A method for creating reliable and low-resistance contacts between carbon nanotubes and microelectrodes

An ultrasonic bonding technique has been developed for bonding single wall carbon nanotubes (SWNTs) onto metal microelectrodes. The bonding was formed by pressing SWNTs against the electrodes with a vibrating press at an ultrasonic frequency. With this technology, low-resistance contacts are achieved between both metallic and semiconducting SWNTs and electrodes. After bonding, the effective Schottky barrier height between semiconducting SWNT and Ti electrode is as low as ∼6.6 meV in the ON-state and the barrier width is ∼0.9 nm at Vg = 0. The performance of carbon nanotube field-effect transistors (FETs) fabricated by this ultrasonic bonding technique is also significantly improved, with a transconductance as high as 3.4 μS for solid-state back-gate individual nanotube FETs.