On-chip photonic tweezers for bacteria capture and characterization
Researchers at IRIG, LTM, and CEA-Leti have developed an almost-instant means of testing bacteria viability after a thermic shock. The new device features an optical nanocavity and two micromirrors. A laser beam bounces back and forth between the mirrors hundreds, or even thousands, of times before escaping: This resonance creates a gradient force (Phenomenon discovered by the American physicist Arthur Ashkin, 2018 winner of the Nobel Prize in Physics) that attracts nearby bacteria. The viability of the bacteria alters their effect on the resonance frequency.
The new nanosystem could be used to check how bacteria react to antibiotics, reducing test times from around 48 hours of culture time in a Petri dish to mere moments. Potential benefits include more targeted use of antibiotics, lowering the risk of antibiotic resistance.
Contact: Emmanuel Hadji
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Advanced computing: Irig researcher honored for second time
IRIG researcher Ivan Duchemin has earned recognition for his work as runner-up in the annual Atos-Joseph Fourier award for advanced computing and artificial intelligence.
Duchemin won a previous award for his expertise in high-performance computing in 2014. Duchemin developed ab initio algorithms to simulate and characterize unique defects in boron nitride flakes of over one thousand atoms in size. These defects are significant as potential single-photon emitters. His new, very-low-power BEDEFT code, parallelizable across thousands of cores, is an important step towards simulating quantum properties in increasingly realistic systems.
The Atos-Joseph Fourier second prize comes with 200,000 GPU hours on the Genci (A national supercomputer infrastructure in France) supercomputers.
Contact: Ivan Duchemin
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A first step towards controlling skyrmion movement
Skyrmions are in the news again, thanks to an advance made by an IRIG team, in conjunction with two other laboratories (Institut Néel and CNRS Villetaneuse). The researchers successfully controlled the movement of skyrmions - quasi-particles with potential applications for magnetic memories - in situ by applying a gate voltage to reverse their chirality, or spin direction.
This is an important step towards controlling the movement of individual skyrmions, a prerequisite to their use as memory units or logic gates. The team now needs to do some basic research into chirality inversion and explore possible applications. The idea is to replicate their initial experiment using nanometric skyrmions, with the long-term goal of optimizing memory density, and to create nano-equipment with movement guidance channels.
Contact: Hélène Bea
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Optoelectronics: goodbye cadmium, hello zinc oxide?
An IRIG team, working alongside Polish researchers (Institute of Physical Chemistry at the Polish Academy of Sciences (Warsaw)) , has successfully synthesized and characterized controlled-thickness, highly stable, nanometric zinc oxide (ZnO) nanoplatelets. These nanoplatelets may offer an alternative to classic cadmium chalcogenide 2D nanostructures in optoelectronics. Cadmium chalcogenide is toxic and rare, and its use is tightly regulated by a European directive.
Irig researchers studied 2D ZnO nanoplatelets using dynamic nuclear polarization (DNP), a high-sensitivity NMR technique. They showed that the benzamidine ligands used in synthesis distribute across all faces of ZnO crystals, limiting the dimensions of each crystal and contributing to the stability of the nanoplatelets.
Contact: Gaël De Paëpe
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Vibration: New hope in the fight against cancer?
Researchers from IRIG and INSERM recently made a surprising and promising discovery: Cancerous cells die spontaneously (apoptosis) on contact with magnetic particles vibrating at between 2 Hz and 5 Hz under the influence of an external field. The phenomenon is being investigated further by a IRIG-LTM PhD candidate, who is measuring the forces at work on the cells in order to understand the underlying mechanisms.
LTM’s traction force microscopy technique is being used to detect cell withdrawal, shrinking, or stretching. Cell mobility, a parameter which is known to impact metastasis, is also being observed. This exploratory PhD research will provide biologists with the data they need to reconstruct the cascade of reactions resulting in apoptosis.
Contact: Robert Morel

