MODELLING AND SIMULATION OF FIELD EMISSION IN CARBON NANOTUBE BASED IONIZATION GAS SENSOR

Gas sensors are of main interest in the field of oil and gas industry. They are used to sense corrosive gases in the pipelines and leakage in the delivery system. One of the recently developed gas sensor that has become the focal point of research is the ionization gas sensor. This sensor technology is still in its infancy and much can be done to increase the efficiency of the sensor.

In this research, a new model to study the gas detection mechanism of carbon nanotube (CNT) based ionization gas sensor has been developed. The model incorporates electron field emission property of the CNTs. The new model consists of three modules, i.e., CNT particle injection module, CNT density and aspect ratio variation module, and CNT velocity assignment module. These three modules are combined together and embedded in the standard Particle-In-Cell / Monte Carlo Collision (PIC-MCC) codes.

The integrity of the enhanced PIC-MCC codes has been validated by calculating the field enhancement factor, β. Furthermore, the functionality of these codes is checked by running simulations of DC discharges in different gases and comparing the results with published experimental and simulated works. With the help of enhanced PIC-MCC codes the simulation of gas breakdown behavior with CNT field emission effects become possible for the first time. From the results, around one order of magnitude decrease in the breakdown voltages is observed when CNT is used in ionization gas sensor. The electrostatic screening effects are reduced to a minimum when inter-tube spacing is equal to the height of the CNT. Faster response time is also observed with the presence of CNT in ionization gas sensor. These results suggest that by properly controlling the growth of CNT structures, an optimized CNT based ionization gas sensor can be realized.