(Funded by the U.S. Department of Energy, U.S. Department of Defense, and the National Science Foundation)
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. Optoelectronic devices are used in light-emitting diodes (LEDs), optical fibers, and medical imaging. The researchers found that when oriented in a specific direction and subjected to linearly polarized terahertz radiation, an ultrathin film of tungsten ditelluride circularly polarizes the incoming light.

(Funded by the National Science Foundation and the U.S. Department of Energy)
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. By shining light on the TMD, the researchers showed unexpected frequencies of light coming from the TMD, which could be explained by the movement of electrons related to the chalcogen vacancy.

(Funded by the U.S. Department of Defense)
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.

(Funded by the National Science Foundation)
Researchers from the University of Illinois Urbana-Champaign have identified how gold nanoparticles transfer charge to a connecting semiconductor and quantified how much charge is transferred using different colors of light. The researchers theorized that by using light to excite collective electronic oscillations (also called a plasmon) in gold nanoparticles, they would get a boost in charge transfer to the semiconductor material. And their study confirmed their theory.

(Funded by the U.S. Department of Energy)
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. “Getting the first atomic-scale look at their surface, using scanning tunneling microscopy, is an exciting development that will open new possibilities for controlling the material surface and enabling applications of MXenes in advanced technologies,” said Yury Gogotsi, the researcher who led this study.