Measuring temperature with neutrons

Researchers from Osaka University, National Institutes for Quantum Science and Technology, Hokkaido University, Japan Atomic Energy Agency, and Tokamak Energy developed a way to rapidly measure the temperature of electronic components inside a device using neutrons.

The technique, called ‘neutron resonance absorption’ (NRA), examines neutrons being absorbed by atomic nuclei at certain energy levels to determine the properties of the material. After being generated using high-intensity laser beans, the neutrons were then decelerated to a very low energy level before being passed through the sample, in this case plates of tantalum and silver. The temporal signal of the NRA was altered in a predictable manner when the sample material’s temperature was changed.

“This technology makes it possible to instantaneously and accurately measure temperature,” said Zechen Lan of Osaka University, in a statement. “As our method is non-destructive, it can be used to monitor devices like batteries and semiconductor devices.”

The technique can acquire temperature data in a window of 100 nanoseconds, and the measurement device itself is about a tenth of the size of similar equipment.

“Using lasers to generate and accelerate ions and neutrons is nothing new, but the techniques we’ve developed in this study represent an exciting advance,” added Akifumi Yogo of Osaka University, in a statement. “We expect that the high temporal resolution will allow electronics to be examined in greater detail, help us to understand normal operating conditions, and pinpoint abnormalities.” [1]

Mapping heat transfer

Researchers from the University of Rochester applied optical super-resolution fluorescence microscopy techniques used in biological imaging to map heat transfer in electronic devices using luminescent nanoparticles.

By applying highly doped upconverting nanoparticles to the surface of a device, the researchers were able to achieve super-high resolution thermometry at the nanoscale level from up to 10 millimeters away.

Rochester researchers demonstrated their super-high resolution thermometry techniques on an electrical heater structure that the team designed to produce sharp temperature gradients. (Credit: University of Rochester / J. Adam Fenster)

“The building blocks of our modern electronics are transistors with nanoscale features, so to understand which parts of overheating, the first step is to get a detailed temperature map,” said Andrea Pickel, an assistant professor from the University of Rochester’s Department of Mechanical Engineering, in a release. “But you need something with nanoscale resolution to do that.”

The researchers demonstrated the technique using an electrical heater structure designed to produce sharp temperature gradients. To improve the process, the team hopes to lower the laser power used and refine the methods for applying layers of nanoparticles to the devices. [2]

ML for predicting thermal properties

Researchers from MIT, Argonne National Laboratory, Harvard University, the University of South Carolina, Emory University, the University of California at Santa Barbara, and Oak Ridge National Laboratory propose a new machine learning framework that provides much faster prediction of phonon dispersion relations, an important measurement for determining the thermal properties of a material and how heat moves through semiconductors and insulators.

Heat-carrying phonons have an extremely wide frequency range, and the particles interact and travel at different speeds. “Phonons are the culprit for the thermal loss, yet obtaining their properties is notoriously challenging, either computationally or experimentally,” said Mingda Li, associate professor of nuclear science and engineering at MIT, in a release.

The researchers started with a graph neural network (GNN) that converts a material’s atomic structure into a crystal graph comprising multiple nodes, which represent atoms, connected by edges, which represent the interatomic bonding between atoms.

To make it suitable for predicting phonon dispersion relations, they created a virtual node graph neural network (VGNN) by adding a series of flexible virtual nodes to the fixed crystal structure to represent phonons. This enabled the VGNN to skip many complex calculations when estimating phonon dispersion relations, making it a more efficient method than a standard GNN.

Li noted that a VGNN could be used to calculate phonon dispersion relations for a few thousand materials in a few seconds with a personal computer. The technique could also be used to predict challenging optical and magnetic properties. [3]

References

[1] Lan, Z., Arikawa, Y., Mirfayzi, S.R. et al. Single-shot laser-driven neutron resonance spectroscopy for temperature profiling. Nat Commun 15, 5365 (2024). https://doi.org/10.1038/s41467-024-49142-y

[2] Ziyang Ye et al., Optical super-resolution nanothermometry via stimulated emission depletion imaging of upconverting nanoparticles. Sci. Adv. 10, eado6268 (2024) https://doi.org/10.1126/sciadv.ado6268

[3] Okabe, R., Chotrattanapituk, A., Boonkird, A. et al. Virtual node graph neural network for full phonon prediction. Nat Comput Sci 4, 522–531 (2024). https://doi.org/10.1038/s43588-024-00661-0

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DNA assembly of 3D nanomaterials

Scientists from Brookhaven National Laboratory, Columbia University, and Stony Brook University developed a method that uses DNA to instruct molecules to organize themselves into targeted 3D patterns and produce a wide variety of designed metallic and semiconductor 3D nanostructures.

