Memory Effect in Metal–Chalcogenide–Metal Structures for Ultrahigh-Density Nonvolatile Memories

A novel memory effect in metal–chalcogenide–metal structures was observed using chalcogenide films connected by two Al electrodes. A bias polarity-dependent switching between a high (RESET) and low (SET) resistance state was observed in current–voltage characteristics of the structure when sweeping voltage in forward and backward directions. The reversible SET/RESET switching was induced by voltage pulses and their polarity. The resistances of the structure changed over a range of approximately two orders of magnitude. In readouts of the resistance, we obtained its retention time for data over 17 days at room temperature.