A simple method for synthesizing VO2 with almost coincident hysteresis loops on Si substrate containing TiO2 buffer layer

Abstract

The overlapped degree of hysteresis loops is critically important for the accurate response of vanadium dioxide (VO2)-based optoelectronics devices. Generally, the hysteresis loops width is not less than 10 ℃ for VO2 thin films deposited on amorphous SiO2/Si or Si substrates. In this work, the almost coincident hysteresis loops of VO2 thin films including a TiO2 buffer layer was synthesized successfully on Si substrate by a simple and controllable method. Here, the thickness of VO2 and TiO2 were 60 nm and 100 nm, respectively. XRD patterns show that the peak of rutile phase TiO2 begin to appear while the thickness of buffer layer increases to about 65 nm, which is more compatible with the lattice structure of VO2. Combined with the XPS spectra, it is found that the VO2 thin films formed on different substrates include quite a few V5+ and relatively few V3+ impurity phases. In addition, theoretical analysis indicates that an inversely proportional relationship exists between the hysteresis loops width and the average grain size of VO2 thin film, The SEM images confirm this point well revealing the average grain size of VO2 thin film does increase with the thickness increase of TiO2 buffer layer.