An investigation of amorphous Ge2Se3 structure for phase change memory devices using fluctuation electron microscopy

Medium range order in amorphous thin films of Ge2Se3, 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−1. 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 Ge2Se3.