Fig. 2. Dependence of the resistance on the temperature for 0.5SZO films at different growth temperature (a: 20 °C; b: 120 °C; c: 230 °C; d: 280 °C; e: 350 °C).Figure optionsDownload full-size imageDownload high-quality image (343 K)Download as PowerPoint slide
Fig. 3. Giant TCR dependence on temperature of SZO films at 350 °C growth temperature (a: 0.5SZO; b: 1SZO; c: 3SZO; d: 5SZO; e: 10SZO).Figure optionsDownload full-size imageDownload high-quality image (264 K)Download as PowerPoint slide
It is worth mentioning that Ag+ ions in ZnO lattice behave as monovalent dopant ions which have the ability to occupy both the lattices and LBH589 sites . In order to explain the result of high TCR of SZO films, we proposed two states of Ag in the structures of SZO films with no peak according to Ag listed in Fig. 1. Firstly, for disparity in their ionic radius, Ag+ as compared to Zn2+, Ag additions substitute in limited quantity into the ZnO lattice through substitution of Zn2+ ions. A site for Zn2+ site displaced by Ag+ ion, the crystal volume can be slightly expanded with the Ag addition, hence the TCR can be increased. Secondly, the Ag+ ions can get into the interstitial sites, as a bridge, and the Ag+ can promote the electron exchange, which increases the concentration of carrier. Large resistivity variation is a main reason to improve high TCR by Ag addition.