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




CHIP TECH
ORNL makes scalable arrays of 'building blocks' for ultrathin electronics
by Staff Writers
Oak Ridge TN (SPX) Jul 27, 2015


Complex, scalable arrays of semiconductor heterojunctions - promising building blocks for future electronics - were formed within a two-dimensional crystalline monolayer of molybdenum deselenide by converting lithographically exposed regions to molybdenum disulfide using pulsed laser deposition of sulfur atoms. Sulfur atoms (green) replaced selenium atoms (red) in lithographically exposed regions (top) as shown by Raman spectroscopic mapping (bottom). Image courtesy Oak Ridge National Laboratory, U.S. Dept. of Energy. For a larger version of this image please go here.

Semiconductors, metals and insulators must be integrated to make the transistors that are the electronic building blocks of your smartphone, computer and other microchip-enabled devices. Today's transistors are miniscule--a mere 10 nanometers wide--and formed from three-dimensional (3D) crystals.

But a disruptive new technology looms that uses two-dimensional (2D) crystals, just 1 nanometer thick, to enable ultrathin electronics. Scientists worldwide are investigating 2D crystals made from common layered materials to constrain electron transport within just two dimensions.

Researchers had previously found ways to lithographically pattern single layers of carbon atoms called graphene into ribbon-like "wires" complete with insulation provided by a similar layer of boron nitride. But until now they have lacked synthesis and processing methods to lithographically pattern junctions between two different semiconductors within a single nanometer-thick layer to form transistors, the building blocks of ultrathin electronic devices.

Now for the first time, researchers at the Department of Energy's Oak Ridge National Laboratory have combined a novel synthesis process with commercial electron-beam lithography techniques to produce arrays of semiconductor junctions in arbitrary patterns within a single, nanometer-thick semiconductor crystal.

The process relies upon transforming patterned regions of one existing, single-layer crystal into another. The researchers first grew single, nanometer-thick layers of molybdenum diselenide crystals on substrates and then deposited protective patterns of silicon oxide using standard lithography techniques. Then they bombarded the exposed regions of the crystals with a laser-generated beam of sulfur atoms.

The sulfur atoms replaced the selenium atoms in the crystals to form molybdenum disulfide, which has a nearly identical crystal structure. The two semiconductor crystals formed sharp junctions, the desired building blocks of electronics. Nature Communications reports the accomplishment.

"We can literally make any kind of pattern that we want," said Masoud Mahjouri-Samani, who co-led the study with David Geohegan. Geohegan, head of ORNL's Nanomaterials Synthesis and Functional Assembly Group at the Center for Nanophase Materials Sciences, is the principal investigator of a Department of Energy basic science project focusing on the growth mechanisms and controlled synthesis of nanomaterials.

Millions of 2D building blocks with numerous patterns may be made concurrently, Mahjouri-Samani added. In the future, it might be possible to produce different patterns on the top and bottom of a sheet. Further complexity could be introduced by layering sheets with different patterns.

Added Geohegan, "The development of a scalable, easily implemented process to lithographically pattern and easily form lateral semiconducting heterojunctions within two-dimensional crystals fulfills a critical need for 'building blocks' to enable next-generation ultrathin devices for applications ranging from flexible consumer electronics to solar energy."

Tuning the bandgap
"We chose pulsed laser deposition of sulfur because of the digital control it gives you over the flux of the material that comes to the surface," said Mahjouri-Samani. "You can basically make any kind of intermediate alloy. You can just replace, say, 20 percent of the selenium with sulfur, or 30 percent, or 50 percent." Added Geohegan, "Pulsed laser deposition also lets the kinetic energy of the sulfur atoms be tuned, allowing you to explore a wider range of processing conditions."

It is important that by controlling the ratio of sulfur to selenium within the crystal, the researchers can tune the bandgap of the semiconductors, an attribute that determines electronic and optical properties. To make optoelectronic devices such as electroluminescent displays, microchip fabricators integrate semiconductors with different bandgaps. For example, molybdenum disulfide's bandgap is greater than molybdenum diselenide's.

