## 3 Results and Discussion
### Electrical Properties  
Figure 4 shows the square resistance variation with temperature in the heating and cooling cycles of the VO\({}_{2}\) thin films with various thicknesses of Cu\({}_{50}\)Zr\({}_{50}\) inserting buffer layers. In Figure 4a, the VO\({}_{2}\)/glass thin films show a resistance-temperature curve with a wide transformation hysteresis. In the cases of the 40- and 80-nm-thick buffer layers, the VO\({}_{2}\) thin films both exhibit sharper decreases in sheet resistance with increasing temperature, as illustrated in Figure 4b,c, strongly implying the occurrence of an MIT. However, no MIT occurs when the buffer layer thickness attains to 160 nm. This result can be attributed to poor crystallization in the VO\({}_{2}\)/Cu\({}_{50}\)Zr\({}_{50}\)/glass thin films, which is good corresponding to the XRD analysis.  
To better comparing, the observed electrical properties of VO\({}_{2}\) films with various buffer layer thicknesses are summarized in Table 1. The transition temperature (\(T_{c}\)) is defined as the center of the derivative curve of the heating curve in the insets of Figure 3. Here, we defined the amplitude of MIT (\(\Delta R\)) as the relative resistance change ratio between room temperature and a temperature of 100 \({}^{\circ}\)C. The hysteresis width (\(\Delta H\)) is the difference between the \(T_{c}\) values that were measured during the heating and cooling cycles. From Table 1, the single-layer VO\({}_{2}\) thin films have higher \(T_{c}\) than the buffered VO\({}_{2}\) thin films. After introducing the buffer layer (40 nm and 80 nm in thickness), the \(T_{c}\) values of VO\({}_{2}\) thin films are similar to that of the bulk VO\({}_{2}\) single crystal (68 \({}^{\circ}\)C), which is generally due to the release of stress [31]. The \(\Delta R\) values of the VO\({}_{2}\)/glass thin films are slightly larger than those of the 40- and 80-nm-thick VO\({}_{2}\)/Cu\({}_{50}\)Zr\({}_{50}\)/glass thin films. This could be due to the larger crystal size in the non-buffered VO\({}_{2}\) thin films [32]. The samples with smaller or larger \(\Delta H\) values can be applied in different fields and the \(\Delta H\) value is closely connected with the quality of crystallization and crystallite  
Figure 3: Scanning electron microscopy (SEM) images and Energy-dispersive X-ray spectroscopy (EDS) element distribution table (insets) of VO\({}_{2}\) films deposited on Cu\({}_{50}\)Zr\({}_{50}\) buffer layers with different thicknesses. (**a**) No buffer layer (**b**) 40 nm thickness (**c**) 80 nm thickness (**d**) 160 nm thickness.  
dimension in the VO\({}_{2}\) thin films [33; 34; 35]. From Table 1, it can be seen that the \(\Delta H\) values of the buffered VO\({}_{2}\) thin films are much smaller than the non-buffered one. The buffer layer serves as a good template for VO\({}_{2}\) thin film growth and it thus results in a better crystallinity in the 40- and 80-nm-thick VO\({}_{2}\)/Cu\({}_{50}\)Zr\({}_{50}\)/glass thin films. These conclusions point out that the electrical characteristic of VO\({}_{2}\) films can be significantly enhanced by inserting Cu\({}_{50}\)Zr\({}_{50}\) buffer layer of appropriate thickness.