Effects of temperature and pressure on the optical and vibrational properties of thermoelectric SnSe

Ilias Efthimiopoulos; Matthias Berg; Annika Bande; Ljiljana Puskar; Eglof Ritter; Wei Xu; Augusto Marcelli; Michele Ortolani; Martin Harms; Jan Müller; Sergio Speziale; Monika Koch-Müller; Yong Liu; Li-Dong Zhao; Ulrich Schade

doi:10.1039/C9CP00897G

Effects of temperature and pressure on the optical and vibrational properties of thermoelectric SnSe†

Ilias Efthimiopoulos,

‡*^a Matthias Berg,

‡*^b Annika Bande,

^b Ljiljana Puskar,^b Eglof Ritter,^c Wei Xu,

*^d Augusto Marcelli,

^ef Michele Ortolani,^g Martin Harms,^a Jan Müller,^a Sergio Speziale,^a Monika Koch-Müller,^a Yong Liu,^h Li-Dong Zhao

ⁱ and Ulrich Schade^b

Author affiliations

* Corresponding authors

^a GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany
E-mail: iliefthi@gfz-potsdam.de

^b Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
E-mail: matthias.berg@helmholtz-berlin.de

^c Institute of Biology, Humboldt-Universität zu Berlin, Invalidenstrasse 42, 10115 Berlin, Germany

^d Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, 100049 Beijing, P. R. China

^e INFN-Laboratori Nazionali di Frascati, Via E. Fermi 40, Frascati, Italy

^f RICMASS, Rome International Center for Materials Science Superstripes, Via dei Sabelli 119A, 00185 Rome, Italy

^g Department of Physics, University of Rome La Sapienza, P.le A. Moro 2, 00185 Rome, Italy

^h AECC-Beijing Institute of Aeronautical Materials, No. 8 Hangcai Avenue, Huanshancun, Haidian District, 100095 Beijing, P. R. China

ⁱ School of Materials Science and Engineering, No. 37 Xueyuan Road, Haidian District, Beihang University, 100191 Beijing, P. R. China

Abstract

We have conducted a comprehensive investigation of the optical and vibrational properties of the binary semiconductor SnSe as a function of temperature and pressure by means of experimental and ab initio probes. Our high-temperature investigations at ambient pressure have successfully reproduced the progressive enhancement of the free carrier concentration upon approaching the Pnma → Bbmm transition, whereas the pressure-induced Pnma → Bbmm transformation at ambient temperature, accompanied by an electronic semiconductor → semi-metal transition, has been identified for bulk SnSe close to 10 GPa. Modeling of the Raman-active vibrations revealed that three-phonon anharmonic processes dominate the temperature-induced mode frequency evolution. In addition, SnSe was found to exhibit a pressure-induced enhancement of the Born effective charge. Such behavior is quite unique and cannot be rationalized within the proposed effective charge trends of binary materials under pressure.

This article is part of the themed collection: 2019 PCCP HOT Articles

Physical Chemistry Chemical Physics

Effects of temperature and pressure on the optical and vibrational properties of thermoelectric SnSe†

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Effects of temperature and pressure on the optical and vibrational properties of thermoelectric SnSe

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