Cakir Mehmet Cihan, Kocer Hasan, Durna Yilmaz, Yildirim Deniz Umut, Ghobadi Amir, Hajian Hodjat, Aydin Koray, Kurt Hamza, Saglam Necdet, Ozbay Ekmel
NANOTAM-Nanotechnology Research Center, Bilkent University 06800 Ankara Turkey
Department of Nanotechnology and Nanomedicine, Hacettepe University 06800 Ankara Turkey.
RSC Adv. 2020 Aug 13;10(50):29945-29955. doi: 10.1039/d0ra05890d. eCollection 2020 Aug 10.
The phase change behavior of vanadium dioxide (VO) has been widely explored in a variety of optical and photonic applications. Commonly, its optical parameters have been studied in two extreme regimes: hot (metallic) and cold (insulating) states. However, in the transition temperatures, VO acts like an inherent metamaterial with mixed metallic-insulating character. In this range, the portions of metallic and insulating inclusions are tuned by temperature, and therefore a gradual change of optical parameters can be achieved. In this paper, a universal hybrid modeling approach is developed to model VO in the intermediate region. For this aim, the measured reflectivity data, is analyzed and matched through the transfer matrix method (TMM) simulations where an effective medium theory (EMT) is employed. Based on the findings of this approach, not only the relative portions of inclusions are tailored but also their grain shapes are significantly altered in the transition range. Finally, the modeling approach is testified by experimental findings through dynamic device applications operating at short and mid infrared wavelengths. In addition, the hysteretic behaviors on electrical, optical, and structural parameters of the VO film along the heating and cooling cycles are demonstrated by the experiments and scrutinized by the simulations.
二氧化钒（VO）的相变行为已在各种光学和光子学应用中得到广泛研究。通常，其光学参数是在两种极端状态下进行研究的：热（金属）态和冷（绝缘）态。然而，在转变温度范围内，VO表现得像一种具有金属 - 绝缘混合特性的固有超材料。在此范围内，金属和绝缘夹杂物的比例由温度调节，因此可以实现光学参数的逐渐变化。本文开发了一种通用的混合建模方法来对VO在中间区域进行建模。为此，通过采用有效介质理论（EMT）的传输矩阵法（TMM）模拟对测量的反射率数据进行分析和匹配。基于该方法的研究结果，不仅夹杂物的相对比例得到了调整，而且它们的晶粒形状在转变范围内也发生了显著变化。最后，通过在短红外和中红外波长下运行的动态器件应用的实验结果验证了该建模方法。此外，实验证明了VO薄膜在加热和冷却循环过程中电学、光学和结构参数的滞后行为，并通过模拟进行了仔细研究。
