Phase relations of semiconductors SnSe and GeSe at high pressures and high temperatures

Abstract

The group IV–VI monochalcogenides have attracted widespread attention because of their rich structural characteristics and diverse physical properties. SnSe and GeSe, as typical IV–VI monochalcogenides, have been extensively investigated due to their potential applications in thermoelectric, electronic, and optoelectronic fields. Both SnSe and GeSe undergo phase transitions at high pressures (P) or high temperatures (T), which have significant effects on their physical properties and further application prospect. However, phase relations of these two materials at simultaneous high P–T conditions remain unclear experimentally. Here, a series of in situ measurements of Raman spectroscopy on SnSe and GeSe have been performed at high P–T conditions up to about 35 GPa and 923 K. SnSe has been observed transforming from the Pnma structure to the Cmcm structure at either high P, or high T, or high P–T conditions. The Pnma to Cmcm phase transition boundary of SnSe at high P–T conditions has been determined experimentally. The phase transition of SnSe at high P–T is reversible after cooling temperature and releasing pressure to ambient conditions. The isostructural GeSe shows no phase transition up to ∼35 GPa and 923 K, the highest P–T conditions in this work. The present study illustrates phase relations of semiconductors SnSe and GeSe at high P–T conditions accomplished by externally heated diamond anvil cell techniques, which lay the foundation for their P–T phase diagrams at high P–T conditions and shed light on their potential applications under extreme conditions.