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

• Published in: Physical chemistry chemical physics : PCCP 2019-04, Vol.21 (17), p.8663-8678
• Main Authors: Efthimiopoulos, Ilias, Berg, Matthias, Bande, Annika, Puskar, Ljiljana, Ritter, Eglof, Xu, Wei, Marcelli, Augusto, Ortolani, Michele, Harms, Martin, Müller, Jan, Speziale, Sergio, Koch-Müller, Monika, Liu, Yong, Zhao, Li-Dong, Schade, Ulrich
• Format: Article
• Language: English
• Subjects: Ambient temperature; Anharmonicity; Carrier density; Charge materials; High temperature; Optical properties; Pressure effects; Temperature effects
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c9cp00897g

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. 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.