Mini-type low pressure helium detection from adsorption enhanced carbon nanotube field emission

The miniature low pressure helium detection technique is of great interest for some important industrial and scientific fields. A novel low pressure helium sensing method from carbon nanotube (CNT) field emission has been developed. The low field emission currents from multi-walled carbon nanotubes (MWNTs) with low crystallinities increase in helium pressure range of 10 −7 -10 −3 Pa. The field emission analysis and first-principles simulation revealed that work functions of CNT emitters remain consistent with helium adsorptions. The simulation showed that the adsorption of He atom results in extra charge aggregation on carbon atoms at the defect, enhancing the field emission current. The helium sensing MWNT emitter normally doesn’t present good hydrogen, oxygen, and nitrogen sensing properties, benefiting the leak detection applications. The mini-type helium sensor in millimeter scale was demonstrated in various gas backgrounds with leak rates down to 10 −8 Pa·l/s, very promising for helium detection and leak checking in wide types of in-situ measurement applications, including vacuum electronic devices, low power consumption instruments, and compact space facilities.