Highly formaldehyde-sensitive, transition-metal doped ZnO nanorods prepared by plasma-enhanced chemical vapor deposition

One of the challenges in realizing metal oxide semiconductor gas sensors is to enhance the sensitivity of active materials in order to respond to the low concentration of detecting gases effectively and efficiently. In this report, transition metals such as Mn, Ni, Cu, and Co are used as dopants for the synthesis of highly formaldehyde-sensitive ZnO nanorods prepared by plasma enhanced chemical vapor deposition (PECVD) method. All the doped ZnO nanorods show improved formaldehyde-sensitivity as compared to undoped ZnO nanorods, and a gas sensitivity maximum of ∼25/ppm was obtained by using 10 mol% CdO activated 1.0 mol% Mn doped ZnO nanorods. Moreover, the ZnO nanorods have a higher sensitivity as compared to ZnO nanomaterials prepared by other methods such as precipitation and hydrothermal, which can be attributed to the abundant crystal defects induced by the dopants in a short crystallization process in this PECVD method.