Sol-gel synthesis of Y2O3-doped ZnO thin films varistors and their electrical properties

Y2O3-doped ZnO-Bi2O3 thin films were fabricated on silicon substrates by sol-gel process and annealed in air at 750 degrees C for 1 h. Microstructure and electrical properties of ZnO thin films were investigated. XRD analysis shows that all peaks of ZnO thin films are well matched with hexagonal wurtzite structure of ZnO. SEM results present that the ZnO grain size decreases with the increase of dopant concentration, which means that rare earth doped can refine the grain size. The thickness of each layer is uniform and the value of thickness is about 80 nm. The nonlinear V-I characteristics with the leakage current of 0.46 mu A, the threshold field of 110 V/mm and the nonlinear coefficient of 3.1 could be achieved when the films contain 0.2% (mole fraction) yttrium ion.