SIMULATION OF CNT BASED SENSORS FOR - ENVIRONMENTAL GASES AND VOC's MONITORING

Abstract

Carbon nanotube is an excellent Nano material for sensing odifferentgas molecules as it possess high surface to volume ratio which is required for the adsorption of gas molecules. The sensitivity of single walled gold contacted carbon nanotube (Au-CNT) for different gas molecules and VOCs (Volatile Organic Compound) has been reported. A detailed study has been done using Extended Huckel method based on 1-luckel basis set with FFT-2D (Fast Fourier Trans forrn-2D) Poisson solver for optimization of molecule position with respect to Au-CNT. The sensitivity of Au-CNT for gas molecules is analyzed by computing Differential Conductance (G i.e., di/dv), Projected Density of States (PDOS) and Electrostatic Difference Potential (EDP) using Virtual Nanolab, Atomistic Toolkit. Sensing device consists of Gold contacts with CNT as channel with channel length of 5nm and electrode length of 0.64nm. The schottky barrier height of Au-CNT is computed to be 0.441eV using energy band modelling. The metal-CNT interface states fill the band gap of semiconducting CNT. Metal contact changes the device density - of states (DOS) of CNT. Landauer's Quantum Transport model elucidates the working principle of the device in which one contact (at low Potential) likes to fill the DOS of CNT and other contact (at high Potential) likes to empty the DOS of CNT. Filling of states results in very high conductance and peaks are observed in the differential conductance. I have simulated the device with fourteen gas molecule and extracted the parameter such as 1-V characteristics, Differential conductance. PDOS, EDP and EDD.