Solar cells and computer chips need silicon layers that are as perfect as possible. Every imperfection in the crystalline structure increases the risk of reduced efficiency or defective switching processes.
If you know how silicon atoms arrange themselves to form a crystal lattice on a thin surface, you gain fundamental insights into controlling crystal growth. To this end, an international research team analyzed the behavior of silicon that was flash-frozen. The study is published in the journal Physical Review Letters.
The results show that the speed of cooling has a major impact on the structure of silicon surfaces. The underlying mechanism may also have occurred during phase transitions in the early universe shortly after the Big Bang.
Air rings blown by dolphins swimming underwater and rings of smoke emitted by jet engines are just two examples of vortex rings. These doughnut-shaped structures and their mesmerizing movement have been studied for decades given their role in propulsion and—in the case of jellyfish and other invertebrates—biological locomotion.
A team of researchers at New York University and NYU Shanghai has uncovered a remarkable property of vortex rings that has been overlooked for more than a century—one that illuminates how these rings respond when they move through water and reach air (i.e., at the water-air interface).
When a vortex ring traveling sideways and up through water reaches the surface and meets air, it can rebound while largely maintaining its shape—much like a tennis ball bouncing off a wall. After the reflection, the ring loses only a small fraction of its energy. However, if the vortex ring moves more directly upward, it breaks apart instead of bouncing.
Finding new materials with useful properties is a primary goal for materials scientists, and it’s central to improving technology. One exciting area of current research is 2D materials—super-thin substances made of just a few layers of atoms, which could power the next generation of electronic devices. In a new study, researchers at the University of Maryland Baltimore County (UMBC) developed a new way to predict 2D materials that might transform electronics. The results were published in Chemistry of Materials on July 7.
Picture a sheet of paper so thin that it’s only a few atoms thick, and that’s what 2D materials are like. One might think they would be fragile—but these materials can actually be incredibly strong or conduct electricity in unique ways. They’re held together by weak forces called van der Waals bonds, which allow materials to slightly deform without breaking under stress. Stacked layers of these 2D materials can slide past each other, further reducing brittleness.
The research team, led by Peng Yan, a UMBC Ph.D. candidate in chemistry, and Joseph Bennett, assistant professor of chemistry and biochemistry at UMBC, focused on a type of 2D material called van der Waals layered phosphochalcogenides. Some of these materials are ferroelectric, meaning they can hold an electric charge in a particular direction, and then the direction can be reversed on command—sort of like tiny, reversible batteries. Some ferroelectric materials are also magnetic, behaving similarly when a magnetic field is applied. That combination makes them ideal for advanced electronics like memory devices and sensors.
