Controlled reactive HiPIMS—effective technique for low-temperature (300 °C) synthesis of VO<sub>2</sub>films with semiconductor-to-metal transition

Vlček, Jaroslav; Kolenatý, David; Houška, Jiří; Kozák, Tomáš; Čerstvý, R.

doi:10.1088/1361-6463/aa8356

Cited by 41 publications

(28 citation statements)

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“…However, all these techniques are restricted by the cost and scale of vacuum systems. Moreover, most of these growth techniques, although they are of high fidelity and can produce good quality thermochromic VO 2 films, demand high deposition temperatures (>400 • C) [11,[14][15][16][17][18], with very few employing sputtering techniques between 250 and 300 • C [12,13,[19][20][21], making it impossible to utilize flexible (polymeric) substrates.Another approach, called the ex-situ approach [22], to the fabrication of VO 2 thermochromic films is to first synthesize the desired material as a powder and then to deposit the material as a film onto the desired surface. Thermochromic VO 2 in the form of powders have been synthesized by various methods, such as thermolysis [23,24], rapid thermal annealing [25], pyrolysis [26], and, the most utilized method, hydrothermal (solvothermal) synthesis [27][28][29][30][31].…”

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Thermochromic Behavior of VO2/Polymer Nanocomposites for Energy Saving Coatings

et al. 2019

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Vanadium dioxide (VO2) is a well-known thermochromic material that can potentially be used as a smart coating on glazing systems in order to regulate the internal temperature of buildings. Most growth techniques for VO2 demand high temperatures (>250 °C), making it impossible to comply with flexible (polymeric) substrates. To overcome this problem, hydrothermally synthesized VO2 particles may be dispersed in an appropriate matrix, leading to a thermochromic coating that can be applied on a substrate at a low temperature (<100 °C). In this work, we reported on the thermochromic properties of a VO2/Poly-Vinyl-Pyrrolidone (PVP) nanocomposite. More specifically, a fixed amount of VO2 particles was dispersed in different PVP quantities forming hybrids of various VO2/PVP molar ratios which were deposited as films on fused silica glass substrates by utilizing the drop-casting method. The crystallite size was calculated and found to be 35 nm, almost independent of the PVP concentration. As far as the thermochromic characteristics are concerned, the molar ratio of the VO2/PVP nanocomposite producing VO2 films with the optimum thermochromic properties was 0.8. These films exhibited integral solar transmittance modulation (overall wavelengths) ΔTrsol = 0.35%–1.7%, infrared (IR) switching at 2000 nm ΔTrIR = 10%, visible transmittance at 550 nm TrVis = 38%, critical transition temperature TC = 66.8 °C, and width of transmittance hysteresis loop ΔTC = 6.8 °C. Moreover, the critical transition temperature was observed to slightly shift depending on the VO2/PVP molar ratio.

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Thermochromic Behavior of VO2/Polymer Nanocomposites for Energy Saving Coatings

et al. 2019

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“…Keeping the RF sputtering power constant, the increase in PDC is synonymous with the increase in on‐time in which the ions are accelerated. As a consequence, changing the PDC value will affect the energy distribution, species, and cross sections of dominant primary ions and, as a consequence, the properties of the secondary target particles can be manipulated . Thus, inter alia, the timescale for ordering at the substrate surface is modified.…”

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Progress in Sputter Growth of β‐Ga₂O₃ by Applying Pulsed‐Mode Operation

Schurig

Michel

Beyer

et al. 2020

Physica Status Solidi (a)

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β‐Ga2O3 thin films are deposited by pulsed radio‐frequency (RF) magnetron sputtering on c‐sapphire substrates, using a stoichiometric Ga2O3 target and a constant gas flux of an argon–oxygen mixture. Pulsed sputtering offers a way to overcome the restrictions of conventional sputtering. The parameters RF power and pulse duty cycle (PDC) are varied systematically to optimize the synthesis of Ga2O3 thin films. Subsequently, the resulting as‐deposited (AD) Ga2O3 layers are analyzed in terms of structural and optical properties and the results are compared with those on the samples treated by postdeposition rapid thermal annealing. Based on this analysis, the process parameters are evaluated in terms of β‐Ga2O3 formation. Postdeposition temperature treatments are found to yield a better crystal quality. However, a strong interdiffusion with the Al2O3 substrate is observed. The optical bandgap of the sputtered thin films is found to be quite independent of the RF sputtering power but to depend strongly on the PDC used, whereas the layer thickness rather strongly increases with both of those growth parameters. These evolutions are assigned to changes in the energy and ionic species of the plasma. Traces of GaOx‐related phases in addition to β‐Ga2O3 are found in the interphase between the growing thin films and the underlying substrate.