Heart attacks could soon be diagnosed in under an hour
Saint-Étienne University Medical Center is gearing up to test a portable device for diagnosing heart attacks based on a technology developed by CEA-Leti and IRIG. This point-of-care test costs less than current techniques. However, it is also faster, a decisive advantage given that every minute counts when it comes to treating heart attacks. Aptamers, which are synthetic DNA strands with a unique 3D shape, are used instead of the animal antibodies of conventional diagnostic tests to capture troponin, a biomarker for myocardial infarction. LAMP, a DNA amplification method similar to PCR, is then used on the sample. The aptamer-plus-LAMP protocol has been integrated onto a self-contained microfluidic cartridge simple enough to be handled by non-specialists. Two patents have been filed to protect the technique.
Contact: Arnaud Buhot
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Frozen pellets reach speeds of 3,600 kph on test bench for the ITER fusion reactor
In tokamak reactors, plasma instability is countered by injecting frozen gas pellets at high speed. The plasma temperature is rapidly decreased, mitigating disruptions and protecting the reactor walls and structure. Pellet injection works well on conventional fusion reactors. But the ITER reactor uses higher-energy plasmas that require a different approach. Researchers at IRIG have developed a 1:1 scale test bench to help address this challenge. The Irig-designed test bench produces frozen pellets measuring 10 mm to 30 mm in diameter and strong enough to withstand high-speed injection—with acceleration of up to 1 km per second—into the reactor. The pellets also have to be produced in under 30 minutes to ensure that there are always enough on hand. Experiments are currently being carried out to determine the exact parameters for ITER.
Contact: François Millet
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ILL investigates little-understood high-temperature superconductivity
The mechanisms that underpin superconductivity at temperatures above 20 K are not fully understood. Researchers at IRIG ran some experiments at ILL that could shed new light on a problem that has long confounded scientists. They observed, at the atomic scale, an iron-nickel-arsenic pnictogen superconducting at 50 K. The images obtained showed iron atoms organized in a square planar lattice, with their magnetic moments pointing toward the center and vibration perpendicular to this square plane. It is the interaction between the magnetic moments and the itinerant electrons in the material that cause the electrons to form bosons, called Cooper pairs, characteristic of superconductivity. It is not yet known whether this mechanism is true for all iron-based superconductors or, potentially, for other materials as well.
Contact: Frédéric Bourdarot
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Microstructure of halogenated hybrid perovskites revealed
Halogenated hybrid perovskites, or HHPs, have garnered interest for their potential as photovoltaic materials. New insights into these materials’ structural properties could shed new light on why their performance decreases so quickly over time. Researchers at IRIG studied MAPbI₃, a leading HHP. They discovered that the deformation that proves to be so detrimental to the thin films’ stability could not be explained solely by the gap between their thermal expansion coefficient and that of the substrate. Their research also revealed that the double crystalline orientation sometimes observed is due to the presence of ferroelastic twinned crystals. Last, but not least, they showed that the nature of the first layer (MAI or PBI2) in contact with the substrate influences the orientation of the perovskite.
Contact: Stéphanie Pouget
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Room-temperature laser emission achieved in germanium-tin alloy
Scientists from IRIG, CEA-Leti, and materials science lab C2N recently showed that a germanium-tin alloy microdisk laser cavity can emit at a record temperature of 32 °C. A tin content of 17% and a pedestal-type architecture that enables better dissipation of the heat from the stacked layers made the advance possible. Tin atoms are larger than germanium atoms, so increasing the tin content to 17% should create crystal defects in the material. Here, the defects were prevented by a series of buffer layers with gradually increasing tin content used during epitaxial growth. The advance marks a major step toward CMOS-compatible room-temperature laser sources. Up next: improvements to push the device’s operating temperature even higher and improve the alloy’s crystalline quality.
Contact: Nicolas Pauc & Vincent Calvo
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Electronic nose could soon sniff out diseases
IRIG’s electronic nose, originally designed for consumer and industrial applications, is now being used in the early detection of diseases. Here’s how it works: some diseases—especially cancer—alter the metabolic production of volatile organic compounds (VOCs), some of which are relevant biomarkers. In this research, which focused on two oeso-gastric cancer biomarkers, record detection limits (around one part per billion by volume) were reported. Instead of a combination of peptides that self-assemble in a monolayer, here the sensitive element is a 3D nanostructure with a perfectly controlled morphology, obtained from a single peptide in solution. The electronic nose is not a medical device, but it could be used in screening.
Contact: Yanxia Hou-Broutin
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3D integration: chip-to-wafer bonding alignment 10x more accurate
An innovative magnetic sensor to help align chip-to-wafer bonds for 3D integrated circuits was recently developed and patented by a team of scientists at IRIG. When used in optimal conditions, the sensor is accurate to within 50 nm: ten times better than the 500 nm today’s optical solutions can achieve. The improvement could help substantially increase the interconnect densities in the stacks that make up 3D ICs. A PhD candidate co-supervised with two other institutions (University of Strasbourg, France and FHNW University of Applied Sciences and Arts Northwestern Switzerland) contributed to the development of this new sensor, which is made up of a magnetic reference layer and a two-state (parallel/antiparallel) readout layer. It is most accurate when the elements being bonded are less than one micron apart. The research was part of an ERC Proof of Concept project called Magalign.
Contact: Ricardo Sousa
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The magnetic superconducting mysteries of heavy-fermion metal UTe₂
UTe₂ , which confounds a 60-year-old theory of superconductivity, has captured the scientific community’s attention ever since it was discovered in 2018. Researchers at IRIG have now determined that a much stronger than normal magnetic field is required to destroy UTe₂ ’s superconductivity. Even more surprising is that the material’s superconductivity actually gets stronger under magnetic fields between 15 tesla and 35 tesla—ten to a hundred times stronger than what conventional materials can withstand. And, under a magnetic field between 45 tesla and 60 tesla, a new superconducting state is observed. A “spin-triplet” state could explain this particularly robust superconductivity. Neutron scattering experiments at ILL point to magnetic fluctuations as playing a role in UTe₂ ’s unusual behavior.
Contacts: georg.knebel@cea.fr; stephane.raymond@cea.fr
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World’s first 2D ferromagnetic materials at 229 K
Researchers at IRIG achieved a world first when they grew Fe₅GeTe₂ thin films on sapphire using molecular-beam epitaxy. They were able to obtain a single-crystal two-dimensional material with controlled composition. Here, the simple bilayer boasts ferromagnetic ordering at temperatures up to 229 K, compared to under 100 K for most 2D magnets made using mechanical exfoliation. France’s national SOLEIL Synchrotron and other advanced characterization resources were used to study the new material’s standout properties. The researchers are pursuing new advances toward ambient-temperature permanent magnets, with several alloys and dopants currently under evaluation. Two-dimensional magnets with controlled structures like these could support the development of ultra-compact spintronic devices that can be activated by light or by an electric field.
Contact: frederic.bonell@cea.fr
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Nickel almost as good as platinum for fuel cells
Fuel cells with platinum electrodes are efficient but, because of the material’s scarcity and high cost, are not a viable long-term option. Nickel, much more readily available, could be used as a catalyst, but only if its efficiency can be improved drastically. A team of researchers from IRIG and CEA-Liten developed an electrode with a nickel catalyst grafted on a gas diffusion layer modified with carbon nanotubes that performed well, delivering a current density of 0.4 A/cm², not too far behind platinum’s 1 A/cm². Here’s how they did it. Based on insights gained from several advanced characterization techniques used simultaneously, they improved surface concentration of the catalyst and, crucially, active layer hydration. Up next: integration of the electrode into a fuel cell.
Contacts: pascale.chenevier@cea.fr; bertrand.reuillard@cea.fr
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Organs-on-chip could give diabetes patients new hope
Researchers from IRIG and CEA-Leti successfully maintained pancreatic cells called islets of Langerhans in culture on a microfluidic chip for a month and were able to measure individual islets’ insulin production.
This breakthrough could improve the efficacy of islet transplants, a treatment given to some diabetes patients. Islets of Langherans are sphere-shaped pancreatic cells between 200 microns and 300 microns in diameter. Although they account for just 3% of the pancreas, they perform the vital function of releasing either insulin or glucagon to keep blood glucose levels in check. Diabetes occurs when these cells no longer function optimally or cease to function altogether. France’s medical regulator approved islet transplants in 2021 for patients with severe diabetes.
Selecting the most promising islets before the transplant.
The joint IRIG-CEA-Leti research team built a special microfluidic chip and “grew” the islets of Langherans in it, keeping the cells alive for a month. This alone represents a significant challenge. However, the researchers went even further, instrumenting the chip and measuring each islet’s insulin production in response to varying glucose levels. The system works, which means that it could be used to identify the best performing islets and study the molecular mechanisms at work inside them. Currently, as there is no way to predict islet behavior, cells are taken from four or five donors per patient to increase the chances of a successful transplant. This advance could help improve the efficacy of islet transplants by providing insights into which islets will work best.
Contact: xavier.gidrol@cea.fr
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Gingko biloba protein used in multilayer nanomaterial
Gingko biloba trees, known for their longevity and medicinal properties, are now being used in nanoscience. Two teams of researchers a IRIG used the plant’s LEAFY protein, which is involved in flowering, to develop a 40-layer nanomaterial made up of cells spaced 8nm apart. The perfectly aligned cells offer excellent mechanical resistance and molecular grafting can be used to functionalize them. It would be impossible to obtain such a small and regular 3D structure using conventional techniques like etching or the elementary assembly of atoms.
IRIG now has a versatile nanomaterial with potential uses in biotechnology, nanoelectronics, biocatalysis, and biosensors. The researchers will start with VOC detectors (Volatile organic compounds) expected to be ten times more sensitive than the current state of the art.
Contacts: pierre-henri.elchinger@cea.fr; renaud.dumas@cea.fr
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ESRF X-ray imaging looks inside the platinum in catalytic converters
Researchers at Irig* leveraged ESRF X-ray imaging, simulation, and a neural network algorithm to characterize the deformations in platinum nanoparticles similar to those used in catalytic converters—a first.
The in operando observations were completed on model particles in contact with carbon dioxide, and measurements were taken on a cycle over twelve hours. The observations and measurements resulted in the identification of two types of defects: rearrangements of atoms in the platinum crystals, and the formation of flat facets on previously rounded areas.
Now the researchers are working on assessing the defects’ impact—positive or negative—on the reaction. The results should lead to engineering work to improve catalytic converter efficiency.
Contact: marie-ingrid.richard@cea.fr
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Could hole qubits be the future of quantum?
Nobody knows whether tomorrow’s silicon qubits will be electron qubits or hole qubits. If this exciting new research by an IRIG PhD student is any indication, the suspense is going to go on a little longer!
This major research showed that hole spin can be manipulated and read based on detailed characterization of the hole spin’s energy spectrum, even when the quantum dot (QD) isolating the hole is at the center of a dense QD array. Unlike electron qubits, which can only be manipulated with an RF magnetic field, hole qubits can be manipulated with a simple radio frequency (RF) electric field—the basis for the demonstration carried out in this research.
Hole qubits are more difficult to fabricate than electron qubits, but they are promising, and Irig is pursuing the research. Up next: The researchers will couple a qubit with a single photon to make a quantum photon bus.
Contact: romain.maurand@cea.fr
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Magnetic microparticles could fight cancerous tumors
For the past decade, two laboratories at IRIG (Spintec and SyMMES) have been investigating how to destroy tumors by injecting and then vibrating magnetic microparticles with an alternating magnetic field. One obstacle stands in their way: It takes too long to produce the perfectly calibrated disc-shaped microparticles. So, instead they used micrometer-sized grains of ground iron oxide powder functionalized with polyethylene glycol.
The production yields are 1,000 times those of the microparticles. In in vitro testing, the grains dispersed better in the tumor, causing apoptosis, or spontaneous death, of the cancer cells, rather than necrosis, which is more likely to cause the tumor to metastasize. The objective of the research, which is ongoing, is to bring the solution through clinical trials.
Contact: robert.morel@cea.fr
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Turbulence in superfluid helium-4
Physicists at Irig recently looked at how to measure turbulence flow velocity in superfluid helium-4, experimenting with two techniques used for “normal” fluids. In the first, they used a hot wire 1.3 microns in diameter as an anemometer fixed in the flow and came up with models for interpreting the signals collected. In the second, they employed a fixed camera to measure the speed of hollow glass microbeads immersed in the flow. This research is part of a wider investigation of how superfluid helium-4, with zero viscosity, dissipates mechanical energy as heat.
The findings could also be useful in the interpretation of astronomical observations of bodies like neutron stars.
Contact: pantxo.diribarne@cea.fr

LEDs in the race against mercury for UV-C emission
A recent paper by researchers from IRIG and Institut Néel presents a method for creating quantum wells in GaN/AlGaN core-shell structures on GaN for UV emission enhancement. The secret of the structures lies in their very small number of cracks—which behave like non-radiative centers, trapping charge carriers. Because of the difference between the two materials’ mesh parameters, the cracks are created beyond a certain elastic energy per unit area threshold. The researchers used an epitaxial growth process in which the aluminum content of the AlGaN increases gradually to avoid reaching this threshold.
The quantum wells, embedded in nanowires, are of interest to research due to their potential to improve UV LED efficiency and, possibly, replace mercury disinfection lamps.
Contact: joel.eymery@cea.fr

The physics of stacked graphene layers is both rich and unpredictable
When two layers of graphene are stacked, even the tiniest misalignment can slow electrons down or bring them to a halt altogether. The underlying physics is particularly rich, with the graphene behaving like a superconductor or, conversely, like an insulator! A recent Irig meta-analysis of around ten studies shed new light on these phenomena. The researchers pointed out that the high variability in behavior from one two-layer stack to another is not only due to differences in alignment. It can also be attributed to fabrication-process-induced deformations and residual strain in the layers. A relative stretch of just 1% can dramatically alter the layers’ electronic properties.
The research was published in Physical Review Letters.
Contact: vincent.renard@cea.fr

IRIG unveils high-potential memristor for neuromorphic computing
IRIG recently completed a proof-of-concept of a promising memristor that could be used as an artificial synapse in neuromorphic architectures. This non-volatile memory’s resistance can have multiple intermediate values between a minimum and a maximum. Thanks to recent advances, the storage layer’s magnetization can be oriented and stabilized in all directions of the layer plane, rather than just parallel or antiparallel to a reference layer. The memristor stands out for its low power consumption, low variability, and write endurance, making it ideal for machine learning applications with their billions of potentially energy-intensive operations.
The next step is to implement the component in circuit architectures for testing.
Contact: bernard.dieny@cea.fr
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MRAM memories stand up to heavy ion abuse
Although IRIG’s latest generation of MRAMs were not necessarily designed for use in radiation-hardened electronics, recent tests on the UCLouvain (Belgium) cyclotron showed that the magnetic tunnel junctions inside the devices can withstand heavy-ion bombardment. Two high-density memory technologies, STT-MRAM and SOT-MRAM, were tested and their main operating parameters measured. The impact of the heavy ions was not significant and did not jeopardize the stability of the memories’ electrical properties. Certain magnetic properties were affected, but this was due to the temperature and not the irradiation itself.
Up next: tests on complete MRAM memories.
Contact: gregory.dipendina@cea.fr
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Peptides could inhibit SARS-CoV-2 replication
IRIG is one of eleven research teams in five countries that have been working on how to inhibit SARS-CoV-2 replication since April 2020. They are investigating synthetic peptides that bind to M^Pro, which plays a key role in the replication of this virus. The researchers combined several biomolecular simulation techniques to observe, at the scale of a single atom, how M^Pro hydrolyzes certain proteins at eleven sites. They then used this information to design synthetic peptides capable of binding more tightly to the enzyme than natural peptides, keeping the virus from replicating.
The research was published in the journal Chemical Science, but it is not ready to use just yet. This new approach could serve as a foundation for the development of Covid-19 treatments. The results are available free of charge on GitHub.
Contact: luigi.genovese@cea.fr

