Depth profile analysis of the structure and composition of a metal-implanted polyimide surface

High-dose metallic ion implantation was performed into polyimide (C22H10N2O5) films, and the structure of nanoparticles and matrices were examined with high-resolution transmission electron microscopy (HRTEM). The depth-resolved profiles of electron mean free paths were analyzed with electron energy loss spectroscopy (EELS). The implantations were performed with acceleration voltages of 100 kV for Cu and 190 kV for W using electrostatic accelerators. Nitrogen implantation at 40 kV was also performed to make a reference specimen. The doses of the implantations ranged from 5×1016 to 1×1017 cm−2. In this study, we fixed the thin specimens on a sample grid by using a focused ion beam (FIB) processing system equipped with a tungsten deposition system and a micromanipulator. Owing to the method of sample preparation, high-resolution observations were possible because the contraction of the specimens was suppressed during transmission electron spectroscopy (TEM) observation. The cross-sectional HRTEM and EELS observations were performed at 300 kV using a field emission TEM. The TEM observations showed migration of Cu atoms toward the surface, and the lattice images of Cu nanoparticles indicated that each particle consisted of a single crystal. We also found amorphous W nanoparticles containing carbon. The electron mean free path observations suggest that alteration reached about four times further than the mean ion range.