We have fabricated and investigated the bipolar resistive switching characteristics of Pt/rutile-TiO2∕TiN devices for resistance memory applications. Data writing for five-level resistance states has been demonstrated by varying the amplitude of 5ns voltage pulses. In addition, data retention of more than 256h at 85°C and an excellent endurance of over 2×106cycles have been confirmed. These results indicate that Pt∕TiO2∕TiN devices have a potential for nonvolatile multiple-valued memory devices.

We demonstrate that both a low resistance state and a high resistance state can be written by bipolar voltage application in a local region of NiO/Pt films by using conducting atomic force microscopy. To investigate how oxygen played a role in the resistance switching phenomenon, a local writing process in O18 tracer gas atmosphere was carried out and the composition change was examined by time-of-flight secondary ion mass spectroscopy. As a result, it was revealed that oxygen moves to the anode side, and the composition of the NiO surface might change thereby causing the change in resistance.

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