Study of gas sensor with carbon nanotube film on the substrate of porous silicon

A new method of obtaining extremely high electric fields in a very small region near the tip of a carbon nanotube, with diameter of nanometer order, is studied. This method makes the self-sustaining dark discharge voltage decrease to less than 220 V, which is in the safe range. The carbon nanotube array film is used as a cathode to form a new kind of gas sensor based on the gas discharge. The discharge current at room temperature and atmospheric pressure increases from the order of nanoamperes to that of microamperes. The electrical characteristics of several gases at atmospheric pressure are studied. The self-sustaining dark discharge voltages of different gases vary, as do the discharge currents. Porous silicon is selected as the substrate for the carbon nanotubes. This can improve the adhesion of the nanotube on the substrate and so prolong the lifetime of the cathode.