Effect of arrangement of carbon nanotube pillars on its gas ionization characteristics

The gas ionization sensors (GISs) using the carbon nanotube (CNT) pillars which has the pillar height (H) of 15 μm with interpillar spacing (R) of 30 μm as the cathode had been proposed for the first time to exhibit the 20 times higher field enhancement factor (β) and the lower breakdown voltage of 350 V with respect to the CNT film ones for nitrogen gas at the pressure of 0.035 Torr. As the H increased from 5 μm to 15 μm, the β increased with increasing the H since the electrical field could be enhanced via the aspect ratio increment. However, as the H increased from 15 μm to 60 μm, the β decreased with increasing the H owing to the increased field-screening effect. Such an optimum GIS with the CNT pillars also exhibited high sensitivity and selectivity for different kinds of gases detection as well as the good linearity for detecting the gas mixture.