二氧化钒薄膜低温制备及其太赫兹调制特性研究

摘要

针对二氧化钒(VO2)薄膜在可调谐太赫兹功能器件中的应用,利用低温磁控溅射技术,在太赫兹和光学频段透明的BK7玻璃上制备出高质量的VO2薄膜.晶体结构和微观形貌分析显示薄膜为单相VO2单斜金红石结构,具有明显的(011)晶面择优取向,结构致密,表面平整.利用四探针技术和太赫兹时域光谱系统分析了薄膜的绝缘体-金属相变特性,发现相变过程中薄膜电阻率变化达到4个数量级,同时对太赫兹透射强度具有强烈的调制作用,调制深度高达89％.通过电学相变和太赫兹光学相变特性的对比研究,证实薄膜的电阻率突变主要与逾渗通路的形成有关,而太赫兹幅度的调制则来源于薄膜中载流子浓度的变化.该薄膜制备简单,成膜质量高,太赫兹调制性能优异,可应用于太赫兹开关和调制器等集成式太赫兹功能器件.%Recently, the applications of vanadium dioxide film (VO2) in terahertz functional devices have attracted much attention because VO2 has a remarkable response to THz wave, In this work BK7 glass a material highly transparent to both THz and optical band is adopted as a substrate. High-quality VO2 film is deposited on a BK7 substrate using low temperature magnetron sputtering technology. The crystallinity and microstructure of the thin film are investigated by X-ray diffraction and atomic force microscopy. The results indicate that the as-deposited film crystallizes directly into single-phase VO2 with (011) preferred orientation and compact nanostruc-ture. Under a heating-cooling cycle, the film undergos a metal-insulator transition with an abrupt resistivity change reaching more than 4 orders of magnitude. Terahertz transmission modulation is characterized by terahertz time domain spectrum, and a giant modulation depth of 89% is obtained. Due to the high transparence and the huge modulation effect, the VO2/BK7 can be widely used for THz devices such as modulators and switches.