Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > New test reveals purity of graphene: Rice, Osaka scientists use terahertz waves to spot contaminants

Rice and Osaka researchers have come up with a simple method to find contaminants on atom-thick graphene. By putting graphene on a layer of indium phosphide, which emits terahertz waves when excited by a laser pulse, they can measure and map changes in its electrical conductivity.Credit: Rice and Osaka universities
Rice and Osaka researchers have come up with a simple method to find contaminants on atom-thick graphene. By putting graphene on a layer of indium phosphide, which emits terahertz waves when excited by a laser pulse, they can measure and map changes in its electrical conductivity.

Credit: Rice and Osaka universities

Abstract:
Graphene may be tough, but those who handle it had better be tender. The environment surrounding the atom-thick carbon material can influence its electronic performance, according to researchers at Rice and Osaka universities who have come up with a simple way to spot contaminants.

New test reveals purity of graphene: Rice, Osaka scientists use terahertz waves to spot contaminants

Houston, TX | Posted on August 13th, 2014

Because it's so easy to accidently introduce impurities into graphene, labs led by physicists Junichiro Kono of Rice and Masayoshi Tonouchi of Osaka's Institute of Laser Engineering discovered a way to detect and identify out-of-place molecules on its surface through terahertz spectroscopy.

They expect the finding to be important to manufacturers considering the use of graphene in electronic devices.

The research was published this week by Nature's open-access online journal Scientific Reports. It was made possible by the Rice-based NanoJapan program, through which American undergraduates conduct summer research internships in Japanese labs.

Even a single molecule of a foreign substance can contaminate graphene enough to affect its electrical and optical properties, Kono said. Unfortunately (and perhaps ironically), that includes electrical contacts.

"Traditionally, in order to measure conductivity in a material, one has to attach contacts and then do electrical measurements," said Kono, whose lab specializes in terahertz research. "But our method is contact-less."

That's possible because the compound indium phosphide emits terahertz waves when excited. The researchers used it as a substrate for graphene. Hitting the combined material with femtosecond pulses from a near-infrared laser prompted the indium phosphide to emit terahertz back through the graphene. Imperfections as small as a stray oxygen molecule on the graphene were picked up by a spectrometer.

"The change in the terahertz signal due to adsorption of molecules is remarkable," Kono said. "Not just the intensity but also the waveform of emitted terahertz radiation totally and dynamically changes in response to molecular adsorption and desorption. The next step is to explore the ultimate sensitivity of this unique technique for gas sensing."

The technique can measure both the locations of contaminating molecules and changes over time. "The laser gradually removes oxygen molecules from the graphene, changing its density, and we can see that," Kono said.

The experiment involved growing pristine graphene via chemical vapor deposition and transferring it to an indium phosphide substrate. Laser pulses generated coherent bursts of terahertz radiation through a built-in surface electric field of the indium phosphide substrate that changed due to charge transfer between the graphene and the contaminating molecules. The terahertz wave, when visualized, reflected the change.

The experimental results are a warning for electronics manufacturers. "For any future device designs using graphene, we have to take into account the influence of the surroundings," said Kono. Graphene in a vacuum or sandwiched between noncontaminating layers would probably be stable, but exposure to air would contaminate it, he said.

The Rice and Osaka labs are continuing to collaborate on a project to measure the terahertz conductivity of graphene on various substrates, he said.

The paper's authors include Rice alumna Mika Tabata, who conducted research as a 2012 NanoJapan participant in the Tonouchi lab, and graduate student Minjie Wang; associate professors Iwao Kawayama and Hironaru Murakami and graduate students Yuki Sano and Khandoker Abu Salek of Osaka; and Robert Vajtai, a senior faculty fellow, and Pulickel Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor in Engineering, professor of materials science and nanoengineering and of chemistry, and chair of the Department of Materials Science and NanoEngineering, both at Rice.

The National Science Foundation (NSF); the Japan Society for the Promotion of Science; the Ministry of Education, Culture, Sports, Science and Technology-Japan and the Murata Science Foundation supported the research. NanoJapan is funded by the NSF's Partnerships for International Research and Education program.

####

About Rice University
Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,920 undergraduates and 2,567 graduate students, Rice's undergraduate student-to-faculty ratio is just over 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is highly ranked for best quality of life by the Princeton Review and for best value among private universities by Kiplinger's Personal Finance.

