Development of low pressure sensor based on carbon nanotube field emission

Abstract

A newly developed low pressure detection technology using carbon nanotube (CNT) field emission effect has been designed and manufactured. The fabricated pressure sensor is of a triode type, consisting of a cathode (CNTs field emitter arrays), a grid and a collector. The principle described here is that, for a constant number of electrons available for ionization emitted from CNT arrays by a grid potential, a constant fraction of gas molecules will be ionized and the number of ions collected in a collector will be proportional to the number of gas molecules in the chamber traversed by the electrons. Due to the excellent field emission characteristics of CNT, it is possible to make a cost-effective cold cathode type ion gauge. A screen-printing method has been used to make the CNT cathode. A glass grid with Cr deposited by an e-beam has been put on the cathode with a gap of 200 µm between two electrodes. Due to the voltage applied to the grid, the electrons emitted from the CNTs ionize gas molecules in the chamber and the ionized molecules are gathered to the collector. Then, the collector voltage is made lower than the grid voltage to obtain a large ionization ratio. The current detected in the collector is proportional to the pressure in the chamber. The ionization characteristics are dependent on the gas and the voltage applied to the grid and the collector. In this paper we will show the various metrological characteristics of the home-made pressure sensor utilizing CNTs.