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2024: Graphene and diamond will combine to create ultra-strong materials of the future
An ultra-strong, stable and flexible composite of graphene and diamond, which can be obtained by irradiating the material with xenon ions, will help improve the quality of nanoelectronic and optical devices. MISIS announced this on August 30, 2024. The study was initiated by scientists NUST MISIS together IFP SB RAS with and. JINR Carbon films containing diamonds ranging in size from 5 to 20 nm retain their structure and properties, demonstrating high mechanical strength and temperature stability. The material is promising for space aviation, and. automobile biomedical industries
 | Diamonds play an important role in science and technology due to their exceptional properties, including mechanical hardness, thermal conductivity and biocompatibility. At the same time, the formation of monocrystalline two-dimensional nanodiamonds in the graphene structure during irradiation is a very interesting question. Our work shows that irradiation of graphene with heavy ions with MeV energy makes it possible to form two-dimensional diamond films. This approach opens up new prospects for obtaining ultra-thin diamond films with special electronic properties, "said Pavel Sorokin, Doctor of Medical Sciences, Head of the Digital Materials Science Laboratory at NITU MISIS. |  |
Two-dimensional nanodiamonds can be widely used in industries that require strong, conductive and simultaneously functional coatings, in particular for coating chip parts, implants, creating sensitive sensors and other technological solutions. Scientists from MISIS University, A.V. Rzhanov Institute of Semiconductor Physics and the Joint Institute for Nuclear Research first studied the possibility of forming nanodiamonds in multilayer graphene, irradiating it with fast heavy xenon ions. As a result of the experiment, embedded nanostructures with a regular diamond structure were found in several layers of graphene, the dimensions of which ranged from 5 to 20 nm. It turned out that at least six layers of graphene are required to form diamonds.
| | The obtained material with different types of carbon bonds can combine the advantages of each individual element of the structure and demonstrate high strength, rigidity and flexibility. Ultra-thin two-dimensional diamond films that can preserve the integrity of diamond-like structures have potential in many areas, from electronics and optics to biomedicine, "added Lev Tomilin, research assistant at the NUST MISIS Digital Materials Science Laboratory. | |
This development makes it possible to better understand the effect of surface structure on the properties of these materials. The introduction of ultra-strong components that provide a strong covalent bond significantly improves the overall mechanical properties.
The work was carried out with the support of the Russian Science Foundation (project No. 21-12-00399).
2023: The first graphene corporation opened in Russia
May 26, 2023 Novokuznetsk in the official opening of the corporation. " "Graphene Valley This is the first Russia in the company to begin comprehensive work on building an industry around such a promising material as graphene. TAdviser This was announced on May 29, 2023 by representatives of the Graphena Valley. More. here
2020
Scientists pumped graphene with light
On October 29, 2020, the press service MIPT announced that physicists from MIPT Vladimir State University managed to increase the efficiency of transmitting light energy to vibrations on the surface of graphene to almost 90%. To do this, they used an energy conversion scheme, like laser and collective resonance effects. The work is published in Laser & Photonics Reviews.
Manipulating light at the nanoscale is one of the most important tasks that must be solved to create ultra-compact devices for converting and storing the energy of optical radiation. Surface plasmon polaritons are light localized at the interface of two materials with a sharp contrast in refractive index, in particular - conductor and dielectric. The advantage of working with such surface waves is the ability to localize light on very small spatial scales on the order of several nanometers. Depending on the combination of conductor and dielectric materials, various degrees of surface wave localization can be achieved; in the simplest case, a combination of metal and air is used. It turns out that the strongest effect can be achieved when light is localized on a two-dimensional material having a thickness of only one atomic layer, since such two-dimensional materials have a sufficiently large refractive index.
Efficiency of energy transmission of light to plasmon-polaritons on two-dimensional surface when using existing circuits is not more than 10%. In order to raise the percentage, it is possible to use intermediate signal converters in the form of nano-objects of different chemical composition and geometry.
