title: Impedance spectroscopic analysis on effects of partial oxidation of TiN bottom electrode and microstructure of amorphous and crystalline HfO2 thin films on their bipolar resistive switching.
abstract: The electrical resistance switching (RS) properties of amorphous HfO2 (a-HfO2) and crystalline HfO2 (c-HfO2) 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-HfO2 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 HfO2/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-HfO2 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.
authors.affiliation: Department of Materials Science and Engineering, Korea University, Anam-Dong, SungbukGu, Seoul 136-714, Republic of Korea. jongheun@korea.ac.kr.
authors.forename: Ji-Wook
authors.initials: JW
authors.lastname: Yoon
authors.forename: Jung Ho
authors.initials: JH
authors.lastname: Yoon
authors.forename: Jong-Heun
authors.initials: JH
authors.lastname: Lee
authors.forename: Cheol Seong
authors.initials: CS
authors.lastname: Hwang