Conductivity enhancement of aerosol-jet printed electronics by using silver nanoparticles ink with carbon nanotubes

Innovative printing technology enables fine feature deposition (below 10@mm) of electronic materials onto low-temperature, non-planar substrates without masks. This could be a promising technology to meet the requirements of present and future microelectronic systems. Silver nanoparticles (NP) ink is widely used for printed electronics; however, its electrical conductivity is low compared to bulk materials. In order to improve the electrical conductivity of printed tracks for the aerosol printing technique, we developed a novel carbon nanotubes (CNTs)/silver NP ink by mechanical stirring and sonication. The produced sample inks with different concentration of CNTs that were printed with a Maskless Mesoscale Material Deposition (M^3D) Aerosol Jet(R) printing system. The dimensions of the printed lines were determined by atomic force microscopy (AFM) and the electrical resistivity was evaluated using the four-point method. Scanning electron microscopy (SEM) was used to characterize the morphology of printed tracks. We found that the CNTs bridged the defects in some printed silver lines, thereby lowering the electrical resistivity by 38%. However, no further improvements were observed with a higher CNT concentration in the silver NP ink samples. We hypothesize that CNT bridges connects the defects thus decreasing the resistivity of printed silver lines when CNT concentration is under the percolation level. However, due to aggregation of CNTs when it is above a concentration threshold, the resistivity of printed silver lines stops decreasing and even increases because of Schottky barrier effect.