As such objects, the authors of the work used semiconductor quantum dots, which have a size of 5 to 100 nanometers and a chemical composition similar to the solid semiconductor from which they are made. However, the optical properties of a quantum dot are highly dependent on its size. Therefore, by changing the size of the quantum dot, we can tune in to the wavelength of light of interest to us. If you shine natural light on an ensemble of quantum dots of different sizes, then some of them respond to one wavelength, others to another.
Quantum dots differ chemically and geometrically. These can be cylinders, pyramids, spheres. The authors in their work used ellipsoid quantum dots with a diameter of 40 nanometers. Quantum dots served as scatterers above the surface of graphene, which was hit by infrared radiation at a wavelength of 1.55 microns. Between quantum dots and graphene was a buffer layer of dielectric several nanometers thick.
The idea of using a quantum dot as a diffuser is not new: there were works in which a quantum dot was above the surface of graphene and interacted with both light and an electromagnetic wave traveling along the surface at one wavelength common to these two processes. This was achieved by selecting the desired quantum dot size. Such a system is quite simple to tune for resonance, but at the same time the processes of extinguishing luminescence - the flow of energy of incident light into heat, as well as the reverse scattering of light begin to play a large role. As a result, the efficiency of energy flow into plasmon-polaritons turned out to be no higher than 10%.
| | We looked at a scheme in which a quantum dot located above the surface of graphene simultaneously interacts with both incident light and a traveling surface electromagnetic wave, but the frequencies at which this interaction occurs are different. It interacts with light at a wavelength of 1.55 micrometers, and with an electromagnetic wave traveling on the surface, that is, with a plasmon-polariton - at a wavelength of 3.5 micrometers. This can be achieved by using a hybrid interaction scheme, - comments co-author Alexei Prokhorov, senior researcher at the Center for Photonics and 2D Materials at MIPT and associate professor at Vladimir State University | |
The essence of the hybrid interaction scheme is that the work does not use two energy levels - upper and lower - but also turns on an intermediate level. That is, the authors decided to use a scheme resembling the energy structure of a laser. Only now, the intermediate energy level serves solely to make a strong connection between the quantum dot and the surface electromagnetic wave. Excitation of the quantum dot occurs at the wavelength of the laser that illuminates it, and conversion to a surface wave occurs already at the wavelength corresponding to the resonance of the quantum dot with plasmon-polariton.
| | We worked with different materials for making quantum dots and with different types of graphene. Graphene can be pure, or it can be so-called doped graphene. Depending on the type of doping in which elements from neighboring groups of the Mendeleev table are embedded in graphene, its chemical potential changes. We optimized the parameters of the quantum dot, its chemistry, geometry and type of graphene so that the efficiency of transmitting light energy to surface plasmon polaritons becomes maximum. As a quantum dot, indium antimonide InSb was used, as graphene - doped graphene, - says Alexey Prokhorov | |
But, although energy is led through a quantum dot to graphene with a sufficiently high efficiency, the intensity of the waves that occur there is negligible. Therefore, it is necessary to use a large number of quantum dots that are located above the surface of graphene in a certain order. The task of scientists was to find exactly the geometry, then the distance between quantum dots, at which signals would be amplified by phasing near fields from each quantum dot located above the graphene. In the course of work, they selected such a geometry, as a result of which the signal formed in graphene became orders of magnitude more powerful than what happened with the random arrangement of quantum dots. For subsequent numerical calculations, the authors used proprietary software modules.
The efficiency of conversion from light in the proposed scheme, according to calculations, reaches 90-95%. Taking into account all possible negative factors, the effectiveness will still remain above 50%, which is several times higher than the previously achieved indicators.
| | The big goal of the research is to create ultra-compact instruments that could convert the energy of light to surface plasmon polaritons on a very small spatial scale with high efficiency and thus write the energy of light into some kind of structure. In addition, polaritons can be accumulated, that is, it is potentially possible to develop an ultra-thin battery in several atomic layers. It is possible on the basis of this effect to create light energy converters like solar panels, only with efficiency many times more. Another promising application is the detection of various nano- and bio-objects, - commented Valentin Volkov, Director of the Center for Photonics and Two-Dimensional Materials of MIPT | |
Infrared and terahertz sensors made of graphene with black phosphorus and arsenic
On March 23, 2020, it became known that scientists from MIPT, together with colleagues from Japan and the United States, calculated the parameters of photodetectors from graphene layers and a mixture of black phosphorus and arsenic. Such sensors are able to capture radiation with energy less than the band gap of these layers without graphene. They are also easily modified to increase sensitivity to the desired wavelength of light. Such sensors can replace far infrared and terahertz receivers. The findings are published in the journal Optics Express.
