We developed small molecular organic nonvolatile $4F^2$ memory cells using metal layer evaporation followed by $O_2$ plasma oxidation. Our memory cells sandwich an upper ${alpha}$-NPD layer, Al nanocrystals surrounded by $Al_2O_3$, and a bottom ${alpha}$-NPD layer between top and bottom electrodes. Their nonvolatile memory characteristics are excellent: the $V_{th},;V_p$ (program), $V_e$ (erase), memory margin ($I_{on}/I_{off}$), data retention time, and erase and program endurance were 2.6 V, 5.3 V, 8.5 V, ${approx}1.5{ imes}10^2,;1{ imes}10^5s$, and $1{ imes}10^3$ cycles, respectively. They also demonstrated symmetrical current versus voltage characteristics and a reversible erase and program process, indicating potential for terabit-level nonvolatile memory.