Electronics

Researchers at the Technical University of Liberec (Czech Republic) and Lodz University of Technology (Poland) have developed a silver/graphene flexible composite electrode using inkjet printing technology for high-performance supercapacitors. 

The scientists chose rGO as the primary material for the electrode active layer. The rGO active layer was in-situ printed and reduced on the polypropylene non-woven fabric, and silver nanoparticles were simultaneously inserted and reduced to increase the interlayer spacing of the rGO active layer, which effectively reduced the self-stacking effect of rGO and improved the overall electrochemical performance. 

Researchers from Queen Mary University of London and Paragraf Limited have reported a 'significant step forward in the development of graphene-based memristors' for potential use in future computing systems and artificial intelligence (AI). 

This innovation, which has been achieved at wafer scale, begins to pave the way toward scalable production of graphene-based memristors, devices crucial for non-volatile memory and artificial neural networks (ANNs). Memristors are recognized as potential game-changers in computing, offering the ability to perform analogue computations, store data without power, and mimic the synaptic functions of the human brain. The integration of graphene can enhance these devices dramatically, but has been notoriously difficult to incorporate into electronics in a scalable way until recently. 

While silk protein has been used in designer electronics, its use is currently limited in part because silk fibers are a messy tangle of spaghetti-like strands. To address this, researchers from Pacific Northwest National Laboratory, University of Washington, Lawrence Berkeley National Laboratory, North Carolina State University and Xiamen University have developed a uniform two-dimensional (2D) layer of silk protein fragments, or "fibroins," on graphene. 

Scheme of silk fibroin assembly on highly oriented pyrolytic graphite (HOPG) characterized by in situ AFM. Image from Science Advances

The scientists explained that their work provides a reproducible method for silk protein self-assembly that is essential for designing and fabricating silk-based electronics. They said that the system is nontoxic and water-based, which is vital for biocompatibility.

Researchers from Advanced Material Development (AMD) and the University of Sussex have announced what they refer to as "a major enhancement" in their carbon nanomaterial-based inks, reaching conductivity levels of 3,000,000 Sm-¹, approaching the performance of incumbent metal-based solutions.

With years of experience with graphitic inks, that previously achieved industry-best conductivity of 500,000 Sm-¹ (several times more conductive than other non-metal inks) - the latest breakthrough seems to significantly raise the bar. 

Hot-carrier transistors are a class of devices that leverage the excess kinetic energy of carriers. Unlike regular transistors, which rely on steady-state carrier transport, hot-carrier transistors modulate carriers to high-energy states, resulting in enhanced device speed and functionality. These characteristics are essential for applications that demand rapid switching and high-frequency operations, such as advanced telecommunications and cutting-edge computing technologies. However, their performance has been limited by how hot carriers have traditionally been generated.

A team of researchers, led by Prof. Liu Chi, Prof. Sun Dongming, and Prof. CHeng Huiming from the Institute of Metal Research (IMR) of the Chinese Academy of Sciences, has proposed a novel hot carrier generation mechanism called stimulated emission of heated carriers (SEHC). The team has also developed an innovative hot-emitter transistor (HOET), achieving an ultralow sub-threshold swing of less than 1 mV/dec and a peak-to-valley current ratio exceeding 100. The study provides a prototype of a low power, multifunctional device for the post-Moore era.

Researchers have used a specially crafted electric potential to manipulate the electronic band structure of graphene, laying the groundwork for on-demand electronic band design. 

Scientists have long been trying to tune the electronic band structures of materials so that those materials exhibit desired physical properties. In the past few years, researchers have shown they can manipulate the band structures of graphene and other 2D materials using electric-field configurations that produce simple periodic potentials. Now, Changgan Zeng at the University of Science and Technology of China and his colleagues have shown that they can achieve greater control over the band structure using an electric potential with a shape that resembles a basket-weaving pattern known as kagome.

The exceptional electronic properties of graphene make it a material with large potential for low-power, high-frequency electronics. However, the performance of a graphene-based device depends not only on the properties of the graphene itself, but also on the quality of its metal contacts. The lack of effective and manufacturable approaches to establish good ohmic contacts to a graphene sheet is one of the factors that currently limit the full application potential of graphene technology. The quality of the graphene-metal contacts is described in terms of the contact resistance (RC). Low RC values are crucial for any high-frequency or low-power application. Graphene’s low density of states near the charge neutrality point (Dirac point) limits carrier injection from metals, often resulting in high RC values.

(a–d) Schematics showing the process sequence for manufacturing the devices and the laser irradiation of graphene in the contact regions. (e) Optical micrograph of one of the measured devices. Image credit: AMO

Recently, researchers from RWTH Aachen University and AMO have developed a scalable method based on laser irradiation of graphene to reduce the RC in nickel-contacted devices. A laser with a wavelength of l = 532 nm is used to induce defects at the contact regions, which are monitored in situ using micro-Raman spectroscopy. 

Researchers at École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland and National Institute for Materials Science in Japan have combined the electrical properties of graphene with the semiconducting characteristics of indium selenide in a field-effect geometry, to create a device that can efficiently convert heat into electrical voltage at temperatures lower than that of outer space. The innovation could help overcome a significant obstacle to the advancement of quantum computing technologies, which require extremely low temperatures to function optimally.

Device schematic representing a fully encapsulated few-layer InSe channel, with graphene electrodes. Image credit: Nature Nanotechnology

To perform quantum computations, quantum bits (qubits) must be cooled down to temperatures in the millikelvin range (close to -273 Celsius), to slow down atomic motion and minimize noise. However, the electronics used to manage these quantum circuits generate heat, which is difficult to remove at such low temperatures. Most current technologies must therefore separate quantum circuits from their electronic components, causing noise and inefficiencies that hinder the realization of larger quantum systems beyond the lab. Now, researchers in EPFL’s Laboratory of Nanoscale Electronics and Structures (LANES), led by Andras Kis, have fabricated a device that not only operates at extremely low temperatures, but does so with efficiency comparable to current technologies at room temperature.

Researchers from the University of Michigan, SLAC National Accelerator Laboratory, Carnegie Mellon University and Harvard University have shown that three layers of graphene, in a twisted stack, benefit from a similar high conductivity to "magic angle" bilayer graphene but with easier manufacturing—and faster electron transfer. The findings could improve nano electrochemical devices or electrocatalysts to advance energy storage or conversion.

Twisting two sheets of graphene at a 1.1° angle, dubbed the "magic angle," creates a "flat band" structure, meaning the electrons across a range of momentum values all have roughly the same energy. Because of this, there is a huge peak in the density of states, or the available energy levels for electrons to occupy, at the energy level of the flat band which enhances electrical conductivity. Recent work experimentally confirmed these flat bands can be harnessed to increase the charge transfer reactivity of twisted bilayer graphene when paired with an appropriate redox couple—a paired set of chemicals often used in energy storage to shuttle electrons between battery electrodes. Adding an additional layer of graphene to make twisted trilayer graphene yielded a faster electron transfer compared to bilayer graphene, according to the team's recent study, that created an electrochemical activity model.

German semiconductor startup, Black Semiconductor, has secured EUR 254.4 million (around USD$275,900,000) in funding to launch graphene-enhanced semiconductor technology in Europe. With the funding, the company says that it is on track to realize the first phase of its vision – advancing a new generation of chip technology from research to mass production by 2031.

The Company has secured EUR 228.7 million (around USD$248,000,000) in public funding from the German Ministry of Economic Affairs and Climate Action and the state of North Rhine-Westphalia over the next 7 years under the IPCEI ME/CT2 program.