Figure 4

Two representative phase-change random access memory cells with different switching behaviors. (a) A cell exhibiting normal memory switching via threshold switching (cell A) and (b) a cell showing early failure after direct memory switching (cell B). The initial microstructure and I–V curve obtained during in situ transmission electron microscopy switching are shown for each cell. (c) Grain size distribution in the Ge–Sb–Te matrix of cells A and B. The average grain sizes of cells A and B were 12.27 and 16.28 nm, respectively.