An investigation of amorphous Ge₂ Se₃ structure for phase change memory devices using fluctuation electron microscopy

Medium range order in amorphous thin films of Ge₂ Se ₃, a phase change memory material, was examined using electron nanodiffraction fluctuation electron microscopy. Variance measurements showed that medium range order existed at 0.36 and 0.58 Å^-1L. The film was not at equilibrium and contained a few monoclinic nanocrystals with weak Bragg maxima at 0.33, 0.54, and 0.63 Å-1, which are related to the GeSe₂ equilibrium phase at this composition. We also determined the variance for amorphous silicon (a-Si) and amorphous silica (a ?SiO₂) and those results agree with others in the literature. It is expected that the medium range order is related to nucleation of the crystallization reaction in Ge₂ Se₃.