Light driven Non-Thermal Amorphization Mechanism of Phase Change Material*

Phase-change materials (PCM) are exploited in modern electronics due to the extreme electro-optical contrast between crystalline and amorphous states. However, atomistic mechanisms governing photoexcitation-induced athermal amorphization processes are still unknown. We perform excited-state dynamics within the framework of density functional theory to understand the mechanism behind such crystalline-to-amorphous transition for Germanium Telluride (GeTe). Amorphous phase induced due to excited-state dynamics was characterized by computing diffraction pattern. Further analysis of bond-overlap population shows charge transfer of electron from Ge-Te bonding orbitals to Ge-Ge antibonding orbitals. Such charge transfer process leads to the destabilization of GeTe crystals, eventually leading to amorphization. Rapid heat extraction during excited-state simulation does not lead to amorphous phase. Since structural transformation limits the lifetime of PCM-based devices, a complete understanding behind mechanism may allow us to a new avenue to design better devices.