EELS Analysis of Oxygen Scavenging Effect in a Resistive Switching Structure of Pt/Ta/SrTiO 3 /Pt
- PDF / 949,607 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 38 Downloads / 175 Views
EELS Analysis of Oxygen Scavenging Effect in a Resistive Switching Structure of Pt/Ta/SrTiO3/Pt Atsushi Tsurumaki-Fukuchi, Ryosuke Nakagawa, Masashi Arita and Yasuo Takahashi Graduate School of Information Science and Technology, Hokkaido University, Sapporo, Hokkaido 0600814, Japan
ABSTRACT
A complex mechanism of interfacial oxygen scavenging is revealed by electron energy-loss spectroscopy (EELS) for a resistive switching oxide of SrTiO3 with a scavenging layer of Ta. When Ta thin layer is inserted at one of the interfaces of Pt/SrTiO3/Pt structure, a large reduction of electrical resistance is induced for the structure, and oxygen defects are introduced at the interfacial part of SrTiO3. In the resistance decrease by voltage applications, simultaneous occurrence of oxidation and reduction of Ta scavenging layer is shown by EELS analyses from the low-loss spectra. The EELS and scanning transmission electron microscopy observations demonstrate that oxygen scavenging by Ta layer is an interfacial phenomenon where the redox reactions occur at the whole part of the interface. In addition, Pt electrode of the structure, which is chemically inert for oxidation, is revealed to have significant effects in the scavenging processes.
INTRODUCTION At a metal/oxide interface, oxygen defects are commonly formed into the oxide through redox reactions between the two layers. The application usage of interfacial oxygen defects into electronic devices have been gaining increasing attention because of their rich chemical and electronic functionalities [1]. Especially, extensive efforts have been devoted toward the control of interfacial oxygen defects in the recent developments of redox-based resistive switching memories or valence change memories [2]. For obtaining their switching operations, oxygen defects have been intentionally introduced into the oxide layer of resistive switching devices, and the introduction has often been made by redox reactions with a reactive electrode material such as Al and Ti [3,4]. In addition to the conventional method, an improved strategy for defect formation has been recently proposed: a thin interfacial layer of reactive metal between an inert electrode and an oxide, i.e., "scavenging" layer has started to be used in many devices [5-10]. Previous studies supposed that the use of scavenging layer offers high controllability of defect concentrations and easy induction of resistive switching phenomena, and the effectiveness of the layer has been suggested through theoretical calculations [6,8] and evaluations of device characteristics [5,7]. However, the mechanism of oxygen scavenging is still not well understood in most of metal/oxide systems because of the difficulty in observing the oxygen migration in scavenging layers with a nanoscale dimension (≤10 nm-thick). For example, a Downloaded from https://www.cambridge.org/core. Cornell University Library, on 19 Jan 2018 at 16:53:32, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.155
Data Loading...