As reported, the far infrared range is extremely important both in various domestic applications and in science. Such waves emit cosmic dust, the knowledge of which is extremely useful for studying the evolution of galaxies. Infrared light sensors are used in night vision devices, remote controls, missile homing systems and heart rate sensors. Terahertz radiation is used in security systems to scan luggage. At the same time, it is safer than X-ray. Infrared and terahertz sensors will find their application in many fields of technology.
The authors of the study considered interband far infrared photodetectors based on a single graphene monolayer. Graphene was surrounded by layers of a mixture of black phosphorus and black arsenic in varying proportions. By adjusting the ratio of these substances, the operating frequency range of the photodetector can be shifted. Black phosphorus and arsenic have different energy ranges not available to electrons. The transition of an electron (or hole) from one permitted zone of graphene to another, followed by the exit to the conduction zone of black phosphorus or arsenic, is recorded in a similar photodetector. However, due to temperature effects in infrared and terahertz sensors, a signal is recorded even "in the dark," that is, without exposure to electromagnetic waves. It turned out that in the considered layered structures such a dark current is much less than in those used for March 2020.
| | We calculated the parameters of photosensitive elements that can capture far infrared light made from a graphene monolayer. Such photodetectors can replace almost any infrared and terahertz radiation sensors used for March 2020. Due to the low dark current and high photosensitivity, a good signal-to-noise ratio can be achieved even when receiving low-intensity radiation. If the desired voltage is applied, the operating range of such receivers can be changed without loss of signal reception quality. Such sensors can increase the efficiency of infrared telescopes. Calculated receivers at high temperatures should give a much cleaner signal than those used for March 2020. told Viktor Ryzhiy, head of the laboratory of two-dimensional materials and nano-devices of the Moscow Institute of Physics and Technology | |
Graphene-based material will extend the life of data storage devices
On January 27, 2020, it became known that an international group of scientists from NUST MISIS and the National Institute of Quantum Sciences and Radiology (Japan) developed material that will significantly increase the density of recorded information in data storage devices, such as solid-state drives and flash drives. The advantages of the material also include the absence of a rewriting limit, which will allow you to introduce devices from the material into the current Big Data technology . An article about the development was published in the journal Advanced Materials.
As reported, the development of compact, roomy and reliable memory devices is an increasing need. As of January 2020, devices in which information is transferred using electric current are traditional; the simplest example is a flash card or external hard drive. At the same time, from time to time, users inevitably face problems: the file may be recorded incorrectly, the computer may stop "seeing" the flash drive, and rather bulky media are required to record a large amount of information.
For January 2020, a promising alternative to electronics is spintronics, where information transfer control is implemented not only with the help of electron charge, but also with the help of spin current - the natural moments of the electron pulse. In spintronics, the devices work on the principle of magnetoresistive effect (magnetic resistance): there are three layers, the first and third of which are ferromagnetic, and the middle one is non-magnetic. Passing through such a sandwich structure, electrons, depending on their back, scatter differently in magnetized edge layers, which affects the resulting resistance of the device. By detecting an increase or decrease in a given resistance, the information can be controlled using standard logic bits, 0 and 1.
