Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. Space Industry and Business News .




TECH SPACE
Tungstenite triangles emit light
by Staff Writers
London, UK (SPX) Feb 28, 2013


Penn State researchers have synthesized triangular single layers of tungsten disulphide. The edges of the triangles exhibit extraordinary photoluminescence, while the interior area does not. The photoluminescent signal disappears as the number of layers increases. (Courtesy: Terrones Lab, Penn State University)

Researchers in the US have succeeded in growing single atomic layers of the naturally occurring mineral tungstenite for the first time. The sheets appear to have unusual photoluminescence properties that might be exploited in optics devices like lasers and light-emitting diodes.

2D materials have dramatically different electronic and mechanical properties from their 3D counterparts and so may find use in a host of novel device applications. Until now, however, most research in this field has focused on the most famous of 2D materials, graphene, but the fact that this material lacks a direct electronic band gap means that scientists are now starting to look at other 2D candidates too.

A team led by Mauricio Terrones and Vincent Crespi of Penn State university in the US grew monolayers of tungstenite (WS2) by depositing tiny crystals of tungsten oxide less than a nanometre tall and then passing these crystals though sulphur vapour at high temperatures of 850C. The result - monolayers of tungsten disulphide arranged in a honeycombed pattern of triangles comprising tungsten atoms bonded to sulphur atoms.

"We were astonished that we could grow such perfect, atomically thick triangle shapes using a chemical vapour deposition method," Terrones told physicsworld.com.

"Moreover, and again to our surprise, we observed that these triangles glow quite strongly at their edges rather than at their centres - a peripheral photoluminescence effect that we never expected and which has not been reported on before."

Photoluminescence occurs when charge carriers (electrons and holes) recombine in a structure to emit light of a different wavelength from that used to initially excite the material.

Normally, light emission is a delicate thing, explained Crespi, and structural defects - like edges - prevent light emission as they tend to give excited electrons and holes ways of recombining without emitting light. "We saw just the opposite effect," he said, "in that the structural defects created close to the edges of a triangle seem to be the favoured place for emitting light."

Direct band gap
2D systems are intrinsically different from their bulk 3D counterparts, and WS2 is no exception. While the bulk material is an indirect band gap semiconductor, the single-layer material boasts a direct band gap. Direct band gaps are important in semiconductors because they allow devices made from these materials to emit light efficiently - as in this case.

According to the Penn State team, the WS2 triangles might find applications in optoelectronics. "They might even come in handy as biomarkers or in drug delivery, but much more research still needs to be carried out before we can say this with any certainty," added Terrones. "They could also be useful in a new generation of planar, 2D optoelectronic devices, such as light-emitting diodes - where we control the propagation of light in thin film layers of material - and even in laser technology."

The researchers now plan to grow other 2D materials that have different optical and electronic properties. Some examples in the pipeline include MoSe2, NbS2 and WSe2, revealed Crespi. "We would also like to better understand and control the light emission from 2D materials in general, and try our hand at sculpting the triangles into multicomponent devices."

The work is detailed in Nano Letters.

.


Related Links
Institute of Physics
Space Technology News - Applications and Research






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





TECH SPACE
Sustainable new catalysts fueled by a single proton
Chestnut Hill MA (SPX) Feb 26, 2013
Chemists at Boston College have designed a new class of catalysts triggered by the charge of a single proton, the team reports in the most recent edition of the journal Nature. The simple organic molecules offer a sustainable and highly efficient platform for chemical reactions that produce sets of molecules crucial to advances in medicine and the life sciences. Unearthing a reliable, trul ... read more


TECH SPACE
Ancient Egyptian pigment points to new security ink technology

Laser mastery narrows down sources of superconductivity

In probing mysteries of glass, researchers find a key to toughness

Glasses.com turns heads with 3-D iPad app

TECH SPACE
Boeing Receives USAF Contract for Integrated C4ISR Targeting Solution

Air Operations Center Modernization Program PDR Completed

Advanced Communications Waveforms Ported To Navy Digital Modular Radios

Astrium tapped for communications network

TECH SPACE
'Faulty Ukrainian Parts' Blamed for Zenit Launch Failure

The light-lift member of Arianespace's launcher family is readied for its second mission

SpaceX 2 Launch Set for March 1

NASA Releases Glory Taurus XL Launch Failure Report Summary

TECH SPACE
USAF Awards Lockheed Martin Contracts to Begin Work on Next Set of GPS III Satellites

Telit Offers COMBO 2G Chip For Multi Satellite Positioning Receiver

Boeing Awarded USAF Contract to Continue GPS Modernization

A system that improves the precision of GPS in cities by 90 percent

TECH SPACE
US chooses Brazilian plane to outfit Afghan force

F-35 soaring costs trouble Australia

Larry Ellison buys Hawaiian airline to go with island

DARPA Developing Next Generation Of Vertical Flight Technology

TECH SPACE
Rutgers physicists test highly flexible organic semiconductors

Quantum computers turn mechanical

Boeing Acquires CPU Tech's Microprocessor Business

Organic electronics: how to make contact between carbon compounds and metal

TECH SPACE
NASA's Aquarius Sees Salty Shifts

Northrop Grumman Delivers First Communications Payload for USAF's Enhanced Polar System

NASA Selects Launch Services for ICESat-2 Mission

New approach alters malaria maps

TECH SPACE
China lawyer appeals 'state secret' pollution claim

Sewage lagoons remove most - but not all - pharmaceuticals

Olympics: Illegal dump tarnishes 'green' Sochi Games

China admits pollution-linked 'cancer villages'




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal 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