Laser induced structural transformation in chalcogenide based superlattices

摘要

Superlattices made of alternating layers of nominal GeTe and Sb_2Te_3 have been studied by micro-Raman spectroscopy. A structural irreversible transformation into ordered GeSbTe alloy is induced by high power laser light exposure. The intensity ratio of anti-Stokes and Stokes scattering under laser illumination gives a maximum average temperature in the sample of 177 ℃. The latter is lower than the growth temperature and of 400 ℃ necessary by annealing to transform the structure in a GeSbTe alloy. The absence of this configuration after in situ annealing even up to 300 ℃ evidences an electronic excitation induced-transition which brines the system into a different and stable crystalline state.