This work reports the growth of vertically aligned and single-crystalline zinc oxide (ZnO) nanorod arrays on the silicon (Si) substrate using a microwave-assisted solution method. The x-ray diffraction and selected area electron diffraction patterns indicated that the ZnO nanorods were grown preferentially oriented in the (001) direction and have single phase nature with a wurtzite structure. Field emission scanning electron microscopy and transmission electron microscopy results showed that the length and diameter of the well aligned rods were about similar to 500 nm and similar to 80 nm, respectively. Raman scattering spectra of ZnO nanorod arrays revealed the characteristic E-high(2) mode that is related to the vibration of oxygen atoms in the wurtzite ZnO. The gas-sensing properties of the ZnO nanorod arrays for oxygen with different concentration were measured at room temperature. It was found that the value of resistance increased with the increase of oxygen gas concentration in the chamber. The ZnO nanorod arrays exhibited high sensitivity and rapid response-recovery characteristics to oxygen gas and can detect low concentration as 5, 10, 15 and 20 parts per million. (C) 2013 Elsevier B. V. All rights reserved.