Femtosecond-laser-induced modifications of Ge2Sb2Te5 thin films: Permanent optical change without amorphization

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Modifications induced by ultrashort laser pulses have been investigated in crystalline Ge 2 Sb 2 Te 5 thin films. The observations comprise optical and structural changes, amorphization, and ablation. By combining optical microscopy and cross-sectional scanning- and transmission electron microscopy, it is found that the threshold for permanent change of the optical properties of Ge 2 Sb 2 Te 5 – responsible for the reduced optical reflectivity – is slightly lower than that for amorphization; no further change in reflectivity is seen upon amorphization. The laser-fluence thresholds for amorphization and change of the optical properties both show a strong dependence on film thickness that can be explained thermally by two-temperature simulations. In the case of sufficiently thick films, two distinct low- and high-fluence ablation thresholds are found. The mechanisms of the ablation thresholds are discussed, and it is concluded that ablation in the low-fluence regime proceeds by photomechanical spallation.

TidsskriftApplied Surface Science
Sider (fra-til)221-231
Antal sider11
StatusUdgivet - 2019

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