Ionization gas sensing mechanism of a hybrid nanostructure with carbon nanotubes and ZnO nanorods

Experimental evidences show that the gas ionization induced positive charge accumulation can lead to the field electron emission from carbon nanotubes, partially covered with ethocel thin film and ZnO nanorods. This effect can lead to a novel ionization gas sensing mechanism, which can be used to identify the gaseous chemical composition based on the characteristic resistivity of the gases without strong field effect of field ionization and gaseous breakdown. The hypothesis for illustration is suggested that: (1) the cosmic ray ionization frequency increases 10(8)-10(10) times due to the metastable population resulted from the interaction between the gases and the CNTs; (2) the flux of positive charges is converged due to the ZnO nanorods. The resulted positive charge local density is high enough to trigger the field emission. The experimental results are shown to be in consistent with the theoretical expectations, qualitatively. The methodology is advantageous in the context of the ionization gas sensors because its I-V characteristics are linear so that the signals can be sampled more easily than that of the gaseous breakdown critical voltage sampling. Besides, the device does not suffer from the degradation effect in the gaseous breakdown processes and exhibits better repeatability. (C) 2013 Elsevier B.V. All rights reserved.