  For the clear understanding of the role of interface reaction between top
metal electrode and titanium oxide layer, we investigated the effects of
various top metals on the resistive switching in Metal/a-TiO2/Al devices. The
top Al device with the highest oxygen affinity showed the best memory
performance, which is attributed to the fast formation of interfacial layer
(Al-Ti-O), as confirmed by high resolution transmission electron microscopy and
electron dispersive spectroscopy. Hence, we concluded that the interface layer,
created by the redox reaction between top metal electrode and TiO2 layer, plays
a crucial role in bipolar resistive switching behaviors of metal/TiO2/Al
systems.
