Controllable synthesis of defective carbon nanotube field emitters for low pressure helium sensing

Gas adsorption enhances the field emission current of carbon nanotube (CNT) cathodes, enabling the detection of low-pressure gases. The enhancement effect of field emission current by helium adsorption is closely related to the defect structure of CNTs. This work investigated the structural characteristics of multi-walled carbon nanotubes (MWNTs) with excellent helium sensing effects explored the controllable preparation of sensing cathode by modifying the catalytic substrate surface micro-structure for CVD direct growth. Carbon nanotubes with small diameters and short tubes behave high defect density and poor crystallinity. On the other hand, the film with high MWNTs density exhibited low crystallinity. The crystallinity could be improved by increasing the growth time period from the reduction of the amorphous carbon content. The MWNTs with poor crystallinity presented excellent helium sensing performance. This work is not only suitable for the controllable growth of CNT emitters for low pressure helium sensing, but also significant for defective CNT based applications.