Crystalline-to-Crystalline Phase Transition between Germanium Selenide Polymorphs with High Resistance Contrast.

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Phase transitions in crystalline materials are vital for fundamental science and applications like phase-change memory.
• Germanium selenide (GeSe) exhibits distinct crystalline polymorphs with varying electronic properties.

Purpose of the Study:

• To investigate the phase transition between GeSe crystalline polymorphs.
• To understand the mechanisms driving the transition induced by thermal or laser heating.
• To explore the potential of GeSe for electronic applications.

Main Methods:

• Global annealing and localized laser-induced heating to induce phase transitions.
• Transmission electron microscopy (TEM) for analyzing structural and electronic properties at interfaces.
• Electrical resistance measurements to quantify property changes.

Main Results:

• γ-GeSe transforms into semiconducting α-GeSe with preserved crystal orientation.
• Ge vacancy clustering in γ-GeSe at high temperatures drives the transition.
• A minor GeSe₂ phase segregation is observed during the transition.
• A high electrical resistance contrast (~10⁷) between γ-GeSe and α-GeSe was measured.

Conclusions:

• Ge vacancy clustering is a key mechanism for the γ-GeSe to α-GeSe phase transition.
• GeSe serves as a model system for studying polymorphic transitions in materials.
• The significant resistance contrast highlights GeSe's potential for phase-change memory devices.