III-V semiconductors sport clathrate structures

Semiconductors composed of one group III and one group V element are widely used in light-emitting diodes, thermal imaging systems, and other commercial devices. These binary materials, which include gallium and indium antimonide, may soon find their way into even more electronic applications thanks to a study showing that the normally nonporous materials can be prepared as inherently tunable clathrates—crystals with cage-like cavities that trap molecules or ions (J. Am. Chem. Soc. 2020, DOI: 10.1021/jacs.9b12351). By using high-temperature methods to react stoichiometric quantities of group III and group V elements (or binary precursors) with either rubidium or cesium, Bryan Owens-Baird, Jian Wang, and Kirill Kovnir of Iowa State University and coworkers synthesized three unconventional III-V clathrates: Cs₈In₂₇Sb₁₉, Cs₈Ga₂₇Sb₁₉, and Rb₈Ga₂₇Sb₁₉. Analyses show that the new compounds retain the high charge-carrier mobility and other critical semiconductor properties of the conventional versions. For example, the values of those parameters in Cs₈In₂₇Sb₁₉ are on par with those of standard InSb, a top-performing semiconductor. Clathrates were discovered in the early 1800s by Humphry Davy. Two hundred years later, “it’s still interesting and exciting to expand clathrate chemistry to unconventional combinations of elements,” Kovnir says.