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2-D Materials

Making tin selenide nanoflakes for thermoelectrics

Vapor deposition route to ultrathin films may lead to device miniaturization

by Mitch Jacoby
April 9, 2018 | A version of this story appeared in Volume 96, Issue 15

This micrograph and model show the structure of an ultrathin film of tin selenide.
Credit: J. Appl. Phys.
Tin selenide’s layered structure (left, Sn = gray, Se = orange) enabled researchers to grow thin films of interconnected nanoflakes (right).

A curious combination of thermal and electrical properties endows thermoelectric materials with the ability to interconvert heat and electricity. For decades, these solids have supplied power and cooling needs for specialty devices. Manufacturers are now developing thermoelectric devices to convert waste heat in engine exhaust to electricity. Yet these devices are not very common, in part because only a handful of materials, including alloys of bismuth telluride and a few lead compounds, work well in applications. Tin selenide recently showed itself to be a strong candidate, but only when prepared as thick single crystals. Xuan P. A. Gao knew that SnSe has a layered structure similar to graphene and other 2-D materials, suggesting it could be made in ultrathin nanostructured form, a first step toward miniaturizing thermoelectric devices. So the Case Western Reserve University physicist and coworkers developed a vapor deposition method for growing individual SnSe nanoflakes and thin films of interconnected nanoflakes from high-purity SnSe powder (J. Appl. Phys. 2018, DOI: 10.1063/1.5018860). The team incorporated the flakes into miniature testing devices and showed that doping with silver can boost the thermoelectric response of pristine SnSe thin films by up to a factor of 10.


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