Larger defect-free graphene layers produced
IRIG and ESRF recently attracted the attention of the global nanoelectronics community when they produced defect-free single-crystal graphene layers measuring several square millimeters. The tiny layers are a million times larger than the square micron commonly obtained until now! The researchers did it by growing the 2D material on liquid copper at 1,100°C rather than on solid copper. Combining the reflection and diffraction measurements of synchrotron X-ray imaging, Raman spectroscopy, and optical microscopy, they were able to monitor and control the formation of the graphene crystals in real time. The layers obtained are as good as exfoliated graphene sheets, but they do degrade as the liquid copper solidifies, and must be separated before the substrate cools.
The research was conducted under EU project DirectSepa, which has been running for a year now.
Contacts: gilles.renaud@cea.fr and maciej.jankowski@esrf.fr
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Neutrons supercharge fuel cell research
Researchers at IRIG recently co-authored a literature review on the growing use of neutron techniques in research on new energy technologies. The authors underscore the rapidly changing landscape, especially when it comes to fuel cells. Protons and hydrogen form the pillars of fuel cell technologies, and neutrons happen to be very sensitive to both.
For research, this means that quasi-elastic neutron scattering can be used to characterize ion dynamics, for example, and that neutron imaging can be used to observe batteries during operation to better understand the phenomena behind aging. Neutron techniques aren’t new to Irig. The lab has published many papers on research using these advanced techniques and has developed a high level of expertise. IRIG’s researchers are also experts at building electrochemical cells for research and processing complex data.
Contact: sandrine.lyonnard@cea.fr
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Mystery of disappearing photons solved
When photons interact with matter, a few per million are transformed into lower energy photons. In a specific kind of superconducting quantum circuit, the proportion of photons that undergo this transformation rises to one in three! Researchers at IRIG recently discovered that the phenomenon is related to the nature of the circuit: a chain of large Josephson junctions terminated by a smaller junction that behaves like a qubit coupled to a transmission line.
The electrical charge displaced in the vicinity of the qubit modulates the qubit’s energy. Quantum jumps in the superconducting phase “break up” the incident photon in resonance with the qubit to form a slightly smaller photon and several low-energy photons. This breakthrough in theoretical physics marks a step toward the long-term objective of generating multiple entangled photons in a controlled manner.
Contact: manuel.houzet@cea.fr
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Creating and manipulating skyrmions with helium ions
Researchers at IRIG and their Paris-based partners (C2N (CNRS) and startup Spin-Ion) successfully generated and controlled the movement of magnetic pseudo particles called skyrmions by first irradiating a magnetic track with helium ions. Until now, skyrmions were impossible to control, moving toward the edges of the track and disappearing. This advance bodes well for the use of skyrmions to build processors and memory. Here, the “trains” of skyrmions the researchers were able to create on the tracks were a few hundred “cars” long. When an electrical current was applied, the skyrmions moved along the irradiated area, even if the current was not perfectly aligned with it. The technique was tested on a 200nm wide track, but simulations indicate that it could work on a track as narrow as 10 nm.
Contact: olivier.boulle@cea.fr

New accelerator at Ganil gets high-precision control system
Ganil (Ganil is the national large heavy ion accelerator, an economic interest group of the CEA and CNRS) in Caen has a new superconducting linear accelerator. Researchers at Irig recently tackled the challenge of achieving millibar-precision pressure control of 26 superconducting accelerator cavities cooled to 4.5K by a liquid helium bath. The researchers used Simcryogenics, Irig’s simulation tool for large cryogenic equipment, to model the accelerator. The modeling and subsequent development of ad hoc control laws were also the topics of a PhD dissertation. A few final adjustments to the control system were made on site during commissioning. The high degree of precision will help ensure robust operation of the accelerator, which is extremely sensitive to even tiny fluctuations in helium pressure.
It should avoid shutting the beamline down several times a day.
Contact: patrick.bonnay@cea.f

Marion Gruart wins award and PhD grant for red LED research
Marion Gruart, who did her PhD research at IRIG from 2016 to 2020, won a Grenoble-Alpes University innovation award for her dissertation. She was also hired for a research position by startup Aledia. Her work on a high-stakes topic, InGaN (indium gallium nitride) nanowire red LEDs, has resulted in four patents. To emit red light, optimally, the material has to contain 35% indium. The problem is that a 35% indium content creates a mismatch in the lattice and dislocations in the standard planar-layered heterostructures. This is detrimental in terms of light emission. Marion developed original structures made up of a network of nanowires with a pyramidal morphology to solve this problem.
Aledia has even decided to co-finance another PhD candidate’s research at the same Irig lab this year.
Contact: bruno.daudin@cea.fr
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Reversing magnetization with an electric field
Researchers at IRIG working with colleagues in Romania (Babes-Bolyai University and Technical University (Cluj-Napoca, Romania)) recently discovered that the magnetization of an MRAM-cell-type nanostructure can be reversed by applying an electric field rather than an electric current. Their results should lead to some exciting developments. When an electric field is applied, the write speed is ten times faster and uses 100 times less energy compared to standard STT-MRAM. And, because Joule effect losses are reduced to a similar degree, the memory stack doesn’t get as hot, which is good news for STT-MRAM reliability and robustness. Simulation was used to determine the optimal switching parameters, which were then confirmed experimentally. The research, which is ongoing, could lead to the design of innovative components.
A patent has also been filed.
Contact: liliana.buda@cea.fr

Antibody engineering: CEA project wins Sanofi award
For the past several years, Institut Joliot (CEA Saclay) and IRIG have been working together to combine their Polaris(MD) multi-scale molecular simulation and BigDFT massively parallel quantum chemistry codes. Pharmaceutical company Sanofi deemed the project worthy of one of its iTech Awards, and will fund research to apply the approach to an antibody-antigen complex to study the impact of mutations.
Polaris(MD) and BigDFT provide a biologically, chemically, and physically coherent description of this type of molecular complex. Based on the same input data, the two codes can eliminate any uncertainties associated with the choices made during the modeling process. The analysis focuses on observable phenomena and their variability.
Contact: luigi.genovese@cea.fr

Bioimaging: quantum dots with fluorophore-like performance
Regular quantum dots are more stable under optical excitation than organic fluorophores; however, the dots cannot be used in biological environments because they can contain toxic metals like cadmium and lead. Several teams of researchers at Irig are putting their heads together to overcome this hurdle. They synthesized core-shell quantum dots that contain three non-toxic metals: silver, indium, and sulfur. Then, to enable the development of biosensors that emit in the near-infrared spectrum, they functionalized the shells with single-stranded DNA sequences.
The quantum dots are biocompatible and as good as the best fluorophores in terms of photoluminescence efficiency. A PhD research project slated for completion in 2023 is tackling further improvements to the synthesis process and biological use cases.
Contact: didier.gasparutto@cea.fr

Nitrogen magneto-ionics for lower power consumption
Magneto-ionics, or the voltage-controlled transport of atoms in and out of a magnetic material to alter the material’s properties, is a relatively new discipline. IRIG researches are part of an international team (Barcelona and Georgetown Universities, Helmholtz-Zentrum Dresden-Rossendorf in Dresden, National Microelectronics Centres CSIC in Madrid and Barcelona, the Catalan Institute of Nanoscience and Nanotechnology) that recently made an important breakthrough. Rather than displacing oxygen atoms, which are widely used in magnetic layers, the researchers utilized nitrogen, which activated or deactivated the material’s magnetism with just half the voltage. Plus, the process is reproducible and faster than with oxygen ions. The potential energy savings could be significant.
IRIG completed the simulations, which turned out to be consistent with the results observed in the lab. The research was published in Nature Communications.
Contact: mair.chshiev@cea.fr

Quantum: CMOS withstands very low temperatures
In the future, quantum devices cooled to 10 mK will be used together with conventional electronics. Which raises the question of how well CMOS components, designed to operate at ambient temperature, hold up in temperatures close to absolute zero. To test out this scenario, researchers from IRIG and CEA-Leti made hybrid circuits with the two technologies.
First, they evaluated a conventional CMOS TIA (transimpedance amplifier), measuring currents in the picoA range. The circuit was able to withstand the cold, but its bandwidth was under 4 kHz.
The test was done on a 28 nm FDSOI circuit. To increase measurement speeds, improvements will have to be made to the design. As the research progresses, other CMOS circuits will be evaluated for quantum applications.
Contact: louis.jansen@cea.fr

