Ionic liquid gating induced insulating phase transition in LaNiO3 thin films

Le résumé fourni par la source

Perovskite rare-earth nickelates exhibit intriguing electrical and optical properties, such as metal-to-insulator transitions, resulting from the strong interplay between charge disproportionation and electron correlation. Of these materials, lanthanum nickelate, ${\mathrm{LaNiO}}_{3}$, is the only exception where the metallic phase is robust at all temperatures. Recently, significant efforts have been made to induce an insulating phase in ${\mathrm{LaNiO}}_{3}$ by dimensionality or stoichiometry control. Electrolyte gating can be an efficient alternative to manipulate such electronic behavior reversibly and controllably. In this work, we performed systematic ionic liquid gating studies with electric double-layer transistor devices to control the electronic properties of ${\mathrm{LaNiO}}_{3}$. The electrolyte gating in ${\mathrm{LaNiO}}_{3}$ leads to an insulating phase transition with an increased film resistivity by over six orders of magnitude. The electrolyte gating behaviors are found to be dependent on not only gating voltage and duration, but also the atmospheric environment and temperature. X-ray photoelectron spectroscopy analysis reveals that the ionic liquid gating changes the O vacancy concentration and Ni valence state with varying gating times. The phase transition is attributed to enhanced electron correlation as well as opening of the charge transfer gap due to the reduced overlap between Ni and O bands. Intriguingly the filling of carriers into the Mott-Hubbard gap vs charge transfer gap is controlled by the gate voltage. These results suggest that electrolyte gating devices can be useful for manipulating electron-electron correlation, boosting materials research to realize exotic physics in correlated systems.

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