The Zn–Bi–O films were deposited by reactive radio frequency magnetron sputtering in oxygen atmosphere from ZnBi alloy target (wt. ratio Zn:Bi=9:1) on glass substrate at room temperature. The XRD patterns show that the films deposited on tin-doped indium oxide/glass substrates were nanocrystalline. The microstructure of Bi-doped ZnO films was studied by scanning electron microscopy in combination with energy dispersive X-ray spectroscopy. All the obtained layers had varistor-type non-linear current–voltage (I–V) characteristics with low breakdown voltage varying from few tenths of a volt to few volts