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采用分子束外延(MBE)技术在单晶蓝宝石衬底上生长了高质量化学计量比二氧化钒(VO_2)薄膜,通过该技术实现薄膜厚度15~60 nm精确控制。对于优化条件下VO_2薄膜,实现了电阻率变化超过4个数量级的优异金属–绝缘体相变,近似于之前报道高质量单晶VO_2相变特性。特别是通过太赫兹时域光谱分析了不同厚度的VO_2薄膜在太赫兹波段的光学特性。结果表明:VO_2薄膜的厚度对其在太赫兹波段的光学特性有很大影响。因此,为了获得更优的可靠性和重复性能,VO_2薄膜的厚度必须得到精确控制。本研究结果对于下一步VO_2基太赫兹器件研究具有重要意义。
A high quality stoichiometric vanadium dioxide (VO_2) thin film was grown on single crystal sapphire substrate by molecular beam epitaxy (MBE) technology, and the precise control of film thickness from 15 to 60 nm was achieved. For optimized VO_2 thin films, an excellent metal-insulator phase change of more than four orders of magnitude resistivity was achieved, similar to the previously reported high-quality single-crystal VO_2 phase transitions. In particular, the THz time-domain spectroscopy was used to analyze the optical characteristics of THz thin films with different thicknesses. The results show that the thickness of VO_2 thin film has a great influence on the optical characteristics of the THz band. Therefore, in order to obtain better reliability and repeatability, the thickness of VO_2 thin film must be precisely controlled. The results of this study are of great significance for the further study of VO_2-based terahertz devices.