Strongly thermochromic W-doped VO2 films with a large temperature coefficient of electrical resistance near room temperature

Kód výsledku v IS VaVaI

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Výsledek na webu

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DOI - Digital Object Identifier

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Jazyk výsledku

angličtina

Název v původním jazyce

Strongly thermochromic W-doped VO2 films with a large temperature coefficient of electrical resistance near room temperature

Popis výsledku v původním jazyce

Vanadium dioxide (VO2) is an extremely interesting and increasingly investigated coating material due to its reversible first-order transition between a low-temperature monoclinic VO2(M1) semiconducting phase and a high-temperature tetragonal VO2(R) metallic phase relatively near room temperature (approximately 68 °C for the bulk material). High modulation of the infrared transmittance, and electrical and thermal conductivity makes VO2-based films a suitable candidate for numerous applications, such as electronic and optical switches, thermal sensors, smart thermal radiator devices for spacecraft, adaptive thermal camouflage, and energy-saving smart windows with automatically varied solar energy transmittance. The application potential of these films depends on the ability to achieve not only the VO2 stoichiometry but also the crystallization of the VO2(M1/R) phase under as industry-friendly process conditions as possible, i.e., at a deposition temperature close to 300 °C (usually used temperatures are higher than 450 °C) and without any substrate bias voltage in case of usually used magnetron sputter techniques. Moreover, the transition temperature needs to be reduced to room temperature for many applications (e.g., energy-saving smart windows, new uncooled infrared detectors and high-performance temperature sensors). Besides the optical transmittance and the electrical resistivity below transition temperature, the characteristics of the semiconductor-metal transition, such as the corresponding phase-transition amplitude, hysteresis width and phase-transition sharpness, are of key importance.The paper deals with crystal structure, electronic band structure, optical and electrical properties, and semiconductor-metal transition characteristics of strongly thermochromic W-doped VO2 films with a large (up to ‒16% 1/K) temperature coefficient of electrical resistance near room temperature (24‒28 °C). They were deposited at a reduced temperature (350 °C) onto soda-lime glass substrates with two versions of Y-stabilized ZrO2 (YSZ) interlayers (serving also as a highly optically transparent bottom antireflection layer) possessing different crystal orientations, and onto bare glass and monocrystalline YSZ and Al2O3 substrates for comparison. The W-doped VO2 films were synthesized using reactive deep oscillation magnetron sputtering (DOMS) with a pulsed O2 flow control and to-substrate O2 injection into a high-density plasma in front of the sputter V-W (3.0 wt.%) target. The DOMS is a modified version of high-power impulse magnetron sputtering with macropulses (500 µs in this work) composed of short high-power micropulses (10 in this work) making it possible to increase discharge stability and deposition rate of films (20–30 nm/min in this work).

Název v anglickém jazyce

Strongly thermochromic W-doped VO2 films with a large temperature coefficient of electrical resistance near room temperature

Popis výsledku anglicky

Vanadium dioxide (VO2) is an extremely interesting and increasingly investigated coating material due to its reversible first-order transition between a low-temperature monoclinic VO2(M1) semiconducting phase and a high-temperature tetragonal VO2(R) metallic phase relatively near room temperature (approximately 68 °C for the bulk material). High modulation of the infrared transmittance, and electrical and thermal conductivity makes VO2-based films a suitable candidate for numerous applications, such as electronic and optical switches, thermal sensors, smart thermal radiator devices for spacecraft, adaptive thermal camouflage, and energy-saving smart windows with automatically varied solar energy transmittance. The application potential of these films depends on the ability to achieve not only the VO2 stoichiometry but also the crystallization of the VO2(M1/R) phase under as industry-friendly process conditions as possible, i.e., at a deposition temperature close to 300 °C (usually used temperatures are higher than 450 °C) and without any substrate bias voltage in case of usually used magnetron sputter techniques. Moreover, the transition temperature needs to be reduced to room temperature for many applications (e.g., energy-saving smart windows, new uncooled infrared detectors and high-performance temperature sensors). Besides the optical transmittance and the electrical resistivity below transition temperature, the characteristics of the semiconductor-metal transition, such as the corresponding phase-transition amplitude, hysteresis width and phase-transition sharpness, are of key importance.The paper deals with crystal structure, electronic band structure, optical and electrical properties, and semiconductor-metal transition characteristics of strongly thermochromic W-doped VO2 films with a large (up to ‒16% 1/K) temperature coefficient of electrical resistance near room temperature (24‒28 °C). They were deposited at a reduced temperature (350 °C) onto soda-lime glass substrates with two versions of Y-stabilized ZrO2 (YSZ) interlayers (serving also as a highly optically transparent bottom antireflection layer) possessing different crystal orientations, and onto bare glass and monocrystalline YSZ and Al2O3 substrates for comparison. The W-doped VO2 films were synthesized using reactive deep oscillation magnetron sputtering (DOMS) with a pulsed O2 flow control and to-substrate O2 injection into a high-density plasma in front of the sputter V-W (3.0 wt.%) target. The DOMS is a modified version of high-power impulse magnetron sputtering with macropulses (500 µs in this work) composed of short high-power micropulses (10 in this work) making it possible to increase discharge stability and deposition rate of films (20–30 nm/min in this work).

Druh

O - Ostatní výsledky

CEP obor

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OECD FORD obor

20506 - Coating and films

Projekt

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Návaznosti

S - Specificky vyzkum na vysokych skolach

Rok uplatnění

2025

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů