Low-temperature growth of SnO2 nanorod arrays and tunable n-p-n sensing response of 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 modifi cation is used to improve the selectivity of the SnO 2 nanorod sensor to H 2 gas. The ZnO-modifi ed SnO 2 nanorod sensor shows a normal n-type response to 100 ppm CO, NH 3 , and CH 4 reducing gas whereas it exhibits concentrationdependent 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.