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Category: materials

Ultra-small, high-performance electronics grown directly on 2D semiconductors

In recent years, electronics engineers have been trying to identify semiconducting materials that could substitute for silicon and enable the further advancement of electronic devices. Two-dimensional (2D) semiconductors, such as molybdenum disulfide (MoS₂), have proved to be among the most promising solutions, as their thinness and resistance to short-channel effects could yield highly performing and smaller electronics.

To create transistors and other electronic components based on 2D materials, however, engineers need to be able to attach electrical connections to them and reliably form ohmic contacts, which allow electrical current to flow freely through the resulting devices. As devices get smaller, however, they also require smaller contacts that have proved to be very difficult to attach to 2D semiconductors.

Researchers at Nanjing University and other institutes in China recently introduced a new strategy to reliably grow ultra-short and low-resistance semimetallic antimony crystal contacts directly on MoS₂

New calibration module offers improved measurement of thermoelectric device performance

A standard reference thermoelectric module (SRTEM) for objectively measuring thermoelectric module performance has been developed in Korea for the first time. A research team led by Dr. Sang Hyun Park at the Korea Institute of Energy Research developed the world’s second standard reference thermoelectric module, following Japan, and improved its performance by more than 20% compared with existing modules, demonstrating the excellence of Korea’s homegrown technology. The findings are published in the journal ACS Applied Materials & Interfaces.

A thermoelectric module is a device that generates electricity by creating a flow of electrons driven by a temperature difference, with one side becoming cold and the other becoming hot. Conversely, when an electric current is applied to a thermoelectric module, one side cools down while the other side heats up.

Thanks to these characteristics, thermoelectric modules are widely used in applications such as compact camping refrigerators and electronic equipment including computers. In addition, because they are environmentally friendly and well suited to miniaturization, they can be broadly applied to emerging fields such as carbon-free power generation and the space industry, which have recently drawn significant attention.

Ultra-strong, lightweight metal composite can withstand extreme heat

University of Toronto researchers have designed a new composite material that is both very light and extremely strong—even at temperatures up to 500 Celsius.

The material, which is described in a paper published in Nature Communications, is made of various metallic alloys and nanoscale precipitates, and has a structure that mimics that of reinforced concrete—but on a microscopic scale.

These properties could make it extremely useful in aerospace and other high-performance industries.

Calculating the spreading of fluids in porous materials to understand saltwater in soil

A solution to a tricky groundwater riddle from Australia: Researchers at TU Wien have developed numerical models to simulate the movement of fluids in porous materials.

Things are complicated along the Murray–Darling River in southern Australia. Agricultural irrigation washes salt out of the upper soil layers, and this salt eventually ends up in the river. To prevent the river’s salt concentration from rising too much, part of the is diverted into special basins.

Some of these basins are designed to let the salty water evaporate, others to slowly release it in a controlled manner in the underground. That keeps salt temporarily out of the river and allows better management of the river’s water—but it increases the salinity in the ground. How can we calculate how this saltwater spreads underground and what its will be?

Material Strength Doesn’t Follow the Rules

A textbook rule for the relationship between the structure and strength of a material breaks down for high-speed deformations, like those caused by strong impacts.

On the microscale, metallic materials are made of homogeneous crystalline regions—grains—separated by disordered boundaries. In general, materials with smaller grains are stronger because they have more grain boundaries, which impede deformation. But researchers have now demonstrated a radical departure from this rule: With rapid deformation, such as that from an explosive impact, finer grained metals are softer, not harder [1]. This new insight, the researchers hope, could be useful for engineers developing impact-resistant alloys for armor, aerospace structures, or hypersonic vehicles.

The yield strength of a material is the stress (force) at which it begins to deform permanently rather than springing back. At the atomic scale in crystalline materials, this deformation occurs when sections of the crystal slide past one another, facilitated by the motion of structural defects called dislocations. But at grain boundaries, dislocations are halted and can pile up, which translates into resistance to deformation and increased yield strength. Materials with smaller grains have more grain boundaries than those with larger grains, so smaller grains are associated with higher strength.

How does glass ‘shake’ and why does it start flowing when pushed hard enough?

Glassy materials are everywhere, with applications far exceeding windowpanes and drinking glasses. They range from bioactive glasses for bone repair and amorphous pharmaceuticals that boost drug solubility to ultra-pure silica optics used in gravitational-wave detectors. In principle, any substance can become glass if its hot liquid is cooled fast enough to avoid forming an ordered crystal.

A distinguishing feature of glass is that its atoms freeze into an irregular, disordered arrangement. This stands in contrast to crystals, where atoms sit in a regular pattern. This disorder gives glass many of its unique and useful properties, but scientists still struggle to understand how atomic-scale disorder produces the properties observed in everyday glasses.

New sodium-sulfur battery may offer safer, cheaper alternative to lithium

Due to our ever-increasing reliance on electronics, researchers are always on the lookout for battery materials with more desirable qualities. Common battery materials, like lithium, can be prone to disadvantages like overheating and material sourcing issues, leading to safety risks and higher costs.

Now, researchers from China have revealed a new battery design that may offer a better alternative to lithium. The new study, published in Nature, describes a sodium and sulfur-based, anode-free design offering a high voltage. The sodium–sulfur (Na–S) batteries are a promising alternative to lithium-based batteries due to sodium’s abundance and potential for high energy storage.

Scientists capture first-ever high-resolution images of topological quantum Hall edge states

Read more here.

By Tom Garlinghouse

Physicists have long known that some materials behave strangely at their edges, conducting electricity without resistance even as their interiors remain insulating. These boundary phenomena, called topological edge states, form the basis of quantum technologies and exotic “topological phases” of matter. But despite decades of study, scientists could only infer how these quantum edges behave—no one had actually seen their microscopic structure in action.

Now, a collaborative team of researchers have achieved a remarkable first: they directly imaged the internal structure of these edge states in monolayer graphene, using one of the most precise tools in modern physics—scanning tunneling microscopy (STM). Their results, published last week in Nature, reveal how fundamental interactions between electrons reshape the very edge of a quantum material, upending long-held theoretical assumptions and opening a new window onto quantum topological behavior.

THz spectroscopy system bypasses long-standing tradeoff between spectral and spatial resolution

Terahertz (THz) radiation, which occupies the frequency band between microwaves and infrared light, is essential in many next-generation applications, including high-speed wireless communications, chemical sensing, and advanced material analysis.

To harness THz waves, scientists rely on functional devices like metasurfaces and resonant gratings, which exhibit sharp and effective resonance features. Characterizing and optimizing these high-performance devices, however, remains a technical challenge.

The difficulty stems from a fundamental tradeoff when performing THz measurements: achieving high spectral resolution versus high spatial resolution. To accurately capture the narrow spectral fingerprints of certain gases and the features of devices with a high quality factor (Q), researchers need very high spectral resolution.

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