title: Evaluation of a ferroelectric tunnel junction by ultraviolet-visible absorption using a removable liquid electrode.
abstract: Ferroelectric memristors offer a significant alternative to their redox-based analogs in resistive random access memory because a ferroelectric tunnel junction (FTJ) exhibits a memristive effect that induces resistive switching (RS) regardless of the operating current level. This RS results from a change in the ferroelectric polarization direction, allowing the FTJ to overcome the restriction encountered in redox-based memristors. Herein, the memristive effect of an FTJ was investigated by ultraviolet-visible (UV-Vis) absorption spectroscopy using a removable mercury (Hg) top electrode (TE), BaTiO3 (BTO) ferroelectric tunnel layer, La0.7Sr0.3MnO3 (LSMO) semiconductor bottom electrode, and wide-bandgap quartz (100) single-crystal substrate to determine the low-resistance state (LRS) and high-resistance state (HRS) of the FTJ. A BTO (110)/LSMO (110) polycrystal memristor involving a Hg TE showed a small memristive effect (switching ratio). This effect decreased with increasing read voltage because of a small potential barrier height. The LRS and HRS of the FTJ showed quasi-similar UV-Vis absorption spectra, consistent with the small energy difference between the valence-band maximum of BTO and Fermi level of LSMO near the interface between the LRS and HRS. This energy difference stemmed from the ferroelectric polarization and charge-screening effect of LSMO based on an electrostatic model of the FTJ.
authors.affiliation: Department of Materials Science and Engineering, Yonsei University, Seodaemun-Ku, Seoul 120-749, Korea.
authors.forename: Hong-Sub
authors.initials: HS
authors.lastname: Lee
authors.forename: Kyung-Mun
authors.initials: KM
authors.lastname: Kang
authors.forename: Geun Young
authors.initials: GY
authors.lastname: Yeom
authors.forename: Hyung-Ho
authors.initials: HH
authors.lastname: Park