VO2 low temperature deposition and terahertz transmission modulation

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 nanostructure. 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.