Photoemission study of the electronic structure of valence band convergent SnSe

Abstract

Monocrystalline SnSe, which is a binary semiconductor, has recently been demonstrated to be a high-performance thermoelectric material with a record-high figure of merit of 2.6 at high temperature (923 K). Using angle-resolved photoemission spectroscopy, the authors probed the full electronic structure of SnSe. They observed three convergent hole bands with small energy differences in their band tops and relatively small in-plane effective masses, in agreement with $a\phantom{\rule{0}{0ex}}b$ $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ calculations. These bands are critical for the enhancement of the Seebeck coefficient, while preserving the high electrical conductivity of the material. Thus, they represent a key factor contributing to the high figure of merit in SnSe.