Structure Evolutions and Metallic Transitions in In2Se3 Under High Pressure

Abstract

Indium selenide (In2Se3) could be used as the phase-change random access memory device and thermoelectric material. The high-pressure investigations are important to the applications on In2Se3 and other A2B3-type materials. In this study, we performed the in situ angle-dispersive X-ray diffraction and Raman spectra experiments and the first-principle calculations on In2Se3 under high pressure, and observed a series of structure phase transitions from experiments and metallized phenomena from calculations. In2Se3 transforms from the original rhombohedral structure (phase I) to a distorted monoclinic structure (phase II) and further to a Bi2Te3-type structure (phase III) at about 0.81 and 5.02 GPa, respectively. And then, phase III′ of In2Se3 adopts a similar structure with phase III from about 20.6 GPa. At pressures above about 32.1 GPa, In2Se3 starts to crystallize into a defective Th3P4-type structure (phase IV). According to the first-principle calculations, the structural transitions in the compression process induce that In2Se3 transforms from an insulator in phase I, across a semimetal in phase II and III, to a novel metal in the body-centered cubic structure (phase IV). The pressure-induced structure and conducting evolution on In2Se3 are helpful to understand the properties of other selenides upon compression.