Electrochemically Triggered Metal–Insulator Transition between VO₂ and V₂O₅

Abstract

Distinct properties of multiple phases of vanadium oxide (VO x ) render this material family attractive for advanced electronic devices, catalysis, and energy storage. In this work, phase boundaries of VO x are crossed and distinct electronic properties are obtained by electrochemically tuning the oxygen content of VO x thin films under a wide range of temperatures. Reversible phase transitions between two adjacent VO x phases, VO 2 and V 2 O 5 , are obtained. Cathodic biases trigger the phase transition from V 2 O 5 to VO 2 , accompanied by disappearance of the wide band gap. The transformed phase is stable upon removal of the bias while reversible upon reversal of the electrochemical bias. The kinetics of the phase transition is monitored by tracking the time-dependent response of the X-ray absorption peaks upon the application of a sinusoidal electrical bias. The electrochemically controllable phase transition between VO 2 and V 2 O 5 demonstrates the ability to induce major changes in the electronic properties of VO x by spanning multiple structural phases. This concept is transferable to other multiphase oxides for electronic, magnetic, or electrochemical applications.induce the phase transition in the bulk via applying gate voltages with solid-state dielectric materials. [9][10][11] On the other hand, suppression of the MIT transition below T c , and reversible control of the electrical conductivity, was achieved by use of an ionic liquid (IL) gate instead of a solid-state dielectric. [12,13] The mechanism behind ionic liquid gating was beyond simple electrostatic polarization or field effect, but instead was electrochemical in nature. The removal of lattice oxygen, leading to reduction of the lattice and creation of oxygen vacancies, was proposed as the source for the suppression of the MIT transition. [14] In spite of the promise of VO 2 as a key component for "more-than-Moore" electronic devices, [15] it has several inevitable shortcomings originating from the character of its MIT. First, the band gap of the insulator phase VO 2 (M1) is only ≈0.6 eV, [2,16] which limits the maximum attainable magnitude of device conductance on/off ratios. The achievable on/off ratio of VO 2 -based devices in single crystal form is ≈10 5 , [17] while this value might be lowered to ≈10 3 or even lower for VO 2 thin films due to the existence of oxygen nonstoichiometry [1] or cation interdiffusion. [18] This value barely suffices for main stream logic devices requiring on/off ratios of 10 3 -10 6 [19] and is far lower than ≈10 7 that is required for low power logic devices (transistors). [20] Moreover, the relatively low T c of the MIT (≈68 °C) limits the maximum device operation temperature, below which VO 2 remains semiconducting. Thus, VO 2 -based electronic devices may require active cooling to maintain temperature below T c , thereby imposing additional constraints on deployment. Electronic StructuresThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

Self-Assembled Vanadium Oxide Nanoflakes for p-Type Ammonia Sensors at Room Temperature

“…The difference in resistance can be interpreted by their different intrinsic electrical properties. V 2 O 5 is a semiconducting/insulating oxide with a band gap of 2.2 eV, and usually exhibits low conductivity due to the empty 3d orbital [41]. VO 2 (M) undergoes a near room-temperature MIT accompanied by a rapid change in resistivity, usually showing high resistivity at room temperature [41].…”

“…V 2 O 5 is a semiconducting/insulating oxide with a band gap of 2.2 eV, and usually exhibits low conductivity due to the empty 3d orbital [41]. VO 2 (M) undergoes a near room-temperature MIT accompanied by a rapid change in resistivity, usually showing high resistivity at room temperature [41]. Although VO 2 (B) is generally regarded as an n-type semiconductor in gas sensing research [38], it is a theoretical semimetal/metal phase at room temperature, usually exhibiting high conductivity compared to VO 2 (M) and V 2 O 5 [42].…”

Al‐Doping‐Induced VO2 (B) Phase in VO2 (M) Toward Smart Optical Thin Films with Modulated ΔTvis and ΔTc

“…Figure b shows the high‐resolution analyses of the O 1s and V 2p peaks of pure and Al‐doped thin films fitted by the Shirley function. In general, V 2p can be split into V 2p 3/2 and V 2p 1/2 with a 2:1 areal proportion, and thus, the spectra can be decomposed into two groups of peaks corresponding to different oxidation states of V. The higher oxidation state involving V 2p 3/2 at ≈517.5 eV and V 2p 1/2 at ≈525.0 eV is associated with V 2 O 5 due to the VTIP precursors used during ALD processes. The lower oxidation state with binding energies at ≈516.6 and 523.8 eV is related to VO 2 due to a partial oxygen loss in the ALD reaction .…”

Strain Induced Orbital Dynamics Across the Metal Insulator Transition in Thin VO2/TiO2 (001) Films

“…This class of oxides bear the seed of a strong electronic correlation and have been widely studied since the early times of X-ray spectroscopy. The electronic transport and the spectroscopic properties of V2O3 [1], VO2 [2] as well as the complex local structure of V2O5 [3] have always attracted interest and still today their investigation is a hot topic in materials science, [4][5][6] with many potentials for technology applications [7]. Among the vanadium oxides, VO2 is one of the most stimulating system.…”