Carbon Nanotube Field Emission Helium Sensing Technology Based on Gas Adsorption

Helium partial pressure measurement is important for the leak detection and quality control of liquid helium equipment.In this work,based on small current emission enhancement effect of MWNTs field emission cathode from gas adsorption,the low pressure He sensing technique was developed.Multi-walled carbon nanotube(MWNT)films were grown directly on nickel alloy substrates by thermal chemical vapor deposition(CVD).Field emission and sensing performance were tested in diode structures.The results showed that in 10^-7to 10^-3Pa range the field emission currents increase with increasing He pressures for some MWNT samples,exhibiting good He sensing behaviors.The experiments for a large number of MWNT samples showed that MWNTs with poor crystallinity(I_D/I_G≥0.9)behaved strong He sensing properties.The first-principles study revealed that the charge transfer and aggregation is the key factors of helium pressure sensing effect generated by MWNT cathode after helium adsorption at the defeet location.This technique is promising to develop miniature He leak detection and partial pressure measurement devices.