Graphene: Everything under control
Research team demonstrates control mechanism for quantum material
Juniks, Dresden, CC BY
Consisting of carbon atoms, graphene is a material just one atom thick where the atoms are arranged in a hexagonal lattice. This arrangement of atoms is what results in graphene’s unique property: the electrons in this material move as if they did not have mass. This “massless” behavior of electrons leads to very high electrical conductivity in graphene and, importantly, this property is maintained at room temperature and under ambient conditions. Graphene is therefore potentially very interesting for modern electronics applications.
It was recently discovered that the high electronic conductivity and “massless” behavior of its electrons allows graphene to alter the frequency components of electric currents that pass through it. This property is highly dependent on how strong this current is. In modern electronics, such a nonlinearity comprises one of the most basic functionalities for switching and processing of electrical signals. What makes graphene unique is that its nonlinearity is by far the strongest of all electronic materials. Moreover, it works very well for exceptionally high electronic frequencies, extending into the technologically important terahertz (THz) range where most conventional electronic materials fail.
In their new study, the team of researchers from Germany and Spain demonstrated that graphene’s nonlinearity can be very efficiently controlled by applying comparatively modest electrical voltages to the material. For this, the researchers manufactured a device resembling a transistor, where a control voltage could be applied to graphene via a set of electrical contacts. Then, ultrahigh-frequency THz signals were transmitted using the device: the transmission and subsequent transformation of these signals were then analyzed in relation to the voltage applied. The researchers found that graphene becomes almost perfectly transparent at a certain voltage – its normally strong nonlinear response nearly vanishes. By slightly increasing or lowering the voltage from this critical value, graphene can be turned into a strongly nonlinear material, significantly altering the strength and the frequency components of the transmitted and remitted THz electronic signals.
“This is a significant step forward towards implementation of graphene in electrical signal processing and signal modulation applications,” says Prof. Dmitry Turchinovich, a physicist at Bielefeld University and one of the heads of this study. “Earlier we had already demonstrated that graphene is by far the most nonlinear functional material we know of. We also understand the physics behind nonlinearity, which is now known as thermodynamic picture of ultrafast electron transport in graphene. But until now we did not know how to control this nonlinearity, which was the missing link with respect to using graphene in everyday technologies.”
“By applying the control voltage to graphene, we were able to alter the number of electrons in the material that can move freely when the electrical signal is applied to it,” explains Dr. Hassan A. Hafez, a member of Professor Dr. Turchinovich’s lab in Bielefeld, and one of the lead authors of the study. “On one hand, the more electrons can move in response to the applied electric field, the stronger the currents, which should enhance the nonlinearity. But on the other hand, the more free electrons are available, the stronger the interaction between them is, and this suppresses the nonlinearity. Here we demonstrated – both experimentally and theoretically – that by applying a relatively weak external voltage of only a few volts, the optimal conditions for the strongest THz nonlin-earity in graphene can be created.”
“With this work, we have reached an important milestone on the path towards to using graphene as an extremely efficient nonlinear functional quantum material in devices like THz frequency converters, mixers, and modulators,” says Professor Dr. Michael Gensch from the Institute of Optical Sensor Systems of the German Aerospace Center (DLR) and the Technical University of Berlin, who is the other head of this study. “This is extremely relevant because graphene is perfectly compatible with existing electronic ultrahigh-frequency semiconductor technology such as CMOS or Bi-CMOS. It is therefore now possible to envision hybrid devices in which the initial electric signal is generated at lower frequency using existing semiconductor technology but can then very efficiently be up-converted to much higher THz frequencies in graphene, all in a fully controllable and predictable manner.”
Researchers from Bielefeld University, the Institute of Optical Sensor Systems of the DLR, the Technical University of Berlin, the Helmholtz Center Dresden-Rossendorf, and the Max Planck Institute for Polymer Research in Germany, as well as the Catalan Institute of Nanoscience and Nanotechnology (ICN2) and the Institute of Photonic Sciences (ICFO) in Spain participated in this study.
Other news from the department science
Argonne and Idaho National Laboratories partner with CMBlu Energy for innovative long-duration energy storage project
The project aims to improve microgrids in cold climates and make fast charging of electric vehicles more affordable in underserved communities
Blue-green algae sugar instead of glyphosate
Cooperation project develops environmentally friendly glyphosate alternative
Using clay to combat eternal toxins
TU Freiberg clarifies basis for innovative PFAS filter made of clay
Unveiling a new era of imaging: Boston University engineers lead breakthrough microscopy techniques
Researchers made significant advancements in the field of vibrational imaging
Phasing out fossil fuels could save millions of lives
The mortality burden attributable to air pollution from fossil fuel use is considerably higher than most previous estimates - a phaseout of fossil fuels would have tremendous, positive health outcomes
Replicating the structure of bird feathers
The new material could be used in batteries or filtration
Quantum tool opens door to uncharted phenomena
Method can contribute to a better understanding of quantum materials
Recovering instead of shredding: recycling batteries more efficiently
KIT researchers are working with industry to develop a more sustainable recycling process to recycle materials from lithium-ion batteries more effectively
Industry 4.0: No impact on energy consumption?
