title: Evolution of Insulator-Metal Phase Transitions in Epitaxial Tungsten Oxide Films during Electrolyte-Gating.
abstract: An interface between an oxide and an electrolyte gives rise to various processes as exemplified by electrostatic charge accumulation/depletion and electrochemical reactions such as intercalation/decalation under electric field. Here we directly compare typical device operations of those in electric double layer transistor geometry by adopting A-site vacant perovskite WO3 epitaxial thin films as a channel material and two different electrolytes as gating agent. In situ measurements of X-ray diffraction and channel resistance performed during the gating revealed that in both the cases WO3 thin film reaches a new metallic state through multiple phase transitions, accompanied by the change in out-of-plane lattice constant. Electrons are electrostatically accumulated from the interface side with an ionic liquid, while alkaline metal ions are more uniformly intercalated into the film with a polymer electrolyte. We systematically demonstrate this difference in the electrostatic and electrochemical processes, by comparing doped carrier density, lattice deformation behavior, and time constant of the phase transitions.
authors: Shinichi
authors: S
authors: Nishihaya
authors: Masaki
authors: M
authors: Uchida
authors: Yusuke
authors: Y
authors: Kozuka
authors: Yoshihiro
authors: Y
authors: Iwasa
authors: Masashi
authors: M
authors: Kawasaki
authors: Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo , Tokyo 113-8656, Japan.
authors: S
authors: S
authors: Nishihaya
authors: Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo , Tokyo 113-8656, Japan.
authors: M
authors: M
authors: Uchida
authors: Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo , Tokyo 113-8656, Japan.
authors: Y
authors: Y
authors: Kozuka
authors: Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo , Tokyo 113-8656, Japan.
authors: Y
authors: Y
authors: Iwasa
authors: Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo , Tokyo 113-8656, Japan.
authors: M
authors: M
authors: Kawasaki
authors: RIKEN Center for Emergent Matter Science (CEMS) , Wako, 351-0198, Japan.
authors: Y
authors: Y
authors: Iwasa
authors: RIKEN Center for Emergent Matter Science (CEMS) , Wako, 351-0198, Japan.
authors: M
authors: M
authors: Kawasaki
keywords: electric double layer; in situ X-ray diffraction; intercalation; pulsed laser deposition; tungsten oxides