Moderating oxygen deficiency induced better thermochromic properties of monoclinic vanadium dioxide thin films
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Moderating oxygen deficiency induced better thermochromic properties of monoclinic vanadium dioxide thin films Ming Li1 · Jiangbin Wu1 · Chaoyang Kang2 · Haitao Zong1 · Qiang Hu1 · Huanhuan Liu1 · Guohua Cao1 Received: 19 August 2020 / Accepted: 3 November 2020 / Published online: 25 November 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Monoclinic vanadium dioxide (M-VO2) is a kind of typical thermal phase change materials, but its relatively high phase transition temperature (68 °C) and low solar modulation efficiency greatly hinder the applications as energy materials. In this work, well-crystalline M-VO2 were prepared by pulsed laser deposition (PLD) under the adjustable oxygen pressure range. By fine adjusting the low oxygen pressure (0.1–0.9 Pa), VO2 maintain the monoclinic crystal and excellent photoelectrical properties, even if oxygen deficiency and other defects exist. Results indicate that the phase-transition temperature (Tc) decreases with the decrease of oxygen pressures while the solar modulation efficiency (ΔTsol) increases with the decrease of oxygen pressures. Moreover, the M-VO2 thin films prepared with 0.3 Pa oxygen pressure showed the best photoelectric performance, in which the sheet resistance changes up to three orders of magnitude, the phase-transition temperature is 61 °C and the ΔTsol is as high as 8.3%. This work has demonstrated the role of moderate oxygen defects in optimizing the photoelectric properties of M-VO2, also provided a feasibility study on how to deposit pure M-VO2 by PLD. Keywords Pulsed laser deposition · VO2 · Oxygen vacancy · Photoelectric properties
1 Introduction Monoclinic vanadium dioxide (M-VO2) is a reversible semiconductor-to-metal phase transition (SMT) material [1], accompanied by a structural change from monoclinic (M) phase to rutile (R) phase at 68 °C (Tc). The structural transition is associated with dramatic changes of optical and electrical properties [2]. These fascinating characters of V O2 materials indicate promising applications in various fields including phase-change memory [3], optoelectronic switch [4], smart windows [5], hydrogen storage [6] and gas sensors [7].
* Chaoyang Kang [email protected] * Qiang Hu [email protected] Haitao Zong [email protected] 1
School of Physics and Electronic Information, Henan Polytechnic University, Jiaozuo 454000, China
Key Laboratory of Photovoltaic Materials of Henan Province, Henan University, Kaifeng 475004, China
2
Compared with their bulk materials, VO2 thin films could undergo the phase transition cycle repeatedly without brittle crack, indicating broader practical applications. The preparation of high quality V O2 films has been one of the hottest topics for thermochromic applications in recent years because the SMT characteristics are closely related to the crystal quality of V O2 films. However, even the perfect single crystal V O2 films will encounter some difficulties in practical application. For example, V O2 is not applied immediately
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