators using a scanning tunneling microscope (STM).

According to NIST Fellow Joseph Stroscio, graphene's ideal properties are only available when it is isolated from the environment.

"To get the most benefit from graphene, we have to understand fully how graphene's properties change when put in real-world conditions, such as part of a device where it is in contact with other kinds of materials," Stroscio says.

Typical semiconductor chips are a complicated "sandwich" of alternating conducting, semiconducting and insulating layers and structures. To perform their experiment, the NIST group made their own sandwich with a single atomic sheet of graphene and another conductor separated by an insulating layer. When the bottom conductor is charged, it induces an equal and opposite charge in the graphene.

Examined under an STM, which is sensitive to the charged state of the graphene, the high electron mobility should make the graphene look like a featureless plane. But, says NIST researcher Nikolai Zhitenev, "What we found is that variations in the electrical potential of the insulating substrate are interrupting the orbits of the electrons in the graphene, creating wells where the electrons pool and reducing their mobility."

This effect is especially pronounced when the group exposes the substrate-mounted graphene to high magnetic fields. Then the electrons, already made sluggish by the substrate interactions, lack the energy to scale the mountains of resistance and settle into isolated pockets of "quantum dots," nanometer-scale regions that confine electrical charges in all directions.

It's not all bad news. Direct access to the graphene with a scanned probe also makes it possible to investigate the physics of other substrate interactions on a nanoscopic scale, something which is less possible in conventional semiconductor devices where the important transport layers are buried below the surface.

"Usually, we cannot study insulators at atomic scale," says Stroscio. "The STM works with a closed loop system that keeps a constant tunneling current by adjusting the tip-sample distance. On an insulator there is no current available, so the system will keep pushing the tip closer to the substrate until it eventually crashes into the surface. The graphene lets us get close enough to these substrate materials to study their electrical properties, but not so close that we damage the substrate and instrument."


Story Source:

The above story is based on materials provided by National Institute of Standards and Technology (NIST). Note: Materials may be edited for content and length.


Journal Reference:

  1. Suyong Jung, Gregory M. Rutter, Nikolai N. Klimov, David B. Newell, Irene Calizo, Angela R. Hight-Walker, Nikolai B. Zhitenev, Joseph A. Stroscio. Evolution of microscopic localization in graphene in a magnetic field from scattering resonances to quantum dots. Nature Physics, 2011; DOI: 10.1038/nphys1866

Cite This Page:

National Institute of Standards and Technology (NIST). "Real-world graphene devices may have a bumpy ride." ScienceDaily. ScienceDaily, 24 January 2011. <www.sciencedaily.com/releases/2011/01/110120111041.htm>.
National Institute of Standards and Technology (NIST). (2011, January 24). Real-world graphene devices may have a bumpy ride. ScienceDaily. Retrieved July 22, 2014 from www.sciencedaily.com/releases/2011/01/110120111041.htm
National Institute of Standards and Technology (NIST). "Real-world graphene devices may have a bumpy ride." ScienceDaily. www.sciencedaily.com/releases/2011/01/110120111041.htm (accessed July 22, 2014).

Share This




More Matter & Energy News

Tuesday, July 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Government Approves East Coast Oil Exploration

Government Approves East Coast Oil Exploration

AP (July 18, 2014) The Obama administration approved the use of sonic cannons to discover deposits under the ocean floor by shooting sound waves 100 times louder than a jet engine through waters shared by endangered whales and turtles. (July 18) Video provided by AP
Powered by NewsLook.com
Sunken German U-Boat Clearly Visible For First Time

Sunken German U-Boat Clearly Visible For First Time

Newsy (July 18, 2014) The wreckage of the German submarine U-166 has become clearly visible for the first time since it was discovered in 2001. Video provided by Newsy
Powered by NewsLook.com
Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Reuters - US Online Video (July 17, 2014) President Barak Obama stopped by at a lunch counter in Delaware before making remarks about boosting the nation's infrastructure. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com
Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

TheStreet (July 16, 2014) Oil Futures are bouncing back after tumbling below $100 a barrel for the first time since May yesterday. Jeff Grossman is the president of BRG Brokerage and trades at the NYMEX. Grossman tells TheStreet the Middle East is always a concern for oil traders. Oil prices were pushed down in recent weeks on Libya increasing its production. Supply disruptions in Iraq fading also contributed to prices falling. News from China's economic front showing a growth for the second quarter also calmed fears on its slowdown. Jeff Grossman talks to TheStreet's Susannah Lee on this and more on the Energy Department's Energy Information Administration (EIA) report. Video provided by TheStreet
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins