Pressure-Induced Structural Phase Transition and a Special Amorphization Phase of Two-Dimensional Ferromagnetic Semiconductor Cr2Ge2Te6

TL;DR

This study investigates how high pressure induces structural phase transitions and amorphization in the two-dimensional ferromagnetic semiconductor Cr2Ge2Te6, revealing unique high-pressure amorphous phases with potential for functional material design.

Contribution

It provides the first detailed high-pressure analysis of Cr2Ge2Te6, discovering concurrent crystalline-to-crystalline and amorphous transitions and characterizing the unique properties of the amorphous phase.

Findings

Cr2Ge2Te6 undergoes crystalline-to-crystalline and amorphous transitions at 18.3-29.2 GPa.

The amorphous phase can be quenched and exhibits metallic resistance.

High-pressure amorphous phase shows behavior unlike other phase-change materials.

Abstract

Layered transition-metal trichalcogenides have become one of the research frontiers as two-dimensional magnets and candidate materials used for phase-change memory devices. Herein we report the high-pressure synchrotron X-ray diffraction and resistivity measurements on Cr2Ge2Te6 (CGT) single crystal by using diamond anvil cell techniques, which reveal a mixture of crystalline-to-crystalline and crystalline-to-amorphous transitions taking place concurrently at 18.3-29.2 GPa. The polymorphic transition could be interpreted by atomic layer reconstruction and the amorphization could be understood in connection with randomly flipping atoms into van der Waals gaps. The amorphous (AM) phase is quenchable to ambient conditions. The electrical resistance of CGT shows a bouncing point at ~ 18 GPa, consistent with the polymorphism phase transition. Interestingly, the high-pressure AM phase exhibits metallic resistance with the magnitude comparable to that of high-pressure crystalline phases, whereas the resistance of the AM phase at ambient pressure fails to exceed that of the crystalline phase, indicating that the AM phase of CGT appeared under high pressure is quite unique and similar behavior has never been observed in other phase-change materials. The results definitely would have significant implications for the design of new functional materials.