A possible mechanism of ultrafast amorphization in phase-change memory alloys: an ion slingshot from the crystalline to amorphous position

TL;DR

This paper proposes a new mechanism for ultrafast amorphization in phase-change memory alloys, where strained bonds in the crystalline phase cause Ge ions to be rapidly displaced to amorphous positions upon photoexcitation.

Contribution

It introduces the ion slingshot mechanism driven by strained bonds, explaining ultrafast crystalline-to-amorphous transitions in GST alloys.

Findings

Strained bonds in crystalline phase drive amorphization.

Photoexcitation causes Ge ions to be shot from crystalline to amorphous sites.

Lattice relaxation stabilizes the amorphous phase.

Abstract

We propose that the driving force of an ultrafast crystalline-to-amorphous transition in phase-change memory alloys are strained bonds existing in the (metastable) crystalline phase. For the prototypical example of GST, we demonstrate that upon breaking of long Ge-Te bond by photoexcitation Ge ion shot from an octahedral crystalline to a tetrahedral amorphous position by the uncompensated force of strained short bonds. Subsequent lattice relaxation stabilizes the tetrahedral surroundings of the Ge atoms and ensures the long-term stability of the optically induced phase.