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HOUSTON – (Sept. 24, 2018) – The ability of metallic or semiconductor materials to absorb, reflect and act on light is paramount for scientists developing optoelectronics – electronic devices that interact with light to perform tasks. Scientists at Rice University have now produced a method to determine the properties of atomic thin materials that promise to fine-tune the modulation and manipulation of light.
Two-dimensional materials have been a hot topic of research since the identification of graphene in 2001, a flat network of carbon atoms. Since then, scientists have begun to develop, in theory or in laboratory, new 2D materials, electronic and physical properties.
Until now, they did not have a comprehensive guide to the optical properties that these materials offer as ultra-thin reflectors, transmitters or absorbers.
Boris Yakobson, the theorist of the rice lab of materials theory, took up the challenge. Yakobson and co-authors, Sunny Gupta, postdoctoral student and lead author, Sharmila Shirodkar, postdoctoral researcher, and Alex Kutana, research scientist, used state-of-the-art theoretical methods to calculate the maximum optical properties of 55 2D materials.
"The important thing now that we understand the protocol is that we can use it to analyze any 2D hardware," Gupta said. "This is a big computational effort, but it is now possible to evaluate any material at a deeper quantitative level."
Their work, which appears this month in the American Chemical Society ACS Nano, details the transmittance, absorbance and reflectance of monolayers, properties that they collectively called TAR. At the nanoscale, light can interact uniquely with materials, resulting in electron-photon interactions or trigger plasmons that absorb light at one frequency and emit in another.
Handling 2D materials allows researchers to design ever smaller devices, such as sensors or light circuits. But first, it is useful to know how much a material is sensitive to a given light wavelength, from infrared to visible colors, via the ultraviolet.
"Generally, the common wisdom is that 2D materials are so thin that they should appear to be essentially transparent, with negligible reflection and absorption," Yakobson said. "Surprisingly, we found that each material has an expressive optical signature, with much of the light of a particular color (wavelength) being absorbed or reflected."
Co-authors anticipate photodetection and modulation devices and polarizing filters are possible applications for 2D materials with direction-dependent optical properties. "Multilayer coatings could offer good protection against radiation or light, such as lasers," said Shirodkar. "In the latter case, heterostructured films (multilayers) – coatings of complementary materials – may be needed, larger light intensities could produce non-linear effects and their consideration will certainly require further investigation."
The researchers modeled 2D stacks as well as single layers. "Batteries can expand the spectral range or bring new features, such as polarizers," said Kutana. "We can think of using stacked heterostructure models to store information or even for cryptography."
Among their results, the researchers verified that stacks of graphene and borophene strongly reflected infrared light. Their most striking finding was that a material composed of more than 100 layers of single atom boron – whose thickness would be only about 40 nanometers – would reflect more than 99% of the light from infrared to ultraviolet, outperforming doped graphene. money in bulk.
There is a secondary benefit that also corresponds to Yakobson's artistic sensibility. "Now that we know the optical properties of all these materials – the colors they reflect and transmit when they are struck by light – we can think of making Tiffany-style stained glass on the scale. nanometer, "he said. "It would be fantastic!"
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Editor's Note: A link to a high resolution downloadable image appears at the end of this release.
David Ruth [email protected]
Mike Williams [email protected]
The work was supported by the US Army Research Bureau and the Robert Welch Foundation. IT resources were provided by Rice's DAVinCI cluster, managed by the National Science Foundation and administered by the Center for Research Computing, in partnership with the Ken Kennedy Institute for Information Technology, the High Performance Computing Modernization Program, and the Department of Energy. National Energy Research Science Center, Science Office.
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Related materials:
Yakobson Research Group: https: /
Rice Department of Materials Science and Nanoengineering: https: /
George R. Brown School of Engineering: https: /
Image to download:
http: // news.
Researchers at Rice University have modeled two-dimensional materials to quantify their reaction to light. They calculated how materials thick in atoms in single or stacked layers would transmit, absorb, and reflect light. The graphs above measure the maximum absorbance of several of the 55 materials tested. (Credit: Yakobson Research Group / Rice University)
Located on a 300-acre forest campus in Houston, Rice University is consistently ranked among the top 20 universities in the country by US News & World Report magazine. Rice has highly respected schools of architecture, business, permanent studies, engineering, humanities, music, natural sciences and social sciences and is home to the Baker Institute for Public Policy. With 3,970 undergraduate students and 2,934 graduate students, Rice's undergraduate / faculty ratio is just under 6: 1. Her residential college system creates united communities and enduring friendships, one of the reasons why Rice is rated # 1 for her many race / class interactions and # 2 for quality of life by the Princeton Review. Rice is also considered the best value among private universities by Kiplinger's Personal Finance. To read "What they say about Rice," go to http://tinyurl.com.
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