DNP probes cellulose nanofibrils
Dynamic nuclear polarization, or DNP, can make solid-state NMR several times more sensitive. Researchers at IRIG have been developing the technique to gain new insights into the surface chemistry of cellulose nanofibrils onto which an active molecule had been grafted.
They were able to distinguish between adsorption and covalent grafting, which allowed them to quantify the active molecules present. They also detected several residual compounds—the pre-oxidation agent, depolymerized cellulose, and coupling agents—resulting from the formation and functionalization of the nanofibrils. This new information will help the scientists (Centre technique du papier (pulp and paper research lab), LGP2, DPM, Cermav) IRIG is working with to study the nanofibrils to improve their processes.
Contact: gael.depaepe@cea.fr
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Lensless imaging could make phage therapy faster
Researchers at IRIG, CEA-Leti, and LTM recently worked with a team at Lausanne University Medical Center (CHUV) bacteriophage and phage therapy lab to develop a lensless device capable of reducing the time it takes to identify active phages on antibiotic-resistant bacteria at least threefold. The large-area image sensor (24×36 mm²) reads the optical signature of areas occupied by bacterial debris. The technique could be more effective than naked-eye observation and would result in fewer false negatives.
An ANR (France’s national research agency) priority program to develop the technique further is about to begin in conjunction with Hospices civils de Lyon, a major university medical center. According to the WHO, antibiotic-resistant infections could cause 10 million deaths per year by 2050, making phage therapy a strategic solution.
Contact: Emmanuel.Hadji@cea.fr
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Silicon can emit single photons at 1.28 microns
IRIG was among the partners on a French national research agency (ANR) project that resulted in the on-demand emission of single photons in silicon at 1.28 µm, a wavelength used in telecommunications. They did it by introducing carefully-engineered defects into the material. The goal is to integrate this photon source into CEA-Leti chips for quantum communications.
There is certainly no lack of research on point defects in silicon and, specifically, light-emitting defects formed by carbon pairs interacting with interstitial silicon atoms called G-centers. However, it had never been posited that these defects could emit single photons. The Octopus project implanted G-centers into the silicon and demonstrated that they could emit single photons. The findings were published in Nature Electronics.
A potential enabler of quantum communications
The G-center the researchers engineered turned out to be a very efficient source of photons that could potentially be embedded into chips. Using an external source to generate photons and then injecting them into the chip creates line losses. Single photons, however, are not affected by these reamplification issues.
The partners are now working with CEA-Leti to integrate the G-center into a chip to assess its potential for quantum communications. They are investigating the degree of spin freedom of isolated G-centers embedded in membranes of silicon 28, a spinless isotope. The G-center could be a future single-spin quantum memory, capable of storing the state of a single photon.
Contact: jean-michel.gerard@cea.fr

Pentagons magnetically frustrated, but still fairly well-organized
Magnetic frustration is a phenomenon resulting from competing constraints in a material, such as when an atom’s magnetic moments want to organize themselves in antiparallel pairs, but can’t due to their geometry. This causes matter to organize itself in complex fundamental states. Researchers have been studying magnetic frustration in triangles, for example, for decades.
In a world-first, researchers from IRIG identified a pentagonal lattice of magnetic atoms, demonstrating that the magnetic moments in iron oxide atoms are organized at 90-degree angles to each other. In addition, this pentagonal lattice is organized around a pair of magnetic moments whose bond is stronger and, therefore, not as sensitive to variations in magnetic field or temperature. This pair controls the ordering of the magnetic moments, even in the presence of magnetic frustration.
Contact: eric.ressouche@cea.fr
This highlight on the IRIG's Website

Spin Hall effect observed in a ferromagnetic material
The spin Hall effect, where a charge current is transformed into a spin current, has been amply documented, but only in non-magnetic materials. Researchers at Spintec wanted to know if the effect could be observed in ferromagnetic materials. Specifically, they have been looking for the reverse spin Hall effect (spin current to charge current) in a copper-nickel alloy. Whether the ferromagnetic alloy was cold or heated, causing it to lose its permanent magnetization, the effect was present to the same degree.
The spin Hall effect can be used to reverse the magnetization of memory and will play a role in the design of beyond-CMOS devices. The idea now is to expand the range of materials that could produce the effect. The research is ongoing. Up next: electrical transport measurements.
Contacts: jean-philippe.attane@cea.fr and laurent.vila@cea.fr
This highlight on the IRIG's Website

New mustard-gas assessment can be used up to fourteen days after exposure
Mustard gas has been banned by international treaties. However, it does remain a threat in certain armed conflicts and could potentially be used by terrorists. Scientists at IRIG, who have been studying the effects of the gas for years, recently developed (with CEA-Joliot (Saclay) and France’s military biomedical research institute) a method for measuring the dose received. It can be used up to fourteen days after exposure. It is also simpler and provides more complete information than the techniques currently in use.
This method, which targets the metabolites produced when mustard gas interacts with an intracellular antioxidant, glutathione, has been tested with success on cells in culture, skin tissue, and animal blood plasma. It could make a real difference in providing an accurate exposure assessment, crucial to prescribing effective treatment and limiting long-term negative health effects. It is used in addition to the non-quantitative assessment of eye and skin damage.
Contact: thierry.douki@cea.fr
This highlight on the IRIG's Website

STT-MRAM memory cells under under the microscope
For the past four years, Spintec has been working on a STT-MRAM memory point geometry that eliminates an etching step that degrades the magnetic layer. Their research required in-depth knowledge of the magnetic behavior of the memory points, which are deposited on 230 nm pillars spaced 400 nm apart. So, they went to the Nanocharacterization Platform (PFNC) to use the Titan™ Ultimate transmission electron microscope.
The electron-holography images obtained showed that if memory points absorb the magnetic flux generated by adjacent points, they “talk” to each other. However, if they line up in the same direction when a magnetic field is applied, the memory works as intended. The magnetic layer is deposited on the substrate in between the pillars. The Titan™ images showed that the magnetic layer’s large surface area allows it to absorb the magnetic flux radiated by memory points..
Contacts: aurelien.masseboeuf@cea.fr and david.cooper@cea.fr

Microwire and quantum dot could connect two worlds
An 18 µm conical gallium arsenide microwire with a quantum dot at its base could one day help connect the traditinal and quantum worlds. This novel device was developed by a research consortium (Institut Néel, ENS Lyon, University of Campinas (Brazil), and University of Nottingham (Great Britain)) that included scientists from Irig. The advance could pave the way toward the development of ultra-sensitive sensors and quantum information technologies one day.
When the quantum dot is excited by a laser pulse, its volume expands slightly, causing the wire to bend. When the optically-induced excitation is repeated at the wire’s resonant frequency, vibration can be induced and measured. Ultimately, they would like to “print” the dot’s quantum state on the mechanical oscillator.
Contacts: julien.claudon@cea.fr and jean-philippe.poizat@neel.cnrs.fr

Radiobiology: X-ray generator delivered to IRIG
IRIG recently received a 250 kV X-ray irradiator with a maximum dose rate of 10 Gy/min. The new equipment is dedicated to the CEA’s radiobiology program, where it is being used by the four Irig labs that provided the funds for the purchase. The labs are investigating the effects of low doses on cells and DNA. They are also studying the behavior of radioresistant bacteria that repair their DNA after exposure to radiation.
Before the new X-ray generator was purchased, the labs had been using the cobalt 60 sources at Arc Nucléart and, much more occasionally, the beamlines at ESRF. This X-ray generator only emits radiation during operation, making it an excellent solution for the work Irig is doing. Outside scientists will also be eligible to use the equipment.
Contact: jravanat@cea.fr

Quantum supremacy still not a given
Nature published Google’s groundbreaking results on a 54-qubit quantum computer in October, effectively declaring that quantum supremacy had been achieved. A few weeks later, however, a team of researchers from Irig and the US-based Flatiron Institute produced very similar calculations on a common laptop computer.
Google did reach an impressive milestone when it successfully operated a “real” quantum machine with 54 physical qubits. The tech giant’s researchers performed a calculation that even the best conventional machine would have taken 10,000 years to do, in just 200 seconds. One thing the research did not factor in, however, is this: Because of the quantum computer’s inherent precision and decoherence problems, the error rate of each operation is 1%.
Multiplying the number of qubits should not be the end goal
The IRIG-Flatiron Institutere searchers posited that Google’s machine did not even come close to utilizing the full power of quantum. They then used quantum-state compression algorithms to simulate the Google machine’s actual operation…on a regular consumer-grade computer! In just a few hours they completed the same calculations that the Google researchers said would take decades.
Their findings refocus attention on the real issue, which is not necessarily to build machines with more qubits, but rather to improve reliability—something that still raises serious theoretical and practical challenges. Another added bonus of the research is that IRIG developed a tool unlike any other for evaluating the performance of current and future quantum computers. IRIG has obtained several grants for further research on this topic.
Contact: xavier.waintal@cea.fr
This highlight on the IRIG's Website

Melanoma: IBS investigates vaccine potential
Researchers at IBS, France’s national blood bank and IAB Grenoble, are using protein antigens characteristic of melanoma, a particularly aggressive form of skin cancer, to explore whether or not stimulating a patient’s immune system can enhance treatment of the disease. The antigens would be vectorized by a non-infectious particle derived from the adenovirus.
Cancer generally attenuates a patient’s immune response. Here, the idea is to stimulate a strong immune response with a vaccine. One additional benefit of this type of vaccine is that it would be easy to volume manufacture.
The scope of this research encompasses vector production and both in vivo and in vitro testing. Solène Besson, the recent winner of an award from the Silab-Jean Paufique Foundation, is supervising a PhD thesis on the project. The award came with a €20,000 grant to be disbursed to her lab over three years.
Contact: solene.besson@ibs.fr

Magnetic 2D materials, the new path to skyrmions?
Spintec recently teamed up with CNRS-Thales joint research unit UMPhy and China’s NIMTE to work on skyrmions. According to their results, the spin quasi-particles, which are heralded as the material for tomorrow’s magnetic memory, can be generated in transition metal dichalcogenide (TMD) monolayers.
Their work focused on Janus MnSeTe and MnSTe TMDs: In these materials, a layer of manganese is placed between two different chalcogen layers to create the asymmetry necessary for the magnetic interactions that produce skyrmions. A magnetic field is applied at temperatures up to 150 K to stabilize the skyrmions.
Lab experiments are already underway to test this new approach. The overriding objective is to broaden the number of potential skyrmion materials beyond just metal magnetic multilayers.
Contact: mair.chshiev@cea.fr

