Nonvolatile memory characteristics of small-molecule memory cells with electron-transport and hole-transport bilayers

We investigated the effect of small-molecule electron-transport (Alq3) and hole-transport (α-NPD) bilayers on the nonvolatile memory characteristics of small-molecule memory cells embedded with Ni nanocrystals. With increasing thickness of the hole-transport layer, the on-state current (Ion) and memory margin (Ion/Ioff ratio) decreased, the retention time decreased, and the standard deviation of Ion and Ioff during erase-and-program cycles increased. These results indicate that the N,N’-bis (1-naphthalene)-1,1’biphenyl4,4”diamine layer in small-molecule-bilayer memory cells behaves as an electron-transport layer rather a hole-transport layer and that the dominant carriers in those memory cells are electrons rather than holes.