Thermochromic properties of vanadium oxide films prepared by dc reactive magnetron sputtering

Cui, H. N.; Teixeira, V.; Li, Meng; Wang, Rong; Gao, Jigang; Fortunato, Elvira

doi:10.1016/j.tsf.2007.03.131

Cited by 42 publications

(24 citation statements)

References 18 publications

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“…Various mechanisms were proposed to explain the thermochromic response in various materials. 6,26,27 But, in the present study, the achieved irreversible thermochromic behaviour in BWO films is attributed to the oxygen vacancies.…”

Section: Resultscontrasting

confidence: 52%

Irreversible thermochromic response of RF sputtered nanocrystalline BaWO4 films for smart window applications

Kumar

Pamu

2015

AIP Advances

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We report irreversible thermochromic behaviour of BaWO 4 (BWO) films for the first time. BWO films have been deposited at different substrate temperatures (RT, 200, 400, 600 and 800 • C) using RF magnetron sputtering in pure argon plasma. BWO films deposited at 800 • C exhibit crystalline nature. Also, BWO films deposited in the temperature range of 400 -600 • C exhibit WO 3 as a secondary phase and its weight percentage decreases with an increase in deposition temperature, whereas the films deposited at 800 • C exhibited pure tetragonal phase. FESEM images revealed that as the average particle sizes of the films are higher as compared with the thickness of the films and is explained based on Avrami type nucleation and growth. The transmittance of the films decreases with an increase in deposition temperature up to 600 • C and increases thereafter. Films deposited at 600 • C show ≤ 20% transmittance, looking at the films deposited at room temperature and 800 • C exhibits 90 and 70%, respectively. The refractive index and extinction coefficient of the films show profound dependence on crystallinity and packing density. The optical bandgap of BWO films increases significantly with an increase in O 2 % during the deposition. The optical bandgap of the BWO films deposited at different temperatures in pure argon plasma, are in the range of 3.7 to 3.94 eV whereas the films deposited at 600 • C under different O 2 plasma are in the range of 3.6 -4.5 eV. The formations of colour centres are associated with the oxygen vacancies, which are clearly seen from the optical bandgap studies. The observed irreversible thermochromic behaviour in BWO films is attributed to the presence of oxygen vacancies that arises due to the electrons trapped at oxygen vacancies causing an inter valence charge transfer of W 5+ to W 6+ and is confirmed through the change in the optical density (∆OD). Further, the Raman spectra are being used to quantify the presence of oxygen vacancies and the formation of pure BWO phase. The obtained optical responses of BWO films are promising for solar cell and smart window applications. C 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License. [http://dx

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Section: Resultscontrasting

confidence: 52%

Irreversible thermochromic response of RF sputtered nanocrystalline BaWO4 films for smart window applications

Kumar

Pamu

2015

AIP Advances

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“…This first-order transition is accompanied by a large change of electrical resistivity and reflectance in the infrared region [1] which makes these materials attractive for applications such as optical/electrical switching devices [2][3][4], electrochromic systems [5], data storage devices [6,7], etc. Among them, VO 2 is the most interesting because its transition temperature is close to room temperature, ~68ºC [1], and therefore is being under many studies in an effort to apply it in smart energy efficient windows with active solar control [8][9][10][11][12]. The stoichiometry of VO 2 has been reported as a determinant factor for an improved thermochromic performance [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Structural and Morphological Characterization of Magnetron Sputtered Nanocrystalline Vanadium Oxide Films for Thermochromic Smart Surfaces

Batista

Teixeira

Carneiro

2008

JNanoR

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Nanocrystalline vanadium oxide thin films have been deposited by reactive DC magnetron sputtering onto glass substrates under different processing conditions. Structural analysis and phase identification have been carried out by means of X-ray diffractometry (XRD). The surface morphologies of the different films have been examined by both scanning electron microscopy (SEM) and atomic force microscopy (AFM). The XRD results revealed single and multiple phase oxides such as VO 2 (B), VO 2 (M), V 2 O 5 , etc. with considerable differences concerning to surface morphologies, as observed by SEM and AFM. The effects the O 2 /Ar flow ratio, DC current, and working pressure on the phases formed and growth rates is discussed. Moreover, VO 2 (M) films exhibited different morphologies concerning to grain size and shape as well as dissimilar preference in crystal orientation, as a result of the processing conditions. The optical/thermochromic response of the VO 2 (M) specimens deposited under different growth rate conditions was evaluated by optical spectrophotometry and related to the respective structural characteristics.

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“…The transmittance values for the annealed samples are recorded as 61 %, 43.9 % and 30.7 %. The surface of annealed samples becomes rough, resulting in light loss by scattering and thus low transmittance [14,15]. In annealed thin films the absorption peak at around 350 nm was red-shifted with an increase in rf power [16].…”

Section: Resultsmentioning

confidence: 99%

Annealing effects on V2O5-x thin films deposited by non reactive sputtering

Rachel¹,

Sivakumar²,

Sanjeeviraja³

2016

Nanosystems: Phys. Chem. Math.

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Thin films of vanadium oxide (V 2 O 5−x ) were prepared by rf magnetron sputtering process and are heat treated to study the annealing effect. As-deposited thin films are amorphous in nature and crystallinity is improved by annealing the sample. Thin layers with high density and small grain size varying from 36 nm to 70 nm were seen in the FESEM images of as-deposited thin films. In the case of annealed thin films, it has been transformed to thin elongated rod like structure with 202.5 nm length and an average diameter of approximately 48 nm. Optical properties were studied by using UV-Vis-NIR spectrophotometer and the reduction in transmission in annealed thin films is due to the crystalline nature of thin films. Studies were done on the samples by taking photoluminescence and Laser Raman spectra.

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Thermochromic properties of vanadium oxide films prepared by dc reactive magnetron sputtering

Cited by 42 publications

References 18 publications

Irreversible thermochromic response of RF sputtered nanocrystalline BaWO4 films for smart window applications

Irreversible thermochromic response of RF sputtered nanocrystalline BaWO4 films for smart window applications

Structural and Morphological Characterization of Magnetron Sputtered Nanocrystalline Vanadium Oxide Films for Thermochromic Smart Surfaces

Annealing effects on V2O5-x thin films deposited by non reactive sputtering

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