Fuel cells: Neural networks provide new insights into Nafion
Not even the powerful beamlines at ESRF and ILL can accurately ascertain the multi-scale (nanometer to centimeter) structure of Nafion as a function of water content, one of the keys to PEMFC performance. Researchers at IRIG found a workaround in the form of a convolutional neural network.
They used nanostructure/water content data on ionic surfactants, whose behavior is well-known, to teach the algorithm. The network then expresses Nafion’s nanostructure for different water contents as a distribution of ionic surfactant behaviors with the corresponding probabilities. Nafion’s self-organization behavior is described by analogy, without a model or initial hypothesis, and the results are much more accurate.
Contact: stefano.mossa@cea.fr

DNP for cooler, more sensitive, and less expensive NMR
Dynamic nuclear polarization (DNP) increases the sensitivity of NMR spectroscopy experiments by several orders of magnitude. Two teams of researchers at IRIG recently leveraged instrumentation developed over a decade and protected by seven patents to increase NMR performance by a factor of ten. Now observations can be carried out at 35 K, rather than 100 K previously, for an operating cost in the tens of euros per day.
The researchers replaced the 77 K nitrogen heat flux cooling system with a cryostat system built on exchangers, a cryocooler, and the NMR probe head. The system cools a closed-circuit helium stream to heat and drive the sample holder at a speed of tens of thousands of revolutions per second. This is the only piece of equipment of its kind in the world. It is available for use by outside partners.
Contacts: gael.depaepe@cea.fr and eric.bouleau@cea.fr
This highlight on the IRIG's Website

NMR and biology: Paul Schanda brings home two awards
IBS scientist Paul Schanda, an expert on NMR techniques for the study of protein dynamics, recently won two international awards (The Varian Young Investigator Award and the ICMRBS Founders’ Medal 2020) for his body of work. Trained in physical chemistry, Schanda has made a name for himself by bringing the physical methods of chemistry to biology. Most notably, he came up with one of the first descriptions of so-called “chaperones,” which escort other proteins from where they are synthesized to their final location in biological membranes.
He also developed an NMR spectroscopy method to observe the process by which proteins are folded from their initial “spaghetti” shape into the 3D structures that determine their interactions with their environment. Finally, he is the author of more than 70 publications.
Contact: paul.schanda@ibs.fr

Spintronics and optronics, better together
In research conducted for the EU Spice project, Spintec demonstrated an optical magnetic tunnel junction that is 1,000 times faster than magnetic tunnel junctions that use an electric write current. This breakthrough could lead to non-volatile MRAM with unprecedented levels of performance.
Earlier in this project, Spintec had shown that a femtosecond laser could effectively reverse the magnetization of a termium cobalt layer. Here, the gap with an electrical current—which maxes out at around 100 picoseconds—was already substantial. At this stage, however, the demonstration was on the material, not on a functional MTJ.
The path toward memory points of 30 nm and possibly even 20 nm
The researchers recently reached this milestone, by replacing the MTJ’s top metal contact (usually aluminum and tantalum) with a transparent material the laser light could pass through. They settled on indium tin oxide, widely used in LCD displays. Memory points measuring 80 nm in diameter were fabricated using standard deposition and etching processes. Ultimately, the researchers hope to come down to 30 nm, and possibly even 20 nm.
MRAM memory could benefit from smaller MTJs that enable faster write speeds while consuming less energy due to the use of the energy-efficient laser. Only the read phase would remain electrical, at least in the near term. This will ensure that each memory point can be read individually. The laser wavelength of 800 nm cannot be focused on MTJs this small in diameter.
Contact: ricardo.sousa@cea.fr

No virus can escape the optomechanical resonator
CEA-Leti and IRIG are developing a mass spectrometry-based technique to “nanoweigh” viruses. And extremely accurate nanoresonators could expand the potential uses for the technique. CEA-Leti and Irig researchers were able to detect and weigh individual biological particles (from several megadaltons to a gigadalton). The technique was effective on bullet-shaped viruses like rabies and Ebola and on the amyloid fibrils that play a role in some neurological disorders. These non-spherical particles were almost impossible to analyze using the previous generation of resonators.
This new technique also works on very low concentrations of particles. The next step will be to test it on airborne viruses. The research, conducted in partnership with the CNRS, was published in the journal Nature Communications.
Contact: sebastien.hentz@cea.fr

An innovative lithium-ion battery anode
In research conducted for the EU Sinbat project, IRIG is pulling out all the stops—electron microscopy, MRI, X-ray diffraction, synchrotron, and neutron scattering techniques—to characterize an innovative lithium-ion battery anode. The anode’s revolutionary composition includes active domains of amorphous silicon and FeSi₂ nanoparticles in a graphite matrix.
The silicon increases the anode’s capacity to incorporate lithium and, as a result, the energy storage density. But it also triples in volume during charging, which can cause more rapid anode degradation. The anode developed by CEA-Liten and Varta, also a partner on the project, is made from a nanostructured material developed by 3M. This material effectively limits degradation. After 700 cycles, the anode still has 70% of its original capacity.
Contact: pierre-henri.jouneau@cea.fr
This highlight on the IRIG's Website.

ERC Proof of Concept grant for SOT-MRAM fabrication process
Researchers at Spintec won an ERC Proof of Concept grant for a SOT-MRAM memory fabrication process developed under an earlier ERC grant. The challenge here is the unusual profile of the memory’s free magnetic layer. Rather than being round, it has a number of angles. This unique geometry eliminates the need to use micromagnets, which would normally be required for the system to operate in a reproducible manner. The downside is that standard UV lithography machines are not suitable for this type of SOT-MRAM fabrication.
Ionic irradiation—provided by startup Spin Ion—offers a potential solution. If it works, the researchers will have made a major advance toward ultra-fast, compact, energy-efficient SOT-MRAM, a potential replacement for SRAM memory.
Contact: mihai.miron@cea.fr
This highlight on the IRIG's Website.

LiteBIRD deep-freezes telescopes to probe the genesis of our universe
Researchers from IRIG are working on the international LiteBIRD space observation satellite project. They have been tasked with developing a cold machine that can deliver 2 microwatts at 100 mK—a level of performance never before achieved in space. The cold machine will be used on the two telescopes in the payload.
The researchers have opted for a four-stage magnetic refrigeration machine that is well-suited to the demands of space. Variations in a magnetic field are applied to a magnetocaloric material to produce cold. The researchers developed and patented a new magnetocaloric material, ytterbium gallium garnet, which offers unparalleled energy density. The design phase should be completed by the end of 2021.
Contact: jean-marc.duval@cea.fr
This highlight on the IRIG's Website.

Two IRIG scientists now members of prestigious French learned society
Two Grenoble-Alpes University faculty members, also scientists at IRIG, became members of the learned society Institut universitaire de France on October 1, 2020 for a five-year term. They were selected for their excellence in research and for the international recognition they have earned.
Junior Member Hélène Malet works at the IBS Electron Microscopy and Methods Group. She conducts research on the structural and functional analysis and replication of bunyaviruses, an order of viruses that affects humans and for which there is currently no treatment.
Senior Member Mairbek Chshiev works at Spintec. His research to determine the best combination of materials for sustainable electronics using spin orbitronics and 2D spintronics won over the selection committee.
Contacts: mairbek.chshiev@cea.fr and helene.malet@ibs.fr
Highlights on the IRIG's Website: Mairbek Chshiev - Hélène Malet.

Tomorrow’s window glass could be photochromic and photovoltaic
Imagine window glass that changes in tint depending on sun exposure and produces electricity, too. Researchers at IRIG and two international partners [Pablo de Olavide University (Seville) and Solaronix (Switzerland)] are trying to develop just such a glass. A specially developed and patented naphthopyrone pigment was placed between two sheets of glass, allowing the researchers to obtain photochromic and photovoltaic effects on a 23 sq. cm piece of glass in the lab.
In terms of scaling up the technology, the partners are working on improving the colorant’s long-term stability and the speed at which it returns to its clear state when ambient light fades. They would also like to improve the PV conversion yield, currently at 4.2%. Prototypes measuring 1,000 sq. cm should be available by 2024.
Contact: renaud.demadrille@cea.fr
This highlight on the IRIG's Website.

Reconstructing a SiC surface is all about order and disorder
How do you reconstruct the C-face of a silicon carbide (SiC) wafer after cutting? The issue has been the subject of great debate since an early observation that dates back to 1997. An international team led by IRIG simulated a novel approach to surface reconstruction never before used for semiconductors. The research was published in Applied Physics Letters.
The cutting process creates a strong disorder in the charge transfer between unpassivated dangling bonds. An all-silicon overlayer forms in an ordered network. Below this overlayer, disorder is observed to offset the dangling bonds of certain carbon atoms. This research will be of interest to any researcher working with SiC on topics related to power electronics or graphene growth, for example.
Contact: pascal.pochet@cea.fr

Nanowires: Overcoming very large differences in lattice constant
Lattice constant is a measure of how structurally compatible two materials are. Researchers from IRIG and Institut Néel recently reduced these differences for GaAs/InAs (gallium arsenide/indium arsenide) nanowires. Their approach was to form a 5 nm ternary (InGaAs) alloy interface between the materials. The alloy’s composition transitions from a composition close to GaAs to one closer to that of InAs.
This gradient effect, achieved using epitaxial growth, is the work of a PhD candidate currently conducting research with the team. Characterization of the interface revealed no defects and minimal strain for an initial gap in lattice constant of 7%. The researchers feel that gaps of up to 11% would be acceptable, something that could open the door to new systems with advanced optoelectronic properties.
Contact: moira.hocevar@cea.fr
This highlight on the IRIG's Website.

