Study of Pressure Sensing Based on Field Emission and Adsorption from Multi-walled Carbon Nanotubes

A vacuum pressure sensor based on field emission of multi-walled carbon nanotube(MWNT)and gas absorption has been developed and investigated.The multi-walled carbon nanotube films with strong adhesion are prepared on Hastelloy alloy by thermal chemical vapor deposition method(CVD),and then the MWNT films are used as field emission cathode material in bipolar structure.Later,environmental pressure is measured by gas absorptions on the MWNT films,which results in the effect of current increasing in the process of field emission.The experiments of N₂and air's sensing properties show that in the condition of low-current field emission in N₂and air,the MWNT emitter demonstrates the sensing effect that low-current emission increases with increasing the vacuum pressure.According to the sensing effect,a miniature sensor has been designed.This sensor has the advantages of wide measurement range(1×10^-7~1×10^-3Pa),small dimension(4 mm×5 mm×9 mm),low power consumption(5×10^-6~0.8 W),no interference to the device,long life,and so on.The tests of the sensor sealed in X-ray tube,show that the internal vacuum degrees of X-ray tubes are about two orders of magnitude higher than that before being sealed,and that the vacuum degrees of the X-ray tubes become lower gradually.The result agrees with the theoretical expectation.