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Distinct Substrate Effect on the Reversibility of the Metal–Insulator Transitions in Electrolyte‐Gated VO 2 Thin Films
Author(s) -
Nakano Masaki,
Okuyama Daisuke,
Shibuya Keisuke,
Mizumaki Masaichiro,
Ohsumi Hiroyuki,
Yoshida Masaro,
Takata Masaki,
Kawasaki Masashi,
Tokura Yoshinori,
Arima Takahisa,
Iwasa Yoshihiro
Publication year - 2015
Publication title -
advanced electronic materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.25
H-Index - 56
ISSN - 2199-160X
DOI - 10.1002/aelm.201500093
Subject(s) - materials science , electrolyte , gating , doping , valence (chemistry) , electrochemistry , optoelectronics , nanotechnology , thin film , metal , chemical physics , electrode , chemistry , physiology , organic chemistry , metallurgy , biology
Electrolyte gating on correlated VO 2 thin films enables electrical control of the “bulk” electronic and structural phases over the electrostatic screening length. Although this unique functionality potentially provides novel electronic and optoelectronic device applications, there are intense discussions on the mechanism of the device operation both from electrostatic and electrochemical viewpoints. Here it is shown that the reversibility of the device operation strongly depends on substrates, suggesting that a governing mechanism might differ depending on substrates. Electrolyte gating on VO 2 films grown on lattice‐matched TiO 2 substrates shows reversible gating effects, whereas that on hexagonal Al 2 O 3 substrates become irreversible, although in both cases metallic states can be induced electrically. X‐ray absorption spectroscopy measurements on irreversibly gated VO 2 /Al 2 O 3 reveal permanent reduction of the valence state of vanadium upon gate‐induced metallization, presumably originating from irreversible electrochemical doping under the presence of the extremely large electric field created at an electrolyte/VO 2 interface. Our findings suggest essential importance of the film quality for future fundamental researches as well as for practical device applications based on electrolyte‐gated devices.