A study on the memristive properties of lanthanum nickel oxide bilayers featured on the front cover of “Journal of Materials Chemistry A”

by Virginia Greco

This research reveals the optimal film growth conditions to obtain memristive behaviour at the interface between oxygen ion conducting La₂NiO₄ and electron conducting LaNiO₃ epitaxial layers. Dr José Santiso, leader of the ICN2 Nanomaterials Growth Unit, is one of the coordinators of the study.

Mixed ionic–electronic conductors (MIECs) –materials that conduct both ions and electronic charge carriers (electrons and/or holes)— are finding important applications in various electrochemical devices, such as solid oxide fuel cells, as well as in recent memory devices. With regard to the latter, one of the most interesting aspects of these materials is the fact that they may exhibit memristive behaviour, where a memristor (from memory-resistor) is a non-linear electronic component whose resistance depends on the “history” of voltage applied to it.

A study recently published in the Journal of Materials Chemistry A and featured on its frontispiece investigates the memristive properties of a MIEC structure obtained by combining lanthanum nickel oxide bilayers. In particular, the authors used La₂NiO₄₊_δ in which overstoichiometric oxygen ions occupy interstitial positions, providing mobile ionic carriers, combined with the metal-oxide LaNiO₃, which acts as the electrode material. The crystal matching of these two materials allowed researchers to easily grow highly textured La₂NiO₄ on a film of LaNiO₃ by means of pulsed-laser deposition. The electrical transport and in particular the memristive behaviour of the resulting structure were studied, focusing on the effect that growth conditions have on them.

This work, coordinated by Dr José Santiso, leader of the ICN2 Nanomaterials Growth Unit, and Dr Mónica Burriel, leader of the Oxides for Nanoionic Devices group at the Laboratoire des Matériaux et du Génie Physique (LMGP, CNRS, Grenoble-INP), reveals the optimal film growth conditions of La₂NiO₄ and LaNiO₃ epitaxial bilayers to exhibit memristive behaviour at the interface between the oxygen ionic and the electronic conducting layers.

Depending on the film microstructure and under an applied external voltage the oxygen interstitials reversibly drift towards (or from) the interface with LaNiO₃, accumulating at (or depleting from) the interface. Therefore, the characteristics of the interfacial electrical barrier can be modulated for the device to show enhanced memristive properties. This work shows that mobile interstitial oxygen defects can be used in resistive switching devices as an alternative to conventional oxygen vacancies.

Cover image credit: Dámaso Torres (ICN2)

Reference article:

Klaasjan Maas, Chloé Wulles, Jose Manuel Caicedo Roque, Belén Ballesteros, Valentin Lafarge, José Santiso and Mónica Burriel, Role of pO2 and film microstructure on the memristive properties of La2NiO4+δ/LaNiO3−δ bilayers. J. Mater. Chem. A, 2022,10, 6523-6530. DOI: 10.1039/d1ta10296f