Effect of Metal Contact on CNT based Sensing of NO2 Molecules

Abstract

The electronic structure of Carbon Nanotubes (CNTs) is highly sensitive to the presence of foreign molecules. Also due to the large surface area of CNTs, there is a higher chance of them getting exposed to the surrounding gas molecules. This property is utilized in CNT based gas sensing applications. In this work, we have studied a zigzag CNT (Z-CNT) and simulated the transmission spectra and I-V characteristics using Density functional theory and Extended Huckel theory. Then the change in electrical properties of the Platinum (Pt) contacted Z-CNT on adsorption of NO2 molecules was simulated. Exposure of NO2 increases the conductance of the CNT by extracting electrons from the CNT making it p-type. Higher concentration of gas molecules results in larger change in the conductance due to the accumulated effects of individual gas molecules underlining its effectiveness in the formation of a gas sensor. Pt makes a schottky contact with the zigzag CNT and it was found that there is an appreciable change in the transmission spectrum as well as I-V characteristics making Platinum contacted zigzag CNT a good material for NO2 detection. This study is aimed at understanding effect of adsorption of NO2 and Pt contact on the I-V characteristics.