Research: 2020 year in review
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.
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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.
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Microneedles could improve treatment of skin cancer
CEA-Leti and Inserm* researchers developed a polymer microneedle patch to treat sun-related skin cancer without surgery. The hundreds of tiny needles are applied to the lesion. They dissolve in less than an hour and, in the process, deliver a drug, which, when exposed to light, is activated and destroys malignant cells.
The researchers determined the optimal needle size and spacing and developed a chemical-free fabrication process. The needles’ length can be adjusted from 400 microns to 750 microns, making treatment pain free, yet still deep enough to reach lesions at the interface between the epidermis and dermis. A patent has been filed to protect the innovation and clinical trials are slated to begin. The microneedle patch could reach the market within three to five years.
Clinatec improves cerebral motor activity location technique
Clinatec has been trying to effectively determine the best location in the brain for its WIMAGINE® implant, which measures the brain activity of tetraplegic patients. The data is used to control an exoskeleton, restoring these patients’ mobility and independence. Where to implant the device is a key challenge for Clinatec. Researchers at the center have been developing and improving on an original magnetoencephalography (MEG) method to position the implant since 2014. The researchers recently published a study of fourteen patients in the journal Sensors. The method proved to be both effective and robust.
Moving the implant by just a centimeter can drastically affect (for better or worse) its ability to detect the patient’s intended movement and, therefore, control the exoskeleton. Clinatec is still engaged in clinical trials of its system under the Brain Computer Interface and Tetraplegia project, and a new patient joined the cohort a few months ago.
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 9 kW equivalent at 4.5 K, 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.
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Miniaturized reconfigurable antennas for IoT devices
What if IoT antennas could be made even smaller without compromising efficiency simply by tuning their frequency? A PhD candidate at Leti did just that! She also developed an analytical model that is as reliable as today’s simulators.
Leti fabricated an antenna whose size is no more than 1/15th of the wavelength, compared to the usual size of around ¼ of the wavelength. The antenna maintains high radiation efficiency by instantly covering only the band of the signal emitted, around 500 kHz.
To cover the rest of the band used in the target application, the antenna’s frequency is tuned by a fast digital management module for RF components designed at Leti and integrated into the antenna.
Manufacturers have already expressed interest
The PhD candidate who did the research also bumped up against another hurdle: The available electromagnetic simulators were not well-suited to investigating the impact of ohmic losses in miniature antennas. So, she solved that problem, too, by developing a faster analytical model to study impedance and radiation efficiency. She used the model to run even more tests and improve the dimensioning and position of the components on the radiating element.
A patent was filed to protect the antenna miniaturization technology, which has already garnered interest from several manufacturers. The PhD candidate, Rana Berro, will spend the last year of her program fabricating and testing prototypes. She won a special award for her research at IWAT2020 in Bucharest in February.
Covid-19 vaccine: Leti and its Lipidots® drug delivery system out in front
Leti and IAB (Inserm/CNRS/Grenoble-Alpes University) started work on a Covid-19 vaccine. Their strategy is to attach SARS-CoV-2 messenger RNA to Lipidots®, the oil microdroplets designed at Leti. Lipidots® are the same size as the virus and have a strong affinity for the dendritic cells that trigger an immune response. And, because Lipidots® are very stable, they should reach their final destination intact.
The mRNA strategy is already getting results in preclinical trials run by other organizations, like Moderna Therapeutics in the US. Now the researchers just have to find the ideal vector, and that could be where Lipidots® will make a real difference. The goal for the Grenoble-based LipiVAC COVID19 vaccine development project is to successfully complete preclinical testing within a year.
Haptic interfaces: Wafer-level manufacturing just around the corner
Touch interfaces can now effectively simulate the feel of sand, fabric, or a control panel button, an advance made possible by placing ceramic piezoelectric switches on a screen and making them vibrate at several dozen kHz. However, the switches must be bonded to the screen manually, which augments production costs. Leti has found a solution in the form of a 200 mm wafer-level fabrication technique.
The 300-micron-thick ceramics were eliminated. Instead, a thin layer (under 3 microns) was used, making integration much simpler. This step also enables several subsequent steps to augment the performance of the materials, deposit a transparent piezoelectric layer, and apply the layer to the entire screen. A demonstrator of the technology can be seen at the Y.Spot showroom.
Power electronics: GaN module sets new records
Leti developed a packaging for its new GaN (gallium nitride) power components that could unlock the components’ full potential. The two-sided cooled module stands out for its extremely low parasite inductance. The risk of overvoltage is reduced, allowing switching at 350 V and 10 A, and a switching speed of 15 ns. The researchers think that their chances of obtaining even better performance in an upcoming round of tests are good.
The module was fabricated with CEA Tech Toulouse and Aspi3D, which contributed two technology bricks. The architecture can still be improved and fine-tuned for even more powerful components. Ultimately, the module could be used in electric-vehicle inverters which require power of 100 kW to 150 kW.
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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.
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.
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!