Characteristics of W- and Ti-Doped VO[sub 2] Thin Films Prepared by Sol-Gel Method

Chae, Byung-Gyu; Kim, H. T.; Yun, Sun-Jin

doi:10.1149/1.2903208

Cited by 57 publications

(27 citation statements)

References 14 publications

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“…The dependence of T MI on doping, studied in V 1−x M x O 2 compounds, can be approximately mapped onto its dependence on applied pressure. Reduction of V 4+ is achieved using M = Nb, Mo, W, Ta, Re, Ir, F, Ti, Os, Ru, Tc and so on, with formal charges of +4, +5 or +6 [32,43,[48][49][50][51][52][53][54][55][56][57][58][59]. The effect on T MI is similar to that of negative (compressive) stress along [001] R , yielding dT MI /dx = −0.3 to − 28 K (at.% M) −1 .…”

Section: Discussionmentioning

confidence: 99%

THz spectroscopy of VO₂epitaxial films: controlling the anisotropic properties through strain engineering

Abreu

Liu²,

Lu³

et al. 2012

New J. Phys.

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Optical properties across the insulator to metal transitions in vanadium oxidecompounds A Perucchi, L Baldassarre, P Postorino et al. Abstract. We use THz time-domain spectroscopy to investigate the farinfrared properties of vanadium dioxide thin films, strain-engineered through epitaxial growth on (100) R TiO 2 substrates. The films exhibit a large uniaxial tensile strain along the rutile c-axis. X-ray diffraction measurements reveal a structural transition temperature of 340 K, whereas independent THz conductivity measurements yield a metal-insulator transition temperature of 365 K along c R . Analysis of these results suggests a Mott-Hubbard behavior along the c R -axis. Along c R the conductivity is approximately 5500 ( cm) −1 , comparable to bulk single crystals. The tensile strain leads to remarkably uniform cracking oriented along the rutile c-axis, resulting in a large conductivity anisotropy in our single-crystal epitaxial thin films. We discuss our results in the context of previous measurements and calculations of the properties of VO 2 , under different strain conditions. This work demonstrates the potential of strain engineering to tune the properties of complex materials while also serving as a powerful discriminatory tool for probing microscopic responses. 4 These authors contributed equally to this work.

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Section: Discussionmentioning

confidence: 99%

THz spectroscopy of VO₂epitaxial films: controlling the anisotropic properties through strain engineering

Abreu

Liu²,

Lu³

et al. 2012

New J. Phys.

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“…Our thin film of VO 2 is deposited by sol-gel technique on a sapphire substrate as described elsewhere [18]. This technique has been shown to produce VO 2 films with up to four orders of magnitude (10 4 ) change in conductivity across the IMT (see Figure 2b).…”

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confidence: 99%

Phase-transition driven memristive system

Driscoll

Kim²,

Chae³

et al. 2009

Applied Physics Letters

347

236

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Memristors are passive circuit elements which behave as resistors with memory. The recent experimental realization of a memristor has triggered interest in this concept and its possible applications. Here, we demonstrate memristive response in a thin film of Vanadium Dioxide. This behavior is driven by the insulator-to-metal phase transition typical of this oxide. We discuss several potential applications of our device, including high density information storage. Most importantly, our results demonstrate the potential for a new realization of memristive systems based on phase transition phenomena

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“…5 The nature of the metal-insulator transition ͑MIT͒ has been much debated, but recent work indicates a Mott transition. 15 It has been found that a few percent of W can decrease c to 20 to 25°C, i.e., to a comfort temperature suitable for practical fenestration. However, the requirement of a high relative modulation of the transmittance at c has invariably limited T lum to Ͻ40%, which in general is too low.…”

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confidence: 99%

Mg doping of thermochromic VO2 films enhances the optical transmittance and decreases the metal-insulator transition temperature

