DESIGN AND SIMULATION OF CNT BASEDGAS SENSOR

Abstract

The behavior of metal-CNT half emerged contact with and without the gas adsorption has been studied. It is found that the metal CNT one side contact forms a rectifying schottky diode. The schottky barrier height is calculated using two different approaches: band modeling and activation energy method. From band modelling it can deduced that, the schottky barrier height not only depends on workfunction of the metal, but also gets affected by the other effects occurring at the contact like dipole formation. Three different metal (Pt, Pd and Au) contacts with CNT is compared. For positive bias hole transport dominates and similarly for negative bias electron transport dominates. It has been calculated that the schottky barrier height is lowest for Palladium and highest for gold metal contacted CNT. In metal-CNT-metal system, due to metal interface states, the DOS of semiconducting CNT gets severely distorted. Gas adsorption to metal-CNT-metal system and its unique interaction with carbon nanotube also has been studied. It is observed that the NO2 adsorbed CNT has significantly higher current than bare zigzag CNT due to the p-doping. The electron difference density is plotted against the length of the nanotube to see charge distribution in the presence of different gas molecules. The point of maxima in conductivity versus voltage curve at OV can be used as a unique identification point for the respective gas. The oxygen adsorption at different positions in metal $ CNT one sided structure has been studied .It has observed that the oxygen makes the CNT ptype and thus for a particular position (above CNT channel) oxygen adsorption makes the gold zigzag CNT, one sided contact as a Tunnel diode and deJivers a negative differential conductance region for positive bias.