Modulation of the Electrical Properties of VO₂ Nanobeams Using an Ionic Liquid as a Gating Medium

Abstract

Vanadium dioxide (VO(2)) is a strongly correlated transition metal oxide with a dramatic metal-insulator transition at 67 °C. Researchers have long been interested in manipulating this transition via the field effect. Here we report attempts to modulate this transition in single-crystal VO(2) nanowires via electrochemical gating using ionic liquids. Stray water contamination in the ionic liquid leads to large, slow, hysteretic conductance responses to changes in the gate potential, allowing tuning of the activation energy of the conductance in the insulating state. We suggest that these changes are the result of electrochemical doping via hydrogen. In the absence of this chemical effect, gate response is minimal, suggesting that significant field-effect modulation of the metal-insulator transition is not possible, at least along the crystallographic directions relevant in these nanowires.

Resistance switching of epitaxial VO2/Al2O3 heterostructure at room temperature induced by organic liquids

“…However, it is often difficult to achieve such high electric fields by conventional dielectric gates. 1,2 Recently, extra-high electric fields are achieved by approaches such as Schottky junctions, 3,4 polar adsorbates 5,6 or ionic liquids [7][8][9][10][11][12] as dielectric gates in field-effect transistor devices. 13,14 For example, Xu et al 15 studied the modulation of grain boundary barriers in ZnMgO/ZnO/sapphire heterostructure by DI water and they found that the electronic conduction property of ZnO layer far beneath the surface could be switched from Ohmic to Schottky junction.…”

Hydrogen Diffusion and Stabilization in Single-Crystal VO2 Micro/Nanobeams by Direct Atomic Hydrogenation

“…[5][6][7][8] In addition, this material has attracted much attention for its potential applications in ultrafast optical and electrical switching. [9][10][11][12][13] Therefore, much effort has been made to modulate the MIT by various approaches such as strain engineering, 14,15 ionic liquid gating, [16][17][18] electric field-induced oxygen vacancy, 19 and chemical doping. [20][21][22][23][24][25] In terms of chemical doping, using metal elements such as tungsten during growth can dramatically change the transition properties 20,26 , but it is an irreversible process.…”

Research Update: Nanoscale electrochemical transistors in correlated oxides

“…[19][20][21][22] According to Ji et al, 19 stray water in an IL gate induces large, slow, and hysteretic conductance modulation under applying gate bias. This operation allows tuning of the activation energy and changes conductance by an order of magnitude, resulting in hydrogen doping through the electrochemical reaction of water.…”

“…10,15 All of these methods require a high temperature of at least 150 • C. Recently, electric fields have been used for both hydrogenation and oxidation of oxides at room temperature. 16,[19][20][21] For example, a strong electric field in an ionic liquid (IL) gate induces oxygen vacancy formation 042303-2 T. Kanki and H. Tanaka APL Mater. 5, 042303 (2017) in VO 2 .…”

“…5, 042303 (2017) in VO 2 . 20 In water-containing gates composed IL or amorphous 12CaO·7Al 2 O 3 with a nanoporous structure, 19,22 H + can be intercalated under positive electric field. Thus, electrochemical gating including water electrolysis has a potential to allow tuning of the doping level of metal oxides at room temperature.…”