Low‐Temperature Growth of SnO2 Nanorod Arrays and Tunable n–p–n Sensing Response of a ZnO/SnO2 Heterojunction for Exclusive Hydrogen Sensors

Abstract Uniform SnO 2 nanorod arrays have been deposited at low temperature by plasma‐enhanced chemical vapor deposition (PECVD). ZnO surface modification is used to improve the selectivity of the SnO 2 nanorod sensor to H 2 gas. The ZnO‐modified SnO 2 nanorod sensor shows a normal n‐type response to 100 ppm CO, NH 3 , and CH 4 reducing gas whereas it exhibits concentration‐dependent n–p–n transitions for its sensing response to H 2 gas. This abnormal sensing behavior can be explained by the formation of n‐ZnO/p‐Zn‐O‐Sn/n‐SnO 2 heterojunction structures. The gas sensors can be used in highly selective H 2 sensing and this study also opens up a general approach for tailoring the selectivity of gas sensors by surface modification.