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Keywords:

  • amorphous;
  • phase-change;
  • polyamorphism;
  • polyvalency;
  • structure

Abstract

Chalcogenide alloys can exist in both crystalline and amorphous phases, with light-induced changes between the two states. While it is generally believed that in the amorphization process light predominantly serves to melt the material that is subsequently quenched into the amorphous phase, there has been accumulating evidence, both experimental and theoretical, that photoamorphization can be athermal. In this review, we present experimental and simulational results demonstrating that both chancogenide glasses, such as pure selenium and As50 Se50, and phase-change materials such as Ge2 Sb2 Te5 can be rendered amorphous without going through a conventional molten phase. The ability of chalcogenides to be amorphized athermally is attributed to the presence in these materials of pronounced bonding energy hierarchy between the shorter and longer bonds.