Highly nonlinear varistors were fabricated by hot-dipping oxygen-deficient zinc oxide (ZnO1-x, x < 1) thin films in Bi2O3. The ZnO1-x, films were deposited on conducting silicon chips by radio frequency magnetron sputtering of a sintered zinc oxide ceramic target. Then the films were hot-dipped at a temperature from 200 to 600 degrees C in Bi2O3. With the increase in hot-dipping temperature, the nonlinear coefficient (alpha) of the film varistors increases first and then decreases, and the leakage current (I-L) correspondingly decreases initially and then increases, owing mainly to the formation and destroying of complete ZnO1-x/Bi2O3 grain boundaries and the roundness change of the ZnO1-x, grains; and the varistor voltage (E-1mA) decreases from 0.0268 to 0.0137 V/nm, due to the decreased number of effective grain boundaries in the materials. The film varistors prepared by hot-dipping at 400 degrees C exhibit the optimum nonlinear properties with the highest alpha = 15.1, lowest I-L = 0.0223 mA/cm(2), and E-1mA = 0.0176 V/nm. Such nanoscaled film varistors will be very promising in electrical/electronic devices working in low-voltage. (C) 2016 Elsevier B.V. All rights reserved.