Stabilizing skyrmions without a magnetic field now possible
The tiny magnetic bubbles known as skyrmions—potential candidates for tomorrow’s memory bits—can now be stabilized at ambient temperature without a magnetic field. Researchers at Spintec just demonstrated this new capability using an exchange coupler already used in MRAM. Specifically, an anti-ferromagnetic layer is combined with the ultra-thin ferromagnetic layer that holds the skyrmions. The size of the skyrmions was also reduced, which could boost future memory storage densities. The smallest skyrmions measured 30nm, five times smaller than anything obtained previously by Spintec.
Also worth noting is that Spintec worked with the University of Montpellier to characterize the device using an innovative technique called nitrogen vacancy center magnetometry.
Contact: olivier.boulle@cea.fr
This highlight on the IRIG's Website.

IRIG to assist with commissioning Japan’s Tokamak reactor
The cryogenic system that cools the superconducting magnets on the Japanese Tokamak JT-60SA reactor has a refrigeration capacity of about 9kW equivalent at 4.5K, and the reactor’s cyclical operation creates substantial variations in the heat loads the system must handle. From 2010 to 2016, when the CEA was designing the cryogenics for the JT-60SA, a team of researchers from IRIG was working on how to smooth these loads. As commissioning draws near, they are taking their research into the field.
Assembly was completed in the spring, and qualification tests are underway. Next, the superconducting magnets will be cooled. Two researchers from IRIG in Grenoble will be on hand (either physically or remotely) during this phase. If all goes well, the reactor will start up in the spring of 2021. The ITER reactor project has already benefited from some of these advances.
Contacts: frederic.michel2@cea.fr and christine.hoa@cea.fr

Tomorrow’s spintronics could use 1,000 times less energy
Researchers from IRIG-CNRS and Thales published a breakthrough advance in spintronics in Nature. Rather than manipulating spin with a nanomagnet, they selected a ferroelectric material to do the job. Their novel approach uses 1,000 times less energy to write information.
Like for ferromagnetic materials, the information stored is non-volatile (it is stored without the need for additional energy). The polarization state of the ferroelectric element can be read without depolarizing, eliminating one of the habitual problems with ferroelectric RAM.
The researchers will now turn their attention to reproducing these effects, which they observed at 45 K, at ambient temperature. Their work lays the foundations for ferroelectric spintronics, which could enable innovative new low-power memory, neuromorphic components, and more.
Contacts: jean-philippe.attane@cea.fr & laurent.vila@cea.fr
This highlight on the IRIG's Website.

Irig’s electronic nose is now even more discerning
IRIG’s electronic nose, which was transferred to startup Aryballe Technologies, now has an even broader range of uses. But first it will have to be usable in the field and at wider temperature ranges. Researchers at Irig redid some of the basic science on the device, comparing theory with lab testing results. They looked at the influence of the emission source wavelength on the system’s sensitivity. £They also probed the impact of the thickness and roughness of the metal layers where the biosensors that capture odor molecules are housed. Finally, they came up with a method for characterizing the optical performance of the prism at the heart of the electronic nose. Their results will be used in a PhD research project to design a temperature calibration method suitable for measurements in the field.
Contacts: yanxia.hou-broutin@cea.fr & arnaud.buhot@cea.fr
This highlight on the IRIG's Website.

A new and sustainable photoelectrode for hydrogen production
Researchers from IRIG, Institut Néel, and EPFL in Lausanne developed a sustainable electrode for the production of hydrogen by photoelectrolysis, a CO₂-free process. This photosynthesis-inspired innovation uses non-toxic and abundantly-available materials, and features a p-type semiconductor interface that absorbs light with a molecular catalyst.
The semiconductor material, a copper iron oxide, is covered with a nanometers-thick layer of titanium oxide deposited using ALD. The cobalt-based catalyst is placed on top of this layer. The system can produce hydrogen from aqueous solutions.
This hybrid architecture is a breakthrough innovation that is still at the basic research stage. One aspect that must be substantially improved is current density.
Contact: vincent.artero@cea.fr
This highlight on the IRIG's Website.

LEDs could soon promise mercury-free UV
What if LEDs could be used instead of mercury-vapor lamps (These will ultimately be phased out under the Minimata Convention on Mercury in 2017) in a wide range of bacteria-killing UV devices? Researchers from IRIG and Institut Néel recently made a major step toward mercury-free UV lamps. They successfully and significantly augmented a UV LED’s p-type doping level of aluminum nitride (AlN) by adding a small fraction of indium to the magnesium, the doping material. They also structured the AlN into nanowires, rather than thin layers, facilitating the relaxation of strain generated by the dopant. An AlN nanowire p-n junction was fabricated and two patents were filed.
This advance could lead to a solution to the main issue with today’s LED UVs: their low efficiency (the ratio of photons emitted to charge carriers injected). A PhD dissertation on research demonstrating the approach on an entire LED is forthcoming.
Contact: bruno.daudin@cea.fr
This highlight on the IRIG's Website.

Photovoltaics: Looking at the instabilities that affect hybrid perovskites
Hybrid perovskite photovoltaic cells can deliver yields of more than 20%. However, they do not age well. Researchers from IRIG and INES joined forces to investigate the mechanisms that underpin the formation of the best-known hybrid perovskite, MAPbI₃ (methylammonium lead iodide), which is synthesized in thin layers.
The research revealed two things that explain the behavior of cells made from these thin-layer materials: First, the intrinsic instability of MAPbI3, which breaks down under mechanical strain (here, it is linked to the spontaneous appearance of MAPbCl₃, a chlorinated perovskite phase); and, second, the substantial variability in the material’s lattice structure.
New and more complex materials derived from MAPbI₃ but with the promise of greater stability will benefit from this novel approach.
Contact: stephanie.pouget@cea.fr
This highlight on the IRIG's Website.


Quantum many-body problem solved to order 15
The finding is a major one for theoretical physics: Researchers from IRIG, Institut Néel, and the Flatiron Institute (US) designed an algorithm that solves the quantum many-body problem to order 15
The quantum many-body problem describes phenomena at the atomic scale that standard approaches (“mean field approximation”) cannot model. One such example is the fact that cuprates, electrically-conductive materials, become superconducting at temperatures as high as 160 K. The solution, however, is hampered by the number of operations. For order 3 processes, the reciprocal influences between three bodies must be calculated; for order 4 processes it is between four bodies, and so on. At order 15, the computer must complete a staggering 1,000 billion operations!
New algorithm successfully makes the jump from order 7 to order 15
Previously, the huge number of operations meant that only processes up to order 7 or so could be solved. Irig’s algorithm lightens the computing load drastically, coming in at just 32,768 operations for order 15 processes. The algorithm delivered the first-ever accurate numerical solution to the non-equilibrium Kondo effect, a behavior specific to certain electrical conductors at low temperatures.
The researchers are still investigating the possibilities this algorithm will create. They have already identified several potential uses in quantum computing. In effect, the quantum many-body problem can very accurately describe the physics of an actual set of qubits, beyond the extremely-simplified forms used by mathematicians.
Contact: xavier.waintal@cea.fr
This highlight on the IRIG's Website.

A step toward controlled Al/Ge quantum disks?
Researchers at IRIG used a transmission electron microscope to observe the behavior of aluminum (Al) heated to temperatures in excess of 250 °C when it comes into contact with a germanium (Ge) nanowire. So, what did they see? Well, the Al propagates in the nanowire along a well-defined front; the Ge is pushed back and escapes through the surface.
They also noted that propagation speed is constant insofar as the temperature applied is also constant and the diameter of the nanowire is regular. A drop of just a few degrees halts the process with no inertia. In this way, it is possible to obtain a nanodisk (less than 10 nm) of Ge with Al on each side. The resulting object makes an excellent quantum disk that combines a semiconductor and two very-low-resistivity metal contacts.
Contact: eric.robin@cea.fr

Magnetic tunnel junction sets new speed record
Researchers at IRIG developed an ultra-fast magnetic tunnel junction (MTJ) that could be used to log events captured by stroboscopic photography. They used a terbium-cobalt layer whose magnetization can be switched using a femtosecond laser. A second magnetic layer is made from a material whose magnetization is not switchable. The magnetizations of these two layers (which are either the same or opposite) control an electrical current measured at the output.
The laser pulses are a million times faster than electrical pulses and use much less energy. The research that led to this advance was part of an EU project that will be completed in 2020. Ultimately, the goal is to build a demonstrator of this spintronic device with optical write and electric read capabilities.
Contact: ricardo.sousa@cea.fr

An original technique for functionalizing microscopes
In research funded by the French National Research Agency (ANR), a team at Irig electrochemically functionalized silicon micropores. The very sensitive biosensors created in this way are suitable for use analyzing living cells.
Their process, inspired by bipolar electrochemistry, involved placing two electrodes on either side of the pore. This technique usually requires voltages that are inversely proportional to the size of the pore. The researchers deposited a nanometric layer of silicon oxide onto the chip, and then selectively removed the oxide only at each micropore. This channels the field lines and reduces the necessary voltage 100-fold. The method, known as contactless electrofunctionalization, can be applied to both planar pores and pores that pass through the material.
Contact: aurelie.bouchet-spinelli@cea.fr
This highlight on the IRIG's Website.

