Photoemission Study of the Electronic Structure of Valence Band Convergent SnSe

Abstract

IV-VI semiconductor SnSe has been known as the material with record high thermoelectric performance.The multiple close-to-degenerate valence bands in the electronic band structure has been one of the key factors contributing to the high power factor and thus figure of merit in the SnSe single crystal. To date, there have been primarily theoretical calculations of this particular electronic band structure. In this paper, however, using angle-resolved photoemission spectroscopy, we perform a systematic investigation of the electronic structure of SnSe. We directly observe three predicted hole bands with small energy differences between their band tops and relatively small in-plane effective masses, in good agreement with the ab initio calculations and critical for the enhancement of the Seebeck coefficient while keeping high electrical conductivity. Our results reveal the complete band structure of SnSe and help to provide a deeper understanding of the electronic origin of the excellent thermoelectric performances in SnSe.

14 pages, 5 figures

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• Lateral heterostructures formed by thermally converting n-type SnSe2 to p-type SnSe
• Widely tunable band gap in a multivalley semiconductor SnSe by potassium doping
• Thermally-Enhanced Fröhlich Coupling in SnSe
• Critical mode and band-gap-controlled bipolar thermoelectric properties of SnSe
• Direct observation of multiple conduction-band minima in high-performance thermoelectric SnSe
• A plausible method of preparing the ideal p-n junction interface of a thermoelectric material by surface doping