[ad_1]
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
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 graphene, a flat network of carbon atoms, was identified in 2001. Since then, scientists have begun to develop, in theory or in the laboratory, new two-dimensional materials. optical, 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 two-dimensional materials.
"The important thing now that we understand the protocol is that we can use it to analyze any two-dimensional material," 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 2-D 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 potential 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 infrared towards the ultraviolet, thus surpassing the doped graphene and bulk money. .
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!"
Explore more:
Borophene shines alone as a 2D plasmonic material
More information:
Sunny Gupta et al, In search of 2D materials for maximum optical response, ACS Nano (2018). DOI: 10.1021 / acsnano.8b03754
Source link
