Just as magnetic materials have opposing North and South poles, ferroelectric materials have opposing positive charges and negative charges that exhibit measurable differences in electric potential. Researchers at MIT and colleagues in China recently demonstrated this ferroelectric behavior along the edges of atomically thin tin-tellurium film at room temperature.
Measurements showed the energy gap, or bandgap, of this ultra-thin (2-D) film to be about eight times higher than the bandgap in bulk (3-D) tin-tellurium, with an on/off ratio as high as 3,000, they report July 15 in the journal Science. Their findings hold promise for making random access memory (RAM) devices from this special semiconductor material, which is known as a topological crystalline insulator.
“This discovery is very exciting because usually when you decrease the thickness from the 3-D to 2-D, the phase transition temperature always decreases and therefore could destroy the ferroelectricity. But in this case, the [ferroelectric] phase transition temperature increased. It’s quite unusual,” explains MIT postdoc Junwei Liu, a first author of the paper. “As far as we know, this might be the first time to observe this very unusual property.” MIT assistant professor of physics Liang Fu is one of the paper’s senior authors.