Subscribe free to our newsletters via your
. 24/7 Space News .

Lighting the Way to Graphene-based Devices
by Lynn Yarris for Berkeley News
Berkeley CA (SPX) May 20, 2014

Long Ju, Feng Wang and Jairo Velasco Jr., have been using visible light to charge-dope semiconductors made from graphene and boron nitride. Image courtesy Roy Kaltschmidt.

Graphene continues to reign as the next potential superstar material for the electronics industry, a slimmer, stronger and much faster electron conductor than silicon. With no natural energy band-gap, however, graphene's superfast conductance can't be switched off, a serious drawback for transistors and other electronic devices.

Various techniques have been deployed to overcome this problem with one of the most promising being the integration of ultrathin layers of graphene and boron nitride into two-dimensional heterostructures. As conductors, these bilayered hybrids are almost as fast as pure graphene, plus they are well-suited for making devices.

However, tailoring the electronic properties of graphene boron nitride (GBN) heterostructures has been a tricky affair, involving chemical doping or electrostatic-gating - until now.

Researchers with Berkeley Lab and the University of California (UC) Berkeley have demonstrated a technique whereby the electronic properties of GBN heterostructures can be modified with visible light.

Feng Wang, a condensed matter physicist with Berkeley Lab's Materials Sciences Division and UC Berkeley's Physics Department, as well as an investigator for the Kavli Energy NanoSciences Institute at Berkeley, led a study in which photo-induced doping of GBN heterostructures was used to create p-n junctions and other useful doping profiles while preserving the material's remarkably high electron mobility.

"We've demonstrated that visible light can induce a robust writing and erasing of charge-doping in GBN heterostructures without sacrificing high carrier mobility," Wang says.

"The use of visible light gives us incredible flexibility and, unlike electrostatic gating and chemical doping, does not require multi-step fabrication processes that reduce sample quality. Additionally, different patterns can be imparted and erased at will, which was not possible with doping techniques previously used on GBN heterostructures."

Graphene is a single layer of carbon atoms arranged in a hexagonal lattice. Boron nitride is a layered compound that features a similar hexagonal lattice - in fact hexagonal boron nitride is sometimes referred to as "white graphene."

Bound together by the relatively weak intermolecular attraction known as the van der Waals force, GBN heterostructures have shown high potential to serve as platforms not only for high-electron-mobility transistors, but also for optoelectronic applications, including photodetectors and photovoltaic cells. The key to future success will be the ability to dope these materials in a commercially scalable manner.

The photo-induced modulation doping technique developed by Wang and a large team of collaborators meets this requirement as it is comparable to the photolithography schemes widely used today for mass production in the semiconductor industry.

Illumination of a GBN heterostructure even with just an incandescent lamp can modify electron-transport in the graphene layer by inducing a positive-charge distribution in the boron nitride layer that becomes fixed when the illumination is turned off.

"We've shown show that this photo-induced doping arises from microscopically coupled optical and electrical responses in the GBN heterostructures, including optical excitation of defect transitions in boron nitride, electrical transport in graphene, and charge transfer between boron nitride and graphene," Wang says. "This is analogous to the modulation doping first developed for high-quality semiconductors."

While the photo-induced modulation doping of GBN heterostructures only lasted a few days if the sample was kept in darkness - further exposure to light erased the effect - this is not a concern as Wang explains.

"A few days of modulation doping are sufficient for many avenues of scientific inquiry, and for some device applications, the rewritability we can provide is needed more than long term stability," he says. "For the moment, what we have is a simple technique for inhomogeneous doping in a high-mobility graphene material that opens the door to novel scientific studies and applications."

A paper on this research has been published in the journal Nature Nanotechnology entitled "Photoinduced doping in heterostructures of graphene and boron nitride." Co-authors are Long Ju, Jairo Velasco Jr., Edwin Huang, Salman Kahn, Casey Nosiglia, Hsin-Zon Tsai, Wei Yang, Takashi Taniguchi, Kenji Watanabe, Yuanbo Zhang, Guangyu Zhang, Michael Crommie and Alex Zettl.


Related Links
Berkeley Lab
Carbon Worlds - where graphite, diamond, amorphous, fullerenes meet

Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks DiggDigg RedditReddit GoogleGoogle

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

Rapid bilayer graphene synthesis for high-performance transistors
Santa Barbara CA (SPX) May 14, 2014
Researchers at University of California, Santa Barbara, in collaboration with Rice University, have recently demonstrated a rapid synthesis technique for large-area Bernal (or AB) stacked bilayer graphene films that can open up new pathways for digital electronics and transparent conductor applications. The invention also includes the first demonstration of a bilayer graphene double-gate f ... read more

LRO View of Earth

Saturn in opposition tonight, will appear next to the moon

Russia to begin Moon colonization in 2030

Astrobotic Partners With NASA To Develop Robotic Lunar Landing Capability

When fantasy becomes reality: first seeds to be planted soon on Mars

NASA Rover Gains Martian Vista From Ridgeline

Opportunity Explores Region of Aluminum Clay Minerals

NASA's Saucer-Shaped Craft Preps for Flight Test

Airbus design of European service module for Orion approved by ESA

Swiss Space Systems launch the ZeroG experience

Britain's Longitude Prize back after 300-year absence

Sea level rise forces US space agency to retreat

Moon rover Yutu comes closer to public

The Phantom Tiangong

New satellite launch center to conduct joint drill

China issues first assessment on space activities

New ISS Expedition Unaffected by Proton Crash

US-Russian Tensions Roiling Outer Space Cooperation

Scientists Seek Answers With Space Station Thyroid Cancer Study

Rounding up the BCATs on the ISS

SpaceX's Dragon spacecraft returns to Earth from space station

Third-stage engine glitch causes Proton-M accident

Russia's Roscosmos plans to launch two more Protons this year

SpaceX Dragon Spacecraft Returns Critical NASA Science from ISS

Starshade Could Help Photograph Distant Planets

Giant telescope tackles orbit and size of exoplanet

Odd planet, so far from its star

New Exomoon Hunting Technique Could Find Solar System-like Moons

MIPT Experts Reveal the Secret of Radiation Vulnerability

Pentagon plans multi-billion dollar project to combat space junk

Russian space agency to create equipment for monitoring space debris

Electrons hurtle into the interior of a new class of quantum materials

The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.