Contact Resistance Effects in Carbon Nanotube Thin Film Transistors

The contact resistance effect in the network type carbon nanotube thin film transistors (CNT-TFTs) is studied by using different contact metals. It is shown that palladium (Pd) can form an ohmic type contact with the carbon nanotube thin film, and gold (Au) forms an almost ohmic contact. On-state current and carrier mobility in the devices of these two contacts are high. In contrast, both titanium (Ti) and aluminum (Al) form Schottky type contacts with the carbon nanotube thin film. The barrier height and the contact resistance of the Al contact are higher than those of the Ti contact. Therefore, the on-state current and carrier mobility are relatively low in the corresponding devices of these two types of contacts. These results indicate that the performance of CNTTFTs can be tuned by the contact metal, which is important for the commercialization of CNT-TFTs.