In Situ Growth of Silver Film on Polyimide with Tuned Morphologies for Flexible Electronics

In this work, the silver films with tuned morphologies have been fabricated on flexible polyimide substrate by in situ direct-ion-exchange technique. The morphology of Ag films with loose nanoparticles, dense polyhedrons, aggregated nanoparticle clouds, and dendrite structure can be obtained by a controlled reduced process as illustrated by scanning electron microscopy (SEM) and optical microscopy, respectively. All of the Ag films show good crystalline and high conductivity, which is confirmed by X-ray diffraction (XRD) and four-point probe resistance measurements. Infrared (IR) spectra demonstrate the occurrence of the polyimide surface metallization, which favors good adhesion between the Ag films and the flexible substrate. The adhesion test proves the strong adhesion of these Ag films, especially for the Ag films with the dendritic structure. Moreover, the mechanical properties of these Ag/PI films have been investigated as well. It can be found that all of the Ag/PI films exhibit low sensitivity to the bending test. However, the strain sensitivity strongly depends on the morphology of the Ag films, which can be applied for diverse flexible electronics.