Basic science

Researchers from the University of Michigan, the U.S. Department of Energy’s SLAC National Accelerator Laboratory, Carnegie Mellon University, and Harvard University have discovered that the electrical conductivity of three layers of graphene, in a twisted stack, is similar to that of “magic angle” bilayer graphene. Stacking three layers of graphene introduced an additional twist angle, creating non-repeating patterns, at small-angle twists – unlike bilayer graphene which forms repeating patterns.

Researchers from the U.S. Department of Energy's Argonne National Laboratory and Universidad de Zaragoza in Spain have discovered that how calcite is synthesized, or chemically transformed, can dramatically change the internal structure of individual mineral particles. The scientists compared the external shape and internal structure of calcite particles grown by two synthesis approaches. For one synthesis approach, calcite crystals were grown slowly, and a 3D map of the crystal structure inside the calcite particles showed the orderly, repeating patterns scientists expected to see.

Researchers from the University of California, Santa Barbara, The Ohio State University, and the University of Hong Kong have, for the first time, characterized the thermoelectric properties of high-quality cadmium arsenide thin films. The researchers created three high-quality films of varying thicknesses – 950 nanometers (nm), 95 nm, and 25 nm – and found that the thinner the material, the higher the thermoelectric sensitivity, resulting in more voltage in response to a temperature gradient, a response enhanced by seven times compared to the state-of-the-art material.

Researchers from the U.S. Department of Energy’s Los Alamos National Laboratory (LANL) and Lawrence Berkeley National Laboratory (LBNL) and Seoul National University in South Korea have developed a way to directly measure such materials' thermal expansion coefficient, the rate at which the material expands as it heats. Due to the thinness of two-dimensional materials, until now, measuring their thermal expansion could only be accomplished indirectly or with the use of a support structure called a substrate.

University of Missouri researchers have developed a novel 3D printing and laser process to manufacture multi-material, multi-layered sensors, circuit boards, and even textiles with electronic components. The researchers built a machine that has three different nozzles: one nozzle adds ink-like material, another uses a laser to carve shapes and materials, and a third nozzle adds functional materials to enhance the product’s capabilities. The manufacturing process starts by making a basic structure with a regular 3D printing filament.

Researchers from Purdue University and the University of Illinois Urbana-Champaign have created a process to develop ultrahigh-strength aluminum alloys that are suitable for additive manufacturing. The researchers produced the aluminum alloys by using several transition metals, including cobalt, iron, nickel and titanium. "These intermetallics have crystal structures with low symmetry and are known to be brittle at room temperature," said Anyu Shang, one of the researchers involved in this study.

Researchers from Drexel University, California State University Northridge, and the U.S. Department of Energy’s Lawrence Berkeley National Laboratory have provided the first clear look at the chemical structure of the surface of a two-dimensional (2D) material called titanium carbide MXene. MXenes form a family of 2D materials that have shown promise for water desalination, energy storage, and electromagnetic shielding.

Researchers at Michigan State University have developed a new technique that combines atomic-scale imaging with extremely short laser pulses to detect single-atom defects that manufacturers add to semiconductors to tune their electronic performance. “This is particularly relevant for components with nanoscale structures,” said Tyler Cocker, a scientist who led this study. The technique is straightforward to implement with the right equipment, he added, and his team is already applying it to atomically thin materials, such as graphene nanoribbons.

Researchers from the U.S. Department of Energy's Princeton Plasma Physics Laboratory and the University of Delaware have provided new insights into the variations that can occur in the atomic structure of two-dimensional materials called transition metal dichalcogenides (TMDs). The researchers found that one of the defects, which involves hydrogen, provides excess electrons. The other type of defect, called a chalcogen vacancy, is a missing atom of oxygen, sulfur, selenium, or tellurium.

Researchers from the U.S. Department of Energy’s SLAC National Accelerator Laboratory and Argonne National Laboratory; Stanford University; Harvard University; Columbia University; Florida State University; and the University of California, Los Angeles, have discovered new behavior in an 50-nanometer-thick two-dimensional material, which offers a promising approach to manipulating light that will be useful for devices that detect, control or emit light, collectively known as optoelectronic devices.