Distinctive finite size effects on the phase diagram and metal–insulator transitions of tungsten-doped vanadium(iv) oxide

Abstract

The influence of finite size in altering the phase stabilities of strongly correlated materials gives rise to the interesting prospect of achieving additional tunability of solid-solid phase transitions such as those involved in metal-insulator switching, ferroelectricity, and superconductivity. We note here some distinctive finite size effects on the relative phase stabilities of insulating (monoclinic) and metallic (tetragonal) phases of solid-solution W x V 1Àx O 2 . Ensemble differential scanning calorimetry and individual nanobelt electrical transport measurements suggest a pronounced hysteresis between metal / insulator and insulator / metal phase transformations. Both transitions are depressed to lower critical temperatures upon the incorporation of substitutional tungsten dopants but the impact on the former transition seems far more prominent. In general, the depression in the critical temperatures upon tungsten doping far exceeds corresponding values for bulk W x V 1Àx O 2 of the same composition. Notably, the depression in phase transition temperature saturates at a relatively low dopant concentration in the nanobelts, thought to be associated with the specific sites occupied by the tungsten substitutional dopants in these structures. The marked deviations from bulk behavior are rationalized in terms of a percolative model of the phase transition taking into account the nucleation of locally tetragonal domains and enhanced carrier delocalization that accompany W 6+ doping in the W x V 1Àx O 2 nanobelts.

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

“…[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. Recently, we have demonstrated that reversible doping with atomic hydrogen alters the electronic phase transition.…”

Direct evidence of tungsten clustering in W0.02V0.98O2 thin films and its effect on the metal-to-insulator transition

“…50 K/at.% for the nano structures. 14,15 The mechanism behind this MIT transition has been debated for several decades and it has attracted great attention from various research areas. Two different points of views, as being more a Motttype transition characterized by strong electron-electron correlations 16,17 , or more a Peierls-type transition triggered by the structural V dimerization, have been supported experimentally and theoretically.…”

The additives W, Mo, Sn and Fe for promoting the formation of VO2(M) and its optical switching properties

“…Moreover, the T c of VO 2 (M) can be tuned by doping with W, Mo, Nb, F atoms, etc. or their mixtures [4][5][6][7][8][9][10][11]. These features make VO 2 to be suitable for applications [5,9,10,[12][13][14][15][16][17] in optical switches, storage medium, smart window coatings, temperature-sensing devices, laser protection, etc.…”

“…In the past decades, a lot of methods [4][5][6][7][8][9][10][11][14][15][16][17][18][19][20][21][22][23][24], such as RF sputtering, pulsed laser, deposition vacuum evaporation, physical vapor deposition, thermolysis, chemical vapor deposition, sol-gel, hydrothermal synthesis and so on, have been developed to synthesize VO 2 (M) or doped VO 2 (M). All of above methods, the hydrothermal method [5][6][7]11] has been paid increasing attention to synthesize W-doped VO 2 (M) because of its uncomplicated route and mass production recently.…”