Comparison of Capacitive versus Resistive Mode of Sensing for Vapor Phase Explosive Detection

This paper presents a comparison of resistive and capacitive sensors with a sandwiched dielectric material as a sensing layer. The paper focuses on a fabrication process along with two different techniques for characterization of sensors aimed for vapour phase explosive detection. The proposed sensors feature a special coating of TiO2(B) nano-particles in between two electrodes of Metal-Insulator-Silicon (MIS) structure which leads to a selective reaction with the target molecules. A comparison between two signal detection approaches namely, a) change in resistance and b) change in capacitance with the same sensor structure, is carried out on the basis of temperature and humidity variations in the atmosphere. It is shown that the capacitive measurements arc more robust to temperature and humidity changes over resistive measurements. Although the change in the resistance due to explosives' exposure is 50%, the base resistance (R) of the structure reduces drastically with 7.5% variation at higher temperatures. This makes the resistive measurements highly prone to false positives. On the other hand, the base capacitance remains almost constant with 0.2% variation during temperature variation with 2.5% change in capacitance on exposure to explosives.