Femtosecond laser irradiation of thin Ge2Sb2Te5−x films: Amorphization and morphological evolution

This study explores the amorphization of a Te-poor Ge–Sb–Te alloy using single 800 nm femtosecond laser pulses. Before irradiation, the phase composition and microstructure of the investigated sample were characterized using synchrotron x-ray diffraction and high-resolution transmission electron microscopy. The threshold fluence required for amorphization with a single laser shot was identified, with a minimum fluence of ∼45 mJ cm−2 necessary to induce structural changes. At higher fluences (≥83 mJ cm−2), surface blistering and layer delamination occurred, also due to laser absorption by the TiN capping layer. This study revealed partial amorphization localized preferentially in the upper part of the layer with a few crystalline residuals closer to the substrate. The formation of cavities in the amorphized zones, close to the interface with the TiN layer, is supposed to be responsible for the delamination of the latter observed in the center of the irradiated zone. No long-range elemental diffusion was observed post-irradiation. These results provide valuable insights into the structural changes that can be induced by femtosecond laser irradiation in Ge–Sb–Te alloys.