Material with High Electron Mobility: A Highway Without Traffic
Researchers have achieved a record-setting level of electron mobility in a thin film of ternary tetradymite, a mineral with a crystal structure consisting of rhombohedral crystals. This material is naturally found in deep hydrothermal deposits of gold and quartz. The ultrathin film, much thinner than a human hair, exhibits the highest electron mobility in its class and is a promising material for future electronics such as wearable thermoelectric devices.
The team grew pure, ultrathin films of the material using molecular beam epitaxy, a method by which a beam of molecules is fired at a substrate, typically in a vacuum, and with precisely controlled temperatures. When the molecules deposit on the substrate, they condense and build up slowly, one atomic layer at a time, minimizing defects in the crystalline structure.
The team was able to estimate the material’s electron mobility by detecting quantum oscillations when electric current passes through. These oscillations are a signature of the quantum mechanical behavior of electrons in a material. The researchers detected a particular rhythm of oscillations that is characteristic of high electron mobility, higher than any ternary thin films of this class to date.
The team’s results could point to ternary tetradymite thin films as a promising material for future electronics, such as wearable thermoelectric devices that efficiently convert waste heat into electricity. The material could also be the basis for spintronic devices, which process information using an electron’s spin, using far less power than conventional silicon-based devices.
The study also used quantum oscillations as a highly effective tool for measuring a material’s electronic performance.
“By studying this delicate quantum dance of electrons, scientists can start to understand and identify new materials for the next generation of technologies that will power our world,” says Hang Chi, a former research scientist at MIT who is now at the University of Ottawa.
The team estimates that the ternary tetradymite thin film exhibits an electron mobility of 10,000 cm2/V-s, the highest mobility of any ternary tetradymite film yet measured. The team suspects that the film’s record mobility has something to do with its low defects and impurities, which they were able to minimize with their precise growth strategies. The fewer a material’s defects, the fewer obstacles an electron encounters, and the more freely it can flow.
The team suspects that the film’s record mobility has something to do with its low defects and impurities, which they were able to minimize with their precise growth strategies. The fewer a material’s defects, the fewer obstacles an electron encounters, and the more freely it can flow.
More information:
Patrick J. Taylor et al, Magnetotransport properties of ternary tetradymite films with high mobility, Materials Today Physics (2024). DOI: 10.1016/j.mtphys.2024.101486