Mlyuka

Niklasson

Granqvist

2009

Applied Physics Letters

250

155

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Thermochromic films of Mg x V 1−x O 2 were made by reactive dc magnetron sputtering onto heated glass. The metal-insulator transition temperature decreased by ϳ3 K/ at. %Mg, while the optical transmittance increased concomitantly. Specifically, the transmittance of visible light and of solar radiation was enhanced by ϳ10% when the Mg content was ϳ7 at. %. Our results point at the usefulness of these films for energy efficient fenestration. © 2009 American Institute of Physics. ͓doi:10.1063/1.3229949͔ Thermochromic VO 2 films transmit more solar radiation below a "critical" temperature c than above this temperature. As shown in this letter, Mg doping of VO 2 enhances the luminous transmittance T lum and lowers c , thus demonstrating that such films are interesting for windows of energy efficient buildings.Worldwide, 30%-40% of all primary energy is used in buildings, and well insulated envelopes as well as radiation control of window apertures are keys to energy efficiency and associated CO 2 abatement. 1 Optimized radiation control requires chromogenic materials, 2 and thermochromic coatings are interesting options either for stand-alone uses, because a single coating can be applied, or for boosting the performance of electrochromic "smart windows." 3 VO 2 is a well studied thermochromic material. 4 Bulk VO 2 is monoclinic and insulating at Ͻ c and is tetragonal and metallic at Ͼ c , where is temperature and c Ϸ 68°C. 5 The nature of the metal-insulator transition ͑MIT͒ has been much debated, but recent work indicates a Mott transition. [6][7][8] 15 It has been found that a few percent of W can decrease c to 20 to 25°C, i.e., to a comfort temperature suitable for practical fenestration. However, the requirement of a high relative modulation of the transmittance at c has invariably limited T lum to Ͻ40%, which in general is too low. 4 Our Mg x V 1−x O 2 films were made by reactive dc magnetron sputtering onto substrates of glass ͑and simultaneously onto carbon plates for compositional analysis͒ from 5-cm-diameter targets of V ͑99.5%͒ and Mg ͑99.99%͒. After evacuation to 0.4 mTorr, Ar and O 2 ͑both 99.997%͒ were introduced via mass-flow-controlled regulators so that the Ar/ O 2 ratio was ϳ19 and the total pressure was ϳ92 m Torr. Cosputtering took place at powers being 210 W and 0-29 W for the V and Mg targets, respectively. The substrates were kept at 450°C, and the target-substrate separation was 13 cm. Deposition rates, via sputtering time and thickness d by surface profilometry, were 0.083 nm/s from V and 0-0.008 nm/s from Mg.Spectral normal transmittance T͑ , ͒ was measured for 300 nmϽ Ͻ2500 nm and 20°C Ͻ Ͻ 120°C as described before. 11 Figure 1͑a͒ refers to VO 2 and Mg 0.072 V 0.928 O 2 films with d =50Ϯ 5 nm. The VO 2 film displays expected thermochromism. 4,11 Importantly, Mg doping yields a significantly larger value of T͑ , ͒ for Ͻ600 nm at both temperatures. Quantitative enhancements were evalua͒ Electronic mail: nmlyuka@yahoo.com. Present address:

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Characteristics of W- and Ti-Doped VO[sub 2] Thin Films Prepared by Sol-Gel Method

Cited by 57 publications

References 14 publications

THz spectroscopy of VO₂epitaxial films: controlling the anisotropic properties through strain engineering

THz spectroscopy of VO₂epitaxial films: controlling the anisotropic properties through strain engineering

Phase-transition driven memristive system

Mg doping of thermochromic VO2 films enhances the optical transmittance and decreases the metal-insulator transition temperature

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Characteristics of W- and Ti-Doped VO[sub 2] Thin Films Prepared by Sol-Gel Method

Cited by 57 publications

References 14 publications

THz spectroscopy of VO2epitaxial films: controlling the anisotropic properties through strain engineering

THz spectroscopy of VO2epitaxial films: controlling the anisotropic properties through strain engineering

Phase-transition driven memristive system

Mg doping of thermochromic VO2 films enhances the optical transmittance and decreases the metal-insulator transition temperature

Contact Info

Product

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THz spectroscopy of VO₂epitaxial films: controlling the anisotropic properties through strain engineering

THz spectroscopy of VO₂epitaxial films: controlling the anisotropic properties through strain engineering