A NH_(3) gas sensor based on a ZnO nanorod array is fabricated by hydrothermal decomposition on a Au electrode.The as-grown ZnO nanorods have uniform diameter distribution and good crystal structure,shown by scanning electron microscopy,x-ray diffraction,high resolution transmission electron microscopy and photoluminescence emission characterizations.The gas sensing results show that the ZnO nanorod-based device responds well to ammonia gas at room temperature(sensitivity𝑆is about 8).