Navigation Links
Competition for graphene
Date:8/26/2014

A new argument has just been added to the growing case for graphene being bumped off its pedestal as the next big thing in the high-tech world by the two-dimensional semiconductors known as MX2 materials. An international collaboration of researchers led by a scientist with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) has reported the first experimental observation of ultrafast charge transfer in photo-excited MX2 materials. The recorded charge transfer time clocked in at under 50 femtoseconds, comparable to the fastest times recorded for organic photovoltaics.

"We've demonstrated, for the first time, efficient charge transfer in MX2 heterostructures through combined photoluminescence mapping and transient absorption measurements," says Feng Wang, a condensed matter physicist with Berkeley Lab's Materials Sciences Division and the University of California (UC) Berkeley's Physics Department. "Having quantitatively determined charge transfer time to be less than 50 femtoseconds, our study suggests that MX2 heterostructures, with their remarkable electrical and optical properties and the rapid development of large-area synthesis, hold great promise for future photonic and optoelectronic applications."

Wang is the corresponding author of a paper in Nature Nanotechnology describing this research. The paper is titled "Ultrafast charge transfer in atomically thin MoS2/WS2 heterostructures." Co-authors are Xiaoping Hong, Jonghwan Kim, Su-Fei Shi, Yu Zhang, Chenhao Jin, Yinghui Sun, Sefaattin Tongay, Junqiao Wu and Yanfeng Zhang.

MX2 monolayers consist of a single layer of transition metal atoms, such as molybdenum (Mo) or tungsten (W), sandwiched between two layers of chalcogen atoms, such as sulfur (S). The resulting heterostructure is bound by the relatively weak intermolecular attraction known as the van der Waals force. These 2D semiconductors feature the same hexagonal "honeycombed" structure as graphene and superfast electrical conductance, but, unlike graphene, they have natural energy band-gaps. This facilitates their application in transistors and other electronic devices because, unlike graphene, their electrical conductance can be switched off.

"Combining different MX2 layers together allows one to control their physical properties," says Wang, who is also an investigator with the Kavli Energy NanoSciences Institute (Kavli-ENSI). "For example, the combination of MoS2 and WS2 forms a type-II semiconductor that enables fast charge separation. The separation of photoexcited electrons and holes is essential for driving an electrical current in a photodetector or solar cell."

In demonstrating the ultrafast charge separation capabilities of atomically thin samples of MoS2/WS2 heterostructures, Wang and his collaborators have opened up potentially rich new avenues, not only for photonics and optoelectronics, but also for photovoltaics.

"MX2 semiconductors have extremely strong optical absorption properties and compared with organic photovoltaic materials, have a crystalline structure and better electrical transport properties," Wang says. "Factor in a femtosecond charge transfer rate and MX2 semiconductors provide an ideal way to spatially separate electrons and holes for electrical collection and utilization."

Wang and his colleagues are studying the microscopic origins of charge transfer in MX2 heterostructures and the variation in charge transfer rates between different MX2 materials.

"We're also interested in controlling the charge transfer process with external electrical fields as a means of utilizing MX2 heterostructures in photovoltaic devices," Wang says.


'/>"/>

Contact: Lynn Yarris
lcyarris@lbl.gov
510-486-5375
DOE/Lawrence Berkeley National Laboratory
Source:Eurekalert  

Related biology technology :

1. MedImmune Announces Winners of Its 6th Annual Global Abstract Competition
2. Quality Standards Established for Competition to Identify Best Researchers in the US
3. DOE-CEA Partnership Awards Mentoring Services to Finalists in National Clean Energy Business Plan Competition
4. Lightning Brewery’s Craft Beer Old Tempestuous Ale Wins Best of Show at 2012 California State Fair Commercial Brewing Competition
5. Albany CrossFit Wins Competition By Raising $32,579 For St. Jude Children's Research Hospital
6. Assay Depot Launches Make Your Mark Science Competition For High School Students
7. Boston Childrens Hospital announces international genomics competition winner
8. First Suit Against Nobel Prize Organization Citing Defamation And Unfair Competition Practices Is Filed
9. The WAV-1 UV/VIS Holmium Oxide Calibration Standard by NSG Precision Stands Alone Above the Competition
10. Wasatch Photonics Named a Finalist in International Innovation Competition
11. Johns Hopkins Student Team Wins $10,000 Biotech Case Competition
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Competition for graphene
(Date:10/10/2017)... , ... October 10, 2017 , ... San Diego-based team ... its corporate rebranding initiative announced today. The bold new look is part of ... the company moves into a significant growth period. , It will also expand its ...
(Date:10/10/2017)... DALLAS , Oct. 10, 2017 International research firm ... IoT Strategy, will speak at the TMA 2017 Annual Meeting , ... key trends in the residential home security market and how smart safety ... ... "The ...
(Date:10/9/2017)... 2017  BioTech Holdings announced today identification and ... ProCell stem cell therapy prevents limb loss in ... demonstrated that treatment with ProCell resulted in more ... compared to standard bone marrow stem cell administration.  ... reduction of therapeutic effect.  ...
(Date:10/9/2017)... ... October 09, 2017 , ... ... in the medical journal, Epilepsia, Brain Sentinel’s SPEAC® System which uses the ... in detecting generalized tonic-clonic seizures (GTCS) using surface electromyography (sEMG). The prospective ...
Breaking Biology Technology:
(Date:3/30/2017)... NEW YORK , March 30, 2017 ... by type (physiological and behavioral), by technology (fingerprint, AFIS, ... recognition, voice recognition, and others), by end use industry ... travel and immigration, financial and banking, and others), and ... Europe , Asia Pacific ...
(Date:3/28/2017)... -- The report "Video Surveillance Market by ... Devices), Software (Video Analytics, VMS), and Service (VSaaS, Installation ... 2022", published by MarketsandMarkets, the market was valued at ... reach USD 75.64 Billion by 2022, at a CAGR ... considered for the study is 2016 and the forecast ...
(Date:3/24/2017)... MILAN , March 24, 2017 The Controller ... Deputy Controller Mr. Abdulla Algeen have received the prestigious international ... Continue Reading ... ... small picture) and Deputy Controller Abdulla Algeen (small picture on the right) ...
Breaking Biology News(10 mins):