So far, many other methods have been attempted to connect CNTs with electrodes and improve their contacts, such as chemical bonding, focused beam radiation or high-temperature annealing. However, all of these applications are faced with difficulties: they either need rigorous process conditions or the contacts lack long-term stability.

"We successfully developed a simple ultrasonic nanowelding technique for quickly and reliably bonding CNTs to metal electrodes by pressing SWCNTs against electrodes with a force vibrating at ultrasonic frequency " Chen explains to Nanowerk. "The contacts formed by this method have demonstrated low contact resistance, good long-term stability and mechanical strength. This ultrasonic nanowelding technique is compatible with traditional silicon IC processes."

"This technique does not depend on a specific kind of nanocomponent or metal electrode" says Chen. "We find that ultrasonic nanowelding can also achieve the robust low-resistance contacts between the metal electrodes (Ti, Au, Al) and the Si nanowire, SiC nanowire, Ga2O3 nanobelt. Therefore, our technique is feasible for a wide range of one-dimension nanomaterials and metals."

The performance of the devices prepared by this technique is also significantly improved. Chen and his colleagues have confirmed that the performance of CNT field-effect transistors (CNTFETs) can be greatly improved by the ultrasonic nanowelding technique.

"Recently, we performed experiments of temperature dependence of two-terminal transport to further explore the contact properties of the semiconducting SWCNT and metal electrode" Chen explains. "Preliminary results indicate that a very low effective barrier height and a small barrier width is obtained after ultrasonic nanowelding. Our technique is very promising for the construction of other nano-devices and possesses the potential for a great many applications."

At present, Chen and his colleagues are working to scale up the ultrasonic welding area in order to achieve a large quantity of bondings on a substrate in one single step, under one single press vibrating at a specific ultrasonic frequency.