CMOS electronics and quantum devices get ready to move in together
Digital and analog electronics could soon be sharing space with a quantum system on a FD-SOI substrate cooled to 110 mK. Sound strange? Researchers from Leti and IRIG recently designed a circuit with these unusual characteristics and presented it at a conference in February. It is only at the proof-of-concept stage. However, it does meet the requirements of tomorrow’s qubit circuits. Specifically, the researchers demonstrated that it is possible to boost the transistors to several GHZ, even at 110 mK, while keeping heat dissipation under the circuit’s dilution cooler temperature of around 300 µW.
They also confirmed the potential of silicon as the basic material for the qubit, with all of the advantages of decades of industrial CMOS experience. The project was part of the Quantum Silicon Grenoble program.
Contact: loick.leguevel@cea.fr

First steps toward a spin valve with electrical insulators
Researchers at IRIG collaborated with an international team to obtain dynamic coupling between two magnetic layers (yttrium iron garnet) separated by a gadolinium-gallium garnet substrate. These materials are all very good electrical insulators. The spin information can cross the substrate (which is neither magnetic nor electrically conductive) when the information is carried by chiral photons, which are elastic deformations of the circularly-polarized crystalline lattice.
The coupling obtained here is much more efficient than coupling with metal. Not only does the coupling require less energy, it also eliminates the Joule effect. This new spin valve could be used for qubit-to-qubit communication in tomorrow’s quantum computers.
Contact: olivier.klein@cea.fr


Germanium makes a foray into spin orbitronics
Can a unidirectional magnetoresistance effect (resistance caused by a current) be obtained with a semiconductor material like germanium? Researchers at Spintec found the answer, and, according to an article they recently published, it is yes! The effect had already been observed with two rarely-used non-magnetic materials. With germanium, however, the effect is 100 times more intense.
The researchers demonstrated that the effect originates in the electron gas at the surface of the material. The electrons’ spin aligns perpendicular to their trajectory. A satisfactory model of the phenomenon was created in partnership with the CNRS-Thales joint research unit in physics in Palaiseau, near Paris. The research will give new impetus to the development of a spin transistor. By varying the voltage of the grid, the effect could make it possible to modify or conserve the states of the spins injected from the source.
Contact: matthieu.jamet@cea.fr
This highlight on the IRIG's Website.

Skyrmions ten times faster than Usain Bolt
A team of researchers from Spintec, Institut Néel, and CNRS obtained the high-speed motion of skyrmions in a three-layered platinum/cobalt/magnesium oxide material, setting a record of 100 meters per second. Even more impressive: the record was achieved at low current densities and at ambient temperature! The key? Layers just a few nanometers thick, synonymous with very low energy consumption. With this latest feat, the nanometric quasiparticles known as skyrmions are well on their way to the finish line in tomorrow’s memory and computing systems.
The skyrmions’ behavior was modelled, and the observations aligned well with the theory. Spintec is leading a new project with six French and German research teams…this time to set a record of 1 km per second!
Contact: olivier.boulle@cea.fr

Germanium laser operates at record low temperature of 273 K
Researchers from IRIG and Leti joined forces with a team from Switzerland* to obtain lasing at temperatures as low as 273 K (0° C) using a slightly deformed germanium/tin (GeSn) alloy resonator. Emission in the infrared spectrum is generated by optical pumping. This achievement marks a new advance toward germanium lasers integrated on silicon. The seminal article on Ge/Sn lasers, which dates back to 2015, reported lasing at 90 K.
Leti handled the epitaxial growth of crystalline GeSn on silicon wafers. IRIG made the resonators and completed the optical characterization. To get even closer to ambient temperature, the researchers are now shifting their focus to two parameters: the proportion of tin in the alloy (currently at 16%) and the intensity of the deformation applied to the material.
Contact: nicolas.pauc@cea.fr et vincent.reboud@cea.fr
This highlight on the IRIG's Website.

Astrophysics: IRIG technologies used to cool DESI sensors
IRIG’s pulse tube cryocoolers were developed in the early 2000s and transferred to Thales in 2005. But the tiny devices are still making news! The 30 sensors that make up the DESI* spectroscope, which will create a giant map of the sky, is cooled by the cryocoolers. Five years from now DESI will have produced the most detailed 3D map of the universe ever, and scientists will be able to use the map to go back billions of years.
The cryocoolers were chosen because their cold areas do not have any moving parts, for maintenance-free reliability. IRIG is still making improvements to the cryocoolers so that they can be used for new, colder applications. The ESA, for example, has asked for a version suitable for cryogenic chains at temperatures close to absolute zero..
Contact: ivan.charles@cea.fr
The press release on the IRIG's Website.


Spin-charge conversion: What could be simpler?
An international team that included researchers from IRIG recently presented a simple, yet effective system for converting a spin current into an electrical current. They deposited aluminum onto a strontium titanate (SrTiO3) substrate at room temperature. The aluminum “pumps” the oxygen contained in the substrate and makes it conductive. The spin built up in the 2D electron gas that forms on the surface of the substrate can then be converted into an electrical current. The conversion is modulated using a simple electrostatic grid.
But perhaps what makes the phenomenon truly remarkable is that no ferromagnetic materials are involved. In addition, the conversion factor is between 10 and 100 times higher than with known high-performance materials like platinum. This advance should open the door to the development of new memory and transistor concepts.
Contact: laurent.vila@cea.fr
This highlight on the IRIG's Website.

Accessing a material’s topological electronic properties could get easier
The winners of the 2010 Nobel Prize in Physics did it using a simple electrical resistance measurement—which required ultra-pure graphene and a very strong magnetic field.
An international team that included researchers from IRIG recently published their discovery of a new and complementary technique in Nature. They used a scanning tunneling microscope (STM) to observe the reorganization of electrons in the vicinity of a hydrogen atom deposited on the surface of the graphene. They observed dislocations in the electronic density that reflect the unique topological structure. This method could provide deeper insights into the properties of materials.
Contact: vincent.renard@cea.fr
The press release on the IRIG's Website.

Wine, cheese, and raspberries on the olfactory biosensor menu
Researchers at IRIG joined forces with a team from Dijon to develop olfactory biosensors capable of fixing and recognizing the aromatic compounds in cheese (hexanoic acid), wine (hexanal), and raspberries (ß-ionone). The researchers designed and tested several genetic variants of proteins from the rat olfactory system for the biosensors. Although their research is still at the proof-of-concept stage, it does bode well for future developments.
The biosensors developed offer the advantages of a very low detection threshold, high selectivity, and good measurement reproducibility. New variants of the proteins could be used to identify other VOCs—a capability that could be useful for industrial and domestic applications. The human nose is very easily “saturated” by VOCs, which makes it difficult for humans to effectively smell these substances.
Contact: yanxia.hou-broutin@cea.fr
This highlight on the IRIG's Website.

SOT-MRAM memory now denser
SOT-MRAM is more reliable over the long term and faster than STT-RAM. The problem with SOT-MRAM, however, is that it is bulky. This is because SOT-MRAM typically has two transistors (one read and one write) as opposed to STT-MRAM’s single transistor. Researchers from Leti and Spintec have recently partially overcome this challenge with a network of SOT-MRAM memory with a unidirectional diode instead of a read transistor. The result is a 20% increase in density with no adverse effects on speed or endurance.
The majority of the research focused on developing and testing the architecture—especially for the read phase. The researchers are determined to further increase memory density and are currently working on an even more compact architecture.
Contact: gregory.dipendina@cea.fr

Proteomics and the p-value trap
Proteomics researchers are not generally well-trained in statistical methods—which often leads them to use the methods incorrectly, resulting in flawed conclusions. Researchers at IRIG are working on a solution to this problem, and their investigations led to four articles in international journals in 2018 and 2019. In particular, the researchers are looking at the risk of incorrectly interpreting the p-value, which indicates how significant a result is depending on the sample studied.
Proteomics is especially vulnerable to this type of error. Due to advances in spectrometry, proteomics researchers must manipulate growing volumes of data that are becoming more and more complicated to analyze. The IRIG team is raising proteomics researchers’ awareness of several issues, from understanding statistics terminology to designing protocols that make it easier to control sample analyses.
Contact: thomas.burger@cea.fr
This highlight on the IRIG's Website.

DFT methods boost the design of new enzymes
How can DFT (density functional theory) and small-angle neutron scattering be combined to create new enzymes? The answer is in an article published by an international team that included researchers from IRIG and ILL. The researchers pointed out that DFT, originally used for systems of tens of atoms, can now attain—or even surpass—100,000 atoms. This was made possible by an approach that entails calculating a system’s electronic structure from the structure of smaller blocks (like each of a protein’s amino acids).
The memory size required and the execution times are kept down to very reasonable levels using this approach. IRIG, which published four articles on wavelet-based DFT methods this year, is working on the topic with researchers from Boston and Kobe (Japan).
Contact: luigi.genovese@cea.fr


How to read and modify a quantum bit, step by step
A team of researchers from Grenoble (IRIG, Leti, and CNRS) made headlines in 2016 with the world’s first FDSOI qubit device—based on holes rather than electrons—made on a 300 mm CMOS fab line. Now they can read the state of the qubit, too. The researchers used a screen-grid reflectometry method, applying microwave signals to the grid to modify the qubit’s state.
The read technique is still lacking in precision. However, it will be useful for the rapid characterization (coherence time, relaxation time, etc.) of qubits made in Grenoble. Plus, the technique will be easy to duplicate on future circuits made up of several qubits. The research was published in Nature Communications in an article that came shortly after another team of researchers from Grenoble published their research in Nature Nanotechnology on gate-based high-fidelity spin readout in a CMOS qubit.
Contact: romain.maurand@cea.fr
This highlight on the IRIG's Website.