Follow Rice News and Media Relations via Twitter @RiceUNews

For more information, please click here

Contacts:
David Ruth
713-348-6327


Mike Williams
713-348-6728

Copyright © Rice University

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

Read the abstract at:

Junichiro Kono Laboratory:

Tonouchi Lab:

Ajayan Research Group:

Related News Press

News and information

Switching with molecules: Molecular switch will facilitate the development of pioneering electro-optical devices May 25th, 2018

Tunable diamond string may hold key to quantum memory: A process similar to guitar tuning improves storage time of quantum memory May 24th, 2018

Remote control of transport through nanopores: New study outlines key factors affecting the transfer of molecules through biological channels May 24th, 2018

2018 Kavli Prizes in Astrophysics, Nanoscience, and Neuroscience to be Announced Live on May 31: Live announcement at the Norwegian Academy of Science and Letters to be streamed live at World Science Festival Event May 24th, 2018

Graphene/ Graphite

Columbia Researchers Squeeze Light into Nanoscale Devices and Circuits: Team is first to directly image propagation and dynamics of graphene plasmons at very low temperatures; findings could impact optical communications and signal processing May 23rd, 2018

Strain improves performance of atomically thin semiconductor material May 11th, 2018

Nanoscale measurements 100x more precise, thanks to improved two-photon technique May 8th, 2018

Hematene joins parade of new 2D materials: Rice University-led team extracts 3-atom-thick sheets from common iron oxide May 8th, 2018

Govt.-Legislation/Regulation/Funding/Policy

Tunable diamond string may hold key to quantum memory: A process similar to guitar tuning improves storage time of quantum memory May 24th, 2018

Columbia Researchers Squeeze Light into Nanoscale Devices and Circuits: Team is first to directly image propagation and dynamics of graphene plasmons at very low temperatures; findings could impact optical communications and signal processing May 23rd, 2018

NIST Puts the Optical Microscope Under the Microscope to Achieve Atomic Accuracy May 22nd, 2018

Magnesium magnificent for plasmonic applications: Rice University, University of Cambridge synthesize and test nanoparticles of abundant material May 22nd, 2018

Chip Technology

Switching with molecules: Molecular switch will facilitate the development of pioneering electro-optical devices May 25th, 2018

Columbia Researchers Squeeze Light into Nanoscale Devices and Circuits: Team is first to directly image propagation and dynamics of graphene plasmons at very low temperatures; findings could impact optical communications and signal processing May 23rd, 2018

Supersonic waves may help electronics beat the heat May 18th, 2018

Deeper understanding of quantum chaos may be the key to quantum computers May 16th, 2018

Discoveries

Switching with molecules: Molecular switch will facilitate the development of pioneering electro-optical devices May 25th, 2018

Tunable diamond string may hold key to quantum memory: A process similar to guitar tuning improves storage time of quantum memory May 24th, 2018

Remote control of transport through nanopores: New study outlines key factors affecting the transfer of molecules through biological channels May 24th, 2018

'Spooky action at a distance': Researchers develop module for quantum repeater May 23rd, 2018

Announcements

Switching with molecules: Molecular switch will facilitate the development of pioneering electro-optical devices May 25th, 2018

Tunable diamond string may hold key to quantum memory: A process similar to guitar tuning improves storage time of quantum memory May 24th, 2018

Remote control of transport through nanopores: New study outlines key factors affecting the transfer of molecules through biological channels May 24th, 2018

2018 Kavli Prizes in Astrophysics, Nanoscience, and Neuroscience to be Announced Live on May 31: Live announcement at the Norwegian Academy of Science and Letters to be streamed live at World Science Festival Event May 24th, 2018

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers

Switching with molecules: Molecular switch will facilitate the development of pioneering electro-optical devices May 25th, 2018

Tunable diamond string may hold key to quantum memory: A process similar to guitar tuning improves storage time of quantum memory May 24th, 2018

Remote control of transport through nanopores: New study outlines key factors affecting the transfer of molecules through biological channels May 24th, 2018

'Spooky action at a distance': Researchers develop module for quantum repeater May 23rd, 2018

Research partnerships

Tunable diamond string may hold key to quantum memory: A process similar to guitar tuning improves storage time of quantum memory May 24th, 2018

NIST Puts the Optical Microscope Under the Microscope to Achieve Atomic Accuracy May 22nd, 2018

Deeper understanding of quantum chaos may be the key to quantum computers May 16th, 2018

Nanoscale measurements 100x more precise, thanks to improved two-photon technique May 8th, 2018

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project