Sputtering Deposition of Sandwich-Structured V₂O₅/Metal (V, W)/V₂O₅ Multilayers for the Preparation of High-Performance Thermally Sensitive VO₂ Thin Films with Selectivity of VO₂ (B) and VO₂ (M) Polymorph

Abstract

For specific application to an uncooled infrared detector, VO2 thin films should have a series of characteristics including purposefully chosen polymorphs, accurate stoichiometry, phase stabilization, a high temperature-coefficient of resistance (TCR), and suitable square-resistance. This work reports controllable preparation of high-performance VO2 films via post annealing of a sandwich-structured V2O5/metal (V, W)/V2O5 multilayer precursor, which was deposited by RF magnetron sputtering. This sandwich structure can dynamically regulate oxygen contents and doping element levels in the films, enabling us to achieve accurate regulation of stoichiometry and polymorphs. The precursor films undergo a B to M phase transition depending on the quantity of the metal layers. At the thickness of the metal layer below a limitation, the resulting film after heat treatment was VO2 (B), and above the limitation, the product was VO2 (M). The optical modulation of the VO2 (M) in the near-infrared region can be tuned from 1.2 to 39.8% (ΔT2000 nm). TCR values can range from -1.89 to -4.29%/K and the square-resistances at room temperature (R0) from 69.68 to 12.63 kΩ. The simplicity in phase regulation of the present method and the superior optical and electrical properties of the films may allow its wide applications in thermo-opto-electro sensing devices.

Crystallization and inter-diffusional behaviors in the formation of VO2(B) thin film with layered W-doping

“…The metastable VO 2 (B) thin films can be prepared by popular film deposition techniques, including pulsed laser deposition [1,[14][15][16][17], metal-organic chemical vapor deposition [13,18], ion beam sputtering [3], and magnetron sputtering [9,[19][20][21][22]. In general, all these deposition processes could be summarized into two routes: the one-step route by direct deposition at high temperature, and the two-step route by deposition first at low temperature and a follow-up heat treatment at high temperature.…”

“…It has been shown that doping W 6+ ions increases the number of 3d state electrons and thus decreases the thermal activation energy, hence to enhance TCR value and reduce resistivity concurrently [9,21,24]. Doping has also an effect on VO 2 (B) crystallization behavior [1,9,14,21].…”

“…It has been shown that doping W 6+ ions increases the number of 3d state electrons and thus decreases the thermal activation energy, hence to enhance TCR value and reduce resistivity concurrently [9,21,24]. Doping has also an effect on VO 2 (B) crystallization behavior [1,9,14,21]. W-doping into VO 2 (B) thin film could be realized in two modes: the in-situ mode via co-deposition [9], and the diffusional mode via layered doping which could be in either sandwich [21] or multi-layered form [23].…”

“…Doping has also an effect on VO 2 (B) crystallization behavior [1,9,14,21]. W-doping into VO 2 (B) thin film could be realized in two modes: the in-situ mode via co-deposition [9], and the diffusional mode via layered doping which could be in either sandwich [21] or multi-layered form [23]. The layered doping is indirect process, which depends on the inter-diffusion between the as-deposited VO x and W layers during deposition or crystallization process; hence the effect of layered doping could be controlled by either altering number of W layers or changing the W layer thickness.…”

Dual phase titanium alloy hot forging process design: experiments and numerical modeling

“…VO 2 smart coatings are usually used in two forms including flexible foils based on VO 2 nanoparticles [31,[43][44][45][46][47][48][49] and VO 2 based multilayer films [11,12,30,[50][51][52]. However, for commercial application as smart coatings on energy efficient fenestrations, there are still several obstacles severely limiting the relative applicability of VO 2 smart coatings.…”