Ge-nanodot multilayer nonvolatile memories

Abstract

1-5 period multilayers of Ge nanodots (NDs) for nonvolatile memories have been self-assembled by ion beam sputtering deposition of an ultra-small amount of Ge between SiO(2) layers at room temperature without post-annealing. High-resolution transmission electron microscopy demonstrates the existence of Ge ND layers well defined with respect to the SiO(2)/Si interface. The memory window that is estimated by capacitance-voltage hysteresis is proportional to the period, and finally reaches a plateau of about 11 V asymptotically over three periods. The program speed is enhanced over the full pulse-time range by increasing bias voltage or period. The charge-loss speed in the programmed state is slower in the samples with larger period. These memory properties are discussed based on possible physical mechanisms.