Three-dimensional atomic evolution of amorphous phase-change materials upon photon irradiation

Phase-change materials show great promise for applications in integrated photonic memory and computing devices, where irradiation resistance is crucial for ensuring long-term operational reliability. However, the atomic evolution of phase-change materials under optical excitation remains unclear, primarily due to the technical challenge in characterizing amorphous materials. Here, we employ atomic electron tomography to resolve the three-dimensional atomic structures of amorphous Ge₂Sb₂Te₅ nanoparticles after femtosecond laser irradiation and room-temperature aging. Combining first-principles calculations, we find that irradiation induces atomic-scale disorder, including compositional segregation, vacancy aggregation, and the formation of wrong bonds, leading to a reduction in optical bandgap. Furthermore, during aging, the material exhibits a self-healing phenomenon, wherein optical properties revert to their initial states, driven by compositional homogenization and vacancy annihilation. Our work establishes a comprehensive atomic-scale structure-property relationship underlying photon irradiation and self-healing processes in amorphous Ge₂Sb₂Te₅, offering valuable insights into the design of durable phase-change photonic devices.