“We have been using DNA to program nanoscale materials for more than a decade,” said corresponding author Oleg Gang, a professor of chemical engineering and of applied physics and materials science at Columbia Engineering, in a release. “Now, by building on previous achievements, we have developed a method for converting these DNA-based structures into many types of functional inorganic 3D nano-architectures, and this opens tremendous opportunities for 3D nanoscale manufacturing.”

Researchers program strands of DNA to “direct” the self-assembly process towards molecular arrangements that give rise to properties such as electrical conductivity, photosensitivity, and magnetism, which can then be scaled up to functional materials.

The team used the method to grow silica on a DNA lattice, which helped to create a robust structure. They then used vapor-phase infiltration and liquid-phase infiltration, which bonds a precursor chemical in vapor or liquid form to a nanoscale lattice, to produce a variety of 3D metallic structures.

Scientists used a new, universal method to create a variety of 3D metallic and semiconductor nanostructures, including this structure revealed by an electron microscope. The scale bar represents one micrometer. The superimposed graphics convey that the researchers combined multiple techniques to layer silicon dioxide, then alumina-doped zinc oxide, and finally platinum on top of a DNA “scaffolding.” This complex structure represents new possibilities for advanced manufacturing at small scales. (Credit: Brookhaven National Laboratory)

“Stacking these techniques showed much more depth of control than has ever been accomplished before,” said Aaron Michelson, a postdoctoral researcher at Brookhaven’s Center for Functional Nanomaterials, in a release. “Whatever vapors are available as precursors for vapor-phase infiltration can be coupled with various metal salts compatible with liquid-phase infiltration to create more complex structures. For example, we were able to combine platinum, aluminum, and zinc on top of one nanostructure.”

They were also able to add on semiconducting metal oxides, such as zinc oxide, to an insulating nanostructure, providing it with electrical conductivity and photoluminescent properties. [1]

Mott insulator transistor

Researchers from the University of Nebraska-Lincoln, Brookhaven National Laboratory, University of the Basque Country, and NYU Shanghai propose a way to make transistors out of Mott insulators.

The researchers were able to direct the Mott transition from insulator to metal and back again by topping a Mott insulator with a gate insulator made of a ferroelectric material and using a voltage to flip the ferroelectric material’s polarization. A third layer beneath the Mott channel that allows charges to migrate from the Mott down to it improved control over the insulator-metal transition with an on-off ratio of 385.

Additionally, the researchers claim that the Mott-ferroelectric pairing is more energy-efficient than other non-volatile but magnetism-based memory, including MRAM.

“We can have very high-performance devices, retaining many manufacturing processes of conventional semiconductors and overcoming some fundamental limitations of them,” said Xia Hong, professor of physics at the University of Nebraska-Lincoln, in a release. “I think it’s ready. It’s really competitive with other non-volatile memory technologies.” [2]

Faster wireless data speeds

Researchers from Osaka University and IMRA America suggest a way to increase wireless data transmission speeds by reducing the noise in the system using lasers.

Future 6G transmitters and receivers are expected to use the sub-terahertz band, which extends from 100 GHz to 300 GHz, using an approach called “multi-level signal modulation” to further increase the data transmission rate. However, this approach is highly sensitive to noise at the upper end of the frequency range.

“This problem has limited 300-GHz communications so far,” said Keisuke Maekawa of Osaka University in a statement. “However, we found that at high frequencies, a signal generator based on a photonic device had much less phase noise than a conventional electrical signal generator.”

The team used a stimulated Brillouin scattering laser, which employs interactions between sound and light waves, to generate a precise signal. They then set up a 300 GHz-band wireless communication system that employs the laser-based signal generator in both the transmitter and receiver. The system also used on-line digital signal processing (DSP) to demodulate the signals in the receiver and increase the data rate.

“Our team achieved a single-channel transmission rate of 240 gigabits per second,” said Tadao Nagatsuma, a professor at Osaka University, in a release. “This is the highest transmission rate obtained so far in the world using on-line DSP.” The researchers expect that with multiplexing techniques and more sensitive receivers, the data rate can be increased to 1 terabit per second. [3]

References

[1] Aaron Michelson et al., Three-dimensional nanoscale metal, metal oxide, and semiconductor frameworks through DNA-programmable assembly and templating. Sci. Adv. 10, eadl0604 (2024). https://doi.org/10.1126/sciadv.adl0604

[2] Hao, Y., Chen, X., Zhang, L. et al. Record high room temperature resistance switching in ferroelectric-gated Mott transistors unlocked by interfacial charge engineering. Nat Commun 14, 8247 (2023). https://doi.org/10.1038/s41467-023-44036-x

[3] Keisuke Maekawa, Tomoya Nakashita, Toki Yoshioka, Takashi Hori, Antoine Rolland, Tadao Nagatsuma, Single-channel 240-Gbit/s sub-THz wireless communications using ultra-low phase noise receiver, IEICE Electronics Express, Article ID 20.20230584, Advance online publication December 25, 2023, Online ISSN 1349-2543, https://doi.org/10.1587/elex.20.20230584

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