Unbroken layers of MoSe₂ over large surfaces now possible
Molybdenum diselenide (MoSe₂) has good optical properties, but is resistant to deposition processes. Microelectronics researchers had all but given up on the material, but research recently conducted by three physics labs at IRIG could change that. The researchers obtained an unbroken and uniform layer of MoSe₂ using molecular beam epitaxy on a graphene substrate. The grains’ crystalline quality is good, and their orientation is the same as the graphene grains. The material can absorb up to 15% of the light spectrum.
Applying the technique to 300 mm wafers is not yet within reach, however: The results were obtained on a surface measuring just 1 cm². Nevertheless, the process can be implemented on a large scale and could be more effective than the exfoliation and attach processes currently used on MoSe₂. The research was published in ACS Nano.
Contact: matthieu.jamet@cea.fr
This highlight on the IRIG's Website.

Graphene oxide caves give supercapacitors a boost
Could graphene sheets perform better than active charcoal in supercapacitor electrodes? Researchers from IRIG collaborated with two CNRS* research teams to find out. And the answer they came up with is yes—but only if you use reduced graphene oxide (rGO) in which nanometric alkanes are used as interlayer spacers.
The alkanes serve as molecular pillars that prevent the rGO layers from clumping back together, a phenomenon that would drastically reduce the surface available for the adsorption of ions, as well as the material’s storage properties. The researchers optimized the density of these pillars to ensure the free circulation of ions in the caves formed in between the graphene layers. The volume capacity of this modified rGO is four times that of conventional rGO.
Contact: florence.duclairoir@cea.fr
This highlight on the IRIG's Website.

Biomarkers: Portable microfluidics lab breaks records
Currently it takes two days to prepare a blood sample for biomarker testing using mass spectrometry. Leti recently unveiled a new portable microfluidics lab that can process blood samples in just two hours. The system automates and integrates all steps in the blood sample preparation process, from extracting the plasma to purifying the peptides used to detect biomarkers that indicate heart, brain, liver, and other diseases.
The PEP’s—for PEPtides Saver—demonstrator system was developed by Leti, Clinatec, and IRIG with funding from the Carnot Network. The system is also flexible: The duration, temperature, and sample volumes can be adjusted as needed. Leti has filed two patents to protect the innovation and is now seeking an industrial partner to scale up and manufacture the system.
Contact: marie-line.cosnier@cea.fr


Error-correcting codes: Is the quantum computer possible?
Quantum error-correcting codes were developed by mathematicians to check the variability of the state of each qubit. But are the codes relevant in practical terms? A physicist at IRIG investigated the issue and his conclusions are not optimistic. He noted that the theories use error models that fail to factor in errors that are rare, but that are nevertheless detrimental to computing precision.
In concrete terms, the error-correcting codes would have to make these errors a quadrillion times less frequent for the quantum computer to produce reliable results. Needless to say, this hypothesis is very unlikely. The study, published in Physical Review, is one of the first to issue a negative verdict, garnering substantial interest.
Contact: xavier.waintal@cea.fr
This highlight on the IRIG's Website.

MRAM memory gets new recipe
Researchers at Spintec have come up with a new way to improve MRAM memory retention, using tungsten instead of tantalum in the magnetic tunnel junction stacks. When the stacks are made, they must be annealed to crystallize the junctions. During annealing, the tantalum tends to diffuse toward the tunnel barrier, absorbing oxygen in the process. It also absorbs some of the iron in the magnetic electrode, modifying the electrode’s chemical composition. These phenomena alter MRAM magnetoresistance and retention (how long information can be stored).
This undesirable effect occurs at temperatures greater than 300 °C; annealing can take place at temperatures of 400 °C. Therefore, it is a good idea to replace the tantalum with tungsten, which migrates less and captures less iron during annealing.
Contact: bernard.dieny@cea.fr
This highlight on the IRIG's Website.

A new step forward toward very-high-density magnetic storage
Grenoble-based researchers from IRIG working at ESRF successfully obtained a single layer of graphene on single-crystal iridium with a periodicity of 2.5 nm using a CVD reactor. Materials research institute Institut Lumière Matière in Lyon had previously obtained iron-platinum nanoparticles, organized them at the atomic scale, and given them magnetic properties. Here, the two teams joined forces, depositing the nanoparticles developed in Lyon onto the substrate developed in Grenoble to create what could one day become an ultra-high-density storage medium. As a comparison, currently the smallest memory points are 72 times larger (15 nm x 30 nm).
The teams are now working together to deposit iron-platinum nanoparticles onto other nanostructured substrates.
Contact: gilles.renaud@cea.fr
This highlight on the IRIG's Website.

IRIG researchers awarded three ERC Advanced grants
Of the 31 ERC Advanced grants awarded by the European Research Council (ERC) to researchers in France at the end of March, five were given to researchers in Grenoble, and three went to researchers at IRIG. Martin Blackledge is investigating the structural and dynamic behavior of viral-replication machines. Renaud Demadrille is developing dye-sensitized photovoltaic cells with variable self-adjustable optical transmission. And Giovanni Finazzi is studying photosynthesis in marine plankton, which is capable of absorbing almost as much CO₂ as rain forests. ERC Advanced grants are awarded to established researchers with at least twelve years of research activity after their PhD. The grants can be for up to €3.5 million per project, including €1 million for equipment or access to large scientific instruments. The exact amount of the grant is determined on a case-by-case basis for each project.
Contact: thibaut.david@cea.fr
This highlight on the IRIG's Website.


Changing the magnetic chirality of skyrmions
The skyrmion—a magnetic quasiparticle measuring just a few nanometers—continues to garner great interest in the world of spintronics. Researchers from Spintec, Institut Néel, and LSPM* recently demonstrated that the interaction that sets skyrmion chirality (or spin direction) is modulated in a linear manner by lattice tension. If the tensions studied are extrapolated further, it appears that the phenomenon could ultimately change skyrmion chirality. If this discovery is accurate, it would make the skyrmion, used as a magnetic logic unit, easy to manipulate by applying tension.
The research is continuing under a project funded by the French National Research Agency and is now focusing on applying greater tensions and confirming that tension can indeed reverse spin direction. The researchers would also like to conduct further investigations into the irreversibility obtained when tension is applied for longer periods.
Contact: helene.bea@cea.fr

It’s amazing what a little spin pumping can do
In 2016 researchers at Spintec used spin pumping to study spin fluctuations in ultra-thin layers. More recently, they joined forces with other researchers (LPS Orsay, OPTIMAG Brest, CIME) to show that the method is generic in nature. In other words, it is effective regardless of whether an electric or magnonic current is used to transport the spin and regardless of whether the phase transition is of the ferromagnetic to paramagnetic or antiferromagnetic to paramagnetic type.
The research investigated several combinations of spin injecting and absorbing materials (spin pumping occurs from one to the other). This advance will make it easier to characterize the order of materials in nanolayered materials. Until now, characterization required advanced lithography techniques.
Contact: vincent.baltz@cea.fr

Progress toward high-performance UV LEDs
Doping the materials that make up the barrier around a UV LED’s active region is challenging, which makes it difficult to improve the yields and lifespans of UV LEDs at the 265 nm wavelength. Researchers from INAC and Institut Néel are tackling the subject, and their work under a French National Research Agency-funded project recently resulted in a significant advance. The team added a small fraction of indium to the doping material, magnesium. At the same time, they used aluminum nitride nanowires (rather than thin layers) for better relaxation of the strain generated by the dopant. The technique increased the maximum solubility of the magnesium tenfold.
The researchers would like to move on to a prototype. As mercury is gradually phased out, 265 nm LEDs will be used increasingly in applications like air and water disinfection and counterfeit bill detection.
Contact: bruno.daudin@cea.fr


Germanium-tin could be a winning combination for silicon photonics
Researchers from IRIG and Leti obtained a mid-infrared laser emission (2.7 microns to 3.2 microns) at 230 K in a germanium-tin (GeSn) alloy nanostructure. The advance paves the way toward photonic integrated laser sources on silicon chips. Currently, laser sources must be added to circuits one by one.
The major challenge was creating a tin-rich alloy, necessary to improving the material’s light-emitting properties without altering its high crystallinity. The researchers came up with a new process resulting in a 16% tin ratio. They then created two types of optical cavities: microdisks and photonic crystals. They will now focus on developing a device that can operate at ambient temperature. With operation currently at 230 K, they have already gone well beyond the 90 K obtained in 2015 by the researchers who pioneered the GeSn laser.
Contacts : vincent.calvo@cea.fr et nicolas.pauc@cea.fr
This highlight on the IRIG's Website.

Noisy cracks, rough material
The acoustical waves emitted when a crack propagates in a material can change the crack’s trajectory. The waves create alternating smooth and rough textures on the changed surface of the material. The phenomenon was observed during research conducted by IRIG, Leti, and Soitec on SOI wafers, which are made by cleaving silicon.
Small cavities, like dotted cutting lines, are made to control the cleavage plane. However, additional roughness (cavities of around 0.05 nm) also appears. We now know that this additional roughness is caused by the “noise” produced by the crack, whose phase speed is equal to the speed of the crack. The researchers will now try to eliminate this additional roughness to continue to improve Soitec’s substrates.
Contact: francois.rieutord@cea.fr
This highlight on the IRIG's Website.

Weighing viruses is not as easy as it looks
How do you weigh a bacteria-eating virus that is too light for precision scales but too heavy for mass spectrometry? Researchers from Leti and IRIG developed and patented a novel “nanoscale” technique to do just that. The technique uses an array of around 20 nanomechanical resonators that are made to vibrate. The virus is then introduced into a chamber with the array, and the system measures the difference in frequency.
The measurement is taken inside the chamber of a new type of spectrometer. The major challenge was to find the best way to introduce the viruses, which are in a solution, into the chamber. The researchers came up with a system to nebulize the solution, vacuum it into the chamber, and focus it onto the nanomechanical resonators. This very promising advance could be used to characterize viruses, biomarkers, and synthetic nanoparticles for medical applications.
Contact: sebastien.hentz@cea.fr
This highlight on the IRIG's Website.