To what extent does the digitalisation of industrial and manufacturing processes (Industry 4.0) improve energy efficiency and thus reduce energy intensity?
New approach to the sensible utilisation of carbon dioxide from car exhaust gases
"A method has been discovered that uses impure CO2 streams and enables a breakthrough in the synthesis of valuable chemicals and pharmaceuticals"
Boosting PET recycling with higher standards for laboratory experiments
New study shows how enzymatic plastic degradation could be brought one step closer to commercialisation
Innovating Optoelectronic Components with Phosphorus
Significant breakthrough: phosphorus chemists develop new method to selectively introduce phosphorus and nitrogen atoms into polyaromatic systems
Artificial intelligence finds ways to develop new drugs
The chemists tested the process using borylation – a reaction that activates hydrocarbon scaffolds
Most read news
Plastic-eating bacteria turn waste into useful starting materials for other products
Microbial Upcycling of Waste PET
Microbes could help reduce the need for chemical fertilizers
A coating protects nitrogen-fixing bacteria: Start-up to commercialise coated bacteria for large-scale use in regenerative agriculture
New designs for solid-state electrolytes may soon revolutionize the battery industry
Scientists achieve monumental improvements in lithium-metal-chloride solid-state electrolytes
Inauguration of the world’s first pilot plant for the cost-efficient production of green methanol
Start-up C1 Green Chemicals AG and research partners develop fundamentally new production process
Dow and Evonik announce startup of hydrogen peroxide to propylene glycol (HPPG) pilot plant
Innovative technology offer flexibility, lower costs, and a smaller environmental footprint
This is a battery
Two colored liquids bubbling through tubes: Is this what the battery of the future looks like?
Converting PFAS “forever chemicals” into valuable compounds
Scientists develop a new method to incorporate harmful perfluoroalkenes into N-heterocyclic carbene ligands
Not so silver lining: Microplastics found in clouds could affect the weather
Low-altitude and denser clouds contained greater amounts of microplastics
Graphene's proton permeability: A switch for future energy technologies
This discovery could lead to the development of more efficient hydrogen fuel cells and solar water-splitting devices
Lithium-ion batteries are no longer the gold standard in battery tech
On the way to safer and more powerful energy sources
CO2-free hydrogen: BASF receives funding approval for 54-megawatt water electrolysis plant
Proton exchange membrane (PEM) electrolyzer expected to produce up to 8,000 metric tons of hydrogen per year
More news from our other portals
Bowel cancer: aspirin activates protective genes
Researchers have identified a signaling pathway by which aspirin can inhibit colorectal cancer.
Dunning-Kruger effect with muesli bars
Those who know the least consider themselves highly competent
Autonomous measuring instruments systematically detect new materials
A new algorithm measures materials libraries up to four times faster than before: It’s based on machine learning
New drug delivery system could reduce daily diabetes shots to just three a year
Dietary management drugs have transformed Type 2 diabetes care, but daily injection routines are challenging for some patients
Naked Clams: The New Superfood Sensation Emerging from the Depths
Researchers found Naked Clams contain almost twice the amount of Vitamin B12 as blue mussels and have developed an efficient way to farm them
Researchers discover new ultra strong material for microchip sensors
A material that doesn't just rival the strength of diamonds and graphene, but boasts a yield strength 10 times greater than Kevlar
Aston University technology to combat the not-so sweet practice of honey fraud
Light technology to be used to detect if honey is blended with cheap additions
How stem cells and immune cells communicate
Lisec Artz Award for Simon Haas: Groundbreaking discovery of an unknown protective mechanism against blood cancer from stem cells
Pushers, overcrowded trains and phone zombies
Sprite presents the world's first vending machine that responds to the things that bother Generation Z the most
Scientists use quantum biology, AI to sharpen genome editing tool
"This study represents an exciting advancement toward, understanding how we can avoid making costly ‘typos’ in an organism’s genetic code"
Tönnies Group launches first nationwide "Meat Climate Platform"
100 guests at the Future Forum for Agriculture
Viral Impostors: Breakthrough for Virus Research
The penetration of viruses into cells can now be tracked with unprecedented accuracy thanks to innovative design for pseudoviruses
From the trough to the plate - digitally calculated
Computer program "ConTrans" estimates how much of an undesirable substance is transferred from animal feed to food
Fatty acid factory filmed at work
High-resolution images provide new insights into cellular fatty acid production: Potential for medicine and biotechnology
Tracking down Environmental Toxins
Detection of per- and polyfluoroalkyl substances (PFAS) by interrupted energy transfer
Textbook knowledge turned on its head: 3-in-1 microorganism discovered
Newly multifunctional bacterial species
Are healthy foods automatically sustainable, too?
Perceptions about sustainability and healthy food choices are closely linked
The weight of pollution: exposure linked to obesity
Chronic exposure to environmental pollutants found to increase risk of cardiovascular disease
Could eating turkey ease colitis?
According to data in mice, extra tryptophan could reduce the risk of future colitis flares