Nanoscale welding by AFM tip induced electric field

The most difficult challenges in fabricating SWCNT-based nanosystems or nanodevices have proven to be the assembly and anchoring of SWCNTs to form a stable physical and electric contact between SWCNTs and the electrodes. For example, for SWCNT-based nanosensors or field effect transistors (FETs), the need to fix the SWCNT between electrodes is extremely important, i.e., it affects the electronic transport properties at the connection point. Currently, researchers usually focus on the assembly between SWCNTs and the electrodes by using dielectrophoresis (DEP), direct growth, or atomic force microscopy (AFM). In this paper, we present a new method to realize nanoscale welding by using an AFM tip coated with conductive materials. This method is very useful in welding the SWCNTs on the microelectrodes after the manipulation of the SWCNTs in between the microelectrodes by AFM-based or DEP-based manipulation. In our experiments, we first assembled individual SWCNTs or bundles of SWCNTs between two electrodes using DEP force. Then, SWCNTs are welded on the surface of the electrodes when a bias impulse voltage is exerted between the AFM tip and sample, which produces an electric field. The experimental results have demonstrated that SWCNTs can effectively be welded on the surface of the electrodes.