Applying voltage to a crystal containing both semiconductors causes electrons and "holes" (positive charges created when electrons vacate) to move from molybdenum disulfide into molybdenum diselenide and recombine to emit light at the bandgap of molybdenum diselenide. For that reason, engineering the bandgaps of monolayer systems can allow the generation of light with many different colors, as well as enable other applications such as transistors and sensors, Mahjouri-Samani said.

Next the researchers will see if their pulsed laser vaporization and conversion method will work with atoms other than sulfur and selenium. "We're trying to make more complex systems in a 2D plane--integrate more ingredients, put in different building blocks--because at the end of the day, a complete working device needs different semiconductors and metals and insulators," Mahjouri-Samani said.

To understand the process of converting one nanometer-thick crystal into another, the researchers used powerful electron microscopy capabilities available at ORNL, notably atomic-resolution Z-contrast scanning transmission electron microscopy, which was developed at the lab and is now available to scientists worldwide using the Center for Nanophase Materials Sciences.

Employing this technique, electron microscopists Andrew Lupini and visiting scientist Leonardo Basile imaged hexagonal networks of individual columns of atoms in the nanometer-thick molybdenum diselenide and molybdenum disulfide crystals.

"We could directly distinguish between sulfur and selenium atoms by their intensities in the image," Lupini said. "These images and electron energy loss spectroscopy allowed the team to characterize the semiconductor heterojunction with atomic precision."

The title of the paper is "Patterned Arrays of Lateral Heterojunctions within Monolayer Two-Dimensional Semiconductors."


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only


.


Related Links
Oak Ridge National Laboratory
Computer Chip Architecture, Technology and Manufacture
Nano Technology News From SpaceMart.com






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

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




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





CHIP TECH
SK Hynix Q2 profit misses analyst estimates as chip prices fall
Seoul (AFP) July 23, 2015
South Korean chipmaker SK Hynix reported a 65 percent on-year increase in second quarter net profit on Thursday, missing analyst estimates, as slowing demand for personal computers and smartphones dampened memory chip prices. But its shares jumped more than five percent in early morning trade after the company announced a buyback of 22 million shares worth 859.1 billion won ($742 million). ... read more


CHIP TECH
NASA Sets Sights on Robot-Built Moon Colony

Russia to Land Space Vessel on Moon's Polar Region in 2019

Moon engulfed in permanent, lopsided dust cloud

Crashing comets may explain mysterious lunar swirls

CHIP TECH
Celebrating 50 years of Martian imagery

Curiosity rover finds evidence of Mars' primitive continental crust

Never Get Lost on Mars Again With NASA's New Red Planet Map

Opportunity Rover's 7th Mars Winter to Include New Study Area

CHIP TECH
Planetary Resources' First Spacecraft Successfully Deployed

NASA selects leading-edge concepts for continued study

US selects four astronauts for commercial flight

Docking Adapter Sets Stage for Commercial Crew Crew

CHIP TECH
Chinese earth station is for exclusively scientific and civilian purposes

Cooperation in satellite technology put Belgium, China to forefront

China set to bolster space, polar security

China's super "eye" to speed up space rendezvous

CHIP TECH
Rocket carrying Russian, Japanese, US crew docks with ISS

Student satellite wins green light for Station deployment

'Jedi' astronauts say 'no fear' as they gear for ISS trip

Relief as Russian cargo ship docks at space station

CHIP TECH
Ariane 5 orbits Star One C4 and MSG-4 on Arianespace's sixth flight in 2015

CRS-7 Investigation Update

Supporting Arianespace's mission cadence: A new fueling facility is ready

30 launches planned in next three fiscals: ISRO chief

CHIP TECH
ARIEL mission to reveal 'Brave New Worlds' among exoplanets

Astronomers bring a new hope to find 'Tatooine' planets

Bricks to build an Earth found in every planetary system

Observing the birth of a planet

CHIP TECH
Cold crystallization has a dual nature

Trapped light orbits within an intriguing material

For faster, larger graphene add a liquid layer

NATO orders deployable 3D air defense radars




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.