| AVS 64th International Symposium & Exhibition | |
| Thin Films Division | Thursday Sessions |
| Session TF-ThP |
| Session: | Thin Films Poster Session |
| Presenter: | DaeHo Jung, Kyung Hee University, Republic of Korea |
| Authors: | D.H. Jung, Kyung Hee University, Republic of Korea H.S. So, Kyung Hee University, Republic of Korea J.S. Ahn, Kyung Hee University, Republic of Korea S.B. Hwang, Kyung Hee University, Republic of Korea H. Lee, Kyung Hee University, Republic of Korea |
| Correspondent: | Click to Email |
Vanadium dioxide (VO2) with high transmittance of visible-ultra violet radiation but the complete blockage of infrared solar radiation can be used for `solar control` windows. A thermochromic smart window is designed such that the VO2 films regulate solar infrared radiation. Polyimide has thermal stability, good film-forming ability, low dielectric constant, high chemical resistance, low coefficient of thermal expansion and high mechanical strength. Due to these reasons polyimides are largely used as matrix for various purposes and the advantages of polyimide (PI) have been utilized as flexible substrate. VO2 thin films with ~50 nm in thickness were grown on TiO2-buffered PI films using RF magnetron sputtering deposition using a VO2 target. The sputtering pressure was set at 6 mTorr with 10 sccm flow of Ar gas. VO2 thin films on TiO2-buffered PI films were grown at 175°C. Since the PI substrates (75 mm-thick) can keep physical properties only up to 260 °C, low temperature growth of VO2 films (≤ 260°C) is necessary, After sputtering deposition, all samples were annealed with 1 sccm of O2 flow for 1hr. The structural and morphological properties of all VO2 films were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. However, no peak for the monoclinic of phase of VO2 appeared in Raman spectrum of growth of VO2/TiO2/PI at under 200oC. It was difficult to observe XRD diffraction peaks of VO2 because VO2 thin films did not crystallize under 200oC. The chemical compositions of VO2 were probed by x-ray photoelectron spectroscopy. The measurement of depth-dependent O/V ratio also showed that the stoichiometry was independent of depth for VO2 films.We measured the hysteresis curve of sheet resistance as a function of temperature. We measured the reflectivities of VO2 films below and above the metal-insulator transition temperature. The ratio of switching resistivity was 10-2. VO2 films grown on plastic films can be applicable as flexible thermochromic films for energy-saving windows.
Reference:
[1] Dae Ho Jung, Hyeon Seob So, Kun Hee Ko, Jun Woo Park, Hosun Lee, Trang Thi Thu Nguyen, and Seokhyun Yoon, J. Korean Phys. Soc. 69 (2016) 1787.