The electrical resistance switching (RS) properties of amorphous HfO 2 (a-HfO2) and crystalline HfO2 (c-HfO 2) thin films grown on a TiN substrate via atomic layer deposition were examined using DC current-voltage (I-V) sweep and AC impedance spectroscopic (IS) analyses. The rapid thermal annealing of the a-HfO 2 film at 500 °C under a N2 atmosphere for 5 min crystallized the HfO2 film and induced an interfacial TiON barrier layer. The a-HfO2 sample showed fluent bipolar RS performance with a high on/off ratio (∼500), whereas the c-HfO2 sample showed a much lower on/off ratio (<∼10), but its switching uniformity was better than that of a-HfO2. Such critical differences can be mainly attributed to the absence and presence of the TiON barrier layer in the a-HfO2 and c-HfO2 samples, respectively. The AC IS especially enabled the resistance states of the HfO2/Pt interface and the HfO 2/TiN interface to be separately examined during one complete switching cycle of each sample. Although the Pt/c-HfO2 interface has a Schottky barrier in the pristine state, it disappeared once the c-HfO 2 was electroformed and was not recovered even after the reset step. In contrast, the Pt/a-HfO2 interface partly recovered the Schottky barrier after the reset.
ASJC Scopus subject areas
- Materials Science(all)