An international group of scientists from NUST MISIS and the National Institutes for Quantum and Radiological Science and Technology have developed material that can increase the capacity of magnetic memory due to an increase in recording density. Scientists used a combination of graphene and the semi-metallic Geisler alloy Co2FeGaGe (cobalt-iron-gallium-germanium).
| | Japanese colleagues managed to obtain a layer of graphene of atomic thickness on a layer of semi-metallic ferromagnetic material and measure its properties. This work became possible thanks to close international cooperation. The Japanese team, led by Dr. Seiji Sakai, is conducting experiments, while our group is engaged in a theoretical description of the data obtained. told Pavel Sorokin, head of the scientific group from the Russian side, Doctor of Medical Sciences, Associate Professor, Scientific Director of the Infrastructure Project "Theoretical Materials Science of Nanostructures" of the laboratory "Inorganic Nanomaterials" NUST MISIS " | |
| | The peculiarity of the alloy used in the heterostructure is manifested in one hundred percent spin polarization at the Fermi level, which is a prerequisite for its use in spintronic devices. narrated by Konstantin Larionov, research associate | |
| | In the heterostructure we studied, graphene does not enter into chemical interaction with magnetic material, which allows it to preserve its unique conductive properties. narrated by Zakhar Popov, Senior Research Fellow | |
Previously, graphene was not used in magnetic memory devices: when trying to manufacture such layered materials, carbon atoms reacted with a magnetic layer, which led to a change in its properties. Thanks to the careful selection of the composition of the Geisler alloy, as well as its application methods, it was possible to create a thinner sample compared to previous analogues. This, in turn, will significantly increase the capacity of magnetic memory devices without increasing their physical size.
The next steps of scientists are to scale the experimental sample and further modify the structure of the element.
2019: Graphene 'melting' is actually sublimation
Scientists from the Moscow Institute of Physics and Technology and the Institute of High Pressure Physics named after Vereshchagin RAS using computer modeling clarified the melting curve of graphite, the study of which lasts more than a hundred years and is replete with conflicting data. They also showed that the "melting" of graphene is actually a sublimation. The findings are published in the journal Carbon.
Graphite is a mineral actively used in various types of industries, including for the thermal protection of spacecraft, so accurate information about its behavior at ultra-high temperatures is very important. Melting graphite began to be investigated at the beginning of the twentieth century. About a hundred experimental works called numbers in the range from 3,000 to 7,000 K. This is a very large spread, it is not clear which of the numbers can be believed, which of the values is really the melting point. Different computer models also gave different results.
The idea of the researchers was to compare several computer models and try to distinguish some common predictions. To do this, Yuri Fomin and Vadim Brazhkin used two methods: classical molecular dynamics and primary principle, which takes into account quantum mechanical effects. The first gives inaccuracies precisely because of the unaccounted for quantum mechanics. The second is due to the fact that it takes into account the interaction of only a small number of atoms and at a short period of time. The scientists compared the results with the available experimental and theoretical data.
Fomin and Brazhkin showed that existing models are highly inaccurate. But comparing the results obtained from different theoretical models and overlapping them allows you to give an explanation for the experimental data.
Back in the 1960s, it was predicted that a maximum should exist on the melting curve of graphite. The existence of a maximum on the melting curve indicates the complex behavior of the liquid - smooth changes in structure should occur in it. Then the existence of the maximum was either opened or closed. The results of Fomin and Brazhkin show that the structure of liquid carbon over the graphene melting curve undergoes changes, which means that the maximum must exist.
The second part of the work is devoted to the study of the melting of graphene. There are no experiments on melting graphene. Previously, it was predicted from computer modeling that the melting point of graphene is 4500 or 4900 K. Accordingly, two-dimensional carbon was considered the most refractory substance in the world.
| | In our work, we drew attention to the fact that the'melting' of graphene occurs in some strange way, through the formation of linear chains. We showed that in fact there is not melting, but a transition immediately to a gaseous state - sublimation, comments Yuri Fomin, Associate Professor, Department of General Physics, Moscow Institute of Physics and Technology
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This result makes it possible to better understand the nature of phase transitions in low-dimensional carbon materials, which are seen as important components of many technologies under development - from electronics to medicine.
The researchers summarized and refined the description of the melting curve of graphite, confirmed the presence of a smooth structural transition in liquid carbon. Their calculations showed that the melting point of graphene in an argon atmosphere is close to the melting point of graphite.
The work was carried out with the support of the Russian Science Foundation using the computing resources of the federal center for collective use "Complex of modeling and processing of data from mega-class research facilities" at the Kurchatov Institute Research Center
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