Facile growth of ZnO nanorod arrays by a microwave-assisted solution method for oxygen gas sensing

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 ∼ 500 nm and ∼ 80 nm, respectively. Raman scattering spectra of ZnO nanorod arrays revealed the characteristic E₂^high 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. - Highlights: • ZnO nanorod arrays using microwave irradiation have been prepared. • Preferential growth along (001) direction. • The sensitivity is linearly proportional to the oxygen concentration