EXPRESS: Novel Method for High-Spatial-Resolution Chemical Analysis of Buried PolymerâMetal Interface: Atomic Force MicroscopyâInfrared (AFM-IR) Spectroscopy with Low-Angle Microtomy.

There is a great need for the analysis of the chemical composition, structure, functional groups and interactions at polymerâmetal interfaces in terms of adhesion, corrosion, and insulation. Although atomic-force-microscopy-based infrared spectroscopy (AFM-IR) can provides chemical analysis with nanoscale spatial resolution, it generally requires to thin a sample to be placed on a substrate that has low absorption of infrared light and high thermal conductivity, which is often difficult for samples that contain hard materials like metals. This study demonstrates that the combination of AFM-IR with low-angle microtomy (LAM) sample-preparation can analyze buried polymerâmetal interfaces with higher spatial resolution than that with the conventional sample-preparation of a thick vertical cross-section. In the LAM of a polymer layer on a metal substrate, the polymer layer is tapered to be thin in the vicinity of the interface, and thus, sample thinning is not required. An interface between an epoxyacrylate layer and copper wire in a flexible printed circuit cable was measured using this method. A carboxylate interphase layer with a thickness of ~130 nm was clearly visualized at the interface, and its spectrum was obtained without any signal contamination from the neighboring epoxyacrylate, which was difficult to achieve on a thick vertical cross-section. The combination of AFM-IR with LAM is a simple and useful method for high-spatial-resolution chemical analysis of buried polymerâmetal interfaces.