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“…Doped VO 2 is commonly prepared by hydrothermal synthesis [6], chemical vapour deposition [14], magnetron sputtering [15], sol-gel synthesis [16], etc. Although these methods usually require long-lasting thermal treatment at high temperatures in an inert atmosphere, VO 2 films can be successfully prepared by fairly low temperature magnetron sputtering depositions [17][18][19][20]. Nevertheless, VO 2 can be prepared by means of facile wet-chemistry synthesis through intermediate vanadyl glycolate, VO(OCH 2 CH 2 O), thus enabling short annealing times and avoiding inert atmosphere requirements [21].…”

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In-Operando Diffraction and Spectroscopic Evaluation of Pure, Zr-, and Ce-Doped Vanadium Dioxide Thermochromic Films Derived via Glycolate Synthesis

et al. 2020

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Pure and doped vanadia (VO2, V0.98Zr0.02O2, V0.98Ce0.02O2) samples were prepared by wet chemistry synthesis from vanadyl glycolate intermediate phase and tape casted into films. Combining in-operando grazing incidence synchrotron X-ray diffraction and Raman spectroscopy, we studied the structural evolution of the films under isothermal conditions. The setup allowed assessment of the thermochromic functionality with continuous monitoring of the monoclinic to tetragonal transition in pure and doped vanadia phases, responsible for the transmission and reflection of light in the infrared part of the solar spectrum. The materials characterisation by X-ray diffraction beamline (MCX) goniometer demonstrated ideal performance, combining flexible geometry, high resolution, and the potential to accommodate the multi-channel equipment for in-operando characterisation. This method proved viable for evaluating the relevant structural and physical, and thereof functional properties of these systems. We revealed that dopants reduce the transition temperature by 5 °C on average. The synthetic route of the films was held responsible for the observed phase separation. The more favourable behaviour of cerium-doped sample was attributed to cerium alkoxide behaviour. In addition, structural, microstructural, thermal, and spectroscopic characterisation on powder samples was performed to gain more insight into the development of the phases that are responsible for thermochromic features in a broader range of doping ratios. The influence of the dopants on the extent of the thermochromic transition (transmission to reflection hysteresis) was also evaluated using (micro) structural, thermal and spectroscopic methods of powder samples. Characterisations showed that zirconium doping in 2, 4, and 6 mol% significantly influenced the phase composition and morphology of the precursor. Vanadium oxides other than VO2 can easily crystallise; however, a thermal treatment regime that allowed crystallisation of VO2 as a single phase was established.

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Controlled reactive HiPIMS—effective technique for low-temperature (300 °C) synthesis of VO₂films with semiconductor-to-metal transition

Cited by 41 publications

References 25 publications

Thermochromic Behavior of VO2/Polymer Nanocomposites for Energy Saving Coatings

Thermochromic Behavior of VO2/Polymer Nanocomposites for Energy Saving Coatings

Progress in Sputter Growth of β‐Ga₂O₃ by Applying Pulsed‐Mode Operation

In-Operando Diffraction and Spectroscopic Evaluation of Pure, Zr-, and Ce-Doped Vanadium Dioxide Thermochromic Films Derived via Glycolate Synthesis

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Controlled reactive HiPIMS—effective technique for low-temperature (300 °C) synthesis of VO2films with semiconductor-to-metal transition

Cited by 41 publications

References 25 publications

Thermochromic Behavior of VO2/Polymer Nanocomposites for Energy Saving Coatings

Thermochromic Behavior of VO2/Polymer Nanocomposites for Energy Saving Coatings

Progress in Sputter Growth of β‐Ga2O3 by Applying Pulsed‐Mode Operation

In-Operando Diffraction and Spectroscopic Evaluation of Pure, Zr-, and Ce-Doped Vanadium Dioxide Thermochromic Films Derived via Glycolate Synthesis

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Controlled reactive HiPIMS—effective technique for low-temperature (300 °C) synthesis of VO₂films with semiconductor-to-metal transition

Progress in Sputter Growth of β‐Ga₂O₃ by Applying Pulsed‐Mode Operation