On the role of Ti adlayers for resistive switching in HfO₂ -based metal-insulator-metal structures: Top versus bottom electrode integration

The authors demonstrate bipolar resistive switching in TiN/ HfO₂ /Ti (top) /TiN devices using a (Bi) complementary metal-oxide semiconductor (CMOS) compatible technology process. The device performance includes a cycling endurance in dc sweeping mode > 10³. The results suggest that HfO₂ -based metal-insulator-metal devices with Si CMOS compatible metal electrodes may be well suited for future embedded nonvolatile memory applications. However, hysteretic current-voltage characteristics were only observed for a Ti top adlayer, whereas a Ti bottom adlayer integration did not show any resistive switching effect. Using x-ray photoelectron spectroscopy, the authors examined the interface chemistry of the Ti/ HfO₂ interface. It is clearly observed that Ti top adlayer deposition results in an increased nitrogen- and oxygen-gettering activity in contrast to Ti bottom adlayer. It follows that the formation of a nonstoichiometric HfO₂ layer at the Ti/ HfO₂ interface is crucial for resistive switching.